British Standards Tunnel

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August 1999 DESIGN MANUAL FOR ROADS AND BRIDGES VOLUME 2 HIGHWAY STRUCTURES DESIGN (SUB- STRUCTURES AND SPECIAL STRUCTURES) MATERIALS SECTION 2 SPECIAL STRUCTURES PART 9 BD 78/99 DESIGN OF ROAD TUNNELS SUMMARY This Standard describes the procedures required for the design of new or refurbished road tunnels located within Motorways and Other Trunk Roads. It gives guidance on the necessary equipment and Operational and Maintenance Systems that need to be considered by the designer to facilitate continued effective and safe operation. INSTRUCTIONS FOR USE This is a new document to be inserted into the Manual 1. Insert Part 9 into Volume 2, Section 2. 2. Archive this sheet as appropriate. Note: A quarterly index with a full set of Volume Contents Pages is available separately from The Stationery Office Ltd. ELECTRONIC COPY NOT FOR USE OUTSIDE THE AGENCY. PAPER COPIES OF THIS ELECTRONIC DOCUMENT ARE UNCONTROLLED

description

British Standards Tunnel

Transcript of British Standards Tunnel

Page 1: British Standards Tunnel

August 1999

DESIGN MANUAL FOR ROADS AND BRIDGES

VOLUME 2 HIGHWAY STRUCTURESDESIGN (SUB-STRUCTURES ANDSPECIAL STRUCTURES)MATERIALS

SECTION 2 SPECIAL STRUCTURES

PART 9

BD 78/99

DESIGN OF ROAD TUNNELS

SUMMARY

This Standard describes the procedures required for thedesign of new or refurbished road tunnels located withinMotorways and Other Trunk Roads. It gives guidanceon the necessary equipment and Operational andMaintenance Systems that need to be considered by thedesigner to facilitate continued effective and safeoperation.

INSTRUCTIONS FOR USE

This is a new document to be inserted into the Manual

1. Insert Part 9 into Volume 2, Section 2.

2. Archive this sheet as appropriate.

Note: A quarterly index with a full set of VolumeContents Pages is available separately from TheStationery Office Ltd.

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BD 78/99

Design of Road Tunnels

Summary: This Standard describes the procedures required for the design of new orrefurbished road tunnels located within Motorways and Other Trunk Roads.It gives guidance on the necessary equipment and Operational andMaintenance Systems that need to be considered by the designer tofacilitate continued effective and safe operation.

THE HIGHWAYS AGENCY

THE SCOTTISH EXEUCTIVE DEVELOPMENTDEPARTMENT

THE NATIONAL ASSEMBLY FOR WALESCYNULLIAD CENEDLAETHOL CYMRU

DEPARTMENT OF THE ENVIRONMENT FORNORTHERN IRELAND

DESIGN MANUAL FOR ROADS AND BRIDGES

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REGISTRATION OF AMENDMENTS

Amend Page No Signature & Date of Amend Page No Signature & Date ofNo incorporation of No incorporation of

amendments amendments

Registration of Amendments

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REGISTRATION OF AMENDMENTS

Amend Page No Signature & Date of Amend Page No Signature & Date ofNo incorporation of No incorporation of

amendments amendments

Registration of Amendments

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VOLUME 2 HIGHWAY STRUCTURESDESIGN (SUB-STRUCTURES ANDSPECIAL STRUCTURES)MATERIALS

SECTION 2 SPECIAL STRUCTURES

PART 9

BD 78/99

DESIGN OF ROAD TUNNELS

Contents

Chapter

1. Introduction

2. Planning, Safety, General Design Considerations

3. Operational Classification of Safety Facilities forthe Road User

4. Geometric Design

5. Ventilation

6. Tunnel Lighting

7. Drainage

8. Fire Safety Engineering

9. Traffic Control, Communications andInformation Systems

10. Plant Monitoring and Control

11. Electrical Power Supply and Distribution

12. Services Buildings and Plant Rooms

13. Tunnel Commissioning, Handover andOperational Documentation

14. Tunnel Operation and Maintenance

15. References and Glossary

16. Enquiries

DESIGN MANUAL FOR ROADS AND BRIDGES

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Appendices

A Secondary Cladding

B Durability and Materials

C Tunnel Documentation: Typical Contents

D Guidelines for Major Incident Operations andFire Tests

E Recent Research by the Highways Agency

F Tunnel Design and Safety Consultation Group(TDSCG) Requirements

G Life Expectancy of Tunnel Equipment

DESIGN MANUAL FOR ROADS AND BRIDGES

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Chapter 1Introduction

1. INTRODUCTION

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General

1.1 This document provides the requirements andessential guidance for decision making relevant to theeffective planning, design, operation and majorrefurbishment of road tunnels in the United Kingdom. Icombines a Directive type Standard with an AdviceNote. The document is intended for a wider readershipthan tunnel designers alone. Throughout, emphasis isplaced on the wider aspects of design as they apply tothe essential aspects of operation and maintenance ofsuch relatively expensive structures over theiroperational lives. For Trans-European Motorways aseparate United Nations document Standards andRecommended Practice: Tunnels, July 1992, applies tsupport the European Agreement on Main InternationaTraffic Arteries (AGR).

1.2 A road tunnel is a subsurface highway structureenclosed for a length of 150m, or more. The operationequipment requirements described in this Standard forsuch structures vary with length, location, speed andtraffic volume. Where security considerations permit, thuse of central light wells may provide economies but thtunnel length shall not be considered to be reduced inany way for classification purposes.

1.3 Aspects of the document will be of particularinterest to parties such as the traffic police, fire andambulance services, maintaining and environmentalauthorities as well as those involved with the severalspecialisms of engineering needed to contribute to aneffective and efficient road tunnel design.

1.4 Emphasis is placed on the early and detailedconsideration that must be given, by the relevant partieinvolved, to the particular aspects of safety peculiar tothe construction and operation of road tunnels and theoverall cooperation, interaction and teamwork thatsuccessful tunnel design and operation entails. Chaptehave been written to be as self contained as possible wa minimum of cross referencing.

1.5 It should be understood that for such a wide andeveloping topic, the guidance provided herein shouldnot be considered as to be exhaustive. It is not intendeto provide any form of substitute for the specialexpertise that is needed to prepare effective and efficieworking designs for a road tunnel.

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Scope of Document

1.6 The document provides information on thegeneral considerations and specific design andoperational requirements of road tunnels, together withdetails of the tunnel maintenance, and operationaldocumentation that is involved. A separate document toadvise further on the specific requirements of roadtunnel maintenance is currently under preparation.

1.7 Many aspects of tunnel design, construction,equipping and operation are currently undergoing rapiddevelopment and improvement. This document haspurposely kept to describing the essential principles ofgood practice rather than to be unnecessarilyprescriptive. Reference is made to a selection of thecurrent publications and research documents whichcould be of assistance to designers and operators.

1.8 Much of the detailed technical specificationrequirements for road tunnel equipment may be found inthe Manual of Contract Documents for Highway Works:Volume 5: Section 7: Mechanical and ElectricalInstallations in Road Tunnels, Movable Bridges andBridge Access Gantries. A separate specificationdocument to advise on the specific civil engineeringrequirements of road tunnel construction andmaintenance is currently under preparation.

1.9 Due to the wide variation in the engineeringconsiderations that influence the structure and form of atunnel, references to civil engineering aspects within thedocument are necessarily limited in scope. Guidance isgiven on such common aspects as for example spacerequirements for traffic, equipment, profile for trafficsafety etc and the consideration to be given to fireprotection of the structure. Separate documents to advison such aspects as the New Austrian TunnellingMethod, Limited Facility (‘low height, car only’)Tunnels and the Observational Method are currentlyunder preparation. The Standard does not cover surfacetunnels, a subject currently being studied in severalcountries including the UK and by PIARC TunnelsCommittee, for environmental mitigation.

Mandatory Requirements

1.10 Sections of the document which form part of themandatory requirements of the Overseeing Organisation(‘the client’) for road tunnels are contained within

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paragraphs in bold text. These are the sections of thedocument with which the Design Organisation (‘thedesigner’) must comply, or will have agreed beforehanda suitable Departure from Standard with the relevantOverseeing Organisation, in accordance with BD2(DMRB 1.1) of the Design Manual for Roads andBridges. Elsewhere in the document, where the word“shall” is used then the requirement is expected to becarried out in full unless, for the circumstances of aparticular scheme, a recorded agreement has been mawith the Overseeing Organisation beforehand that amore suitable way, of conforming with the intention of aparticular requirement, is to be used. The remainder ofthe document contains advice which is commended todesigners and operators for their consideration. Legalrequirements are non negotiable and are not describedwithin emboldened text.

Tunnel Design and Safety Consultation Group(TDSCG)

1.11 It is necessary for various interested parties (seebelow) to meet together as a group in order to contributtheir specific specialist knowledge and experience toclarify requirements for tunnel construction orrefurbishment projects. For effective design,construction and operation of a road tunnel theagreement and setting of appropriate standards of safequality and economy depend heavily on early discussiobetween the parties concerned and on a clear definitionof the scope of work and performance and reliabilityrequirements. Such meetings shall be arranged to be aefficient and effective as possible with respect to stafftime and budget restraints of contributing parties.

1.12 In order to confirm basic design and operatingprocedures in the context of fully integrated systemsfor traffic management, signs and signalling,communication, information, plant monitoring andcontrol a Tunnel Design and Safety ConsultationGroup shall be set up. It shall comprise appropriatelevels of representation from the OverseeingOrganisation, Design Organisation, Police or othercontrol authority, Maintaining Agent and EmergencyServices. The TDSCG will review and co-ordinatestandards of communication and the appropriate, butnot excessive, means of equipping and operating atunnel in the light of consultations between allinterested parties. The Project Manager of theOverseeing Organisation (Design Organisation forDBFO schemes) shall ensure that the Group hasterms of reference that will enable it to identifypotential hazards involving vehicle breakdown, trafficcongestion and full scale emergencies, including fire.

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or DBFO schemes, the Overseeing Organisationhall formally approve such terms of reference. Theroject Manager of the Overseeing Organisation

Design Organisation for DBFO schemes) shall chairll such meetings and make provision for allecretarial duties.

.13 The Group shall meet regularly throughout theesign and construction periods and agree workingrocedures for day to day operation, plannedaintenance requirements (including contra-flow)nd ensure that in the event of an emergencyontingency plans will enable tunnel services andraffic flows to be restored as quickly as possible.lthough not party to the technical approvalsrocedures, the agreed recognition and acceptance ofhe proposals by the Police or other control authority,mergency Authorities and the Tunnel Operatinguthority shall be recorded. Similarly, acceptance by

he Water Authority of likely drainage outfalls fromhe tunnel must also be recorded. The decisionsffecting the design and operation confirmed andgreed at TDSCG meetings must be formallyecorded into a finalised Report of the TDSCG, andccepted as an agreed addenda to the Approval Inrinciple (AIP) document required by BD2

DMRB 1.1).

.14 The TDSCG should complete most, if not all, ofts work prior to the start of construction and therocurement of any operational equipment relevant to

he agreement of the TDSCG. For schemes procured esign and build (D&B) and design, build, finance andperate (DBFO) methods the Overseeing Organisationhall hold at least one inaugural TDSCG meeting prioro tender. Following tender award the TDSCG willontinue to meet throughout the design andommissioning stages of the project until the emergencrill requirement of BD53 (DMRB 3.1.6) prior to tunnelpening to traffic, has been completed and any advers

indings from the drill have been formally addressed.

.15 Appendix F gives a summary of the itemsormally to be discussed by the TDSCG. Additional

opic items may be required to deal with specificequirements of particular road tunnel projects.

eference to British Standards and Legislation

.16 Any reference to a British Standard can be takeo include any other International Standard or Nationatandard of another Member State of the Europeanommunities, which is comparable in its scope andafety requirements to the given British Standard.

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Chapter 1Introduction

1.17 This document is not intended as a legal manualand any references made to legislation are intended onlyas an indication of the possible legal requirements.Reference should be made to the latest relevant UK andEEC legislation, ISO, BS or other EC Member States’Standards and relevant Department of EnvironmentTransport and Regions documents, at an early stage inthe tunnel planning process. Under the Highways Act1980, a special order/scheme is required for a trunkroad/motorway in tunnel under a navigable watercourseTolled tunnels under estuaries may be controlled byspecial legislation eg the Dartford- Thurrock CrossingAct 1988. The designed provisions and operationalprocedures shall not discriminate unlawfully againstdisabled road users of a tunnel.

Implementation

1.18 This document should be used forthwith on allschemes for the construction, refurbishment andmaintenance of tunnels on trunk roads includingmotorways, currently being prepared, provided that,in the opinion of the Overseeing Organisation, thiswould not result in significant additional expense ordelay progress. Design Organisations shall confirm itsapplication to particular schemes with the OverseeingOrganisation.

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2. PLANNING, SAFETY, GENERAL DESIGNCONSIDERATIONS

Chapter 2Planning, Safety, General Design Considerations

General

2.1 This Chapter describes factors influencing thedesign and operation of road tunnels in order to estabthe broad planning and safety issues that are involvedpreliminary design stage. Other Chapters of thisdocument contain information on the more detaileddesign considerations and particular requirements thawill need to be applied once a tunnel project has reachthe detailed design stage.

2.2 Because of the relatively high capital cost, thermay be justification for carrying out road tunnelschemes on a staged basis, eg only initially building obore of a twin bore tunnel. Conversely, there may beeconomies of scale in carrying out more extensive woat an earlier stage. All such factors shall be considereat the initial route selection and planning stages.

2.3 Current planning and scheme appraisalprocedures for new road schemes provide the framewto enable road tunnel options to be considered in direccomparison with open road proposals, including bridgalternatives. Although tunnel options are recognised abeing generally, but not exclusively, more expensive thopen road options they are capable of providingconsiderable environmental benefits and practicalsolutions in schemes with existing congestedinfrastructure, navigable river crossings or through hiland mountainous terrains.

2.4 For each project containing a road tunnel, acomprehensive appraisal of factors contributingtowards a safe tunnel environment for road users,local inhabitants, operators, maintenance staff, policeand emergency services, shall be undertaken at anearly stage of the planning process.

2.5 The planning and design of tunnel options shouinitially be to the same highway standards as for openroad options. However, a number of characteristics ofroads in tunnel differ from open roads and suchdifferences require consideration. These include capitoperating and whole life costs, ventilation, lighting andmaintenance requirements. The nature and mix ofvehicles in the traffic flow will also affect the physicaldesign of tunnels - flows with a higher percentage of

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HGVs requiring extra ventilation, especially at steepgradients.

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2.6 Value Management and Value Engineering, RiskAnalysis and Management (Value for Money Manual:Highways Agency: June 1996) shall be used to consideralternative solutions to meet the needs and to evaluatethe most appropriate options, noting that, in addition toconstruction costs, the particular location of the tunneland the input from equipment manufacturers caninfluence ongoing maintenance and operational costs.

2.7 The four main stages in tunnel planning anddesign ie Feasibility Studies and Investigations;Planning; Agreement and Design , are shown inFigure 2.1.

Basis of Tunnel Operation

2.8 There are two broad categories of tunneloperation to be considered:

i. Tunnels that have their own dedicatedmanagement structure and resources to operatethe tunnel and which retain responsibility fortraffic surveillance and the safe operation of thetunnel, including response to incidents andemergencies. This type of tunnel operationincludes tunnels built under Acts of Parliamentsuch as toll tunnels and the major estuarinecrossings (Clyde, Dartford, Mersey, Tyne etc).The tunnel manager’s responsibilities include theenforcement of any bye-laws concerning vehicleswhich carry dangerous goods.

ii. Tunnels that are designed to operate as fullyautomatic facilities and do not entail theresources of permanent operating and monitoringstaff. Tunnels on motorways and other trunkroads will generally be designed to operate in thisway. It is policy for such tunnels to allow the freepassage of dangerous goods vehicles operatingwithin the law. To divert such vehicles off themotorway and trunk road system would transferrisk to locations that may not have facilities orready access to deal with any emergency incidentinvolving fire or spillage.

2.9 Adequate safeguards shall be in place before atunnel is opened to the road user. Plant and equipment tocontrol the tunnel environment, with provision formonitoring its status and notification of alarm states andpotential emergencies shall be provided. All shall be

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maintained at an acceptable level of public safety,economy and efficiency.

Safety

2.10 Safety in tunnels covers a wide range of issues.This section gives guidance on some of the importantand more common issues to be considered but, togetherwith the guidance elsewhere in this document, should nobe considered to be exhaustive. It is important that theOverseeing Organisation’s appointed person with overallresponsibility for ensuring that the operational safety ofa tunnel is maintained has sufficiently cleardocumentation made available to carry out his/herduties. For Highways Agency tunnels, the appointedperson will normally be the relevant Network AreaManager.

2.11 In conjunction with the work of the TDSCG, theplanning and designing engineers for the road tunnelmust have a proper understanding of how the tunnel willbe operated and ensure that there is adequate and safeprovision for maintenance, economic running andoperational safeguards. Each must be satisfied that alloptions concerning tunnel operating policy, such as thepassage of hazardous goods, and tunnel planning, suchas the locations of the traffic control centre andequipment for on-site, remote surveillance and control,are considered well in advance since there is little or noscope for subsequent physical alteration (eg changingventilation shafts, emergency access, etc).

2.12 Operational and safety aspects have a significanteffect on development of the detailed design, particularlyof M&E functions. Preliminary proposals shall be basedon adequate consultation with the Technical ApprovalAuthority (TAA), Project Manager, Police, EmergencyAuthorities and the proposed Tunnel OperatingAuthority (TOA). For UK Government road tunnelschemes, and also where a Local Highway Authorityrequires, the TAA will be the appropriate person withinthe Highways Agency or Scottish ExecutiveDevelopment Department responsible for grantingapproval in principle, see BD2 (DMRB 1.1).

2.13 During the development of the design, the detailsof the systems and nature of equipment to meet therequirements and objectives of the BD2 (DMRB 1.1),Approval in Principle (AIP) submissions will becomeapparent, and any uncertainties in the preliminarystudies will be gradually resolved. Regular meetings ofthe TDSCG will facilitate this process. At suchmeetings, the designers, TAA and parties having anecessary input into the design and safe operation of thetunnel, shall confirm the basis of the design and the

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oposed scale of provision to the Police, Emergencyervices and Tunnel Operating Authority, to allow them commence their own planning.

14 BS 6164: Safety in Tunnelling in theonstruction Industry provides guidance on safeactices within tunnelling works, including theiraintenance and repair. For compressed air working thllowing regulation applies Work in Compressed Airpecial Regulations 1958, SI 61 and the guidancentained in CIRIA Report 44: Medical Code of

ractice for Work in Compressed Air: 1982.

15 The requirements of road safety audits are given HD19 (DMRB 5.2.2) and accompanying advice inA42 (DMRB 5.2.3). The agreed working party reportm the TDSCG shall provide a substantial input to

lfilling the requirements of the Road Safety Auditorr the highways within and immediately adjacent to aad tunnel.

16 The Highways Agency have issued to their staffe following Health and Safety Notices with particularlevance to road tunnels: No 9 Working in Confinedpaces; No 10 Working in Tunnels; No 11 Stafforking with Lighting Equipment, Signing Equipmentd Electrical Services on Roads and in Tunnels.

17 The Health & Safety Executive produce acument EH40: Occupational Exposure Limits, which

regularly updated, and gives guidance and legalquirements for the limits of harmful substances tohich employees may be exposed. Chapter 5 givesquirements for road users. For those at work innnels, at any time, the more common hazards includerbon monoxide, oxides of nitrogen, benzene,rticulates and dust. Mechanical ventilation, ifovided, shall be used to purge the tunnel with clean afore any authorised persons enter the tunnel. Forturally ventilated tunnels, the polluted air shall be

lowed to clear sufficiently for satisfactory personal gasonitor readings to be established before any authorisersons shall enter the tunnel.

18 BS 7671 IEE Wiring Regulations shall bemplied with to meet the requirements of the Electricity Work Act: 1979, in particular the requirements ofegulation 4(4) of the Act which require regularectrical testing to be carried out. For external highwaywer supplies eg to street lighting and traffic signals

is period is every 6 years. For fire alarms (BS 5839)d emergency lighting (BS 5266) the cycle of testing isery one and three years respectively. Other tunneluipment shall be tested at frequencies laid down by thuipment designer/supplier in accordance with the

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Chapter 2Planning, Safety, General Design Considerations

relevant British Standards and as recorded in theplanned maintenance sections of the Tunnel Operationand Maintenance Manual. Such frequencies ofinspection and testing shall be regarded as the minimustandard to apply and shall be increased, if necessarythe light of operational experience.

2.19 Measures shall be taken, and regularlymaintained, to minimise the risk of any rockfalls,landslips etc from endangering the safety of road userand bystanders within open cut approaches and portaareas of road tunnels.

Incidents and Emergencies

2.20 Two broad situations influence the planning foremergencies. The more common event is a vehicleincident or breakdown which causes a degree of laneblockage, and consequential restriction or eventemporary loss of use of the tunnel. The resulting delamay rapidly extend to the surrounding road network.Prompt remedial action is then called for to restore freflow and minimise the congested conditions that inthemselves can aggravate the risk of further breakdowand/or incidents. The second situation involves collisioand possible fire or explosion and is potentially moredangerous for the tunnel user and requires a rapidresponse from the emergency services.

Risk Analysis and Management

2.21 Refer, for general guidance, to the Value forMoney Manual: Highways Agency: June 1996:StationEry Office. For a particular tunnel, potentialhazards must be identified and related to the tunnellayout and to standards of equipping, communicationsand traffic information and control systems. Suchstandards of provision shall meet the needs of theoperators for the day to day running of the tunnel, andthe emergency services in their response to tunnelincidents, including fire. Special attention shall be giveto aspects that affect driver behaviour eg signing,signalling, traffic movements in the tunnel and on thetunnel approaches.

2.22 The selected tunnel cross section shall becarefully related to the approach road standards,geometry and visibility and procedures for dealing withincidents. Limited data available suggests that the tunnapproach, entrance and exit zones have a higher leverisk than the open road. Conversely, the tunnel interiorhas a lower level of traffic incident risk. For increasedsafety, verge widths over and above the minimumcarriageway requirements for traffic flow, shall be

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related to traffic demand and speed. Full consideratishall be given to cross connections between tunnel bor alternative means of escape for vehicle occupantsto vehicular cross overs, outside the tunnel portals, fthe purposes of contra flow and emergency access.

2.23 Fires or the spillage of hazardous materials agreater consequence in tunnels than on the open roaproper safeguards must be based on an assessmenrisk implications of traffic carrying dangerous loads(explosives, flammables, radioactives and toxins). Thdecisions made shall be fully taken account of for thestructure design, basic equipping and operating crite(to include adequate fire protection) and ventilationcapacity for fire and smoke control, and amplyproportioning drainage sumps to cope with spillageshazardous material and any sluicing water, foams, eapplied. Such safeguards as fire protection, ventilatiand drainage shall also be considered in relation topipelines carrying gas or chemicals belonging to thirdparty users. A major international research project bPIARC/OECD is under way to provide guidance(http://www.oecd.org/dsti/sti/transport/road) on thetransport of dangerous goods through road tunnels.

2.24 Consideration shall be given to the means ofmanaging traffic under total power failure conditions.should be expected to close the tunnel to traffic if bothe normal power supply and standby, to power lightand variable message signs, fail. If standby power isbrought into use at a level lower than for normal powthen speed control must also function to reduce traffspeed, so that the risk of an accident occurring isminimised.

2.25 Availability and security of power supply shallassessed, and unless complete reliability, in all but vexceptional circumstances, can be guaranteed by thsupply authority, an alternative source shall be provifor essential safety related services.

2.26 The likely risk scenarios which may occur in aon the approaches to the tunnel shall be identified. Tshall be considered in detail with the appropriate parand engineering solutions developed by the DesignOrganisation when appointed, for all relevant areas othe tunnel and its approaches. A possible methodolosystematically deal with risk is shown in Tables 2.1 t2.4. Risk scenarios include, but are not limited to:

i. Vehicle related incidents:

Fire in tunnelAccidentsBreakdowns

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Debris on roadOverheight vehicles.

ii. Non vehicle related incidents:

Lighting failureVentilation failurePumping failureTelephones out of orderPedestrians in the tunnelAnimals in the tunnelVandalismTerrorist attack.

iii. Traffic queues:

Traffic queues due to other causes egvolume of traffic.

iv. Vehicle loadings:

Hazardous loadsSlow moving loadsWide loadsAbnormal Indivisible Loads.

v. Weather hazards:

FogRapid, air vapour condensation onwindscreen, mirrors etcHigh windsIceSnowFloodDazzle from the sun (particularly east towest tunnel alignments)

(It might be considered that snow, fog and high winds donot relate to tunnels. However, drivers may encounterthese when they exit a tunnel and may need to bewarned, or the Highway Police may need to considerother appropriate action).

vi. Planned maintenance:

Lane closuresCarriageway closuresTunnel bore closuresTotal closureContraflow operationTemporary signing.

2.27 Having identified and defined the scenarios,strategies for dealing with them shall be decided takingconsideration of the management, coordination,

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peration, mobilisation, access, procedures andommunications requirements of the various partiesnvolved and the needs of the road user. Considerationeeds to be given to the level of human resourcesequired during an incident, both at the control centrend on the ground. Response strategies shall deal with

he initial occurrence of a situation and also anyesulting developments, for example, a breakdown in aunnel may lead to initial local queuing which mayevelop into wider scale area congestion and gridlock.

lassification and Decisions on Safety Facilities

.28 Criteria for, and the related expenditure onquipping road tunnels shall be related as closely asossible to the particular needs at individual sites. Theasis of equipping and operating tunnels therefore useslassification system for tunnel type on motorways andub divisions of all purpose roads.

.29 From the strategy decisions and incident scenaronsiderations it will become clear as to what type ofquipment and systems are necessary and also what th

nteraction between systems should be. It should also bossible to identify the necessary levels of information

low between the parties involved, which will determinehe technical links and communication facilities needed.

.30 Once the equipment and systems involved haveeen determined, technical specification can be carriedut. The necessary communication infrastructure canlso be determined and specified once the equipment anystem needs are understood.

raffic Management

.31 Current road policies and design standardsontribute to a reduction in accidents and, by way ofhrough routeing, particularly for heavy goods traffic,mprove local traffic management and control in newighway schemes. These objectives shall be maintainedhen selecting the criteria on which to base the designnd operation of a road tunnel.

.32 Traffic management shall cater for normal trafficlow and for special movements, planned and emergencaintenance and emergency incidents.

estriction on Tunnel Use

.33 For safety reasons, restrictions are necessary fohe type of traffic permitted to use a road tunnel.edestrians, pedal cycles, motor cycles with engines les

han 50cc, animals and animal drawn vehicles,

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pedestrian controlled vehicles and invalid carriagesshould not be permitted. Such classes of road users arecurrently prohibited from motorways and unless thereare very exceptional circumstances they should also beprohibited from trunk road tunnels. Consideration shallbe given to the provision of alternative routes, wherenecessary, see also TD36 (DMRB 6.3.1).

Speed Limits

2.34 The imposition and, in particular, enforcement ofspeed limits within road tunnels on the open highwayrequires careful consideration. The costs of constructionand operation of a tunnel designed to meet the geometristandards of the adjacent open road may lead topressures to adopt a marginally lower design speedwithin the tunnel. There is little evidence to supportpropositions that traffic will naturally tend to slow at theentry to a tunnel and only to speed up inside, ifconditions permit. Any such assumptions would need tobe confirmed by monitoring once the tunnel is open totraffic - it may then be too late to make the necessarymodifications if such assumptions proved to be false.See Chapter 4.

Establishment of Tunnel Profile

2.35 It is important, for informed design progress onother aspects of the road tunnel design, to establish thelocation, cross sectional shape and gradient profiles forthe tunnel as early as possible in the planning process.See Figures 2.2, 2.3, 4.2 and 4.3 for typical crosssectional profiles. The most desirable profile foraccommodating road traffic containing HGVs isrectangular.

2.36 In certain situations planning constraints maywell determine tunnel location and consequent choice ofconstruction method. Ground conditions and appropriatechoice of tunnel construction method are importantfactors determining the structural form of a road tunnel.Tunnel cross sectional shape profile for a given trafficspace, and the consequent space available for tunnelequipment, is largely determined by the most economicamethod of construction, which in turn depends onconstruction access, depth of tunnel, the nature of theground and its stability during excavation.

Consideration of Future Widening and MaintenanceLanes

2.37 It is not normally possible to widen a road tunnelstructure to cater for a future increase in the number of

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affic lanes required. It may be possible to increase theumber of traffic lanes by one, if the existing trafficnes are narrowed, or the hard shoulder, if any, isplaced. Consideration shall be given to minimising the

otential increase in risk of traffic accidents, reducedmergency access and egress, and to cater for anydditional ventilation and headroom requirements thatuch widening will require. Similarly, if tunnel closureeriods for maintenance are anticipated to be of limitedvailability a marginally wider tunnel may be decidedpon so that the safety zone requirements of Chapter 8f the Traffic Signs Manual: Traffic Safety Measuresnd Signs for Roadworks and Temporary Situations: SOan be accommodated. A study of the anticipated trafficeak flow, tidal flow and hourly demand variations isecessary. A possible option to consider is whether, forxample, three 2 lane tunnel bores would be better thano 3 lane bores. The former has the advantages,

articularly for uneven traffic flows, of option to closene bore in quieter periods for more effectiveaintenance, traffic management flexibility and reduced

ongestion effect should there be an incident in one borffective foresight and provision for such needs willduce the additional costs and disruption to a minimum

ervice Tunnels, Space Requirements

.38 Where land availability and funding permit andlanned maintenance constraints make desirable, then eparate service tunnel, adjacent to the live trafficnnels, should be considered on a whole life cost basisr providing access on maintenance demand to service

abling and other operating equipment, without requirin tunnel closure. Such tunnels may also be used forvacuation purposes during an emergency. Otherdvantages include their use as an exploratory (pilot)nnel in advance of main tunnel construction.

riven Tunnels Profiles

.39 Driven tunnel profiles in rock which may bexcavated using eg drill and blast or boom cutterchniques, are mainly dependent on the shape requiredr the stability of the excavation during its temporary

tages. Other rock tunnels using full face machinesormally have circular cross sections. Circular crossections are not well suited for the ideally rectangularhape of road tunnels. Tunnels lying in, or partially in,oft ground are often driven with a shield and will beircular or part circular. Driven tunnels using full faceachines normally have circular cross-sections, whilstart face tunnelling machines are less restrictive inhape.

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Cut and Cover Tunnel Profiles

2.40 Cut and cover tunnels are generally rectangularwith a clear headroom close to the structure gauge.

Immersed Tube Tunnel Profiles

2.41 Immersed tube tunnels are usually rectangular isection and constructed in reinforced or prestressedconcrete. These may be provided with separate cells fouse as buoyancy during placement and subsequently ftunnel services. In steel/concrete composite constructiosuch tunnels are sometimes circular or part circular inshape.

Space for Equipment

2.42 The space between the equipment gauge and thprofile set by the structural lining or secondary claddingof the tunnel is available for the equipment required forthe tunnel environment. Such space shall be usedefficiently to suit the equipment required, otherwise anyenlargement of the tunnel cross-section will lead tosignificant increase in cost. In rectangular tunnels, theupper corners might be haunched to benefit structuralefficiency but possibly cause a disbenefit in regard to thspace and optimal location of equipment.

2.43 Care shall be taken to identify the optimumpositions for electrical and mechanical equipmentlocated in the tunnel, since ease of access can have asignificant effect on ongoing maintenance costs and thenumber of traffic lanes requiring closure.

Ventilation Space Requirements

2.44 Ventilation can have a considerable influence onspace requirements, depending on the system chosen.

2.45 It is important for tunnels to be asaerodynamically efficient as possible. Naturally andmechanically ventilated tunnels, with one way traffic,partly rely for ventilation upon the vehicle induced airflow. This effect can be maximised, for a given size oftunnel, if the tunnel interior surface is as smooth aspossible and abrupt changes in cross-section,particularly at air entry/exit points are avoided.

2.46 In the event of a fire within a tunnel, the hot airand smoke will form a layer at ceiling level, movingoutwards from the source and leaving a zone of clear abeneath it for a distance either side of the source. Dowstands from the ceiling and other obstructions whichmight break up this layer and prematurely fill the tunne

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with smoke, obstructing escape and rescue, shall beavoided.

2.47 Ducted ventilation systems may have shafts anadits connecting fan rooms to the main ducts within thetunnel. These shall be as smooth as possible and anybends or junctions be as aerodynamically efficient aspossible.

2.48 Space requirements for longitudinal ventilation,using booster (jet) fans normally has little effect on thegeometry of arch roofed tunnels providing the fandiameters are kept below 1.5m diameter. The fansshould be placed over the carriageway lanes within theequipment gauge, rather than above the verges. In thecase of rectangular tunnels, one solution is to increasethe height of the tunnel over its full or partial length toaccommodate the fans. Where constraints or increaseconstruction costs preclude this solution, fans can beplaced in aerodynamically shaped recesses (niches) inthe soffit or at the tops of the side walls. Howeverventilation efficiency may be reduced and significantlyso for the latter. The life time additional costs from sucefficiency losses shall be established before deciding othe profile to be adopted.

2.49 Space requirements for transverse and semi-transverse ventilation systems normally have littleinfluence on arched or circular tunnel geometry, as thegenerally contain space above or below the road deckwhich can be used for ventilation ducts. However, whelarge volumes of ventilation air are required, an increain structure size may be required. In the case ofrectangular profiles such systems have an importanteffect on tunnel geometry, sometimes requiring a greatheight of tunnel and sometimes increased width. In alltypes of tunnel these systems of ventilation requireancillary shafts and/or tunnels and ventilation fanbuildings. The buildings and their intake and exhauststructures and emissions may have importantenvironmental consequences. Their location, if not ideacan significantly affect ventilation space requirementswithin the tunnel.

Lighting Space Requirements

2.50 Generally tunnel lighting has little bearing on thetunnel geometry. In arched roof profiles, without falseceilings or ventilation duct soffits, there is normallyample space for luminaires. Only arched tunnels withfalse ceilings and rectangular profiled tunnels, where thluminaires are located above the traffic lanes, requirevertical space of between 350mm and 500mm toaccommodate the 250mm additional clearance and theluminaires themselves.

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Signs and Signals Space Requirements

2.51 Signalling equipment, if located on the sidewalls, has little influence on the cross section of archedtunnels, with two lanes, or of rectangular tunnels.

2.52 For tunnels with more than two lanes and havinga false ceiling or rectangular profile and where thesignalling equipment is fitted over the traffic lanes, abou350mm vertical height is needed.

2.53 Full sized direction signs are difficult to locatewithin a tunnel and are best positioned outside of theportals.

Toll Booth Space Requirements

2.54 Where tolls are to be collected as cash theprovision of toll booths will be necessary. The numberand siting of these will be dictated by their effect ontraffic flow in the tunnel and on land availability, whichwill vary from site to site. Toll booths may be situated atone or both ends of the tunnel, or series of tunnels.Collection and control is by a mix of manual methods,coin receptacle from a moving vehicle or electronictagging with prepayment. Booths will require heating,ventilation, till, seating, signing, communication andsecurity facilities and protection against impact fromvehicles and robbery. Air conditioning may berequired, see Chapter 5.

Tunnel Services Buildings, Tunnel Portals: Landand Royal Fine Art Commission /Commission forArchitecture and the Built EnvironmentRequirements

2.55 Services Buildings to house the substation, planroom, control centre, etc. will normally be required.Their location will be dictated by the requirements ofthe electrical distribution system (ie as close aspossible to the tunnel to avoid excessive voltage drop),by the type of ventilation system and by landavailability.

2.56 Services Buildings are part of the complete tunneland highway scheme and are not treated as a separatedevelopment. The buildings and tunnel portal areas,particularly for a major scheme, or one in an Area ofOutstanding Natural Beauty or near listed buildings orconservation areas may need referral to the Royal Fine ACommission (RFAC). RFAC is to be replaced by CABE,the Commission for Architecture and the BuiltEnvironment. The Overseeing Organisation shall consultthe Highways Agency Architect on the need to refer detailsof the proposed service buildings and tunnel portals for

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e comment of the Royal Fine Art Commission, andform the appropriate Design Organisation according Scotland the Scottish Executive Developmentepartment shall be consulted regarding thequirement for submissions to the Royal Fine Artsommission for Scotland.

.57 The need for a tunnel services building to fit into iurroundings shall not result in the provision of less thdequate space for housing necessary equipment.onsideration shall be given to the need for adequateentilation and air conditioning to avoid excessive roommperature, particularly in UPS rooms, battery rooms

nd areas containing electronic equipment. Serviceuildings shall be located clear of any road drainageumps because of the inherent dangers of electricalquipment in close proximity to explosive gases frompills etc. For habitable buildings, the requirements ofe Building Regulations, Fire Regulations etc apply.

econdary Cladding Function and Space Requirements

.58 Where secondary cladding is to be provided itsually constitutes an additional layer of lightweightonstruction, placed over the internal face of therimary (main load bearing) lining. The main functionsf secondary cladding are to provide a reflective surfa assist tunnel lighting; to smooth the interior of thennel to facilitate mechanical cleaning of the tunnelalls; to reduce ventilation energy losses and to shedrips to drainage in the case of seepage through therimary tunnel lining. It also may provide a beneficialffect, where anti-drumming layers are added, on noisvels within the tunnel. Where the secondary cladding used to blank off dead space within the tunnel, it hainimal effect on the cross section. The lower part ofe tunnel wall shall be designed to minimise the risk oaffic collision with the secondary cladding. Internalnishes to the tunnel structure, visible to the travellingublic, shall be attractive and functional without beingistractive to safe driving.

abling and Ducted Services Space Requirements

.59 The duct space required for the distribution andre protection of cabling for tunnel M&E functions andossible future services must be determined at an eartage because of the significant structural influence throvision of such space can have on certain types ofnnel. Where secondary cladding is used, it may be

ossible to utilise the space between cladding and matructure for services, this will normally have to beesigned into the original concept.

.60 In long tunnels, de-rating of cables and pressurrop in piped services can lead to an increased size o

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these services, and the need for larger ducts to housethem. In circular tunnels, duct space is usually availableunder the roadway by virtue of the tunnel shape. In flatbottom shaped tunnels, however, an increase in depth isusually required to locate the cabling and/or pipeworkbeneath the walkway zone. Placement of manhole andother duct covers within the traffic lanes shall beavoided as planned access to maintain, replace loosenecovers etc may only be available during a tunnel closure

Utilities

2.61 The construction of a road tunnel often offersopportunities to owners of utilities and communicationcompanies to seek to use the tunnel to carry additionalservice pipelines, transmitters and cables for the benefitof such companies and their customers. It is left to theOverseeing Organisation to consult with the relevantTunnel Operating Authority to decide which, if any, suchadditional pipelines and cables may be accommodated.Points to consider include the effect on tunnel safety,operations and maintenance; access to effect repairs;liability for any curtailing of or damage to services; fireor explosion from eg gas leaks; corrosion and heat fromhigh voltage cables; ventilation energy loss from theadditional drag caused by the larger diameter pipelines;interference with broadcasting of the emergency andmaintenance staff broadcasting frequencies; the need todiscourage use of mobile telephones whilst drivingwithin a tunnel; and competition policy. Thedevelopment of in-car communications could be ofsignificant benefit to contact and guide road users duringa tunnel emergency. Rental levels shall be set sufficientlyhigh to cover fully such costs and risks, and fullyinclude, pro rata, for the alternative costs the utilities etcwould need to bear if the road tunnel were not available,as well as an agreed share of the continued income fromthe provision of such services. Legal advice shall besought by the Overseeing Organisation on any rights ofStatutory Undertakers and Public Utility serviceproviders relevant to services in a public highway, wherethe public highway passes through a road tunnel.

General Design Considerations and Requirements

2.62 Elsewhere in this document, more detailed tunneldesign considerations and requirements are provided foraspects of road tunnel schemes which have reached amore advanced stage of development. Issues involved,however, are not necessarily limited to those that havebeen described.

2.63 The Overseeing Organisation responsible forcommissioning highway projects shall ensure that the

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anning and design considerations for road tunnels arerried out in consultation with appropriate andperienced design specialists. The specialists shallnsider all design, operations and maintenanceplications for the tunnel and its associatedfrastructure. If the responsibility for maintenance isssed to a third party, appropriate standards must also agreed by the parties concerned.

64 It shall be recognised that the construction anderation of road tunnels is often one of the most costlypects of all highway structure provision. Every effortall be made to minimise such costs, whilst providing afe and reliable facility for the road user.

65 For mechanical and electrical (M&E) plant anduipment that is to be installed, much of the detailedsign will be undertaken by the manufacturerspointed by the successful Contractor and undertaken

accordance with the requirements of the contractecification. Contract documentation will need tontain a clear presentation of design, maintenance anderational requirements, including the interfaces with

her equipment etc.

66 Where design under the (construction) Contract required, the requisite information is usually provided the invitation to tenderers and, depending on the type contract employed may be either a basic design of thennel layout and geometry, together with the plant anduipment that is to be installed, or, in the case of designd build forms of contract, take the form of Employers

equirements, with the additional option of including anustrative Design of core requirements.

67 The final design should be the outcome of alanced and coordinated response to the needs and

rcumstances applying at individual road tunnel sites,e requirements of relevant Authorities consulted ande views of the TDSCG.

68 The five key elements of a road tunnel design orfurbishment normally relate to:

For a new tunnel, the tunnel profile andprotection of the tunnel structure againstaccidental damage, such as fire from vehiclecollisions or spills.

The role and extent of the equipment and plantthat is required to monitor, communicate andcontrol the tunnel environment and respond totunnel emergencies. The level of futuremaintenance and operational costs are closelycorrelated to the level of installation of suchequipment and plant.

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2.72 The range of settlements (vertical andhorizontal), rotations and differential displacementsthat the likely tunnelling construction method, plant,expected rates of advance and changes to the watertable level are likely to produce during and aftertunnelling shall be estimated, and the likely effects onadjacent structures (including utilities) disclosed to,and agreed with, the owners. Where such estimatedsettlements place an unacceptable strain ordisplacement on the adjacent structures (includingutilities) then agreed mitigation measures shall beproposed to limit such values to acceptable levels.Adjacent structure (including utilities) conditionsurveys shall be carried out prior to, during and aftercompletion, of the tunnelling works, until any furthersettlements are of no account. The survey results shallbe agreed at the time between the parties concerned.Measures to record and control tunnelling settlementshall be in place before construction commences, asshall rapidly activatable contingency measures, andshall be subject to continuous review.

2.73 The incorporation within the tunnel ofmaterials which give off toxic fumes during a fireshall be avoided or otherwise minimised. Thecollection of traffic dust, which often contains toxicsubstances and is a potential fire risk, in areasdifficult to clean on a regular basis, such as withinfalse ceilings, shall be mitigated against. The use ofasbestos products such as asbestos cement air ductformers and asbestos rope gaskets between tunnellining segments shall not be permitted. The injectionof materials into adjacent ground which may be ofharm to the environment shall not be permitted.

2.74 Whilst road tunnels provide a drier and moresheltered environment for road users than the openroad it shall be recognised that the atmosphere withina tunnel is often humid and polluted with dust andacidic gases from vehicle emissions. Such conditionscould be harmful to maintenance staff, unless safeworking procedures are adhered to, and areaggressively corrosive to any equipment installedwithin the tunnel. Chlorides, particularly from theuse of road salt, have also caused considerabledamage to several UK tunnel structures andequipment and alternative, less damaging, de-icingmaterials shall be considered for application, limitedto the actual need, within and close to tunnel sectionsof the highway. Consideration of de-icing materialsshall be undertaken by the Design Organisation at thedesign stage and shall be appropriate for theenvironment and the tunnel structural and equipmentmaterials proposed. Protection to reinforced concreteelements is detailed in BD43 (DMRB 2.4) and BD47

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iii. Whether the tunnel is to be permanently mannedor operated remotely.

iv. The tunnel maintenance and operating proceduresrequired to facilitate day to day operation and torespond to emergency conditions.

v. The number and duration of tunnel closuresduring which preventative and correctivemaintenance works can be efficiently carried out.It is essential that the designer makes every effortto minimise the need and efforts required for andduring such works.

2.69 Virtual Reality modelling, by computer, of thetunnel design and construction stages, equipmentpositions and maintenance/spares/performance history,operation phases and planned and emergency closuresand training are considered, with the continued reductionin processing costs, to offer considerable benefits interms of communications and decision making for allparties contributing to the successful design,construction and operation of a road tunnel. The earlierthat such modelling is introduced into the procurementand operation process the greater are the potentialbenefits. The requirement for Virtual Reality modellingfor a particular project shall be confirmed by theOverseeing Organisation.

2.70 BD2 (DMRB 1.1) gives the requirements fortechnical approval of the road tunnel structure andequipment. Compliance with statutory requirements andrecognised Standards and Codes, including appropriatesections of the Design Manual for Roads and Bridges,shall be managed within an approved quality system tocover all phases and aspects of the project.

2.71 BD31 (DMRB 2.2), (in Scotland SB3/88) doesnot apply to road tunnel designs. For site investigationrequirements refer to HD13 (DMRB 4.1), HD22(DMRB 4.1.2), (in Scotland, SH4/89), HA34 (DMRB4.1) and HA73 (DMRB 4.1.7). For “cut and cover” typeroad tunnels the guidance of BD42 (DMRB 2.1.2)applies for the design of any embedded walls includingsecant piled walls. An Advice Note BA80 (DMRB2.1.7) on the design of rock bolts is now published.Design to mitigate against heave loadings anddisplacements at the tunnel road base slab shall beundertaken from first principles. For structuresvulnerable to thaumasite sulfate attack the advice andguidance contained in IAN 15 (DMRB 2.1) and thereport of the Thaumasite Expert Group: The ThaumasiteForm of Attack: Risks, Diagnosis, Remedial Works andGuidance on New Construction: January 1999.

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(DMRB 2.3.4). Solutions to wash tunnel walls tomaintain light reflectance are often caustic in nature.The effect on structure and component durability aswell as Health and Safety aspects shall be consideredby the Design Organisation and the appropriatematerials used. Stainless steel grades believed to beresistant to such environments include BS1449316S13, S16 and S33, which contain in excess of 2%molybdenum. Further advice is contained inAppendix B.

2.75 Water leakage into tunnels through structuralcracks and joints can be hazardous when flow collects inareas with, for example, high voltage cables and otherelectrical equipment such as tunnel lighting. Freezing ofthe water may lead to areas dangerous to the travellingpublic and tunnel maintenance staff, thawing may leadto hazards such as icicles falling on to road users fromthe tunnel roof and portals, as well as increasing the rateof deterioration of the structure, particularly around theregions of inflow at cracks and open joints. Exposedleaks are unsightly and may alarm the public as to thesafety of the tunnel structure. Heavy leakage is costly inenergy terms, if additional pumping out of the roadwaysumps is required. Any associated lowering of theground water table may be environmentally detrimentaland/or lead to settlements of adjacent structures.

2.76 Where tunnels lie totally or partially below thewater table or are in ground subject to water flows,the tunnel structure designer and tunnel constructorshall take all reasonable measures (eg controlledcollection and discharge of ground water) to reducethe possibilities of water leakage through and into aroad tunnel structure for the whole of its 120 yeardesign life. Tunnels where any joint or crack isweeping at handover to the Overseeing Organisationshall not be accepted and effective remedial sealingworks shall be undertaken. Where leakage has beensuccessfully sealed then provisions shall be made sothat re-sealing of the defect or sealed joint is readilyeffected should leakage reoccur during the design lifeof the tunnel structure. Sealing or resealing shall notreduce the effectiveness of any internal or externaldrainage system provided. CIRIA Report 81: TunnelWaterproofing (now withdrawn) provided adiscussion on the principals to be considered. Anyproduct, method or material proposed forwaterproofing or sealing a road tunnel structure thatdoes not have a proven record of satisfactory servicewithin road tunnels, to the satisfaction of theOverseeing Organisation, shall be subject tocomprehensive and successful trials, off the tunnelsite, before its adoption may be considered forapproval. BD47 (DMRB 2.3.4) and BA47 (DMRB

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.3.5) apply to the waterproofing and surfacing ofuspended road tunnel decks.

.77 All installed software and hardwareomponents and systems, embedded or otherwise,rovided at, or linked to, a road tunnel, which areritical for the safety of the travelling public or to theliability of continuous operation of the tunnel shall

e designed and certified, as checked and tested, thato value of a current date, in the future, will causeny interruption or false output to their operation.ear 2000 conformity shall be to DISCPD2000-1SI).

.78 Where buildings or other developments arelanned to be constructed over, or adjacent to, roadnnels then account shall be taken, in the tunnelesign or assessment, of the additional loading to beposed (or equivalent uniformly distributed loading)

nd the construction methods such as piling,xcavation, ground anchoring, ground waterwering, diversion of services etc which could beasonably expected to take place in the construction

nd use of such developments. A “build over”ocument shall be prepared by the Designrganisation defining the parameters, effecting theading condition of the tunnel, within which theuild over” developer is constrained to comply.

echnical approval of any “build over” proposals,cluding existing road tunnels, shall be carried out toD2 (DMRB 1.1). It is important to use a consistentpproach throughout, for both tunnel and “buildver” for partial factors concerning loading,aterials and section design assessment. Road tunnel

tructures of concrete and/or steel shall be designed the DMRB requirements of BS5400. Theverseeing Organisation shall instruct the Designrganisation on the need for such allowances foruild over”.

.79 Air pollution, arising from the vehicles passingrough a road tunnel, is concentrated and exhausted ae tunnel portals and any ventilation shafts. Fornvironmental reasons, in locations with adjacenthabited buildings, it may be necessary to providedditional forced ventilation so that the polluted aireing expelled has sufficient velocity and turbulence toix and distribute with the ambient air, so that ambientir pollution regulation levels are not exceeded. It willormally be necessary, in such cases, to establish theverage background level of the ambient air pollution atn early stage. For site readings, exhausted air from thennel shall be measured at the nearest inhabiteduilding which is not part of the tunnel operation or00 m from the portal or the point of issue, whichever is

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the lesser. PIARC (Road Tunnels: Emissions,Ventilation, Environment: 1995) have publishedmathematical formulae to estimate tunnel dispersiondistances, but physical scale models are presentlybelieved to be more reliable for predictions in areas ofcomplex topography and infrastructure.

2.80 Highway loadings, over and through a roadtunnel, are as described in BD37 (DMRB 1.3). Forcases such as transverse spanning, suspended road and road slabs supported on the ground, where it is npossible to determine the effective loading lengths forHA udl (uniformly distributed loading), then the vehicleloadings given in BD21 (DMRB 3.4.3): Appendix Dshall be used. For design (as opposed to assessmentloadings of BD21 (DMRB 3.4.3): Appendix D shall beincreased by 10%. The Overseeing Organisation will

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Description Scenario

Highly likely Very frequent occurrence

Likely More than evens chance

Fairly likely Occurs quite often

Unlikely Could happen but not very

Very unlikely Occurrence is not expecte

Extremely unlikely Just possible but very sur

Note: Intermediate values may be interpolated.

Table 2.1 Event Probability

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provide details of any Abnormal Indivisible Loading(AIL) vehicles to be included in design or assessm

2.81 The internal walls, claddings and false ceilinetc of a road tunnel shall be designed for an additioperational loading due to the wind pressures and‘suctions’ caused by the moving vehicle traffic. Nomloadings to be used for preliminary design are +/-1.5KPa, applied in the combinations for wind loadsdefined in BD37 (DMRB 1.3). Such nominal loadinvalues shall be reviewed for adequacy with respectraffic speed and range of vehicle heights, once thetunnel cross section and lining clearances becomedetermined, and for any contraflow traffic operationAny necessary redesign resulting from the review sbe undertaken. For fatigue on metal elements withcladding the stress cycle value shall be taken as 5million.

Probability Score

Over 85% 16

51 - 85% 12

21 -50% 8

often 1-20% 4

d to happen Less than 1 - 0.01% 2

prising Less than 0.01% 1

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Description Scenario Examples Score

Disastrous Tunnel operation could not be sustained 1000

Severe Serious threat to tunnel operation 100

Substantial Increases operational costs/difficulties substantially 20

Marginal Small effect on operational cost/difficulty 3

Negligible Trivial effect 1

Note: Intermediate values may be interpolated.

Table 2.2 Event Impact

Risk Priority Number (RPN) Category Action Required

Over 1000 Intolerable Eliminate risk

101 -1000 Undesirable Avoid or transfer risk

21 - 100 Acceptable Retain and manage risk by prevention or mitigation

Below 20 Negligible Could be ignored

Note: Identified risk scenarios should be ranked in RPN reverse order.

Table 2.3 Risk Priority Numbers (Event probability x Event Impact)

Risk Action Required Possible Response

Elimination Change provision such that risk cannot occur

Avoidance Modify provision so that risk is greatly reduced

Transfer Not likely to be able to do this for safety aspects

Prevention Action taken to prevent risk from occurring

Mitigation Measures taken to reduce impact of risk if it were to occur

Acceptance It is accepted a risk may occur but it is neglible or there are no costeffective solutions available

Note: Risk response strategies should be listed and recorded.

Table 2.4 Risk Response Strategies

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FEASIBILITY STUDY

HIGHWAY OPERATOR- existing- new- maintenance demand

TRAFFIC POLICEEMERGENCYSERVICES- capacity- response time

RISK ASSESSMENT- accidents- breakdowns- fire- hazardous load incident

GEOMETRY- length, width- gradient- curvature

DETERMINE OPERATIONAL & MAINTENANCE REQUIREMENTS- Policy & procedures- Traffic rules & exclusions- Staff, permanent or temporary- specialists & general contracts- etc.

CONFIRM WITH CUSTOMER- statutory powers and regulations- agreements with Police, Fire, Ambulance, Breakdown Recovery- Maintenance Contracts in Principle

DESIGN THE TUNNEL- structure- systems- highway

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TRAFFIC FORECAST- flows- type- hazardous loads

LOCATION- topography- environment- ground conditions- hydrogeology

ROUTE- national or local- rural or urban- special crossing

POLICY- level of service- precedent

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Additional Allowance

Typical Cut and Cover Tunnel Section(Looking In Direction Of Traffic Flow)

CarriagewaySurfacing

CCTV Camera

SecondaryCladding

CommunicationsCables In Ducts

Fire Main

Slab Thickening For Duct /Fire Mains Crossing Tunnel

Filter Drain

No Fines ConcreteCarrier Drain

GulleyPower And ControlCables In DuctsWith FoamedConcrete Backfill

High Pressure SodiumLuminaires

Verge

Ducts / Fire MainCast Into Slab

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Leaky Feeder Aerial Luminaire Mounting System Equipment Space Fans

Figure 2.2

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Carbon Monoxide,NOX and Obscuration Monitor

Chapter 2

Planning, S

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Side Cells

No Cell Centre Cell

Immersed Tube Tunnels

Segmental Construction

Typical Hard Ground Profile Typical Soft Ground Profile

Sprayed Concrete Tunnels

Typical Cross Sections of Bored TunnelsFigure 2.3

Chapter 2Planning, Safety, General Design Considerations

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EmergencyTelephones

PolicePatrols

Signs

Traffic

CCTV

Traffic

Weather

Lighting

CO/smokesensor

Levelsensor

Lumination

Fans

Pumps

Power

Fire

Tunnel ServicesBuilding

Traffic ControlCentre

Monitoring and control of tunnel

environment and plant

Surveillance and controlof tunnel traffic

Response to tunnelalarms and emergencies

BreakDown

Fire

MaintenanceDepot

Basis of Tunnel Organisation

Tunnel Operation Surveillance Monitoring Control

Figure 2.4

Chapter 2Planning, Safety, General Design Considerations

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Chapter 3Operational Classification of Safety Facilities for the Road User

3. OPERATIONAL CLASSIFICATION OF SAFETYFACILITIES FOR THE ROAD USER

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General

3.1 This Chapter describes the classification criterfor the selection of operational safety facilities to beprovided in a particular road tunnel, such as space foemergency points, pedestrian access, escape routesvehicle cross-overs and equipment relating to emergepoints, ventilation override, traffic surveillance andcontrol, communication and information systems. Whebye laws permit, road tunnels shall allow, and beappropriately equipped for, the free passage of vehicllegally carrying dangerous goods.

3.2 Any additional demands on a driver travellingthrough a road tunnel will vary between individuals anto a large extent, on the length of the tunnel and itsstructure and form. Those of a nervous disposition orsuffering from certain phobias could, in some situation(eg very long tunnels or river crossings) find theexperience daunting and in the extreme traumatic. Unnormal free flow conditions, however, the majority ofroad users find little problem in driving through tunnelOnly in the event of vehicle breakdown, trafficcongestion, or the rare occurrence of a serious accidewithin the tunnel, will some experience unease orsensations of panic.

3.3 To mitigate such effects, clear communicationand guidance shall be provided for tunnel users in theevent of disruptions to the normal traffic flow such asmaintenance, tunnel closures, diversions etc. In additto the standard operating procedures devised for sucevents, and arrangements made for rapid response toaccidents, breakdowns or other emergencies physicameans of escape must be clearly indicated.

Basic Requirements

3.4 Facilities for operational safety must beconsidered for each tunnel in terms of its length, trafficonditions, and the type of road involved (ie motorwayor other trunk road). This entails a review of thestructural features affecting the tunnel layout,communications, response to emergencies, includingemergency lighting and the role of mechanical ventilat(where provided) in the event of a fire. In twin boretunnels the unaffected bore offers the possibility ofemergency services access, a refuge and an escape

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route.

It is also important to consider the tunnel with respect tothe surrounding road network.

3.5 There are advantages in adopting a classificationsystem to define the basic facilities to be provided for thoperational safety of road tunnels (see Table 3.1).However, care must be taken to avoid misusing suchsystems, because no two tunnels are alike and the natuand variety of the safety issues involved requires thateach tunnel be dealt with as a separate entity.

3.6 A tabulated system provides an effective meansfor conveying the key issues to non-specialists,particularly those employed in the general planning oftunnel projects. It also provides a basis for establishingpreliminary design requirements and cost estimates.

3.7 At the stage when tunnel design and operationalsafety issues are being developed in more detail, atabulated system of facilities provides a convenientframework for the TDSCG to ensure that systematicconsideration is given to the specific safety issues ateach site.

3.8 In matters relating to telecommunications andtraffic control, only general guidance can be given,because the development of detailed design requiremenin this area entails close cooperation with the OverseeinOrganisation, in order to take account of relevantsystems in place or planned on the surrounding network(NMCS etc).

3.9 The following traffic flow type and tunnellocation factors shall be taken into account:

Unidirectional or bi-directional traffic flow within atunnel bore

i. This will affect the placement of emergency/distribution panels, traffic control measures andsmoke control philosophy.

Urban or inter-urban location

ii. Access and attendance times for the emergencyservices can vary considerably according to thelocation.

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Location above or below water

iii. Tunnels below the water table may be moresusceptible to flooding and if passing underwaterways the means of escape can only be viaeither end of the tunnel or into adjacent andunaffected tunnel bores.

Trunk road or Motorway

iv. Traffic speeds and drivers’ preparedness forpossible obstructions will vary according to thecriteria applying to the road of which the tunnelis part.

Classification of Facilities

3.10 The provision of safety facilities is related to theannual average daily traffic flow (AADT) for the tunneldesign year, which is typically 15 years from the date ofopening, and the length of the tunnel. Tunnels areseparated into categories AA, A, B, C, D and Eaccording to length AADT as shown in Figure 3.1.Categories for AADT in excess of 100,000 vehicles perday may be calculated by extrapolation of the graph.

3.11 Table 3.1 gives the recommended basicprovisions for each category. The provisions should beregarded as a starting point for establishing designrequirements rather than be rigidly adhered to if thereare valid reasons not to do so. The requirements andconsiderations of tunnel layout, structural features,communications, emergency facilities, duplicate systemsfor reliability in operations and incidents, and valueengineering all play a part in reaching the final decisionson provision.

Tunnel Layout and Structural Features

3.12 Emergency Points: Tunnel structures shallaccommodate emergency points at intervals along thetunnel. Such points shall be large enough to housefire-fighting facilities and emergency roadsidetelephones connected to remote, permanentlymanned, police or tunnel control centres. The spacingof emergency points is determined by therequirements for spacing of emergency telephones,and fire hose reels and hydrants which shall bedetermined in consultation with the fire authority.The nominal spacing for emergency points is 50m,with emergency roadside telephones and fire hosereels (if fire brigade require) at every emergencypoint and hydrants at alternate points (ie at 100mintervals).

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13 Vehicle Refuges for Tunnel Incidents: The initialst of providing additional traffic space in the tunneloss section to cope with incidents and breakdownsust be balanced against the operational needs ofmmunications, surveillance, stand by recoverycilities, consequence of traffic delays and pressure one surrounding road network. Such factors will depend the length of tunnel, its location (rural, mountain,ban, sub aqueous) and on traffic demand. Advice fromose experienced in the management of risks in roadnnels, rather than accident statistics, shall be sought tfine the need for any additional traffic standing space.

14 Emergency Stopping Lanes: Due to the highsts involved there are very few examples ofntinuous emergency stopping lanes within tunnels.

owever, additional lane width or widened vergesovide a temporary expedient for traffic to be able toss a stranded vehicle. Such temporary provisions shat be a basis for justifying traffic throughputs duringolonged periods of tunnel restriction. The first priorityd whole basis of safe tunnel operation must always be

remove, as a matter of urgency, any obstacle torestricted lane use.

15 Emergency Walkways: Unobstructeddestrian access, at low level, to emergency pointsall be provided. [The high raised and protected

alkways, which originated from the circular profiles TBM (tunnel boring machine) constructed tunnels,ve rise to distinct disadvantages: the loss ofmporary standing for stranded vehicles; forivers, the unwelcome side wall effect (avoidance)fluencing driver behaviour; restricting the nearsideening of doors of stranded vehicles; loss of readycess to the emergency points and cross tubennections for all tunnel users, especially thesabled. Maintenance is also more problematical (egct walls, rapid deterioration of hand railing andneral cleaning difficulties)].

16 Escape Routes: In twin bore tunnels,ssenger escape routes through fire doors positioned

central walls or cross-connecting passages, shall beovided. These shall be positioned at 100m nominaltervals and provided with permanently lit signs,

ergency roadside telephones etc. Single bore tunnelcape route and safe refuge requirements shall beamined and established by the Design Organisationm first principles, to the agreement of the TDSCG.

ee Chapters 5, 8 and Appendix D for additionalidance.

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Chapter 3Operational Classification of Safety Facilities for the Road User

3.17 Tunnel Cross Connections: Tunnel cross-connections are generally of three types:

i. A single set of fire doors in the partition wallbetween two traffic bores.

ii. A cross passage with fire doors at both endsproviding a safe refuge and an escape route fromone bore to the other.

iii. Access doors to a central escape shaft orpassage, leading to a safe exit.

The second and third types above require ventilation tomaintain a supply of fresh air to the escape route andpositive pressure or other provisions to exclude smokefrom any fire within a traffic bore. Where two or morebores are linked by cross connections, the effect ofopening one or more of those cross connection doorsshall be considered in both normal and emergencysituations. The design shall incorporate features whichreduce or eliminate any hazard caused by the openingsuch a cross connection.

3.18 Vehicle Cross Overs: Vehicle cross overs shallbe provided on tunnel approaches to enable contraflow working in twin bore tunnels, or convoy working(see TA63 DMRB(8.4.5)) in single bore tunnels formaintenance etc. If there is a junction near the tunnel,care shall be taken to ensure that all traffic can usethe cross overs. Care shall also be taken with sightlines through cross-overs, particularly those adjacentto widely spaced twin bores and provision made forsuitable temporary or permanent signing, includingany necessary speed limit signs. During normaloperation, suitable means of preventing vehicles fromcrossing from one carriageway to the other shall beprovided to avoid a safety hazard. Movable ordemountable barriers, when implementing contraflowoperation, shall be evaluated in terms of possiblereductions in maintenance costs.

3.19 Turning Bays: In tunnels of over 5 km length,turning bays of sufficient size to enable a lorry to turnaround shall be provided, not more than 1 km from themiddle of the tunnel.

3.20 Emergency Services Parking: If necessary, anarea close to the tunnel portals shall be provided for thparking of police and emergency services vehicles andequipment when attending a tunnel incident.

3.21 Toll Booths: Toll booths, if required, shall besited at sufficient distance from the tunnel portals toallow traffic to return to free flow conditions before

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entering the confines of the tunnel. This affects not onlysafety, but also the pollution levels in the tunnel. Ingeneral, toll booths should be sited at least 300m from atunnel.

3.22 Drainage Sumps: Drainage sumps shall be sizedto accept, and be equipped to contain with safety, thelargest spillage that may reasonably be expected tooccur within the tunnel. Unless bye law restrictions areimposed and enforced, the volume to be assumed is30m3, which approximates to the total contents of alarge tanker vehicle.

Tunnel Communications and Emergency Facilities

3.23 Communications: Emergency roadside telephoneswithin the tunnel allow road users to communicatedirectly with the tunnel or police traffic control centre.Radio rebroadcasting equipment will enable emergencyservices and maintenance staff operating within thetunnel to maintain communications. To warn, guide andassist road users during tunnel emergencies use offlashing signals, RDS radio broadcasting, in-carcommunications, klaxons and public address systemswhich are effective in high ambient noise conditionsshould be considered, as an effective means of reducingthe risks of loss of life or injury.

3.24 Traffic Controls: The safety and pollutionhazards from traffic disruption within a tunnel may bereadily appreciated. Appropriate levels of equipment formeasurement of traffic speed and density, trafficsurveillance (eg CCTV) and control, together with acomprehensive system of signs and signals shall bedeveloped in close cooperation with the OverseeingOrganisation (which has the overall responsibility forauthorising such installations on its motorways andother trunk roads). Tunnel traffic control systems shallbe integrated with local networks and neighbouringtraffic control systems

3.25 Tunnel Systems - Emergencies: Systems relatingto emergency points and the response to tunnelemergencies shall be linked with the tunnel plantmonitoring and control centre.

3.26 Fire Alarm, Extinguishers, Smoke Control:Facilities for raising an alarm, either by manual orautomatic means, and responding to a fire shall beprovided to safeguard all areas of the tunnel includingthe tunnel services building. Extinguishing equipment,and where relevant, facilities for controlling smoke bymeans of ventilation override shall be in accordance withthe relevant chapters of this document.

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3.27 Emergency Lighting and Power: In the event offailure of the normal power supply an alternative sourceof power will maintain power to operational and safetysystems and permit use of the tunnel to continue. SeeChapter 11.

Value Engineering

3.28 It shall be recognised that safety equipment isexpensive to install and maintain, and can in some

insttherthanacctunnHig

SAFETY AND FIRE PREVENTION EQUIPMENT

Communication and Alarm Equipment Emergency Telep

Radio Rebroadcasti

Traffic Loops

CCTV

Fire Extinguishing Equipment Hand Held Fire E

Pressurised Fire Hy

Fire Hose Reels

Signs and Rescue Equipment Emergency Exit

Lane Control and Tu

Other Provisions and Equipment Emergency Stopp

Emergency Walkway

Escape Doors

Turning Bays

Ventilation for Smok

l Normal provision

¡ Requirements to be determined by TDSCG

* Provision determined by local requirements

See Figure 3.1 for tunnel category.

Table 3.1 Basic Safety Provisions For Each Tun

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ances be subject to failure and short service life. It isefore essential that no more equipment is installed is absolutely necessary to keep safety at an

eptable level, while maintaining the confidence ofel users. Suitable guidance may be found in the

hways Agency Value for Money Manual.

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TUNNEL CATEGORY

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100

length of tunnel (metres)(Note: Tunnels start at 150m length)

traf

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Determination of Tunnel Cate gory

100

1,000

10,000

100,000

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D C B A AA

Figure 3.1 Chapter 3

Operational C

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4. GEOMETRIC DESIGN

Chapter 4Geometric Design

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General

4.1 This Chapter describes the requirements for thegeometric design of carriageways within road tunnelsand the provisions to be made for traffic space inrelation to the structure and form of tunnel that has beenchosen following the engineering appraisal of schemeoptions. The requirements provide the adjustments thatare to be made to the Standards used for the design ofcarriageways on open roads. These adjustments makeallowances for the special demands and conditions ofapproaching and driving through tunnels.

4.2 Geometric design and traffic space requirementsare presented from the standpoint of providing safepassage, under free flow conditions, for the type oftraffic that is permitted to use the tunnel. Basic layoutand tunnel geometry, however, shall also be related toother aspects concerning the design and operation of atunnel. This may affect tunnel geometry or requireadditional space beyond that needed to enclose specifiecarriageway widths and traffic clearances egrequirements for:

i. Ventilation (length and gradients)

ii. Traffic movements (maintenance, emergencies)

iii. Portals (provision for parking/turning emergencyvehicles)

iv. Operational Safety (verge widths, lay-bys andlong tunnels)

v. Traffic escort (marshalling facilities in portalareas)

vi. Adjacent road network (disruption or queues dueto tunnel closures, etc).

For further information, reference should be made torelevant sections of this document.

4.3 The geometric planning and design of tunnels isan iterative process. Initial plans shall be based on thedesign criteria and hourly traffic flows for comparablesections and classes of open road. Consideration shallthen be given to the physical characteristics of the tunneprofile and cross section, the design of the approachroads, and the proximity of the tunnel portals to anysurface junctions. Account shall be taken of high and

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w traffic demands, the composition and speed of theaffic flow, construction costs, and the economic andafety benefits that ensue. Drivers shall be aware of theipproaching a tunnel and of any need to adjust theirriving style accordingly.

unctions in Tunnels

.4 The safe provision of junctions within, and inlose proximity to, tunnels is made difficult by limitedight lines, limited space for advance warning andirection signs and the high constructional cost ofroducing variations to a tunnel cross-section. Thecreased accident risk at junctions is undesirable in annel because of the restricted access for the attendancf the emergency services. The provision of junctions innnels should be avoided and alternatives determined.

eometrical Standards

.5 Geometrical design standards are influenced bye special features of tunnels which distinguish themom open road conditions. Departures from Standardsat would normally be adopted for comparable sectionsf open road could be considered by the Technicalpproval Authority of the Overseeing Organisation,earing in mind that tunnels are special sections of roadquiring high investment for their construction,

peration and maintenance.

.6 The nature and extent of any modifications to theriteria that are used for open roads, particularlytandards TD9 (DMRB 6.1.1), TD20 (DMRB 5.1) ande Traffic Appraisal Manual (DMRB 12.1), will varyccording to the circumstances at each tunnel and aetailed consideration of the following:

Traffic composition and design flows

Design speed

. Sight distances and the relations betweenalternative tunnel cross-sections and minimumhorizontal radii

. Scope for tunnel widening at curves

Basis of tunnel operation (one way, two way,contra flow)

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vi. Tunnel cross section

vii. Approach road geometry and trafficmeasurements (lane merge, diverge, climbinglane, proximity of junctions)

viii. Any other aspects peculiar to a particular tunnel.

Tunnel Traffic

4.7 Confirmation of carriageway width andnumber of lanes shall be based on the maximumhourly design flow rates set out in Table 4.1 andcorrection factors of Table 4.2. Cut and cover tunnelsshall be designed for the flow rates set out in TD20(DMRB 5.1).

4.8 The figures in Table 4.1 shall be corrected forthe tunnel gradients and percentage of HGVs.Correction factors are set out in Table 4.2 and applyto bored/driven tunnels and immersed tube tunnels,but not to cut and cover tunnels. The gradient shallbe based on the average of a 0.5 km section.

Design Speed, Stopping Sight Distances (SSD) andOvertaking

4.9 Additional definitions are required for roadtunnels:

i. Approach Zone: The length of approach roadfrom the portal equal to 1.5 times the open roadSSD.

ii. Threshold Zone: The length of tunnel, measuredfrom the portal, which an obstruction shall beclearly visible, so that a driver approaching atunnel, having passed the last point at which heor she could stop before the portal, will be able toavoid the obstruction.

4.10 The tunnel design speed shall be the same asthe approach road design speed.

4.11 Table 4.3 shows the recommended relationshipbetween the speed limit, the design speed and stoppingsight distances (SSD) and Table 4.4 between the desigspeed and the horizontal curvature, based upon TD9(DMRB 6.1.1) alignment standards.

4.12 Stopping sight distance (SSD) is determined fromthe design speed, the driver’s reaction time and theaverage deceleration rate to stop. The desirable SSD isbased on a 2 second reaction time and 0.25g deceleratand is shown in Table 4.3.

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ion

.13 A reduction of one design speed step (10mph)ay be used for determining SSD on approach and

hreshold zones where drivers are alerted by signing for tunnel ahead. Inside the tunnel, away from the portals

he road surface can be expected to retain a higher skidesistance and a further one design speed step Relaxatay be applied. The resultant minimum SSDs are given

n Table 4.3.

.14 Such Relaxations shall only be used over thedoption of desirable standards to TD9 (DMRB.1.1) where they are warranted by benefits, and shallot be used in combinations with any other layoutelaxations or Departures.

.15 SSD and Full Overtaking Sight Distance (FOSD)hall be verified in both vertical and horizontal planes, ahe centre of the inside lane on curves, as described inD9 (DMRB 6.1.1).

.16 Overtaking in a road tunnel, involving accesso the lanes open to traffic travelling in the oppositeirection shall not be permitted.

orizontal Curvature

.17 On tight curves on open roads, the required SSDan be achieved by widening verges etc to provide theecessary sight lines. As this is impractical in most

unnels, the degree of horizontal curvature attainableill be restricted by the need to achieve the minimumSD.

.18 For many situations, TD9 (DMRB 6.1.1) permitselaxations below the desirable minimum horizontaladius of between 2 and 4 design speed steps, dependinn the type of road. Table 4.4 compares these minimumorizontal radii with those required to achieve theinimum SSD for a tunnel of typical cross-section. It

an be seen that in most instances it is the SSDequirement which limits the horizontal curvature,specially for all purpose roads where more relaxationteps are permitted.

.19 It is important to check the SSD for eachorizontal curve, as it depends on the length of the curvs well as its radius and the tunnel cross-section.

ertical Alignment

.20 Crest Curves: At crests, visibility may bebstructed by the intervening road. TD9 (DMRB 6.1.1)ives details of crest curve and visibility requirements.

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4.21 Sag Curves: To accommodate long full heightvehicles, TD27 (DMRB 6.1.2) requires additionalheadroom clearance for sag radii of 6000m, or less. SSand FOSD shall be checked for a driver’s eye height of2.0 m. If the minimum values are not achieved either thtunnel headroom should be increased (which will notnormally be economical, particularly in a bored tunnel),or, if practical, the speed limit reduced. Visibility on sagcurves will not normally be a problem with full heighttunnels.

4.22 Gradients: For tunnels the penalties of steepgradients are more severe than on open roads and willinclude higher ventilation costs, due to increased vehiclemissions. Also traffic speeds may be reducedunacceptably with large proportions of HGVs. Trunkroad tunnels with gradients exceeding 6% are unlikely be practical. A climbing lane is not normally a practicalprovision within a tunnel. In a steeply graded bi-directional tunnel, for example, a climbing lane might bprovided by a 3 lane carriageway, two lanes up and ondown. Where adequate alternative routes can beprovided, it may be advantageous to prohibit heavyvehicles from steeply graded tunnels. Any proposeddeparture in a tunnel from the open road desirablemaximum gradient shall be subject to a cost-benefitstudy.

4.23 Superelevation: To provide comfortable levels oflateral acceleration, it is desirable to providesuperelevation for certain levels of horizontal curvatureThe standards for superelevation are set out in TD9(DMRB 6.1.1). However, the provision ofsuperelevation may have an adverse effect on the tunncross section and on the provision of service ducts undthe road. The full recommended levels of superelevatioprovide only small compensation for lateral accelerationand, where necessary, may be relaxed to the minimumcrossfall needed for occasional drainage requirements.

4.24 Crossfalls: On the open road, where thesuperelevation is not greater, a crossfall of 2.5% (1 in40) is used to provide stormwater drainage of the roadsurface. For tunnels, the need to drain the road surfacearises from routine wall washing, flushing awayaccidental spillage and any seepage. It is recommendethat the normal cross-fall of 2.5% is providedthroughout the tunnel.

Clearances for Traffic

4.25 All equipment in a road tunnel shall be placedoutside of the equipment gauge. The equipment gaugefor a road tunnel is determined by the traffic gauge

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vehicular traffic ie maintained headroom etc) plus, forvertical clearance, an additional allowance of 250mm.This additional clearance gives some protection to“soft” equipment, such as luminaires, from highvehicles carrying compressible loads that have passedunder the portal soffit, loose ropes, flappingtarpaulins etc. Clearances shall be carefully related tocarriageway and side verge widths and to thestructure gauge ie the minimum “as-built” structuralprofile that the tunnel must achieve. [Dimensionaltolerances of bored, cut and cover and immersed tubetunnels are strongly influenced by the constructionprocess].

4.26 Additional clearances to avoid damage toelectrical, mechanical and communicationsoperational equipment shall be provided as follows:

i. 600mm horizontally from edge of kerb

ii. Other dimensions as given in Figures 4.1 and4.2.

Width

4.27 Traffic lane widths in tunnels shall be inaccordance with TD27 (DMRB 6.1.2). These clausesdo not apply to limited facility tunnels, see Chapter 1.

4.28 The need for provision of carriageway hard stripswithin a road tunnel shall be subject to a cost benefitstudy undertaken by the Design Organisation andconsidered for approval by the Technical ApprovalAuthority of the Overseeing Organisation.

Height and Asphalt Types

4.29 The maintained headroom, in Figures 4.1 and4.2, shall be based on the same requirements of TD27(DMRB 6.1.2): Chapter 5, as for over-bridges onopen roads, and may need to be compensated for onsag curves. Further guidance is contained in BD65(DMRB 2.2.5): Design Criteria For CollisionProtection Beams. The maintained headroom doesnot include any allowance for pavement overlays forwhich appropriate (and minimal) adjustments toheadroom shall be made. The OverseeingOrganisation will confirm whether the tunnel is toform part of a High Load Route. This clause does notapply to limited facility tunnels, see Chapter 1.

4.30 The life of asphalts within tunnels can be longerthan on the more exposed open roads. The planned useof micro-surfacing (coarse graded slurry seals) or thinwearing course surfacing should be considered to reduc

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whole life costs of surfacings and the disruption, dustand fumes of planing out and relaying operations withintunnels. Porous asphalts are unsuitable as they mayretain flammable or toxic spillages arising from anincident.

Side Verges

4.31 Pedestrians are prohibited from using trunk roadtunnels. However, verges need to be provided aswalkways for road users during emergencies and fortunnel maintenance and operating personnel. Vergesprovide a convenient location for drains, fire mains,fireproof cable ducts etc, free from the regular poundingof heavy vehicles.

4.32 Verge widths will often be determined by theextent of provision for services beneath or the need fordriver visibility. A 250mm width is needed to preventvehicles from contacting the sides of a tunnel. Theminimum verge width shall be 1.0m. The maintainedheadroom need be provided over only the first 0.6m ofthe verge as shown in Figures 4.1, 4.2 and Table 4.5. Akerb height of 0 to 75mm facilitates the opening of cardoors, on the nearside, so that occupants are not forcedto exit into the offside fast moving traffic. A low kerb iseasier to mount, particularly by those who are disabledor injured. It is also easy for a vehicle to mount to allowstopping out of the traffic stream, especially if a halfbattered profile is used. The verge is to be designed totake the weight of a fully laden HGV. For rectangularcross section tunnels, if drainage aspects for allcircumstances permit, then the need for any raised kerbshould be considered. Drainage shall not pond againstthe tunnel wall structure to cause structural corrosion.For tunnels of a circular cross-section, the provision of alow level kerb is necessary to guide vehicles away fromareas of low headroom. Particularly for multi-lanecircular tunnels, care is needed to avoid unnecessarilyincreasing the cross section and consequent constructioncosts.

4.33 In the exceptional circumstance of a need ofprovision for pedestrian use of a road tunnel, thenconsideration should be given to a separate bore for thepedestrians. If this is not possible, a guarded walkway atleast 1000mm wide shall be raised 500mm or moreabove the road surface to protect the pedestrians fromtraffic. A partition from the main tunnel with separateventilation for the walkway, should also be considered.When a raised walkway is used, it is desirable tomaintain the provision of a low-level verge foremergency use by vehicle occupants and to improvesight-lines on bends.

Sa

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fety Fences

34 Provided that the lower 1.2m of tunnel side wae smooth and continuous (to avoid “snagging” durinhicle impact) and are structurally resistant to impacm vehicles, then the walls shall be considered toovide the same function as vertical concrete safetyrriers, as used on the open road, and the provisionditional safety fencing is neither desirable norcessary. At emergency cross passage doorways anen recesses, the exposed, upstream vertical lower e

the doorway or recess shall be chamferedrizontally, over a height of 1.2m, at an angle of 1 in to the traffic direction. The horizontal depth ofamfer, at the leading edge, shall be 30mm. Onlance, it is also not considered desirable to providedestrian safety barriers opposite the exits fromergency cross passages. Such barriers may hinde

tal work of the rescue services during an emergencyithin a congested tunnel. Cross passage doors areovided with glazing to ensure awareness of oncominffic within the bore exited to, as well as establishing

e presence of any smoke from a fire.

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Tunnel Flow/Type Cut and Cover Bored Tunnels Immersed Tubes

Uni-directional v/hr/lane TD20 (DMRB 5.1) 2000 2000

Bi-directional v/hr/lane TD20 (DMRB 5.1) 1800 1800

Note: Over or underestimation of traffic capacities can lead to severe economic penalties especially for majortunnels. Special scheme specific studies may be beneficial. Refer to PIARC Technical Committee on Road Tunnelsreport XVII World Roads Congress, Sydney 1983.

Table 4.1 Maximum Hourly Design Flows

% HGVs Gradient

< 2% > 2% < 4%

5 - -15

10 -5 -20

15 -10 -25

20 -15 -30

Table 4.2 Percentage Correction Factors

Speed Limit mile/h 70 60 50 40 30

Design Speed km/h 120 100 85 70 60

Desirable SSD m 295 215 160 120 90

One Step Relaxation m 215 160 120 90 70

Two step Relaxation m 160 120 90 70 50

Table 4.3 Design Speed, Stopping Site Distances

Chapter 4Geometric Design

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Design Speed km/h 120 100 85 70 60

Super- Radius (m)elevation *

Desirable minimum 5% 1020 720 510 360 255for open road fromTD9 (DMRB 6.1.1):Table 3

Typical SSD DeterminedMinimum HorizontalRadii for 2 or 3 laneone-way tunnels with3.65m lane width, 1.0mhard strips and 1.0mverges on both sides

Desirable Minimum 5% 2850 1510 840 470 265

One Step Relaxation 7% 1510 840 470 265 160

Two Step Relaxation 7% 840 470 265 160 80

* Superelevation in tunnels may be relaxed as stated in text.

Table 4.4 Horizontal Curvature in Tunnels to Provide SSD Standards

Dimension Description Box Profile Arch Profile

A Walkway headroom 2300mm 2300mm

B Width of verge with full headroom 600mm 600mm

C Width of verge 1000mm 1000mm

Table 4.5 Minimum Dimensions (See Figures 4.1 and 4.2)

Chapter 4Geometric Design

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CMaintainedHeadroom

Equipment

MaintainedHeadroom

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Example Box Profile

Additional Clearance

Additional clearance

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Figure 4.1

Figure 4.2G r a p h i c S e r v i c e s 9 8 0 9 8 3 . D S F

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5. VENTILATION

General

5.1 This Chapter provides information and criteriafor the evaluation and basic design of tunnel ventilatiosystems. Ventilation systems shall be designed to supsufficient fresh air to all parts of the tunnel; maintainvehicle exhaust pollutants within prescribed limits;provide a hazard free environment for tunnel users, thlocal community and any amenities likely to be affecteby the discharge of fumes from the tunnel. Forced tunventilation is also normally required to control smokeand heat in the event of a fire in a tunnel and direct itaway from tunnel users, whilst they escape, and inproviding cool, fresh air for fire fighters tackling theblaze. For some tunnels, natural ventilation will besufficient to maintain the required air quality but forcedventilation will be needed if fire smoke control isrequired.

5.2 Thresholds for the dilution and control of toxicemissions and smoke from vehicles are provided,together with selection criteria for the choice ofappropriate systems of tunnel ventilation. Requiremenfor the day to day operation of mechanical systems ofventilation are described, including the response theyshall provide in the event of a fire.

5.3 A forced ventilation system is an importantfacility for restoring safe conditions in the event of atunnel fire. The relationship between the length of thetunnel; distance to emergency exits; highway gradientthe traffic (one way, two way, volume and compositionwith respect to percentage of HGVs, transport ofdangerous goods (see Chapter 2)); safety installationand the planned response to emergencies are all relevfactors in deciding the most appropriate ventilationregime to deal with a fire situation.

5.4 The actual number of vehicles in a tunnel at anone moment will depend on the average vehicle speedand the traffic density. Typically, as traffic slows, thetotal number of vehicles within a tunnel will increase.The vehicle induced air movement referred to as ‘thepiston effect’, is significantly reduced at lower trafficspeeds. The larger number of vehicles will increase thtotal drag resistance to air movements. Many tunnelslikely to be self ventilating for long periods when trafficis flowing freely, but can lose almost all of their selfventilating capacity when traffic is congested, at rush

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hours, say. In addition, fuel combustion is less efficientin congested conditions, increasing pollution rates.

5.5 An assessment of the needs of a tunnel ventilatsystem shall be based on providing tunnel users withadequate protection from the toxic effects of vehicleemissions; adequate visibility from the accumulation ofsmoke emitted by diesel vehicles; the need to control thdisposal of tunnel pollution to the atmosphere.

5.6 As part of the analysis of factors that determinefresh air requirements for the dilution of vehiclepollutants, consideration shall be given to establishingthe tunnel ventilation capacity available to control thedirection of smoke and assist evacuation and firefighting procedures, as described in Chapter 8.

5.7 The form of ventilation applied to a specifictunnel will depend on many factors including:

i. Location of the tunnel with particular regard tothe potential impact on the local environment

ii. Design year in respect of forecast traffic levelsand its composition

iii. Tunnel geometry, altitude and local topography

iv. Fire safety considerations

5.8 Tunnel ventilation design standards areconstantly evolving through international initiatives. Thprime influences on this process are:

i. The steadily tightening of vehicle emission laws

ii. Improved understanding of fire behaviour

iii. Developments in modelling techniques andanalytical tools

iv. Increasing concern for heath and safety and theenvironment.

5.9 The following international bodies are prominenin the advancement of ventilation design standards anmethods and many organisations arrange conferencesand symposiums to advance the designer’s awareness

i. World Roads Association PIARC PermanentInternational Association of Road Congresses

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ii. BHRG British Hydraulic Research Group

iii. WTC World Tunnelling Congress

iv. WHO World Health Organisation.

5.10 The following bodies shall be consulted inconfirming the ventilation system/s to be adopted for aspecific tunnel:

i. Local Planning Authority

ii. TDSCG Tunnel Design and SafetyConsultation Group

iii. Proposed Tunnel Operating Authority

iv. Traffic Control Authority for the area.

Systems of Tunnel Ventilation

5.11 There are several types of ventilation system,natural and mechanical, that have been proven effectivin use. Many factors have an influence on the choice omechanical ventilation system and should be taken duaccount of in accordance with their relative importanceto a particular scheme. The end result for a mechanicventilation system shall be an aerodynamically soundsystem, one that provides satisfactory environmentalconditions inside the tunnel and adjacent to it, controlssmoke in the event of fire, has acceptable capital andrunning costs, and satisfies the operator in terms ofcontrol, maintenance and cleansing.

5.12 The parameters of a suitable and economicalventilation system for a particular tunnel layout will bedetermined by:

i. The purpose, length, gradient, cross-section angeneral configuration of the tunnel.

ii. Its location and general impact on the localenvironment. Environmental considerations atportals and shaft outlets (if provided).

iii. Predicted traffic conditions, taking into accountnumber of lanes, whether traffic flow is one waytwo way, or tidal flow, design flows, traffic speedand its composition, dangerous goods traffic.

iv. The nature and frequency of traffic congestion inthe tunnel including any requirements for contraflow working during maintenance periods.

v. The influence of road layouts either side of thetunnel.

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vi. Vehicle emission levels.

vii. Fires and their likely severity

viii. Capital investment and running costs,maintainability.

5.13 In many short one-way tunnels, of up to 300mlength, the ‘piston effect’ of vehicle induced air flow willprovide satisfactory natural ventilation for normalenvironmental needs, also emergency evacuation routesto places of refuge can be made acceptably short (100mpreferred limit, 150m maximum limit). For tunnels ofbetween 300m to 400m length, mechanical ventilationplant will need to be considered with respect to firesmoke control, for example, where traffic is relativelylight and/or gradients are not steep, the length of tunnelwhere mechanical ventilation plant is unlikely to berequired may be increased to 400m. Mechanicalventilation is required for all longer (400m and above)tunnels and for (200m and above) tunnels on steepgradients or those subject to frequent congestion, eitherdue to high usage or external traffic conditions, where itis self evident to be unacceptable to close the tunnel totraffic for short periods to clear pollution levelsnaturally.

Natural Ventilation

5.14 The natural longitudinal draught through all roadtunnels is made up from ‘the piston effect’ of movingvehicles, the wind forces and to a lesser extent pressuredifferences due to other meterological conditions. For airmovement to occur, such forces need to overcome thedrag resistance of the tunnel interior surface and thevehicles within the tunnel. Natural ventilation can createconsiderable pressure and air velocities within a tunnelwhich must also be taken into account in the design ofmechanical ventilation systems.

5.15 With a steady natural air flow through a one waytunnel, in the direction of traffic flow, the exhaustemission concentration increases from the entrance(ambient air or background value) up to a maximumvalue near the exit portal. If the combined resultant forceon the tunnel air changes direction, an oscillatingmovement of the air can result, causing the maximumexhaust concentration to be nearer the centre of thetunnel. Because there will be no certain control of airdirection or velocity, natural ventilation cannot be fullyrelied upon to prevent the build up of unhealthy fumes,obscuration or contamination occurring within a tunnelduring still, adverse wind or slow moving trafficconditions. For tunnels without mechanical ventilation,arrangements will need to be planned for that, under

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adverse pollution conditions, prevent further vehiclesentering the tunnel and communicate to drivers ofstationary vehicles, already in the tunnel, to switch offengines. Natural ventilation will not provide control ofsmoke etc in the event of a fire.

Longitudinal Mechanical Ventilation

5.16 Longitudinal ventilation is the simplest form oftunnel ventilation and because of lower capital andrunning cost benefits, is often the first choice. See Fig5.1. There are three basic methods of providinglongitudinal mechanical ventilation:

i. Jet fans mounted within the tunnel at a limitednumber of points to create a longitudinal flow oair along the length of the tunnel. Air enters atone portal and is accelerated to discharge at thother.

ii. Injectors, directing jets of fresh air into thetunnel, which induce a secondary flow throughthe entry portal and enhance the longitudinal flo

iii. Push-pull arrangements of axial type/jet fans.

5.17 Longer tunnels can be split into two or moreventilation sections, with discharge and inlet shaftsforming the junction of each section.

5.18 The longitudinal system is widely used for shorto medium length tunnels to enhance natural longitudventilation. It may also be used for longer tunnels withthe introduction of intermediate ventilation shafts, or acleaning provisions. Friction losses increase with thelength, cross section perimeter and roughness of thetunnel interior surface. Ventilation energy losses atportal entrances and exits may be reduced by a flarinthe structural form.

5.19 With longitudinal flow, the degree of pollutionrises progressively along the length of the tunnel to amaximum at the point of discharge. The polluted air isnormally discharged directly through the tunnel portalbut this may be unacceptable in certain urban conditiin which case a discharge shaft and extract fan couldnecessary.

5.20 With two way traffic, ‘the piston effect’ ofnatural ventilation is largely lost, pollutionconcentrations are more evenly distributed along thelength of the tunnel. Exhaust shafts may need to belocated at intermediate points in longer tunnels. In itssimplest form, where a single shaft is located centrallthe system shall create inward air flows from each poto this central point.

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5.21 For shorter tunnels, with two way traffic,longitudinal ventilation could be from portal to portalbut has an adverse effect on long term running costs tconsider. Smoke control and emergency service respoin the event of a fire will need careful consideration.

5.22 Calculations of jet fan capacity shall take intoaccount that air velocities shall be sufficient for controof fire smoke. The fans shall be capable of reverseoperation so that with eg contra flow traffic, smoke canbe moved to the nearest exit.

5.23 Longitudinal ventilation systems, designed forone way tunnels, are usually unsuitable for contra flowoperations in tunnels for the following reasons:

i. With one way operation, the system benefits frothe traffic induced ‘piston effect’ and, undercertain traffic or weather conditions, the tunnelbecomes self-ventilating. With contra flow, notonly is there a tendency to neutralise the ‘pistonand wind effects, but turbulence occurs givingrise to pockets of polluted air that remainundetected by the ventilation control sensors,placed towards the normal exit of the tunnel.Tunnel lighting levels, if designed for one wayoperation, will also be incorrect.

ii. In the event of a fire, the ventilation systemwould initially respond automatically to thereduced visibility (due to fire smoke) byventilating in one direction to control air quality.This will lead to hot smoke being passed over thopposing queue of traffic. The worst scenario iswith a fire located closest to the supply (normalentrance) portal or shaft, where the smoke woube passed over the longest queue of traffic.Reversing the airflow of the fans would take tim(notionally 20 minutes) leading to smoke loggingof the whole tunnel and the risk of massasphyxiation.

5.24 Nevertheless, contra flow operation may be usesparingly in order to facilitate maintenance operationsone bore of a twin bore tunnel, say. Such operationrequires close supervision and shall be limited to perioof light tunnel traffic (eg at night time closures).

5.25 In exceptional cases, longer two way tunnels mbe considered for longitudinal ventilation if traffic flowsare low and risk analysis demonstrates that theprobability of a fire is remote. This may be achieved, finstance, by enforced restriction of the use of the tunnby vehicles carrying hazardous loads or by implementsuitable traffic control measures to limit the number ofvehicles in the tunnel at any one time.

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5.26 Generally, longitudinal ventilation is the mosteconomical type of system since it places the smallesoperating burden on the fans and does not requireseparate air duct provision. Power consumption canbecome significant where longitudinal ventilation isprovided by jet fans which are needed to operate morless continuously. With one-way traffic flow,longitudinal ventilation with jet fans is the normalsolution.

5.27 The tunnel profile will influence the position ofjet fans within the equipment gauge. Driven tunnels wicircular or inverted ‘U’ profiles allow the fans to bemounted within the arched ceiling. ‘Cut and cover’rectangular profile tunnels may require extraconstruction height to accommodate the fans or, wherconstraints preclude this, fans can be placed in wall oceiling recesses (niches) but with some loss ofventilation efficiency, particularly at corner locations.Fans shall be positioned at some distance from signagand other fixed equipment. Reversible fans are able toovercome adverse wind forces and directions byreversing to the direction of the wind. Fans aresequenced in running to even out wear. Allowance mube made in fires that fans local to the fire may burn oualong with their supply cables.

5.28 The strategy is to make as much use of naturalongitudinal ventilation as possible and supplement thifor short periods by jet fans. Relative to semi transveror transverse ventilation this means reduced operationand construction costs.

5.29 With normally free moving traffic, longitudinalventilation with jet fans, moving air from portal toportal, is feasible for tunnel lengths up to 5km,depending on the design criteria for traffic density andemissions. Reversible jet fans should normally operatthe same direction as the main traffic flow. Themaximum allowable longitudinal air velocity for safety,from forced ventilation, is 10 m/s.

Fully Transverse Ventilation

5.30 Fully transverse ventilation is the mostcomprehensive form of mechanical ventilation butbecause of its high capital and operational costs, isseldom adopted for new tunnels.

5.31 Fully transverse ventilation works independentlof any natural longitudinal flow. It depends on “verticaflow, across the tunnel cross section, from a supply duto an extract duct, each with separate fan systems.Supply and extract connections to the road space arelocated along the whole length of the tunnel.

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5.32 Air movements within the traffic space impose nlimitations on the suitable length of tunnel. There is noa progressive build-up of pollution, as is the case oflongitudinal flow, since pollutants are extracted almosat source. Using controlled dampers, maximumallowable air velocities do not impose limits on the duclengths used. Localised requirements, for example atincreased pollution sections along gradients, can be mby increasing supply and exhaust rates at that sectionThe pattern of ventilation is not affected by the directioof traffic flow.

5.33 Transverse ventilation systems may be classifias upward, lateral, or downwards (extracting) accordito the positions of the supply and exhaust ducts. Theupward air flow ie. inlet air at low level with exhaust ahigh level is the most effective layout both for normalpollution control and for smoke control in an emergencSee Fig. 5.2. In the event of a fire, smoke is extracteddirectly, aided by its buoyancy, and thus the longitudinspread of smoke and hot gases becomes effectivelylimited.

5.34 Downwards extraction is not suited to smokecontrol as it would interfere with stratification (smokeetc in the upper layer with cooler fresh air below) anddraw smoke down to the evacuees.

5.35 Lateral extraction is a compromise betweenupward and downward extraction and may be acceptafor smoke control if extraction is effectively achieved inthe upper reaches of the tunnel bore.

5.36 Fully transverse ventilation is, in theory, the idesystem for long tunnels for two way traffic and forsmoke control and removal. A tunnel of circular sectioprovides space for a transverse ventilation system bethe road level and above the traffic gauge. Capital cosare higher, compared with semi transverse systems,because separate ducts must be provided for supply exhaust. As a rule of thumb, operational energy costsincrease in proportion to the fourth power of the ductlength, assuming a consistent cross section throughoSoot accumulations in the exhaust duct making cleannecessary.

Semi Transverse Ventilation

5.37 Semi transverse ventilation has frequently beenused in UK tunnels at river crossings. The flow is morcomplex than for fully transverse ventilation but it isable to cope with contra flow traffic more readily thanlongitudinal ventilation. See Fig. 5.3.

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5.38 A semi transverse system typically comprises asupply duct along the tunnel whilst the whole trafficspace acts as the exhaust duct, discharging either at portal or through one or more extract shafts.

5.39 The distribution of exhaust pollutants isreasonably even throughout the tunnel, provided thefresh air supply along the tunnel is proportional to theexhaust gas produced at each location. This is achievby baffle plates which can adjust, as necessary, theapertures of the fresh air inlets into the road space. Asemi transverse system is not suitable for a reversepattern of longitudinal supply with transverse exhaustinto a duct, as large quantities of air exhausted near thpoint of supply will be almost unpolluted while the lessquantities of air exhausted at the point of nil fresh airflow, towards the upstream traffic end, will lead tolocalised heavy concentrations of exhaust fumes.

5.40 If there is a fire in the tunnel, the fresh air suppduct shall not be turned into an exhaust duct. This worequire time for the supply fans to be reversed, to drawsmoke out of the traffic space and lead to smokeconvection destratification problems. Little smoke woube extracted for a fire mid way between supply shafts.Care would also need to be taken to avoid damagingequipment or parts of the structure within the ventilatioducts.

5.41 Semi-transverse systems are a compromise. Thare effective for one way traffic and may tolerate alimited amount of two way traffic. They canaccommodate changes in the section of a tunnel eg.circular bored central region and rectangular cut andcover portal and exit sections. By the provision ofintermediate ventilation shafts, ventilation beyond thelengths that are normally satisfactory for purelylongitudinal ventilation are possible. The maindisadvantage is the low longitudinal air velocity,particularly at the centre of the tunnel length, and caremust be taken to ensure that the velocity does not fallbelow the requirements for efficient smoke movement ithe event of fire. The mid-point null effect can be offsetby boosting fresh air supply to the road-space at the nlocation. Care must also be taken to eliminate localstagnant areas of air and build up of pollutantconcentrations on uphill gradients.

Hybrid (Combination) Ventilation Systems

5.42 Various combinations of the three basic system(natural, transverse and semi transverse) are possibleSuch arrangements have been designed to suit particuconditions. For example, a long tunnel may require acentral section with transverse or semi-transverse

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ventilation to provide fresh air input to an otherwiselongitudinal ventilation system.

5.43 For several subaqueous tunnels (of circularsection) a ventilation station, on land at the quarter pointon each side of the crossing, supplies fresh air along themid section of the tunnel through the space under theroadway. Such air is fed into the traffic space byregulated apertures at kerb level. At mid-river there isminimal longitudinal flow and from that point back tothe exhaust shafts on each side the air velocity in thetraffic space increases progressively. The end sections othe tunnel have longitudinal ventilation assisted by jetfans.

5.44 Maximum acceptable air velocities both in theducts and in the traffic space impose limitations on thelength of tunnel able to be ventilated from each station.

5.45 By using one set of exhaust fans only ieexhausting at the outlet portal and inducing fresh air atthe tunnel inlet portal, it is possible to generatelongitudinal flows of varying velocity over sections of atunnel.

Air Cleaning Devices

5.46 In the unusual situation where there is arequirement for a long tunnel used by a high proportionof diesel engined vehicles there may be a particularproblem of obscuration of visibility from engine fumes.There is not expected to be a problem in controlling thelevels of carbon monoxide and oxides of nitrogen withinrequired limits.

5.47 Excessive obscuration by diesel smoke and dusthas not so far been a problem in the UK but it has had tobe faced in the longer tunnels of Japan (mountain andsubaqueous tunnels) and Norway (environmental andstudded tyre dust pollution reasons) .

5.48 One way of overcoming the diesel smoke anddust problem, and avoiding intermediate fresh air shafts,is to filter out some of the smoke and soot byelectrostatic precipitation, as is used in large airconditioning plants. Basically a precipitator consists ofhigh voltage emitters and adjacent collecting electrodes.Most particles in the gas stream become ionisednegatively and are therefore attracted to the positivecollecting plates. Collected material has to be removedfrom the plates by either rapping the plates with flailhammers (if the material is dry), or by air or water blast.The Norwegian tunnels use hot water cleansing, those inJapan use compressed air. The filtering system isinstalled in a bypass at about 2 km intervals along the

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tunnel. See Figure 5.4. Through flow velocities are ofthe order 7m/s and removal efficiencies are around 80Such filtering is hugely expensive to construct and run(air pressure loss is 1 to 1.5 bar). The system offers libenefit in the case of fire smoke control or gaseouspollutant removal (catalytic and biological methods areunder investigation elsewhere for the latter). Theadditional power consumption, land take, materialsconsumed and disposal of waste products offer fewenvironmental or sustainability benefits.

5.49 It is also possible, in theory, to use electrostaticprecipitators to limit the amounts of smoke and sootdischarged into the atmosphere, by cleaning a substanportion of the exhaust air at tunnel portals andventilation shafts and thus to reduce the impact of thetunnel on the local environment. The overall cost beneand environmental benefit case would need to be studto determine if such methods would be viable or evendesirable.

Environmental Impact of Ventilation

5.50 For traffic on open roads vehicle emissions tendto be uniformly distributed. Tunnels, on the other handtend to concentrate vehicle emissions to apertures(portals and shafts) that link with the externalatmosphere.

5.51 With the simplest form of longitudinal ventilationthe polluted air is discharged to atmosphere from the eportals. This should prove to be acceptable at mostlocations, particularly for rural tunnels.

5.52 The predicted effect of emissions from tunneltraffic on external ambient conditions and particularbuildings located in the vicinity of a proposed tunnelshall be fully investigated. Nitrogen dioxide may be thecritical gas for long term exposures. Atmospherictemperature inversion conditions shall be considered.Where the levels are in excess of acceptable limits it wbe necessary to enhance dispersal of the polluted airdischarge. For complex situations, environmental impastudies and/or wind tunnel tests may be necessary toconsider dispersion. See also Chapter 2.

5.53 Where portal emissions have to be limited,ventilation extract shafts could be introduced to increadispersal. These shafts, subject to any planning consemay be located either close to the portals or atintermediate locations along the length of the tunnel,depending on the form of ventilation adopted.

5.54 Ventilation shafts will significantly reduce theimpact at ground level by enabling dilution and dispers

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to be spread over a greater outfall height and distance.The location of such shafts may dictate the ventilationsystem (longitudinal, semi-transverse, fully transverse orhybrid) to be adopted.

5.55 Extract fan outlets shall be located so as tominimise impact on local inhabitants or the generalpublic in accordance with relevant national, EC andWHO recommendations. In locating shafts account mustbe taken of their visual impact on the local environment.Fan noise may also be environmentally unacceptable andthis needs to be taken into account in the design andlocation of fan buildings and ventilation plant and shafts.

Ventilation Effects of Tunnel Location and Form

5.56 At the planning stage, it should be borne in mindthat ventilation requirements are affected by the locationand siting of the tunnel. The orientation, absolute andrelative datum levels of the tunnel will affect exhaustemission flow and levels of pollution. Incorrect geometryof portals and ventilation shafts may cause recirculationof polluted air or fire smoke. For coastal/estuarinetunnels the design and orientation of such shafts shallavoid intake of salt spray, particularly during adverseweather conditions.

5.57 Emissions will be increased for vehiclestravelling up a gradient in a tunnel, and may be severaltimes greater than those for level ground. Such inclinesparticularly affect large diesel engined vehicles carryingheavy pay loads. Conversely, emissions of pollutantsgenerally decrease on descending gradients.

5.58 Vehicle engines operating at high altitudes emitmore pollution than vehicles at sea level, since engineefficiency decreases with thinner air.

5.59 The arrangement of ventilation shafts and/ortunnel portals shall be designed to minimise therecirculation of polluted air or fire smoke back throughthe tunnel. In considering recirculation and pollutiondispersal, the local topography and wind direction roseshall be considered. Recirculation increases theventilation fan duty under normal conditions andintroduces the potential risk of smoke logging in theevent of a fire.

5.60 There may be conditions, particularly with strongwinds, in which the air exhausted from one tube of atwin tube tunnel is drawn into the other tube,particularly if close together. Whilst this is undesirable itmay be that the likelihood is low and that the tunnelventilation system can still be controlled to maintain therequired standards in both normal and emergency

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situations. It shall be considered during the design stand measures taken to avoid recirculation of pollutedand fire smoke into adjacent or non-incident bores.Procedures shall be put in place, to deal with anyrecirculation, so that the safety of road users is notendangered. Extending the central dividing wall atsufficient height for some distance (up to 40m) beyonthe portal may reduce recirculation between adjacententry and exit portals. More positive methods includestaggering the portals longitudinally by some 50m,separating the portals transversely or using portalcanopy extract fans. See Figure 5.5.

5.61 Where ventilation shafts are adopted, and theexhaust shaft is located adjacent to the intake shaft, arrangement shall also minimise or prevent recirculatTraditionally the exhaust shaft rises above ground todischarge vertically upwards as both vehicle pollutedand fire smoke are buoyant until cooled. The intake tthe supply shaft is positioned closer to ground level aarranged such that fresh air is drawn in horizontally.

5.62 Longitudinal ventilation pressure heads need tovercome the drag of vehicles in the tunnel increasedthe tunnel blockage effect, and reduced by convoyshielding effects, adverse winds, thermal chimney effeand the drag from the tunnel wall, protrusions, portalshape etc. Semi transverse ventilation systems with tway traffic have to overcome the overpressure zonebetween approaching trucks. Guidance is provided inPIARC documents and the most up to date advice shbe sought.

Junctions in Tunnels

5.63 The inclusion of junctions within a tunnel givesrise to additional considerations concerning ventilatioThe effect of a junction will depend entirely upon thespecific case, its location in relation to the mainventilation shafts, its size, its length and whetherseparately ventilated. It shall be considered from firstprinciples.

Fire

5.64 Many fatalities as a result of a tunnel fire havebeen caused by inhalation of the products of combusie toxic smoke and hot gases. The first priority, for thsafety of tunnel users, is to control the movement of tfire gases.

5.65 This Section shall be read in conjunction withrelevant sections of Chapter 8 - Fire Safety Engineer

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5.66 Two factors adversely influence attempts to fighttunnel fires:

i. Concentrations of smoke

ii. Temperature and radiation conditions in thevicinity of the location of the fire.

5.67 Smoke removal is one of the most importantfactor in the rescue of tunnel users and facilitating theintervention of the emergency services. Ventilationequipment helps with smoke removal, and, by supplyingfresh air which is relatively clear and cool, theevacuation from and access (for firefighting and rescueto the location of the fire. The basis for dealing withemergency fire conditions is to provide sufficient airflowwithin the tunnel to move the heat and smoke away frompersons who may be trapped and to leave a visibly cleaaccess route for the emergency services. The requiredairflows are based primarily on consideration of thevehicle types allowed and consequent potential fire sizeand the type of ventilation system, including the positionof any ventilation shafts. Various fire situations shall besimulated, to give an accurate picture of air velocityrequired in all sections of the tunnel.

5.68 When flames and combustion products reach thtunnel ceiling they will be deflected and elongated.Radiation of flames, and smoke from the ceiling, cancause skin burns and further ignition of flammablematerials of adjacent vehicles (‘fire jumping’). Lowtunnel ceiling heights would worsen the situation and arto be avoided. Vaulted ceilings have the advantage ofproviding a higher zone for smoke escape, above anypeople below. It is important to control the spread offlames along the ceiling in order to prevent the firespreading and to permit the emergency services a safeaccess to the seat of the fire. Lights, lighting diffusers,cables and tunnel linings above shall be non-flammableto remove a potential hazard to fire fighters below.Heavy items such as fans, subject to temperatures of450C, should not fall during the firefighting period.Measures to reduce concrete spalling from concreteceilings at 150+ C shall be applied.

5.69 To clarify the correct fire incident responses todesign for, it will be necessary to define a range of firescenarios with variations of location of incident andprevailing tunnel conditions. This is particularlyimportant for tunnels where ventilation is provided by anumber of balanced sections. The nature of the scenarto be considered, and the appropriate ventilationresponse and control provisions, shall be established apart of the design process through dialogue with theemergency services and other relevant bodies at TDSCmeetings.

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Types of Fire and Their Size

5.70 Fires in a road tunnel can be due to a number reasons and vary in intensity according to their source

i. Private cars (engine, fuel tank)

ii. Parts of heavy vehicles (tyres, brakes, engine,tarpaulins)

iii. Entire loads of heavy vehicles catching fire

iv. Accidents involving the transport of hazardousmaterials in general; certain hazardous materiamay ignite following a collision or a fire in thevehicle itself.

5.71 Typical fire loads from single vehicles with non-hazardous cargoes range from 2.5 to 8 MW for cars,15MW for vans, 20MW for buses, 30MW typical for aheavy goods lorry, 50MW+ for petrol tankers ifsignificant spillages of fuel occur. Recent transport fireinvolving HGVs carrying “Non-Dangerous Goods”loadings have developed fire loadings that may havereached, or exceeded, 100MW. In very rarecircumstances, petrol tankers could produce a fire loawell in excess of 100MW depending on the number offuel cargo compartments involved, rates of fuel drainainto tunnel system, time elapse before fire fighting staetc. Where the integrity of a tunnel structure is vital thfires of up to 350MW have been designed for egimmersed tube tunnels below dykes in the NetherlandFire loads from multiple vehicle incidents leading to firewill depend on the physical locations of the vehiclesinvolved and the rate of spread of fire. See Chapter 8

Design Fire Size

5.72 The Overseeing Organisation will confirm thefire loadings to be assumed in the design of ventilationplant and structural protection for each new or upgradtunnel, after submission by the Design Organisation obalanced proposals which take into consideration factof traffic usage, response times, safety provisions andavailable accident statistics etc. Proposed provision sinclude a risk assessment of the likelihood, balancedagainst the consequences, such as potential loss of liand risk of loss of tunnel structure, any consequentinundation, and any prolonged traffic disruption forrepair. Unavoidable risk to life shall at no time be atlevels greater than those accepted upon the open roaGovernment targets to reduce such risks. See Chapte

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Advance of Smoke Front

5.73 Without ventilation or still air, the layers ofsmoke from a fire would move, upstream anddownstream, along the tunnel ceiling for distances of upto about 300m (dependant on fire size and tunnelgeometry), before cooling and dropping down towardsthe road level. The air below the smoke layer remainingrelatively clear and cool. The velocity of advance of asmoke front, from a vehicle fire, is related to the poweroutput of the fire. The latter is governed by the size ofthe vehicle, the quantity and layout of combustiblematerials carried, and the rate at which the vehicleburns. It is also affected by the fanning effect of anyforced or natural ventilation, including any chimneyeffect on gradients.

5.74 The initial velocity of smoke layer advance isabout 1.3m/s for a 3 MW car fire and 3.0m/s for a 25MW lorry fire, depending on the tunnel geometry. Apetrol tanker fire of 50 to 100 MW could generate asmoke velocity of 7.0m/s or more, which requires largeand high cost ventilation plant provisions to be able tocope successfully.

Control Air Velocity

5.75 The movement of the products of combustion inthe tunnel can be controlled and directed by providing aflow of air with a velocity marginally greater than thecritical control velocity. Critical control velocity is thelongitudinal air flow velocity at which the advance of thesmoke front is just halted for a defined steady state firecondition. The design ventilation capacity shall besufficient to achieve this critical control velocity underthe worst case design fire conditions.

5.76 Account shall be taken of the prevailing tunnelconditions and the fanning effect of ventilation. Mostvehicle fires will generate smoke that can be controlledby a velocity of between 3 and 5m/s, depending on thetunnel geometry and type of ventilation system installed.

Fire: Smoke Control Strategies

5.77 The smoke control strategy adopted depends onthe tunnel geometry, type of ventilation plant, trafficflow direction, escape arrangements, natural windforces, the types of vehicle likely to be involved inincidents, their fire load and the ways in which theventilation system can control smoke.

5.78 The strategies applicable to the main ventilationsystems are illustrated in Figure 5.6 and discussedbelow:

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i. No Mechanical Ventilation

Even if the wind and any remaining trafficmovement could produce an air velocitysufficient to move the smoke front, the haltedtraffic, behind a fire incident, would be at risk ofsmoke logging by wind reversals, cooling andturbulence. Except for shorter tunnels, where thconsequently short escape route distances provboth the most suitable means of quickly reachinsafety, and sufficiently reduced access distancefor the emergency services, tackling the fire andassisting any trapped persons, a lack of positivecontrol of smoke direction is not acceptable,whether the traffic flows one or both ways.

ii. Longitudinal Ventilation Air Flow

For one way tunnels, fans should operate suchthat air movement is in the direction of trafficflow. This allows upstream traffic to drive out,and downstream traffic, trapped behind theincident, to remain smoke free. Further traffic(except of the emergency services) shall beprevented from entering the tunnel. Mobile traffiin the tunnel shall be directed to move out.

Layering of hot smoke in the tunnel ceiling (for alimited time and distance from the seat of the firallows people, within the relatively clear andcooler air below, to escape safely from the tunnTurbulence and cooling will cause such smokelayers to fall, at some distance from the fire.Unless the fans are started quickly, and at amoderate flow rate, the smoke may billow in alldirections. An override smoke control, for fanoperation, to be used only by appropriatelytrained fireman, shall be provided. Firemen willneed to be informed of the current direction setfor fans and, where necessary, the time it couldtake to reverse tunnel air flow completely.

Longitudinal fire ventilation is less safe in twoway traffic, since smoke may be forced overvehicles approaching the fire in the non-incidentlane. Scenarios need to be planned for in advanand the ventilation procedure, to best suit theactual situation, decided at the time.

iii. Transverse Ventilation Air Flow

Although costly to install and maintain, this is aneffective system to provide safe escape for peopover a lengthy period, and to remove smoke atand near the source of the fire. It is equally

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effective for one way or two way traffic.Memorial Tunnel, Virginia, USA fire testsindicate that a longitudinal ventilation systemgave the most effective control of smoke. Theexhaust duct should be at the tunnel crown sothat the buoyant hot smoke layer is extracted athigh level.

iv. Semi-transverse Ventilation Air Flow

Since the whole tunnel space is the exhaust paththe system is effective for one way traffic but lessso for two way traffic.

Factors Affecting Ventilation System Performance

Meterological Effects

5.79 Meteorological records for the area shall beobtained, so that the ventilation system performance canbe assessed in the worst likely conditions of wind, winddirection, humidity and extremes of temperature. Theeffect of the immediate local topography shall also beconsidered. The designer shall consider carefully anyeffect that the weather may have on traffic flow, forinstance on routes that carry a significant amount oftourist traffic where fine weather with high temperaturesand light winds may induce more people to travel.

5.80 The cases to be studied shall include:

i. Weather conditions adversely affecting the tunnelenvironment, and

ii. Weather conditions adversely affecting thedispersion of airborne pollutants from the tunnel.

5.81 The former (i) is likely to happen at high windspeeds in excess of 10m/s and the latter (ii) atcomparatively low wind speeds (often around 2m/s), theatmospheric stability shall not be assumed only to beneutral.

Precontaminated Air, Pollution Concentration Effect

5.82 The background levels of ambient aircontamination shall be taken into account whenassessing pollution levels. These levels shall be obtainedby a local survey and applying appropriate design yearpredictions. Recent 1997 research (EnvironmentalTransport Association Trust, telephone: +44 (0)1932828882, www.eta.co.uk) carried out for Department ofEnvironment, Transport and the Regions indicates thatvehicles travelling towards the middle of the road, iedirectly following other vehicles, suffer higher

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concentrations of pollution than pedestrians or cyclisthe road sides. Concentration ratios for eg cars abovbackground pollution levels, irrespective of vehicleventilating systems, are in the range 4-5 for CO (carbmonoxide), 3 for NO

2 (nitrogen dioxide), and 4-6 for

VOCs (volatile organic compounds). Account is takenTable 5.2 of such concentrating ratios within roadtunnels and the time road users will be within the tunnconfines. The relatively confined nature of the polluteair within the tunnel enclosure leads to a more evenmixing than the open road. Tunnel pollution sensorreadings will measure closer to the average pollutionvalue at any one time. It is estimated that the correctfor concentrating effect (with respect to tunnel sensorreadings) will be achieved by reducing concentrationvalues to half of that of the open air.

5.83 The levels assumed shall be clearly stated anagreed with the appropriate Regulating Authority eg. local EHO (Environmental Health Officer).

Fans

Axial Fans

5.84 Axial flow main fans are used in ventilatingmajor road tunnels. Capacities are typically in excess100m3/s. The large diameter fans are mounted in inleexhaust shafts, or in a plant room, supplying air ducta full or semi transverse system. Such fans supply oextract air for a complete tunnel section.

5.85 An axial fan, in which air passes betweenaerodynamically shaped blades to enter and exit axiato the direction of rotation. Reverse flow may beachieved by reversing the direction of rotation of themotor. An axial fan with blades set to be optimised fospecific flow direction will produce a reduced volumewhen the motor is reversed. Volume control andreversibility can also be achieved using fans withvariable pitch blades.

5.86 Axial fans can be manufactured with individuablades bolted to the hub, so as to allow for limited blaangle (pitch) adjustment.

5.87 The driving motor can be mounted inside thecasing, within the airstream, with an apparent savingspace, however, motor components will require accesspace for withdrawal during maintenance. Larger fancan have external motors and gearbox drives enablinindividual components to be accessed more easily fomaintenance and inspection.

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5.88 Axial flow fans, at high pitch angles, may sufferan aerodynamic stall characteristic which occurs at lowflow/high pressure conditions. Operation of a fan inconditions close to stall, results in pressure and powerfluctuations, with the additional risk of excessivevibration leading to damage and fatigue. The fan desigshall ensure that, under all duty conditions, acomfortable margin is provided between the operatingpoint on the fan performance characteristic and the stacondition, or stall control measures incorporated into thdesign of the fan. Fans shall normally operate at theirpoint of maximum efficiency.

Centrifugal Fans

5.89 Centrifugal fans have given excellent servicesince 1934 at Mersey Tunnel and are to be used in themajor Boston Central Artery project USA, however,they are not normally suitable for modern tunnel airflowcontrol as they require more space than axial fans of thsame duty and reverse airflow can only be achieved byuse of dampers and a reversing duct arrangement.Centrifugal fans have advantages over axial fans ofbeing more efficient and less noisy.

Jet Fans

5.90 Jet fans are relatively small in output and sizeand can be housed in groups within the tunnel, spacedlengthwise in series, to give a multi-fan longitudinal airflow or at the tunnel entrance, as blowers. The fans arof the horizontally mounted, axial impulse type andmaintain a longitudinal velocity of air within a tunnel. Ajet fan increases the velocity of the air mass it passesthrough. The subsequent exchange of momentumbetween the high velocity jet (typically between 30 and35m/s) and the slow moving air within the traffic spaceis utilised to maintain the required overall air velocityfor ventilation and smoke movement. It should be notedthat:

i. Jet fans are not as efficient (10% loss over stillair conditions) as axial fans operating in a ductesystem. However, low capital cost and simplicityof installation and maintenance justifies their useespecially as a control system is not required toregulate the number of fans in use. Developmenin new blade forms have efficiencies in excess o70%.

ii. The distance between fans in the longitudinaldirection of the tunnel requires carefulconsideration. To prevent the flow from one fanreducing the performance of another they willnormally be mounted at a minimum (without fan

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blade deflectors) of 10 hydraulic tunnel diamet(4 x ratio of cross sectional area and tunnelperimeter) apart or 6 to 8 diameters with 5 to 1degree fan blade deflectors which allow morerapid momentum transfer. Siting of signingboards close to these distances should be avo

iii. Fans shall be provided with anti vibrationmountings which shall fail safe, eg by theprovisions of safety chains, to prevent the fansfalling onto traffic in the event of failure of afixing. Vibration monitoring for determiningservice requirement purposes shall be consideCare shall be taken to avoid galvanic and othecorrosion of any fixings. Water entering a jet fafrom washing activities etc will need to drain oand sealed for life bearings shall also beconsidered. Self cleaning blade shapes may bbeneficial in reducing maintenance needs.

iv. Jet fans act by the combined effect of many faThe design shall make provision, as describedfor a loss of output from a certain number of fa(in maintenance and fire conditions) withoutjeopardising the overall minimum airflow.

v. Jet fans can be located at various places in thtunnel cross-section. They are most efficientwhen located at 3 fan diameters from acontinuous surface. Fans in ceiling or wallrecesses are not desirable for loss of ventilatioefficiency (17% loss) reasons, and particularlycorner locations (31% loss) but may be justifieeconomically compared with the alternative ofhigher civil construction costs, particularly forimmersed tube tunnels. Deflector blades at thejet exit can be beneficial in reducing energylosses at such locations. Inclining fans at a smangle (around 5-10 degrees) increases efficienFor reverse flow, a facility to reverse theinclination angle would be required.

vi. The number of fan groups, their transversealignment or staggering, together with details oany niche recess shapes, all efficiency losses,ensuring local re-circulation does not occur,cabling and maintenance requirements and anfunctional loss during a fire shall be assessedcomprehensive ventilation study to balanceinitial, maintenance and operational costs for agiven traffic flow and the probabilities of eachcritical scenario occurring simultaneously, andcollective fan noise.

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Fan Reversibility

5.91 Fans for tunnel air control shall be reversible forthe following reasons:

i. One Way Traffic

Longitudinal ventilation by jet fans will normallybe in the traffic direction and fan blades shall beset to achieve maximum efficiency in that mode.However, for twin bore tunnels in the event thatone bore has to be closed, the bore in use mayhave either two-way traffic or one-way traffic inthe reverse direction to the norm, and reversal othe fans is required. In this situation, fanefficiency is likely to be less than when operatingin the normal direction and hence to produce therequired velocity for smoke control more jet fansmay have to be brought into use than would bethe case for smoke control in the normaldirection.

ii. Single Bore with Two Way Traffic

In contrast to the previous case, the predominantraffic direction may change twice or more eachday. In such circumstances, depending upontunnel length and prevailing wind conditions, itmay be more efficient to reverse the fans so as tthrust in the direction of a predominant trafficflow. There is a need for operational measures tbe implemented to prevent such fan reversalscoinciding with a tunnel fire. Jet fans used insuch circumstances shall deliver near equal thruand efficiency in both directions.

5.92 Fan reversals should be kept to a minimum, asthey introduce a period of high risk in being temporarilyunavailable in the event of a fire. The time taken tocompletely reverse the air flow in a tunnel bore variesaccording to the characteristics of the individual tunneland traffic conditions at the time, but may indicativelybe as long as 20 minutes. In the interim smoke loggingcould occur.

5.93 Large axial fans mounted in shafts will eitherexhaust air, or, supply air, but will not be required tochange direction and need not be reversible except inpush-pull longitudinal systems. The possible exceptionan axial fan supplying ducted air at high level in a semtransverse system where, in a fire emergency, it may bnecessary to reverse the fan and extract smoke, howethe blades should be set for maximum efficiency in thenormal direction, provided at least 70% of normalthroughput is achieved in the reverse direction, and tha

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this reduced throughput is adequate for smoke controIn the unusual circumstances that a reverse flow of eqvalue is required then the fan blades must be designeaccordingly and the motor size increased to allow for tpermanent drop in fan efficiency.

Fan Speed and Reversal Control

5.94 For the majority of tunnel applications, jet fansare single speed, reversible, with soft-start or star-delstarters to reduce starting currents. Control of multiplefans from one starter is not good practice. For economgroups of fans may be connected to a single controlpanel, with individual switches to dedicated fan motorstarters. Longitudinal ventilation air volume control isnormally regulated by varying the number of jet fans inoperation.

5.95 Starting of fans shall be sequenced to reduce tpeak load demand on the power supply and to facilitaup to 6 stages of ventilation, if required.

5.96 Jet fan motor characteristics shall be such thathe fan shall be able to accelerate from standstill to fuforward running speed in not more than 5 seconds, anachieve full running speed in the reverse direction with30 seconds of being switched from the forward directiMotors shall be capable of undertaking 10 starts perhour, in either direction, with up to 1 start and 2reversals in a minimum of 10 minutes.

5.97 Jet fan motors are typically rated at up to 75kWwhereas, large axial fans are commonly rated at up tosome 10 times higher and consequently require moresophisticated starting and output control devices. Thepreference is for variable speed control, rather than thless efficient blade angle variation, to control air outpuWith variable speed control, by frequency converterconsideration shall be given to matching gearing withmotor thermal characteristics and the control circuitsshall maximise power factor. Such control has theadvantages of ‘soft start’ (important with loads of say300kW and above) and low fan noise level at thenormal, low speed, operation. Blade angle variation donot give comparable noise reduction at reduced fanoutput, but maintains high fan and motor efficiency.

Jet Fan Aerodynamic Performance

5.98 The specification of each jet fan shall beexpressed in terms of the minimum actual thrust, in bodirections, produced in standard air (ie. atmospheric ahaving a density of 1.2 kg/m;) in a still atmosphere. Thminimum fan exit air velocity shall also be specified.Performance requirements for fan thrust and exit airvelocity are to be proven in works tests.

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Fire Rating and Testing of Fans

5.99 All electrical and structural components essentiato the continued operation of ventilation fans (locatedwithin the tunnel bore) shall, in the event of a fire, besuitable for operating in smoke-laden air at atemperature of 250oC for 2 hours. The system shall bedesigned to prevent failure of a fan (or its associatedequipment) leading to a system failure of the remaining,otherwise serviceable, fans. Electrical supplies to fanswithin the tunnel shall be dualled.

5.100 There is not a specific standard for fire testing oftunnel fans, although CEN PREN 12101-3: Smoke andHeat Control Systems: Part 3: Specification for PoweredSmoke and Heat Exhaust Ventilators is being expandedto include for jet fans. Any proposed test proceduresused to demonstrate suitable fire resistance in operationshall be subject to agreement with the TechnicalApproval Authority of the Overseeing Organisation, inaccordance with the following advice:

i. Jet Fans:

The fire test may comprise a ducted recirculationsystem, with a heating element within the circuit.Once 250oC is reached at the fan inlet, the 2 hourtest can commence. During the test period thereshall not be any significant reduction in fanperformance nor failure of any essentialcomponent, including silencers. For reversiblefans these shall be reversed at least once towardthe end of the test period. The test is consideredto be destructive and, subject to agreement, amanufacturer’s ‘type test’ certificate may beacceptable if equivalent performance has beenpreviously demonstrated.

ii. Axial and Centrifugal fans:

The temperatures (notionally 200 - 250oC) andduration (notionally 2 hours) for which such fanson extracting duty are required to operate willdiffer for each fire scenario considered, locationof fire and cooling effects over distance to fanlocation and content of fresh air within the flow.The Design Organisation shall determine theappropriate fire rating for the fans throughmodelling. Destructive fire testing of such fans isnot required provided the manufacturer is able todemonstrate, that the proposed fans areadequately rated.

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Noise

General

5.101 Ventilation equipment can be a major source onoise in tunnels and therefore limitation of noiseemission is an important factor in the choice of fans.Acoustic treatment by means of inlet and outlet silencand/or casings with sound absorbent lining may berequired in order to reduce the amount of fan noisetransmitted to the outside environment.

Plant Design: Noise

5.102 Careful attention to plant detail design willachieve the required sound levels at lower cost to theuser than the use of sound attenuating equipment. Thsound power level of a fan increases very rapidly withincreasing tip speed. For a given volume of air, a largand slower rotating fan will be quieter (but moresusceptible to stall). Similarly, reductions in mechanicnoise can be achieved from efficient design of motorcouplings, driving gear, adequate stiffening of thecasing, etc. Reduction in vortex noise is obtained bycareful duct design with the minimum amount ofturbulent flow from sharp bends, obstructions etc.Mounting of machinery on insulated entablatures willreduce transmission of noise and other vibrationsthrough the ground.

Jet Fans: Noise

5.103 For jet fans, additional sound absorbent materin the fan casing, and inlet or outlet silencer shall beconsidered. Any increased head loss caused by asilencer, in some designs, can only be compensated bincreased fan energy consumption and hence higherpotential noise levels. Lower jet velocities of 20m/s arquieter but increase the size and number of fans. Abalance has to be determined by the DesignOrganisation.

Noise Levels

5.104 The control of noise to the outside environmenwill depend on individual circumstances and the areabackground noise levels during fan operation. In the cof an external ventilation building, it will be appropriatto specify the maximum installed noise and vibrationlevels at 10 m from the building. See also BS7445,BS8233 and BSEN1793.

5.105 Care shall be taken that the fan noise levels intunnel, particularly at times of emergency fan use, arenot so high as to interfere with the use of emergency

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communication systems. A maximum level of NR85shall be specified in the tunnel at a plane 1.5m above road surface.

Tunnel Pollution

5.106 The major factors affecting the extent of vehiclepollution within and from road tunnels are as follows:

i. Form of tunnel ventilation used

ii. Pollution control limits within the tunnel - ie forCO, NOx

( a mixture of nitric oxide and nitrogendioxide gases) and visibility

iii. Tunnel geometry eg gradients, length and crosssection of bores

iv. Evolving laws on fuels and permissible vehicleemissions and the age of vehicles

v. Average distance vehicles travel from a cold stabefore reaching the tunnel

vi. Wind direction and strength in respect of both thinfluence on the ventilation system and thedispersal of polluted air from the tunnel

vii. Traffic flow characteristics and risk of congestioleading to inefficient combustion, loss of pistoneffect and reduced air flow from blockage causeby large, slow moving vehicles

viii. Altitude.

Tunnel Form

5.107 The form of ventilation shall be resolved to suitthe specific tunnel site concerned. The trend is to uselongitudinal ventilation in its basic form (ie no shafts)wherever practical. For two way flow, two one waytraffic bores are preferred, and may be essential from heath and safety point of view.

5.108 Any inclusion of ventilation shafts or other formof ventilation shall be based on establishedenvironmental, safety, planning and operating criteria.

Tunnel Design Year

5.109 The design year is nominally the planned year oopening the tunnel to traffic. However, where trafficlevels are expected to rise with time, design years maybe determined as up to 10 years after the year of

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opening. The design year assumed is relevant indetermining the fresh air requirements to maintain tunnair quality.

Traffic: Influence on Ventilation Requirements

5.110 Average vehicle emission rates for each class ovehicle will vary according to speed and gradient.Traffic speed, density and composition are material todetermining the fresh air requirements in tunnels and textent to which forced ventilation is required.

5.111 The piston effect of free flow traffic can reduceany forced ventilation needs by keeping the traffic speeabove 30km/hr. The ventilation system’s energyconsumption will be reduced and may limit theventilation demand to that required for fire smokecontrol purposes.

5.112 The scope to implement traffic controlprocedures, to ensure free flowing traffic, shall beestablished at outline design stage. Recognition shall bgiven to the implications of such measures on thesurrounding traffic flows. Where appropriate, suchproposals shall be supported by a regional trafficassessment.

Fresh Air Requirements: Calculation Method

5.113 The designer shall take into account relevantinternational developments in determining the calculatimethod to be applied.

5.114 World Roads Association, PIARC represents thinternational consensus on the practical application ofcurrent scientific and technological developments forroad tunnels.

5.115 PIARC 1995 Tunnels Committee has publishedRoad Tunnels: Emissions, Ventilation, Environment. Thdocument includes the findings from a joint internationresearch effort into actual vehicle emissions undersimulated travelling conditions and improved methods calculate the fresh air requirements for ventilation.

5.116 Establishing appropriate data for a specifictunnel remains, however, the responsibility of the DesiOrganisation.

5.117 Table 2.2 of PIARC 1995: Road Tunnels:Emissions, Ventilation and Environment provides valuefor average peak traffic densities for both one and twoway traffic flows at 0, 10 and 60km/hr. Values shall beapplied with due consideration given to the particular

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tunnel and TD20 Appendix 2 (DMRB 5.1.3) and TA46(DMRB 5.1.4).

5.118 Passenger car units (pcu) shall be convertedaccording to the method given in PIARC 1995: RoadTunnels, Emissions, Ventilation Environment: Section II:Passenger car units.

5.119 The traffic composition shall be determined foreach case. However, in the absence of more precisetraffic data, it may be assumed that 15% of the totaltraffic consists of diesel powered heavy goods vehicleswith equal proportions of 10, 20 and 30 tonne units.

5.120 Fresh air ventilation requirement shall bedesigned for, for worst case congested traffic conditions(typically at, or below, 10km/hr traffic speeds forlongitudinal ventilation) and for free flowing traffic.Peak traffic density often occurs at around 60km/hr.

5.121 Fresh air calculations shall consider trafficspeeds of 0, 5 and 10km/hr and, thereafter, speedsincreasing by 10km/hr up to the design speed limit. Thiswill allow the maximum fresh air ventilation duty andthe worst case tunnel portal and/or shaft emissions to bdetermined. A partial exception could be where trafficcontrol provisions prevent slow moving congested trafficfrom occurring.

Vehicle Emissions

5.122 A quantitative assessment of vehicle emissionsfor the tunnel during its design year shall be made usingthe levels described in PIARC 1995: Road Tunnels:Emissions, Ventilation and Environment. Additionalallowance, for a particular tunnel site, shall be made forthe increased pollution levels over ambient backgroundlevels within vehicles, as reported by the EnvironmentalTransport Association Trust, 1997. Typical ratios ofaverage concentrations to background levels for carshave been given as 4 to 5 for CO, 3 for NO2

and 4 to 6for VOCs (volatile organic compounds).

5.123 The main air pollutants from road traffic includecarbon monoxide (CO), diesel smoke, particulates,oxides of nitrogen (NO

x), sulphur dioxide, hydrocarbons

and lead. The most significant of these are:

i. Carbon monoxide from petrol and diesel engines

ii. Smoke (carbon particles) particularly from largerdiesel engines

iii. Oxides of nitrogen (nitrogen monoxide andnitrogen dioxide).

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5.124 Petrol engine exhaust contains a relatively laamount of carbon monoxide compared to diesels.However, heavy goods vehicles with their larger diesengines may emit similar quantities to a petrol engincar.

5.125 Emissions such as sulphur dioxide andhydrocarbons are relatively low in toxicity, andconstitute a small proportion of the total vehicleemissions. It can be safely assumed that adequatedilution for these will be provided for by the ventilatiosystem controlling either carbon monoxide or dieselsmoke, whichever is the greater requirement at the t

5.126 Emissions of lead although highly toxic are nlonger considered to be a design consideration due greatly increased use of unleaded petrol and therequirement that from 1990 all new cars must be caof running on lead-free fuel.

5.127 Changing legislation for engine emissions anfuels lead to changing emission qualities and quantiThe full effects take time as older vehicles and fuelsgradually disappear from use.

5.128 Carbon monoxide and diesel smoke will becoless important relative to oxides of nitrogen.

Carbon Monoxide

5.129 Emission rates are given for light and heavy vehicles, with relative rates for different years, thegradient factor and the altitude factor.

Diesel Smoke

5.130 The most apparent effect of diesel smoke is treduce visibility in the tunnel. Even low levels of hazgive tunnel users a misleading impression of a pooratmosphere.

5.131 In urban tunnels, the base smoke (particulateemission from a heavy goods vehicle shall be taken100 m2/hr, at 60 km/hr. For longer distance routes,where the proportion of heavier vehicles is greater,160 m2/hr shall be used.

5.132 Current legislation on diesel smoke is expectlead to a reduction in particulate emissions from heagoods vehicles.

Oxides of Nitrogen

5.133 When calculating the emission of oxides ofnitrogen it shall be assumed that the initial emissionsolely NO (nitric oxide) and that this subsequently

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ime.

oto the

pable

dties.

me

duty

oe

) as

ed tovy

is

converts to NO2 (nitrogen dioxide) with a half life of one

week. Some conversion may occur rapidly, within atunnel, in the presence of ozone. The rate of NOconversion depends on complex factors including,oxygen levels, presence of other gases and particles,temperature and exposure to sunlight.

5.134 Values for the percentage of NO2 in total nitrogen

oxides (NOx) are not certain but may lie between 10%

(heavy traffic) and 20% (light traffic) in tunnels. Atdesign stage, the latter figure should be used, asconservative, in the absence of firm data from similartunnels.

5.135 The toxicity of NO2 is five times that of NO and

any conversion to NO2 tends to increase the overall

toxicity of the tunnel atmosphere. Control of NO2 levels

is by either monitoring for such, or imposing reducedCO levels. Tunnel sensors (other than personal monitorto measure low concentrations of NO

2 are not yet

believed to be fully reliable. An estimate from NOx

measurements is recommended at present.

5.136 Emission rates are given in PIARC 1995: RoadTunnels: Emissions, Ventilation and Environment, withrelative rates for different years for light duty vehiclesand heavy duty vehicles. See, also, Table 5.5.

Lead

5.137 Because of the reduction in the amount of lead inleaded petrol and the increasing use of unleaded petrol,lead emissions are no longer considered in road tunnelventilation design.

Oxides of Sulphur

5.138 The emission of sulphur dioxide (SO2) can be

calculated as a proportion of the carbon dioxide (CO2)

emission.

Carbon Dioxide

5.139 Carbon dioxide emissions, while important fortheir overall effect on the atmosphere, are not a problemfor tunnels. However, calculation of CO

2 levels may be

carried out as CO2 emission is directly proportional to

the amount of fuel burned and is therefore a useful wayof assessing the levels of pollutants such as lead andSO

2.

Pollution Limits (Tunnel Interior)

5.140 The limits, given in Tables 5.1 to 5.3, are basedon PIARC 1995: Road Tunnels: Emissions, Ventilationand Environment and Health and Safety Executive

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(HSE) document EH40: Occupational Exposure Limi(editions are regularly updated) recommendations anare applicable for new design or refurbishment purpo

Vehicle Age and Emission Laws

5.141 In order to apply the calculation methodrecommended by PIARC 1995: Road Tunnels:Emissions, Ventilation and Environment, it is necessato understand the history of the vehicle emission lawsand their impact. It is also necessary to establish theprofile of the vehicles in the traffic flows concerned.

Emission Laws

5.142 European and UK emissions legislation for nevehicles has evolved over recent years leading to areduction in the levels of emissions permitted. It isimportant, when predicting emissions, to take intoaccount the legislation in force when the actual vehicwere manufactured. A history of the various emissionstandards and their dates can be found in Fact Sheeand 2 published by the Department of Transport VehiStandards and Engineering Division.

Vehicle Age

5.143 Renewal of vehicles needs to be estimated forparticular area concerned. Table 5.4 provides anindicative age spectrum for a national fleet, that reflethe finding of PIARC 1995: Road Tunnels: EmissionsVentilation and Environment.

Cold Start Factor

5.144 A cold start factor needs to be applied to addrthe additional emission to be expected from vehicles catalytic converters that operate most efficiently athigher engine temperatures as well as the normal colengine inefficiencies. The factor is more relevant tourban areas where possibly 10 to 30% of local vehiclmay not have attained full working temperature onentering the tunnel.

5.145 In assuming the cold start factor to be applieddue consideration shall be taken of the tunnel locatioand the forecast traffic flow conditions during peaktraffic periods, particularly for the winter.

Traffic Weight Influence

5.146 The average weight of goods vehicles reflectsamount of emissions for a given traffic composition.PIARC 1995: Road Tunnels: Emissions, Ventilation a

tsdses.

ry

age

w

lessts 1cle

the

cts,

esswith

d

es

,n

the

nd

Environment reports the typical weight ranges of Table5.5, but the average weight to be assumed shall bededuced from the peak traffic forecast for the particulartunnel.

External Environmental Conditions

5.147 Ambient air standards for the environmentoutside of a tunnel are given in EnvironmentalAssessment: Air Quality: Table 5 (DMRB 11.3.1).These standards apply to longer term exposures than fthose passing through road tunnels and shall be met atthe nearest inhabited building which is not part of thetunnel operation or 100m from the portal, whichever isthe lesser. See also Chapter 2.

5.148 The 8 hour CO concentration which may beexceeded once a year, Cx

, can be calculated by:

Cx = 1.19 + 1.85 C

Where C is the maximum predicted 1 hourconcentration.

5.149 There is no ambient air limit set for NO. Thepredicted NO concentration should either be doubledthen added to the CO concentration, and the CO limitapplied, or it should be treated as having been fullyconverted to NO

2, and the NO

2 limit applied, whichever

is the more onerous. Two of the objectives of theNational Air Quality Strategy limits for NO

2 are to

achieve by Year 2005 an hourly mean of 150ppb (partsper billion) and an annual mean of 21ppb. Theobjectives apply in non-occupational near-ground leveloutdoor locations where a person might be reasonablyexpected to be exposed over the relevant averagingperiod. They do not apply for drivers within theirvehicles, whether travelling inside or outside of a roadtunnel.

5.150 As a guideline for outside of a portal, 50% of theNO produced in a tunnel should be taken as having beeconverted to NO2. For exhaust shafts, the conversionshould be assumed to be 60%.

Occupational Exposure Limits for Staff in Tunnels orToll Booths

5.151 Standards and limits for occupational exposureare given in the latest HSE document EH40:Occupational Exposure Limits (editions are regularlyupdated). Extracts are given in Tables 5.6, 5.7 and 5.8for illustrative purposes. These standards are for persoat work at a tunnel site and differ from the longer term

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ambient standards and those for the more sedentarydriving through a road tunnel over a normally short timperiod.

5.152 The exposure of persons working near the tunportal, eg toll booth attendants, shall be assessed unthe meteorological conditions which would produce thhighest pollution levels at the points under consideratfor both short (15 minute) and longer term (8 hr)exposure. It may be necessary to provide airconditioning in toll booths. Staff who are smokers maalready have high CO levels in their bloodstreams beentering a tunnel.

5.153 When calculating the longer term exposure levit shall be assumed that the traffic flow over 8 hours i6.5 times the maximum hourly flow.

5.154 Standards for lead in air are set out in Append4 of EH40.

Ventilation System Safeguards

5.155 The vital importance of ventilation for the healand safety of tunnel users in well recognised. Failurea mechanical system could cause the tunnel to be cloto traffic. Closure could cause severe disruption totraffic over a wide area with serious consequences. Areasonable safeguards must therefore be built into thventilation system to avoid unplanned tunnel closure undue restrictions on traffic flow. Duplication ofessential equipment will facilitate maintenance work,planned or unforeseen, and limit disruption to normaltraffic flow. The main features to provide safeguards or build in redundancy are described.

Electricity Supply and Distribution

5.156 Two high voltage (HV) supplies, generally at11kV and derived from separate sources, are requireensure maximum security of the power supplies. SeeChapter 11. Each supply shall be separately and evedistributed throughout the tunnel, including supplies tjet fans, to fans in inlet/outlet shafts and to fans inducted transverse systems.

Fan Operational Security

5.157 The ventilation system shall be designed tooperate to its design requirement even when a fan isunavailable either due to routine maintenance oroccasional failure. In order to accommodate this, it wbe necessary to provide a level of standby fans in ordto give an acceptable level of redundancy. Theproportion of jet fans assumed to be out of service fo

e

neldereion,

yfore

els,s

ix

th ofsed

lleor

for,

d to

nlyo

iller

r

maintenance could be greater for short tunnels.Conversely, the proportion of jet fans destroyed by firein a longer tunnel should be less than for a shortertunnel. Generalised guidance is as follows:

i. Jet Fans:

Fan redundancy levels to be assumed for desigpurposes shall be determined according to thespecific tunnel concerned. The following may beconsidered as indicative:

a. Normal operations: 2 fans or 10% of the fan(to the next whole fan number), which ever is thgreater, shall be considered to be out of service

b. Fire situation: In addition to the fanredundancy level assumed under normaloperations, fans within the distances from theseat of a fire indicated by Table 5.9 shall beconsidered to be destroyed:

ii. Axial or Centrifugal Fans:

Fans shall be arranged on a duty standbyarrangement such that switching from one fan tanother occurs automatically. Where more thanone fan serves a particular duty, only one standunit is required.

5.158 With jet fan systems extra units may be held instore, ready for immediate installation using purposemade cradles and vehicle mounted working platformssuitable stores holding could be 5% of the total numbeof jet fans installed, with a minimum holding of three.For guidance, a typical tunnel may have some 40 jet fper km length, per bore.

5.159 Non-jet fans (large axial or centrifugal fans)should normally have 100% standby capacity. Thestandby fan or fans may be permanently installed withdedicated ducting. Alternatively each fan could bemounted on a trolley and the fans changed bydisconnecting the duty fan, traversing it across the duand connecting the standby fan.

Air Monitoring, Ventilation Control

5.160 The measurement of carbon monoxide andvisibility levels currently form the basis of control forventilation. In the near future, as carbon monoxide levcontinue to fall and air opacity clears then nitrogendioxide etc levels may need to be used for ventilationcontrol and values are given in Table 5.2 for guidancefor new tunnel design and refurbishments. A logical

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method for control shall be developed, which caters fonormal and abnormal operations, and safeguards thefans from frequent switching. Control of the ventilationsystem shall be an integral part of the tunnel operatinprocedures. See Chapters 10 and 14.

5.161 Instruments for measuring carbon monoxide anvisibility level shall be located adjacent to the tunneltraffic space, at each position where a maximum levelpollution (or minimum visibility) is anticipated. Accessfor maintenance shall not be hindered. Fans willnormally be automatically controlled by signals fromthese instruments. In certain instances, eg exposed tuportals, the tunnel air velocity may also be used as acontrol parameter. Other methods include countingvehicles and detection of congestion via CCTV.

5.162 Sampling stations should be positioned, ideallyat the general level of vehicle air ventilation inlets. Thiideal is not practical for instrument types depending obeam transmission where vehicles (particularly ifstationary) could shield the beam. The latter instrumeshould be positioned at about 2 to 3m height from theroad level. It is common practice for the instruments tobe installed over the tunnel verges for ease of accessbe located within wall recesses or secured to bracketsroof mountings. However, to avoid false readings, themeasurement beam shall not be located so as to passthrough the immediate vicinity of fresh air inlets or airclose to jet fans. Instruments shall be calibrated torepresent the average air quality within the tunnel.

5.163 Electronic instruments, particularly those withoptical components, are sensitive to environmentalconditions normally found in road tunnels i.e a damp,possibly saline, acidic, cold and dusty atmosphere,subject to air velocities up to 10m/s. Tunnel washingprocedures often involve use of high pressure watersprays and aggressive chemicals and detergents whiccould have an adverse effect on electronic equipment.Therefore, special attention is necessary for the desigand construction of the instrument enclosures andmountings. Protection shall be to at least IP65.

5.164 Monitoring systems (including a backupmonitoring station) shall be provided and all operationdata recorded and stored for analysis. Data includespollution levels, tunnel air speed, fan operations and aalarm states. Plant monitoring and control shall be baon the use of PLCs, microprocessors or computers,depending on the size and complexity of the facility.Programmable Logic Controllers (PLCs) have provenbe more reliable.

r

g

d

of

nnel

,sn

nts

and or

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al

nysed

to

5.165 Signals from the instruments shall also betransmitted to a manned control centre, where emergenprocedures can be initiated should any readings exceedthe allowable limit. Operation of special fan regimes willbe necessary to deal with incidents involving a fire in thetunnel and will normally be carried out from the mannedcontrol centre.

SCADA System for Ventilation

5.166 A primary objective of the SCADA (SupervisoryControl and Data Acquisition) system is to ensure a safenvironment for tunnel users under a wide variety ofoperating conditions. Functions for ventilation arediscussed in Chapter 10.

Measurement of Carbon Monoxide Concentrations

5.167 Instruments for measuring concentrations of COshall cover a range of 0-300ppm.

5.168 In a longitudinally ventilated tunnel at least threesampling points would typically be provided to makeallowance for two way flow in the tunnel, even if normaloperation is one way. The location of sampling pointsshall avoid dilution by air circulating from the portals. Amonitoring station (regular and back up instruments)shall be located at about 50m inside from each portal,with the third station typically positioned at the centre ofthe tunnel. The regular and back up instrument pointsshould be located close together, for ease ofmaintenance. The specific arrangements shall bedetermined from pollution and ventilation calculation.

5.169 In semi transverse and transverse ventilationsystems the sampling stations are located at eachposition of maximum concentration, as established bycalculation. Two points per ventilation section aregenerally sufficient, one being a backup for the other.

5.170 Currently, measurement of carbon monoxideconcentrations uses an infra-red absorption technique.Instruments compare the absorption of certain infra-redwavelengths when passed through a tunnel atmospherewith that through a cell containing carbon monoxide.The equipment is accurate and requires lowmaintenance.

5.171 Carbon monoxide concentration could bemeasured by catalytic oxidation and electro-chemicalanalysis but these methods are not suitable for long termuse in tunnel environments.

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Measurement of Visibility

5.172 There are three types of instrument available measuring reductions in the range of visibility. The typin current use in most UK tunnels is theTransmissometer which measures light transmittanceconsists of two basic units, a transmitter and receivewith or without a reflector depending on type, which cbe fitted outside of the traffic envelope. The cleardistance between the measuring head and the receivreflector is normally a minimum of 2m but can be up 50m. Visibility is assessed by measuring the variationlight power transmitted over a base length.

5.173 Reduced visibility can also be measured bymeans of diffused light measurement (opacimeters) alight scatter measurement (nephelometers). To date,methods have given rise to operational problems withtunnel environment and are not recommended.

5.174 Instruments are usually set for zero obscurati(maximum transmittance). Most instruments provideauto calibration facilities to allow for contamination ofthe optics, using intermittent mirror reflecting and/ortime-variant software compensation.

5.175 Visibility is expressed in terms of the ExtinctionCoefficient, K (units m-1). Extinction is typically definedas the rate of attenuation (reduction) of light intensityalong a path length. K = - log

e(I

o/I

x) /X, where I

o and I

xare the light intensities at the start and end of a pathlength X metres. Approximate visibility distance D(m)2/K for reflecting signs, and D(m) = 6/K for illuminatesigns. Visibility of illuminated signs through fire smokeis down to below 15m when K = 0.4. Evacuationwalking speed greatly reduces when visibility reducesbelow 7m.

5.176 Instruments will normally be located inconjunction with those for monitoring of carbonmonoxide and will have similar standby arrangement

Measurement of External Wind Speed and Direction

5.177 Wind speed is usually measured using a vanetype anemometer.

5.178 Wind measurement devices may also benecessary in the case of exhaust air shafts if such share near pollution sensitive areas. By monitoring windvelocity and direction, the tunnel air expulsion velocityshall be adjusted so that the polluted air plume carrieaway by the wind does not affect pollution sensitiveareas.

fore

. Itr,an

er/to in

nd bothin a

on

=d

s.

afts

d

Measurement of Tunnel Air Velocity

5.179 In the case of longitudinal ventilation with two-way traffic or where there are known to be strongprevailing winds, measuring devices may be needed todetermine the wind’s influence on the tunnel ventilatingairflow. Air velocity monitors situated within the tunnelcan observe such effects. Wind effects are of particularimportance for short tunnels ie those up to 500m long.

5.180 Anemometer, ultrasonic flow or orifice platedevices shall be installed in the tunnel to give a readingof the tunnel air direction and velocity to the controlroom. The range shall be 0 -15 m/s in either directionwith an accuracy of + 0.5 m/s.

5.181 The instrument may be placed at any suitablelocation within the tunnel outside of the traffic space andnot within 50m of either portal. Non-ultrasonicinstruments placed close to the tunnel wall shall becorrected for boundary flow conditions.

5.182 In cases where the external wind is sufficientlystrong to make the operation of jet fans ineffective, it isdesirable to use the condition as a control parameter toreverse the direction of their operation.

Fan Control in an Emergency

5.183 An emergency condition will normally bedetected by the traffic control centre from the publicemergency telephones, CCTV cameras etc. Trafficcontrol are responsible for alerting the tunnel operator tprovide control of the ventilation

5.184 In an incident involving fire an assessment shallbe rapidly made of the size and location of the fire, andthe fans operated in the mode best suited to theparticular conditions. See Chapter 8, including forinformation on smoke control panels.

5.185 Vehicle occupants shall be evacuated from theside of the fire to be used for smoke clearance as amatter of urgency.

5.186 In the case of a fully transverse system, the fansshall be switched to full extract as soon as fire isdetected. In a semi transverse system, depending oncircumstances, but particularly if the ducting is at highlevel, the fan normally supplying the input ducting maybe reversed to extract smoke until people have beenevacuated, after which, normal longitudinal extractairflow shall be resumed.

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Operating Arrangements

5.187 Operation of ventilation plant is an essentialcomponent of the overall framework set up to operaeach tunnel on a day-to-day basis, execute plannedmaintenance, control tunnel traffic pollution and respto tunnel emergencies depending on the particularcircumstances and deal with a wide range of issuesaffecting safety and economy.

Toll Tunnels

5.188 In the particular case of a major toll tunnel,permanent staff dedicated to the operation of the tuncomplex will be provided.

Free Tunnels

5.189 More generally, tunnels on motorways or othtrunk roads will be designed to operate automaticalland unattended. However, there must be a rapidresponse in the event of equipment failures or otheremergencies. For the ventilation aspects this requirethat the TOA responsible for the tunnel have adequaplant and equipment and a nucleus of trained staff ware fully familiar with the operation, inspection andmaintenance requirements of all ventilation equipmeand are capable of providing advice and assistanceemergency services in the case of a fire.

5.190 TOA staff shall provide emergency cover on hour basis, are required to oversee all maintenance(including that contracted out) eg replacing jet fans,cleaning exhaust ducts, and, where necessary, incluqualified and authorised personnel to comply withstatutory safety procedures, with permit-to-worklimitations in certain areas such as electricity supplywith safety rules and procedures for entry into confinspaces.

5.191 The emphasis that needs to be given to thesvarious considerations shall be brought out in themanuals to be prepared as tunnel documentation. SChapter 13 and Appendix C.

System Upgrade

5.192 A tunnel ventilation system or major parts of iare likely to have a practical and economic life of 1520 years. Practical difficulties arise as plant becomeoutdated, the original manufacturer may no longer bbusiness, or have jigs, tools and spares available. Tcosts of repairing or refurbishing old plant can becomprohibitive, particularly if spares have to be specially

e

ond

nel

r

steho

ntto the

24work

de

ored

ee

, tose inhee

made. Decisions will then need to be made as to whethea major system upgrade is the best way forward.

5.193 The main reasons for a system upgrade orreplacement are:

i. The ventilation performance is inadequate tomeet the current environmental and emergencycondition needs (the original design may haveproved inadequate in operation, standards havebecome more demanding, or traffic morecongested or its component mix changed).

ii. Repairs have become unacceptably difficult andcostly.

iii. A Civils Work refurbishment is necessary whichaffects mechanical and electrical equipment andmakes a total upgrade the most economic wayforward rather than accept a second majordisruption to tunnel availability soon after thefirst.

5.194 A ventilation system upgrade will be preceded bya principal inspection to BD53 (DMRB 3.1.6) that willtake into account the TOA views from operationalexperience, the performance and condition of plant, thelikely costs, timescale and operational arrangementsinvolved in an upgrade and the overall view of anindependent review body.

Extent of an Upgrade

5.195 As the term implies, an upgrade is not replacinglike with like, but providing a ventilation system tocomply with the current standards that would apply for anew tunnel. Complete renewal may not be necessary ifventilation performance is adequate. Major items ofequipment could be refurbished if it is economic andoperationally feasible, eg for motors, fan blades,bearings, silencers, dampers, etc. Jet fans or a reservemain axial fan could be released for worksreconditioning to an agreed schedule. However, aftersome 20 years life, some older cable types and mostelectrical controls would probably need to be replaced.Modern cable types may last for 50 years or more.

Disruption to Traffic

5.196 If a ventilation upgrade is part of a moreextensive programme involving civil works, then at leastone tunnel bore may have to be closed either entirely, orpart-time (nights, weekends etc), with a detailed plan ofwork and safe opening/closing procedures to berigorously followed. New cabling and switchgear could

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be installed as traffic movement allowed with finalconnections, changeover and testing during plannedclosure periods.

5.197 Contractor’s operations and permits to work wbe controlled by the TOA. Because of the national

ill

economic importance of maintaining traffic flow, and inthe case of toll tunnels the loss of revenue when closed,penalty clauses for late handback against formalprogrammes should be considered for inclusion intoworks contracts.

Traffic Situation CO limits [ppm]

Fluid peak traffic, above 50 km/h 100

Daily congestion, standstill all lanes 100

Seldom congested 150

Tunnel closure necessary 250

Note: PIARC 1995: Road Tunnels: Emissions, Ventilation and Environment gives lower values for Design Y2010. Traffic control to prevent congestion will reduce ventilation cost, particularly in long tunnels. VisibilityNOx

limits may govern as modern engine systems and fuels reduce harmful emissions. Table 5.1 has beenrecently constructed UK Tunnels and is included for reference only. It does not distinguish, for pollution exptimes, between different tunnel lengths. Table 5.2 is to be used for design and control purposes.

Table 5.1 Reference Only: PIARC Carbon Monoxide Limits (Design Year 1995)

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Substance Application Type Tunnel Sensor Limit EH40 LevelLevel

CO Tunnel Road Users Short-termlimits: A: 100ppm

Carbon Monoxide Fifteenminutes, or B: 50ppm 200ppmless, averageexposure C: 35ppm

NO Tunnel Road Users Short-termlimits: A: 30ppm

Nitric Oxide Fifteenminutes, or B: 20ppm 35ppmless, averageexposure C: 10ppm

NO2Tunnel Road Users Short-term

limits: A: 4ppmNitrogen Dioxide Fifteen

minutes, or B: 3ppm 5ppmless, averageexposure C: 1.5ppm

Notes:

1. EH40 Occupational Exposure Limits are set with thresholds below which, on existing knowledge, there athought to be no adverse effects on people. In the absence of more specific scientific data, the values have bconservatively adapted for road users within tunnels.

2. With respect to EH40 levels, tunnel sensor limit values allow for pollution concentration for in-vehicle roausers as described, and time of exposure with respect to length of tunnel for congested traffic, travelling at 10hr. Tunnel sensors shall start mechanical ventilation, if provided, in stages before measured pollution reachelimiting levels for any of above gases. Tunnel closure procedures shall be implemented if pollution levels appset to continue to rise above the recommended carbon monoxide EH40 levels (15 minute reference period vaLimit values for tunnels longer than 2500m shall be derived from first principles.

A = tunnels up to 500m in lengthB = tunnels 500m up to 1000m in lengthC = tunnels 1000m up to 2500m in length.

Table 5.2 Carbon Monoxide and Oxides of Nitrogen Limits for Road Users Within a Tunnel (based onHSE EH40 values)

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Application K - “V isibility Loss” at peak traffic (m -1)

Fluid traffic Vmax = 60 - 80 km/hr <= 0.007Vmax = >80 - 100 km/hr <= 0.005

Congested traffic <= 0.009

Tunnel to be closed >= 0.012

Maintenance work, with tunnel traffic <= 0.003

V = traffic speedK = extinction coefficient.

Table 5.3 Visibility Limits (haze from vehicle fumes etc)

Age of vehicle Percentage innational fleet (%)

1 12

2 12

3 11

4 10

5 10

6 9

7 8

8 7

9 6

10 5

11 4

12 3

13 2

14 1

15 and older 1

Table 5.4 Indicative Age Breakdown for National Vehicle Fleet

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Traffic Condition A verage Mass(tonnes)

City tunnel with a large percentage of light weight trucks, delivery vans and buses 10 - 15

Highway tunnels on typical national highway networks 15 - 25

Tunnels on major transport networks with a high percentage of fully loaded trucks 25 - 35

Table 5.5 Average Weight of Goods Vehicles

Exposure Period Mixed Pollutant Concentrations of

CO, NO and NO2 gases in ppm

Long Term ExposureLimit (8 hour time CO/30 + NO/25 + NO

2/3 < 1.0

weighted average)

Short Term ExposureLimit (15 minute CO/200 + NO/35 + NO

2/5 < 1.0

reference period)

Notes: See text for estimating concentrations of NO (nitric oxide) or NO2 (nitrogen dioxide) where only NO

xcombined gas or NO is monitored. CO is carbon monoxide for which proposed EH40 values for 1999 have bincluded. Parts per million is abbreviated to ppm. For intermediate exposure periods apply as per EH40. Forcurrent state of knowledge, combining the limits of the three gases is believed to be conservative.

Table 5.6 Mixed Exposure: Occupational Exposure Limits(For Maintenance Staff, Police etc Working Within Road Tunnels)

Pollutant 8 Hour Time Weighted 15 Minute ReferenceAverage, Limit (ppm) Period, Limit (ppm)

CO 30 200

NO 25 35

NO2

3 5

Note: For reference only, as Table 5.6 limits govern.

Table 5.7 Individual Pollutant: Occupational Exposure Limits(For Maintenance Staff, Police etc)

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Chapter 5Ventilation

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EH40 Occupational Exposure Standard Maximum concentration by mass

Long term exposure limit(8 hour time weighted average) 3.5 mg/m3

Short term exposure limit(15min reference period) 7 mg/m3

Note: Provisional limit values have been given based on carbon black limits pending HSE recommendationEngine Exhaust Emissions currently under review on the ACTS/WATCH programme. Proposed particulatePM

10 limits to Air Quality Framework Directive 96/2/EEC is to achieve a 50 µg/m3, 24 hour limit for the open air

by year 2005.

Table 5.8 Diesel Smoke Particulates (Carbon Black): Total Inhalable Dust Occupational Exposure Limits(For Maintenance Staff, Police etc)

Fire Size (MW) Distance Upstream of Fire (m) Distance Downstream of Fire (m)

5 - -

20 10 40

50 20 80

100 30 120

Table 5.9 Distances Over Which Jet Fans may be Considered as Destroyed During Fire

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Chapter 5Ventilation

Longitudinal Ventilation with Central Exhaust Shaft(Two way traffic - Long tunnel)

Longitudinal Ventilation with Air Exchange(1 way or 2 way traffic - long tunnel)

Basic Longitudinal Ventilation (1 way or 2 way traffic - short tunnel)

Examples of Longitudinal VentilationFigure 5.1G h i S i 9 8 0 9 8 3 D S F

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Semi-transverse Ventilation

Polluted Air (or smoke)Exhaust Duct

Fresh AirInput Duct

Full Transverse Ventilation

Invert Void used as aFresh Air Distribution Duct(Plenum). If located at high level then Plenum may be used for smoke extraction with fans running in reverse.

Figure 5.3

Figure 5.2

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Chapter 5Ventilation

Example Electrostatic Precipitation StationWithin a Tunnel

Safety Grill

Electrostatic Precipitator

Supporting Equipment

Controls

Fans

HighLevelOutlet

Main Tunnel

High Level Outlet

Plan

Section

Figure 5.4

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Anti-recirculation WallFigure 5.5

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Outlet at Portalor Shaft

Tunnel Ventilation Systems and Fire

SMOKE - Controlled indirection of Traffic Flow

Velocity

POLLUTION

SMOKE - Equal andconsiderable spread

both sides

Velocity - Nil

POLLUTION

NATURAL VENTILATION

SMOKE - Effectively controlledby high level extract

Velocity - NilPOLLUTION

FULLY TRANSVERSEVENTILATION

SMOKE - Considerable spread(less control than longitudinalor fully transverse systems)

Velocity

POLLUTION

SEMI-TRANSVERSE(HYBRID) VENTILATION

LONGITUDINAL VENTILATION

igure 5.6

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Chapter 6Tunnel Lighting

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General

6.1 A high standard of lighting is provided in roadtunnels to enable users of the tunnel to see their way to identify potential hazards quickly. Good lighting alsohelps to make a tunnel to appear less claustrophobic daunting. See Chapter 9 for the lighting of signs.

6.2 This Chapter provides the backgroundinformation and technical criteria that influence theplanning, design, maintenance and operational aspectunnel lighting. Guidance is given on the options forcarriageway and wall surface finishes, location ofluminaires, choice of light source, together with factorsrelating to life cycle costs, energy saving considerationand the cleaning and maintenance regimes. The controf the threshold, transition and exit levels of lighting (sFigure 6.1) is directly related to continuous readings oexternal ambient conditions. A luminaire is theapparatus which distributes, filters or transforms thelight given by a lamp and includes the necessary itemfix, protect and connect to electrical supply. Thethreshold zone is the first entrance section of a tunnelwhich is brightly lit so that drivers on the access zone(tunnel approach) can see obstructions when past thestopping sight distance to the portal. The transition zois a further section which provides a gradual reductionin lighting to the levels of the interior zone. The exitzone is a section where the driver’s eye readapts to thoutside lighting levels and provides lighting for driver’srearward vision on exit. Direct illumination in the exitzone also increases the visibility of any smaller vehiclepositioned in the shadow of larger vehicles in front.

6.3 On entering a tunnel from the brightness ofdaylight surroundings, it takes a short time for driverseyes to adapt to the relatively dimly lit tunnel interior.The distance travelled whilst this adaptation takes plais directly proportional to the speed of the vehicle. Toensure that vision is not impaired, lighting is reducedprogressively in the threshold and transition zones (seFigure 6.1) of the tunnel to give a safe adaption fromexternal to internal light levels. A similar provision ismade at the exit to assist the reverse transition back idaylight. The exit zone is shorter than the entrance zobecause drivers’ eyes adapt from dark to light morequickly than from light to dark. Allowance needs to bemade for tunnels of an east to west orientation, when sun is low.

6. TUNNEL LIGHTING

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6.4 Unlike lighting for open roads, tunnel lighting isat its peak during bright daylight, reducing to aminimum at night (BS5489: Part 7). Automatic controlsshall be provided to regulate the tunnel lighting to suitexternal conditions and to minimise energy consumptionby ensuring that no more lighting is used than is actuallyrequired.

6.5 Visual flicker (impression of fluctuatingluminance or colour) of between approximately 2.5 and15 Hz, caused by spacing luminaires at certain intervals,may lead to discomfort or distress for drivers passingthrough the tunnel. Luminance is the amount of lightemitted in a given direction from a unit area of surface.

6.6 The Standard to be used for tunnel lightingdesign is BS5489 Pt. 7 (Code of Practice for theLighting of Tunnels and Underpasses). The Standardcontains a full explanation of the parameters andprocedures involved, worked examples, definitionsand terminology. Counterbeam lighting has hadmixed success in use overseas and some countrieshave had to combine such lighting with symmetricallighting for safety reasons.

6.7 Tunnel lighting shall be designed for traffic,moving at design speed, to approach, enter, travelthrough and exit a road tunnel at a safety level equalto that on adjacent stretches of open road. The designshall take account of day and night time conditions ofdriving, and operation and maintenancerequirements.

6.8 Decisions relating to tunnel length, location,orientation, cross sectional profile, approach roadconditions, designated design speed, surface finishes andthe structure and form of the portals are importantfactors that affect the detailed design and cost of tunnellighting. Early consideration shall be give to thesefactors and tunnel operation and maintenanceprocedures. The quality of the reflective interior wall orlining finishes together with the lighting design stronglyinfluence the driver’s sense of well being about tunneldriving safety.

6.9 Tunnel lighting is designed to ensure that thebackground lighting to obstacles on the carriageway isbright enough to enable obstacles to be recognised insilhouette, at an appropriate sight stopping distance.This depends on the levels of lighting and on thereflective properties of the background. For tunnels, the

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background to be illuminated is the road surface and tlower sections of tunnel walls.

6.10 The measure of light reflected towards theobserver, from carriageway and walls, is calledluminance. The ease of detecting an obstacle is verymuch influenced by the contrast in luminances betweethe obstacle and the background, which are a functionthe reflectance of their surface finishes. Reflectance isthe ratio of radiated to incident light.

6.11 In terms of lighting provision, the main demandfor the change from daylight to interior tunnel lightingconditions and the reverse on exit. The zones (accessthreshold, transition, interior and exit) of luminancereduction and increase are illustrated in Figure 6.1. Thpenetration of natural daylight into the tunnel at theentrance and exit portals generally means that artificialighting is not required for the first 5 metres inside eachportal.

6.12 Lighting in the threshold and transition zones isdesigned to provide a staged reduction of the level ofluminance from that in the access zone and portal areThe calculated lengths of these zones depends on sighstopping distances for the design traffic speed; the upplimit of external luminance determined for the particulasite; the overall reduction required to match interior zolevels of lighting. Because a driver’s eyes adapt morerapidly from dark to bright, reinforced exit zone lightingrequires a shorter transition between the tunnel interioand external conditions (one way traffic). For two way,contraflow operation, in a normally one way tunnel,speed restrictions may need to be imposed, sufficient tallow time for oncoming drivers’ eyes to adapt at therate allowed by the exit zone lighting.

Choice of Light Source

6.13 Luminaires are normally aligned with their longaxis parallel to the road. Their light is predominantlydirected transversely across the tunnel giving alongitudinally symmetrical light distribution.Counterbeam (asymmetric longitudinal) lighting directetowards the oncoming traffic is not recommended fortraffic safety reasons, where contrast has not beensufficient to distinguish obstacles reliably.

6.14 A wide variety of light sources are available.Choice for a particular application and performanceshall offer the minimum whole life cost, taking intoaccount energy consumption, lamp replacement intervand costs of luminaires and lamps. Table 6.1 providesguide to typical characteristics of lamps commonly

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considered for tunnel lighting installations, together withinduction and sulphur lamps etc which are beingdeveloped. Fluorescent lamps are of the discharge typewhere fluorescent material is excited by ultravioletradiation. They are most suitable for the interior zoneand night time lighting. Lengths of 1.5m to 1.8m arepreferred and lamps and starting gear shall be suitablefor starting in temperatures below 0oC. Restrike timesand flicker are minimal, light distribution is even withgood colour control and lamps are dimmable for energysaving. Sodium vapour lamps are of high pressure(10,000Pa) SON or low pressure (5Pa) SOX partialvapour types. They are suitable for the higher lightinglevel zones. No more than 3 wattage types shall be usedLouvres shall be used in the luminaires of SON toreduce glare. Dimming is possible with specialequipment. Flicker and restrike time shall be consideredfor any use of SOX or SON in interior zones.

6.15 The following characteristics shall be consideredwhen determining the most appropriate types of lamp:

i. Lamp Circuit Luminous Efficacy: A measure ofthe energy efficiency of a lamp, presented interms of lumens of light output per watt of powerconsumed by the lamp and its associated controlgear.

ii. Lumen Maintenance: The average number ofoperating hours from new when light output willhave dropped to 80% of the initial value.

iii. Lamp Survival: The number of operating hoursfrom new when 20% of lamps in an installationwill have failed.

iv. Restrike time: The time taken to restore full lightoutput after restoration from interruption of thenormal electricity supply.

v. Colour Rendering Index: A measure of the easewith which different colours can be distinguishedunder the light from the lamp. This is particularlyimportant if compatibility with colour CCTV isrequired.

vi. Shape: Linear sources emit light over the fulllength of the lamp and therefore differ in beamappearance and apparent brightness from moreconcentrated point sources.

vii. Dimmable: Dimmable luminaires offer greaterflexibility of control for energy saving but withhigher capital and possibly higher maintenancecosts.

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6.16 The design of luminaires shall be related totunnel profile, systems of support, ease of access andvulnerability from traffic. Luminaires shall be ofrobust construction, sealed to IP65 requirements toprevent the ingress of moisture, and adequatelyprotected against the harsh conditions of the tunnelenvironment ie the combined corrosive effects ofvehicle pollution, dust, chemicals used in tunnelcleansing, and road salts thrown up by trafficturbulence. See Chapters 2 and 11.

Spacing and Location of Luminaires

6.17 To prevent light flicker, Table 6.2 gives theintervals between light sources that shall be avoided ithe interior zone. BS5489 provides details of relaxatiopossible for tunnels less than 1000 metres long or whthe bright areas of luminaires are larger than the darkintervals between them.

6.18 Luminaires shall be located so as to permitsimple and easy access for cleaning, re-lamping andcomplete replacement when required. The selectedlocation has a significant impact on the light distributiowithin the tunnel and should be determined at an earlstage.

6.19 Centrally Mounted Luminaires: For many twolane tunnel interior zones a single central line offluorescent luminaires, mounted continuously end to ecan provide the required illuminance. This is the mostefficient means of lighting the carriageway evenly.However, access to luminaires is likely to requirecomplete closure of the tunnel bore since both lanes wbe obstructed. Additional lighting required to reinforcethe entrance and exit zones is achieved by the additiofurther adjacent lines of luminaires.

6.20 Cornice Mounted Luminaires: Mountingluminaires on either side of the carriageway offers thepossibility of maintenance access, if safetyconsiderations permit, to one row of lighting whilst,permitting traffic flow in the remaining lanes. Howeversmaller tunnels may not require two continuous lines luminaires. If one line only is provided, the far trafficlanes will receive a reduced level of illumination. Thelatter problem may be overcome with asymmetricalreflector shapes.

Light at Tunnel Portals

6.21 Apart from the attention that will need to begiven to the aesthetic appearance of portal designs, torientation, general layout and surface finishes will ha

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a significant effect on levels of reinforced lightinginstalled at tunnel entrances.

6.22 The location and orientation of tunnel portals willgenerally be decided by optimising tunnel length andgradients in terms of construction and operating costs.The portal areas shall allow and encourage a safe andsmooth transition from the open road to the tunnel.

6.23 Although commonly used as a means of reducingenergy consumption of threshold zone lighting, the useof daylight louvre or screen structures over the tunnelentrance to reduce the amount of direct sunlight reachingthe road surface and walls, has the followingdisadvantages:

i. The degree by which the screens exclude naturaldaylight will vary according to the position of thesun and the amount of diffusion of sunlight bycloud. Actual performance of the screens istherefore very difficult to predict.

ii. The presence of screens can promote icing of theroad surface beneath from water drips, icicles,and areas in shadow.

iii. Structures requiring maintenance are introducedat critical points of the tunnel.

iv Structure is open to vandalisation.

6.24 If screens are considered, the following aspectsshall be carefully studied in addition to the above:

i. The possible effect on drivers of any flickerinduced by passing through alternating bands ofbright sunlight and shade

ii. The frequency of cleaning required to maintainperformance

iii. The possible effects of strong winds or theaccumulation of snow and ice

iv. The effect on dispersal of polluted air from thetunnel.

6.25 The effect on levels of light pollution from thetunnel portals shall be considered.

Whole Life Costs

6.26 The overall objective is to achieve the optimumdesign that will keep the costs of lighting as low aspossible throughout the lifetime of the installation.Account shall be taken of the initial capital installation

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costs, the maintenance factor (anticipated permitteddeterioration) that will determine the nature of theoverall cleaning and maintenance commitment, togethwith the energy and maintenance costs over a 20 yeaperiod which is deemed to be the design life of theluminaire. Switching stages are the predeterminednumber of levels of lighting. Six stages have beencommonly used but research in France has indicated three, or even two, stages may be more economic whinstallation costs are also considered. When calculatinenergy costs it is important to identify the hours run foeach stage of lighting rather than adopt average value

Colour and Surface Reflectance

6.27 On the immediate approaches to the tunnel,darker coloured, less light reflecting portals, retainingwalls, and asphalt road surfaces, trees and extendedfacades assist the adaptation process, by reducingsurface luminance and the effects of low sun angle, anprovide a relative reduction in the length of the threshozone.

6.28 The wall and road surfaces within the tunnelshall have high reflectance of diffused light. This leadsto significant power savings, will reduce the numberof luminaires required in the transition zone andprovide a high luminance background to silhouetteany obstructions (see Fig 6.2). The effect on lightingreflectance shall be taken into account with anyproposal to change the road surface from thatoriginally designed for.

6.29 Road surface reflectances vary according tomaterials of construction used. An asphalt surface hareflective value of 0.15, and a plain concrete surface uto 0.3. Reflectivity depends on colour and texture, eg smooth or coarse surface finish. The dependence ofreflectivity on the composition of the road surface isdiscussed in CIE66 and the method of calculation of theffect on luminance in CIE 30.2. Some countriesintroduce ballotini strips into asphalt surfacing for lowlighting level tunnels.

6.30 Choice of wall finish may depend on the form otunnel construction dictated by civil engineeringconsiderations. It can range from plain concrete, facinblocks with an applied surface coating to purpose masecondary linings. Wall reflectance shall be not less th0.6 and the height of the part of the wall having highluminance to obtain maximum silhouette shall be at le4 metres. The light distribution cut-off angle shall bearranged to coincide with the 4 metre line. See Figure6.3. Cut-off is the technique to conceal lamps fromdirect view, to reduce glare.

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6.31 High gloss textured finishes shall be avoidedbecause of the specular (mirror like reflection withoutdiffusion) and glare problems from daylight, vehicle stoplamps and traffic signs. Specular reflection from vehicleheadlights is particularly disadvantageous when two waytraffic flow is in operation. See Figure 6.4.

6.32 Colour schemes shall be:

i. Light colours from road surface level up to the 4metre line.

ii. Darker colours above the 4 metre line includingthe roof space.

6.33 The dark colour area above the 4 metre lineserves three functions:

i. In the case of a circular/horseshoe shaped tunnelit avoids the claustrophobic reflective tube effect,which can be disturbing to drivers in longtunnels, and replaces it with a tunnel of visualrectangular appearance, giving apparent width tothe tunnel.

ii. It obscures the hardware installed above theluminaires and improves the aestheticappearance.

iii. Provides a visual limit for the wall cleaningmachine and hides a soiled appearance where thesurface is not cleaned.

6.34 High wall reflectivity contributes to the luminairelight distribution onto the road surface.

Cleaning, Maintenance and Lamp Replacement

6.35 The continued reflectivity of the tunnel surfacesdepends on their state of cleanliness. Tunnels shall bewashed periodically to maintain the wall reflectivity tothe level adopted in the design. The period betweencleaning operations varies according to tunnel usage,season, geographical location of the tunnel and theactual design of the tunnel. An initial cleaning frequencyshall be set which can then be varied accordance toactual experience and cost-benefit case.

6.36 The cost of maintaining and cleaning the tunnelwalls and luminaires should be set against the additionalcost of lighting the tunnel to the required standardwithout cleaning. The state of the walls and internalluminance shall be monitored periodically and thecleaning interval varied accordingly to achieve theoptimum cost benefit. Once established, cleaning

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routines and lamp replacement schedules shall beadhered to in order to maintain the minimum levels ofillumination. The design maintenance factor shall be nless than 0.8. Apart from the deterioration componentwhich can be corrected by cleaning, there is the longterm permanent deterioration of luminaires and wallfinishes. Site tests shall be carried out at not more thayear intervals to check that photometric performance acceptable.

6.37 The means of access to the interior of luminairfor replacement of lamps and control gear will have animpact on maintenance costs. End-opening luminairesare easier to seal against the ingress of moisture butrequire complex and expensive mounting brackets anaccess is generally more complicated. Front openingluminaires offer improved access with simpler mountinarrangements are preferred but care needs to be takeensure that the considerably longer gaskets provide areliable seal at all times.

Provision for Special Operating Conditions

6.38 The lighting system may need to be designed fthe tunnel operating under a number of specialconditions. For example, in the case of a twin boretunnel, one bore could be completed and opened to twway traffic for a considerable time before the secondbore is completed. Even when completed, maintenanccould require that one bore was closed to traffic and tsecond bore operated two way. Maintenance workinvolving two-way working will often be carried out atnight, and so not require any modification of the lightinsystem. However, when maintenance is carried out indaytime, contraflow lighting arrangements shall beconsidered.

6.39 Under emergency conditions, two way trafficmay become necessary in a tunnel designed for one wflows, in which case entry speeds would have to berestricted at both portals since the normal exit lightingwould be inadequate for contraflow entrance operatioat normal operating speeds.

6.40 If two way tunnel operation is required duringdaylight hours, an assessment shall be made by the Tregarding a safe working speed, and sufficient speedwarnings and restrictions shall be in place to ensure thsafe operation of the tunnel. The lighting must besuitable for the clear visibility of the sign and signalsystem needed to control such special working.

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Monitoring and Control

6.41 The monitoring and control of tunnel lighting isbased on measuring external lighting values, based oneither illuminance or luminance (ie light incident onsurfaces). The luminance method is more precise forenergy cost control and should be adopted. See alsoChapter 10.

6.42 The luminance method adopts the use of a polemounted photocells or photometer located at theapproximate adaptation point outside the tunnel portaThe adaptation point is where the driver’s eye starts toadapt to the relative darkness of the approaching tunnThe photometer is aimed towards the centre of the tunportal to a point 1.5m up from the road surface, andrecords the average luminance level from within a 20o

cone. The value is similar to the veiling luminanceimpinging on a driver’s eye approaching the tunnel ietaking into account the reflective factors of the varioussurfaces surrounding the tunnel portal and the sun’slocation etc. CCTV luminance cameras could be usedinstead of photometers.

6.43 Paired photometers are normally used, bothfacing the same portal, the average value from each isused to determine the automatically operated switchinstages. On failure of one photometer an alarm would braised and the other photometer would continue theswitching sequences. Periodic calibration or selfcalibration of the units is required.

6.44 Control of the switching stages is by a computebased system to switch various lamps on or off atprescribed daylight levels. Frequent switching of stageshall be prevented and cooling times for certain types luminaire provided by computer control. A time delay omoving average system is incorporated so that any shlived changes such as caused by cloud movements ardiscounted. For economy, dimming controls shall beconsidered so that lighting levels between fixed stagescan be achieved. Time switches are also used to augmthe photometers. Light switching and control gear shabe designed to prevent flickering by locking outluminaires which do not achieve or sustain continuousdischarge.

6.45 Photometers or light meters can also be usedinside the tunnel to compare lighting levels with thoseoutside. By matching the two levels via a computer answitching the lighting accordingly, sharp contrasts inbrightness are avoided. See also Chapter 10.

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Incoming Power Supply

6.46 See Chapter 11.

Emergency Lighting

6.47 See Chapter 11.

Lighting Distribution and Cabling

6.48 See Chapter 11.

Lamp Type Efficacy Lumen Survival Restrike Time Colour Rendering Shape Dimmable

Maintenance Index

Lumens/circuit

watts Hours to Hours to Minutes Ra

80% output 20% failed

Fluorescent (MCF) 75 - 80 16,000 9,000(1) Instant 50 - 85 Linear Yes

Mercury (MBF) 45 - 50 6,000 16,000 4 50 - 60 Point No

Low Pressure 130 - 150 14,000 8,000 10 Monochromatic: Linear No

Sodium (SOX) no colour

discrimination

High Pressure 90 - 130 24,000 16,000 1 (2) 25 Point(4) Limited (3)

Sodium (SON)

Deluxe High 90 - 130 9,000 8,000 1 60 Point(4) Limited (3)

Pressure Sodium

(SON-DL)

Table 6.1 Typical Characteristics Of Light Sources

Notes: (1) The life of fluorescent lamps may be extended if high frequency electronic control gear is used.However, such control gear is more expensive than conventional ballasts and may have a shortservice life.

(2) The figure given is for conventional lamps and control gear. Lamps with twin arc tubes offer thepossibility of near instant re-strike, but at increased cost.

(3) Devices which offer a limited degree of dimming are available but are largely unproven.

(4) A linear effect can be attained by the use of tubular guide lights.

Maximum Traffic Speed km/h 120 100 85 70 60

Prohibited Spacings metres 2.0 - 13.0 1.8 - 10.5 1.6 - 10.0 1.3 - 8.5 1.2 - 8.0

Table 6.2 Luminaire Spacings Which May Cause Perceived Flicker

Note: (1) The term spacing is taken to mean the distance between ends of adjacent lamps, in the longituddirection.

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xample

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Access ZoneThreshold ZoneTransition ZoneInterior ZoneExit Zone

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Chapter 6Tunnel Lighting

Example of Light Reflected fromFigure 6.2 Wall and Road Surfaces

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Chapter 6Tunnel Lighting

0.6 Wallreflectance(averagelight colour)

Darkercolour 0.3

Reflectedlight Obstruction

Road surfacereflectance0.15 to 0.3

Cut off angle

High reflectivewall finish

Cut-off pointfrom luminairelight distribution

Luminaire

4m

Light DistributionFigure 6.3

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Chapter 6Tunnel Lighting

Undesirable Reflections fromFigure 6.4 Specular Surfaces

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7. DRAINAGE

Chapter 7Drainage

General

7.1 This Chapter describes the provision to be madfor drainage arrangements in tunnels. It providesbackground information and technical criteria relating the collection and discharge of inflows, the siting andsizing of sumps, separators and pumping stations,including related operational and safety aspects. Theprocedures to ensure compliance with effluent standarand the requirements of the local water authority aredescribed.

7.2 Unless the vertical alignment of the road througa tunnel is a crest curve (more achievable in mountaintunnels), it is normally necessary for a road tunnel to bprovided with drainage sumps and pumping equipmento collect water from the road surface and discharge itsafely. Where approach roads run downhill towards onor both portals it is normal to provide sumps to intercestorm water flowing down the approach roads and toprevent it from entering the tunnel. For such cases thecatchment areas can be large and consequently portasumps need to have a generous capacity.

7.3 In addition, where there is low point within thetunnel, an additional sump is provided to collect anywater from the road surface inside the tunnel. Becausemost storm water will be collected at the portals, thissump is normally sized to receive water from predictedground water seepage, tunnel washing and the use ofhydrants, as well as possible spillages from vehicles. Icolder areas, subject to heavy snowfall, allowance shabe made for meltwater from snow and ice brought intorelatively warm tunnel by vehicles.

7.4 To cater for the wide range of possible inflowrates, sumps are provided with automatic controls whiwill regulate the number of discharge pumps operatingaccording to the water level in the sump. The rate ofpumping water out of a sump does not necessarily neeto be the same as the rate of inflow provided that thesump has adequate storage capacity, and the sumpdesign needs to be coordinated with that of the pumpinequipment to achieve an optimum solution.

7.5 Because of the risk of spillages of petrol and oilwhich in quantity could give rise to an explosiveatmosphere in a sump and a major safety risk, sumpsequipped with ventilation and sensors which will detecbuild-up of common hydrocarbons and will initiate

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automatic protective measures to prevent an explosiveatmosphere developing. These measures include floodingthe sump with foam to prevent ignition, and shuttingdown pumps and sump ventilation fans to confine thehazard until it can be dealt with, and purging electricalmachinery and switchgear rooms with eg carbondioxide.

7.6 The design of an appropriate system of drainageto channel calculated inflows of water via road gulliesand longitudinal drainage in to one or more sumps, willdepend on the length, depth, structure and form oftunnels in relation to the considerations described in thisChapter..

7.7 The relevant requirements andrecommendations of HA71 (DMRB 4.2.1) and HD33(DMRB 4.2.3) shall be taken into account in thedesign of drainage systems.

Inflows

7.8 The calculation of expected inflows involves adetailed investigation of the nature and extent of:

i. Ground water and the drainage of the tunnelstructure

ii. Rainfall

iii. Tunnel wall washing

iv. Fire fighting and wash down following spillagesof dangerous goods within the tunnel.

Drainage Systems

7.9 A tunnel drainage system can be an integral partof a local road drainage system, or be designed as a selfcontained facility. It collects both ground water andsurface water which drains from the tunnel roadways viaroad gullies and longitudinal drains and discharges intoone or more main sumps. An impounding sump tocontain road tanker spillages, and tunnel wash downwater, which is likely to be heavily polluted must also beprovided. A typical pumped drainage systemarrangement is shown in Figure 7.1.

7.10 Pump stations and sumps are normally sited atthe lowest point of a sag curve in the tunnel, and near

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the portals. Control rooms or other buildings should notbe located near sumps, due to the risk of explosion.Where there is no alternative, full safety precautionsmust be incorporated into the design of such buildings.

7.11 Pump stations, sumps and separators shall besited where they have a minimum effect on the operatioof the tunnel, particularly where regular access for theirmaintenance is required. Depending on designconstraints, the sumps should be outside of the tunnelrather than under the tunnel carriageway.

7.12 A pumped system delivers drainage waterthrough single or twin rising mains, passing along thetunnels below the road deck or by an external route, todischarge into a surface water sewer, or water course (permitted).

7.13 The pumping installation shall be of the wet-wellor dry-well type. For the former, the pumps areimmersed in the water of the collecting sump, for thelatter, the pump is mounted in a dry chamber, alongsidethe collecting sump or above it.

7.14 Dry-well installations are more usual when thepumps are large, mainly to enable maintenanceoperations to be carried out without removing thecomplete pump.

7.15 The sizing of sumps and separators is largely aniterative process in conjunction with the pump capacityand maximum inflow rate. Constraints on availablepower, size of pumping main, allowable discharge rateand the size of sump that can be accommodated allcontribute to deciding the final sump volume and pumpcapacity. The working volume for the sump would bebetween high and low level limits with allowance forsurge and residual water cover where submersiblepumps are used.

7.16 Care shall be taken to size pumps appropriatelyfor the volume of water to be discharged. Large pumpswhich only operate for short periods can increase thecost of energy supply disproportionately because of theincreased starting and running current demands.

7.17 As a general rule, the number of pump starts pehour shall not exceed 12 and this shall be taken intoaccount when determining the size of pumps/sumps ancontrol levels.

7.18 Transverse interceptor drains shall not be used remove storm water as they silt and can break up undeheavy traffic. Provision shall be made for adequatecrossfalls in conjunction with gullies at regular intervals

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o remove the water and avoid ponding on thepproaches to a tunnel.

.19 Tunnel structure drains often become blocked byg calcium compounds leaching out of concrete,roundwater salts, silt and construction site debris.versize drainage pipes shall be provided to makellowance for such problems. It is essential therefore to

lush the drains regularly and to provide inspectionhambers every 50m for ease of inspection and rodding.

.20 As far as possible, all manhole and inspectionhamber covers, such as those for access to sumps,ump chambers, valve pits etc, shall be located away

rom the carriageway, in order that maintenance andepair operations can be carried out without the need for lane or bore closure. Where this is not possible, covershall be positioned outside of wheel tracks. There isreat potential for disruption to tunnel operation in thevent of access cover failure or coming loose, presenting hazard to traffic which needs to be dealt with

mmediately.

.21 Road gullies shall be of a pattern suitable fornstallation in the kerb. Inspection chambers shall beocated in the verge for better access and to avoidamage by traffic. Design data for gully spacing isontained in TRRL (Transport Research Laboratory)eport LR 277 and TRRL Contractor Report CR2.ullies shall be installed at not greater than 20 m

ntervals. The minimum gradient for cross-falls is givenn Chapter 4.

ffluent Standards: Consultation with Authorities

.22 The Local Water Authority shall bepproached for agreement at an early stage in theesign concerning any discharge to the local foulater sewer. Constraints concerning quality anduantity of tunnel discharge shall be agreed with theocal Water, Environmental and Public Healthuthorities together with any requirements for arade Effluent Agreement.

.23 Highway Authorities (in Scotland, Roadsuthority) have a statutory right, subject to the

equirements of the Local Water Authority for dischargeo sewers, or the appropriate Environmental Protectiongency for discharges to rivers or similar stretches ofpen water.

.24 It is an offence to discharge any Class A productsPetroleum Spirit) into a public sewer. All wateruthorities will insist on the separation, and separateisposal under special arrangements, of any petrol, oil or

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grease that may be spilt in a tunnel, before the drainagwater is discharged.

7.25 There may also be a requirement that dischargeshould cease if the salinity of the drainage water exceea certain figure or, if the acidity or alkalinity are outsidea certain range. The precise restrictions will depend onthe place of disposal agreed. Rivers are classified forcleanliness and the quality of discharges into rivers willbe governed according to the river’s classification.

Calculation of Anticipated Inflows

Ground Water

7.26 The quantity of ground water flowing into atunnel is dependent on the ground conditions, the desigand constructional quality of the tunnel structure. Someof the common factors are itemised below:

i. Tunnels Beneath the Water Table

Water inflow into a tunnel will depend upon thewater proofing system used. With a full waterproofing system an inflow of less than 1.0 litre/m²/day would be expected (where the area in m²is the total internal surface area) this correspondto Class A or O in Table 2 of CIRIA Report 81:Tunnel Waterproofing (now withdrawn but Table2 is often used for reference). Substantially largeinflows are experienced where tunnelsincorporate specific measures to drain the grounwater and lower the water table.

ii. Tunnels Above the Water Table

Tunnels in this category may experience onlyintermittent water inflow from rainfall seepage orfrom leaking or burst water pipes or sewers locato the tunnel.

Precipitation and Runoff

7.27 The maximum quantity of precipitation to beexpected within a given rainfall catchment area can beobtained from records and hydrographs published by thMeteorological Office, classified according to various“storm return periods”, usually 20 year, 50 year and 10year storms. The maximum quantity of water to bestored is usually assessed, by integrating the area undthe hydrograph, for a storm and runoff of 60 minutes.

7.28 The amount of storm water that enters the tunneand its approaches, and has to be removed, will depenon the position and level of the tunnel in relation to thelocal topography and the sizes of the catchment areas.

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.29 An estimate is to be made of the impervious areasxternal to the tunnel which will drain towards it.

.30 A method of calculating run off is recommendedn Road Note 35 using the Wallingford Procedure:olume 4: Modified Rational Method.

all Washing

.31 The quantity of water from wall washingperations is dependent on the techniques employed. Forurposes of calculation, a water use rate of 5 l/m² ofall area can be used over the period of cleaning.

ydrant Water

.32 Most tunnels are equipped with hydrants atrequent intervals, fed from wet fire mains running alongheir lengths. For such cases, a reasonable allowanceould be that two hydrants are used by the Fire Brigade

or wash down purposes giving a flow of approx 66 l/s.

.33 In cases where a fire main could be vulnerable toamage from a traffic incident, the duty of the pumpingystem may need to include for the potential outflowrom a broken pipe based on its pressure/flowalculations.

umps, Separators and Pumping Stations

.34 Each sump, or interconnected series of sumps,hall be of sufficient capacity to contain not only andequate volume of drainage water, but also to retainny spillage of flammable or other hazardous liquids, up

o the maximum capacity of one road tanker load.

.35 Adequate water storage capacity must berovided to contain any inflow in excess of theaximum pumping rate. Where large sumps can be

ustified, they offer the opportunity to keep down the sizef pumps.

.36 Sump structural depths shall be calculated tollow sufficient space above the highest water levelullage) for ample formation of a suppressant foamlanket and to accommodate a floating skimmer pump oruction head, if provided. The overall depth shall beufficient for correct operation of level detectionquipment.

.37 The general arrangement of the sump shall beesigned to minimise any turbulence around the pumpinglant, arising from high inflow rates, and which may

mpair the performance of the pumps.

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7.38 A forced ventilation system is required for anyclosed sumps, within the tunnel, in order to maintain asafe atmosphere for personnel working in the void; todilute any potentially dangerous atmosphere, includingthat due to accidental spillage on the carriageway; toremove any fire extinguishing gases.

7.39 Sumps outside the tunnel shall be naturallyventilated.

7.40 With the possibility of flammable liquidflowing into the drainage system, a combustible gasdetection system shall be provided. Sensing shall bearranged in two stages corresponding to low and highconcentrations of hydrocarbon gases.

7.41 Design of sumps shall include precautions tominimise structural damage due to explosion, and itstransmission where there is an adjacentinterconnecting sump.

7.42 Interceptors/separators shall be of sufficient sizto allow adequate separation of the pollutants,particularly where their operation depends upon reducvelocity across the unit.

7.43 Separators shall be designed for ease of cleaniand be ventilated to prevent the accumulation ofdangerous gases. They shall be designed to minimiserisk of oil or other hydrocarbon substances, trapped inthe separator, from being flushed through under highflow conditions.

7.44 The impounding sump shall be equipped withfacilities for skimming oil and delivering it to roadtankers, and removal of sludge, which otherwise couldbe discharged into foul sewers.

7.45 Sumps shall be classified as hazardous areas,generally Zone 2, except in exceptionalcircumstances, as defined by BS5345: Part 2. Allpumps and electrical equipment located in these areasshall have the standard of protection appropriate tothe zone, as specified in BS5345: Part 1.

Pumping Plant

7.46 The pumping duties required for a tunneldrainage system will be influenced by a number offactors including:

i. The maximum expected inflow to the sump

ii. The average normal expected inflow to the sum

iii. Design constraints imposed by structural works

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iv. Maximum discharge limitations

v. Discharge system parameters

vi. The size of the sump.

7.47 When the parameters are determined, pumpsystem calculations, using suitable formulae or software,can be carried out. System/duty curves shall include forseveral options of pipe size, in order that minimumcarrying velocity and acceptable power requirements canbe considered. A typical graph is shown in Figure 7.2.

7.48 The maximum rate at which water can bepumped out may be determined by the Local WaterAuthority’s Consent to Discharge, but this may beconsiderably greater than the expected rate underaverage conditions. Two or three pumps could beconsidered, which with all in operation, would beadequate to pump at the maximum rate, but individuallywould be sufficient to handle only the average rate.

7.49 Where a standby pump is provided, its duty is notnormally included in the calculations. Pump operationshall be rostered to ensure that pumps share the duty andstandby operations evenly.

7.50 Pumps are mostly of the single entry centrifugaltype and shall be designed to pass water borne solidsubstances without choking. Pumps designed for sewagehandling, passing round solids up to 100mm diameter,are well suited to tunnel application.

7.51 If the pump is installed above sump water levelthe pump must either be of the self-priming type or mustbe fitted with some auxiliary equipment designed toensure that the pump will always be full of water beforeit is started.

7.52 The pumps may be of vertical or horizontalconfiguration, depending on design constraints. Verticalspindle submersible types are preferred as an additionalroom to house the pumps is not required, and they do notneed ancillary equipment for priming.

7.53 Submersible type pumps have to be removed intotal when inspection, repair or overhaul is required. It isusual to provide a permanently installed standby pumpto maintain full functionality whilst one pump isremoved. The pumps are frequently installed on verticalslide rails with automatic pipe couplings to facilitateremoval and replacement. Electrical connectors, suitablyrated for use in wet and hazardous atmospheres, shall beprovided in an accessible position within the sump tofacilitate electrical disconnection when the pump has tobe removed.

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7.54 Electrical driving motors may be mounteddirectly on the pumps or they may be mounted on aseparate entablature at a higher level, driving the pumpby means of extended shafts. The latter arrangement wpreferred to ensure that the electric motor remainedaccessible for maintenance above the water level.Submersible type pump and motor units, can now bespecified for installation in dry wells as coolingarrangements no longer require the unit to be submerge

7.55 Plant shall be electrically bonded to ensure thatmetalwork is maintained at the same potential.

7.56 In addition to the main pumps and electricalmotors the following are normally required:

i. Motor control gear, cables and transformers. Allthese items shall be installed in a separate non-hazardous area away from the sump.

ii. Water level sensing equipment to control thestarting and stopping of pumps and to generatehigh level and flood alarms. Options includeultrasonic or radio frequency level detectors, floaswitches and fixed electrodes. In selecting levelcontrols, consideration shall be given to theresolution and accuracy of measurementsrequired and the effect of turbulence and rippleson the water surface. Float switches may be thecheaper option and with proven reliability, butare unsuitable for very shallow sumps such asmay be provided in immersed tube tunnelsections. Level detectors for a wide, shallowsump need to detect much smaller changes inlevel than those in a narrow, deep sump, and wilbe much more susceptible to false readingscaused by surface effects. Ultrasonics and radiofrequency devices have the advantage of notrequiring contact with the water.

iii. Skimming equipment to remove oil, petrol or anyother liquid that may float on the surface of thewater in the collecting sump. A floating pumpcould be employed, or a floating weir with anoutlet pipe leading to the suction side of a pump,which would then discharge the liquid through aseparate pipe into a road tanker.

iv. Sludge pumps may be necessary to removedeposits of solid matter in the invert of the sumpand thus avoid the need for periodic cleaning bymanual labour.

v. A reflux (or non-return valve) and an isolatingvalve shall be provided adjacent to each pump.The isolating valve would normally be located

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downstream of the reflux valve to enablemaintenance to be carried out on the latter, aswell as the pump. Valves shall be situated in anaccessible place within the sump, pump room ovalve pit.

i. Pipework for connection to a bowser vehicle topermit the sump to be emptied of spillages,independently of the main pumps or dischargepipework.

ischarge Pipework

.57 Discharge pipework comprises the pipework,alves and fittings situated between the outlets from thumps and the point of discharge. It may be a single o

win pipe system and incorporate hatch boxes ifechanical cleaning (by ‘pigging’) is planned.

.58 Pipework shall be designed to avoid sharphanges in direction, in order to minimise friction lossend prevent erosion where abrasive suspensions can xpected to be carried.

.59 Anchor and thrust blocks shall be provided wheuried pipework incorporates spigot and socket joints.

.60 Pipe fittings shall include air release valves andrain down points.

.61 The choice of pipe materials and protectivereatments will depend upon whether the pipework isuried, cast in, or in an open situation. Other factors we the expected contaminants in the water, costs andase of installation and maintenance.

.62 The use of plastic and related materials shall bevoided in a tunnel, where, in the event of fire, toxic

umes could be generated.

.63 Where flood banks or berms form part of theivil works it may be necessary to provide dischargerrangements on the berm that adopt principals indica

n Figure 7.3.

afety Considerations

.64 Typically, bifurcated duty and stand-byxtraction fans shall be provided in sump areas. Theormal operation of the fans shall be on an automatic

imed basis for 15 minutes per hour (based on ainimum of four air changes per hour when running

ontinuously). Suitable ducting shall be provided for thupply and exhaust air to the sump. Flame traps shallncorporated, as necessary.

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7.65 In order not to prematurely expel gases used ffire protection in the sump, the automatic fan systemshall be interconnected with the fire prevention systemheat detectors so that the fan(s) are switched off upodetection of a rise in temperature, within the sump.Similarly, the gas detectors located in the sump shallswitch off the fans in the event that a combustible gasor oxygen deficiency, is detected.

7.66 To expel gas, a manual override for use by thefire brigade or maintenance personnel will allow the fato be operated continuously from the pump controlpanel. Where gas is vented into the tunnel, this shall ooccur in conjunction with operation of the main tunnelventilation system. To ensure dilution below theexplosive limit within the tunnel, where electricalequipment, etc may not be fully protected, a minimumdesign criterion of 1 part of sump gas to 50 parts oftunnel air shall be adopted. Where possible, provisionshall be made to empty sumps before venting, as forcventilation of a sump containing volatile fuel willgenerate excessive quantities of combustible vapour.

7.67 Detection of gas at low and high concentrationshall raise an alarm via the SCADA system, and shalalso be displayed on the pump control panel. The ala(high) condition shall normally initiate automaticoperation of a fire extinguishing system, if fitted, torender the sump inert.

7.68 Where a nitrogen foam system is installed,nitrogen bottles shall be continuously monitored for galevels to alert the TOA to any leakage and ensure thathe bottles are fully charged and available to respondan emergency.

7.69 Sampling from one of the gas detection systemdetectors shall take place just above water level. Thiscan be achieved by attaching the sampling tube to a or float that can rise or fall with the water level.

7.70 The fire extinguishing system shall be initiatedautomatically upon detection by heat detectors, of a rin temperature (to over, 600C) due to a fire in the sumand operable manually from a local fire control panel.

7.71 Spillage of hazardous or other substances whdo not give off combustible gases, but which would beundesirable to pump into local water systems must beidentified by the TOA using the monitoring andsurveillance systems. Detection of substances, thatreduce the amount of oxygen in the atmosphere, canachieved by oxygen deficiency detectors arranged to alarms when oxygen falls below a preset value.

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7.72 On detection of a hazardous substance enterinsump, the detection system shall switch off the plant toallow manual operation and control.

7.73 All detector sensors shall be duplicated andinternal detectors such as pelistors shall be capable obeing replaced in-situ as they generally have a short liSensors need to be water protected.

Fire Precautions

7.74 Closed sumps shall have fire protection asdetailed in Chapter 8.

7.75 Sump ventilation air supply and exhaust ducts,where connected into the tunnel atmosphere, shall beprovided with flame traps. A combination oflongitudinal gradient, crossfall and gully spacingcontrols the potential for large, flowing pool fires. Tolimit flame passage through the drains, in the event ofa fuel spillage and fire, U-bends shall beincorporated, where there is adequate access forcleaning the drain, at the inlets to the sump and at thecarriageway gulley pots or traps, alternatively,equivalent “fire-proof” drainage systems may beconsidered.

7.76 Open sumps shall be sited approximately 10mclear of carriageways and buildings, and shall beaccessible to the Fire Brigade should they need toextinguish any fire.

Operating and Emergency Procedures

7.77 Emergency procedures shall be detailed in theTunnel Operator’s Guide and include for dealing withhazardous spillages and fire.

7.78 Operating procedures shall include provision foremoving hazardous material from sumps by specialiscontractors.

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Typical Pum ped Draina ge System

Discharge tosurface watersewer orwater course

Discharge totanker

Discharge tofoul sewer

Oil skimmingpumps

Dry sump Impounding sump

Sludge sump

Skimmers

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Standby Duty Duty

IsolatingvalvesNon returnvalves

Submersiblepumps

To tunnel(or to atmosphere)

Ventilationsystem

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Figure 7.1

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7/8

Typical System/Duty Curves forThree Submersible Pum ps Runnin g in Parallel

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OptionalPipe Sizes

DutyPoint

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Figure 7.2

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Bellmouth(above floodlevel)

Manhole access

Cover slabAir vent

Floodbank(or beam)

Pumpeddischargemain

Benching

Manhole

Gravitydischarge

Flap valve

Headwall

Manhole access

Valve pit Siphon breakingvalve

ARRANGEMENT 1

ARRANGEMENT 2

ARRANGEMENT 3- Could include for aninterceptor where required

Optional Floodbank Dischar ge Arran gementFigure 7.3

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Chapter 8Fire Safety Engineering

General

8.1 This Chapter provides background informationand technical criteria to be used for the fire safetyassessment of road tunnels and plant and safety facilitieto be provided as ‘Active Fire Protection’ for tunnelusers. Further guidance is given on the criteria for theevaluation of fire loading to be used in Chapter 5(Ventilation) and for the ‘Passive Fire Protection’ oftunnels in the form of protection to structural elements,cabling, mechanical and electrical plant and the fire andsmoke resistance of doors, fixtures and fittings. HomeOffice Technical Bulletin 1/1993: Operational Incidentsin Tunnels and Underground Structures: HMSOprovides guidance on tunnel incident pre-planning,staged incidents, operational tactics and communicationfrom the Working Group chaired by the Fire ServiceInspectorate. This document, BD78 (DMRB 2.1)replaces the document “Draft Design Guidelines forPlanning, Equipping and Operating Tunnels onMotorways and Other Trunk Roads, referred to. Furtheguidance will become available in PIARC: Fire andSmoke Control in Road Tunnels.

8.2 Fires in tunnels are particularly hazardous to lifebecause of the potential concentration of fumes andpoisonous gases, temperatures and heat radiation thatcan reach very high levels (1200oC and above), thepossibility of panic among tunnel users and thedifficulties which can be experienced by fire fightersworking in an enclosed space. During evacuation, airtemperatures of 80oC for 15 minutes, heat radiation of2.5kW/m2 (bare skin) and 5kW/m2 (fireman in breathingapparatus for 30 minutes maximum) can be tolerated.Visibility in smoke of 7m (necessary to make steadyprogress by walking) and 15m (to be able to read signsis required. Normal walking speeds of 1.5m/s may bereduced to 1.0 - 0.5m/s within smoke. A fire incident ina tunnel can cause congestion or blockage of thecarriageways, both inside the tunnel and on itsapproaches, such that fire appliance access could bedelayed.

8.3 Fire involving a heavy goods vehicle can beespecially hazardous because of the large amount of fucarried and the combustible nature of many payloads.Depending on the vehicles considered, fire loads fordesign purposes could range from 5 to 100MW. Sincepetrol tanker fires cause the most rapid and intense risein temperature they are to be adopted as the basis for

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esign, checking and controlling fire effects in tunnelshich permit such vehicles.

.4 For longer tunnels, the first objective of usingorced ventilation during a tunnel fire is to provide theonditions that allow the road user to escape safely frohe site of the incident. This is achieved by eitheremoving smoke from the tunnel tube (transverseentilation systems) or by driving the smoke away fromhe escape route direction, normally in the direction ofraffic flow, in order to protect vehicle occupants whoay be trapped behind the incident (longitudinal

entilation systems). The second objective is to provideafe access to the fire by the emergency services, inrder to control its spread and to extinguish it, therebyeducing the duration of the fire and its structuralonsequences.

.5 Fire resistance of the tunnel structure is necesso reduce the damage caused by the fire and minimisehe time and cost of any reinstatement. Damage isependant on both the fire load and the fire duration, t

atter being determined by the capacity of the drainagend ventilation systems within the tunnel, the quantity oombustible material involved in the fire and the fireighting provisions available. Cost benefit analysis maye used to make a case for either higher or lower fire

oads than those specified for ventilation design, theatter being primarily dependant on life safety issues.or tunnels under rivers the consequences of relativelymall areas of structural damage from fire, leading tolood inundation could be very serious.

anagement of Fire Risk

.6 Effective fire fighting, in response tomergencies, depends on a comprehensive approach he management of the potential risks involved andntails appropriate communications, traffic surveillancend control, adequate ventilation and drainage system

unnel layout for safety, emergency lighting andreplanned and tested fire fighting procedures. Relatedctive and passive protection measures are considereithin the decision framework of Figures 8.1 and 8.2.

.7 An essential part of active fire protection of theoad user is the provision of easily accessible emergenoints at regular intervals throughout the tunnel.mergency points shall be equipped with firextinguishers, hose reels, fire mains and hydrants as

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agreed with the relevant local Fire Authority. Escapefacilities (eg cross connection passages), appropriatecommunication procedures and effective means of smokcontrol shall also be agreed at an early stage in thedesign process. Usage, by the public, of equipmentprovision intended for minor incidents shall not beallowed to be prolonged, where any risk of escalationinto a major incident may delay their safe exit from thetunnel.

8.8 Passive fire protection shall safeguard thestructural integrity of the tunnel eg providing adequatecover to structural reinforcement, spalling resistance etcincluding protecting firemen from spalling material andfalling equipment; protecting power and communicationscabling and ensuring appropriate provision is made forthe fire resistance of mechanical components within thetunnel. Consideration shall be given to the effects of higtemperatures on the integrity of fixings and supports,particularly for heavy or suspended items of equipmentsuch as jet fans.

Procedure for Designing Fire Protection

8.9 The design procedure for fire protection in roadtunnels is illustrated in Figure 8.2 which shows thedesign steps to be taken and how these relate to Chapt5 (Ventilation). The first step is to define a specificdesign fire load for ventilation, representative of thetunnel type and its location. Where different levels ofstructure and equipment protection, and fire smokecontrol ventilation capacity are to be provided, then thefire protection (or resistance) design load subsequentlyestablished may not necessarily match that used forventilation design.

8.10 Once the fire protection design load isestablished, the size, temperature and duration of the fican be estimated. Heat transfer calculations are thenmade to determine the temperature rise within thestructure and this is compared for agreement with thestructural design criteria specified for the tunnel.

8.11 If the tunnel fire protection fails to protect thestructure to within the criteria specified, then furtheroptions shall be considered and the design amendedaccordingly.

Fire Quantification

8.12 The methodology for quantifying the fireprotection size, duration and temperature is shown inFigure 8.1. The first step is the specification of thedesign fire load to be used in the design of the ventilatio

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ystem and the fire resistance required of the tunneltructure. Again, it should be understood that theentilation design fire load does not necessarily matchhat used in the design of fire protection (resistance).

.13 Having established the design fire protection loador the tunnel, its duration is calculated taking intoccount the effect of drainage in reducing the potentialuration of a liquid fuel spill fire and any unavoidable

oss from fire of fans and supply cables, reduced fanfficiency with less dense gases etc, which could prolong

he duration. The fire size and spread of smoke are thenstimated, giving consideration to the effects of tunnelradient and ventilation. The fire temperature profilelong the length of the tunnel can then be calculated andsed with the fire duration to calculate the total heat thatould be transferred to the tunnel structure andquipment. The following tunnel wall and ceilingemperatures may be used for guidance purposes:

. 400oC, passenger car fire (higher if flames reachwalls etc)

i. 700oC, bus or small lorry (higher if flames reachwalls etc)

ii. 1000oC, HGV with burning goods (not petroltanker)

. 1200oC, petrol tanker (general case)

. 1400oC, petrol tanker (severe case, no drainage).

esign Fire Load for Ventilation

.14 During a tunnel fire, the primary purpose of aentilation system is to ensure the maximum opportunityor road users to escape from the site of the incident.

.15 Table 8.1 defines the equivalent longitudinalentilation design fire loads for road tunnels. Thequivalent longitudinal ventilation design load is defineds that which produces an air flow velocity equal to the

nitial smoke velocity of the fire in a zero gradientunnel. The strategy is based on deterministic and risknalysis arguments, as discussed.

.16 A severe incident within a tunnel involving aetrol tanker spillage vapour fire may reach an intensityf up to 100MW almost instantaneously. The roadradient within the majority of road tunnels is sufficient

o increase the spread of smoke so rapidly thatentilation is unlikely to be able to contain such a fire.

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8.17 Incidents that do not involve a petrol tankerspillage may still reach fire intensities of up to 100MWsuch as those involving the larger, fully-laden HGVs, bthe fire will take a longer time to reach the maximumintensity, as its rate of growth is determined by its spreto adjacent combustible items of the vehicle and itscargo. A lower ventilation design load of 20MW shouldallow sufficient time for the road user to escape beforethe fire has grown to its maximum intensity.

8.18 Based on consideration of traffic volume, trafficcomposition, traffic speed and generic tunnel design, ranalysis can identify tunnel categories and lengths whthe probability and consequences of major fire incidenare small. For such tunnels, on non built-up routes orshorter tunnels on built-up major routes, a lower desigload, as given, is warranted.

8.19 Table 8.1 gives guidance as to the minimumventilation fire load to be used when designing theventilation system of a road tunnel and is based on thventilation sufficiently slowing the smoke spread toallow evacuation of the public from the site of theincident via emergency escape doors etc. The absencescape passages in older tunnels may indicate a needconsider a higher ventilation fire rating. Also, theimposition of restrictions on hazardous goods is almosimpossible to enforce totally under currentcircumstances and should be discounted as it cannot guaranteed that vehicles carrying hazardous loads winever use the tunnel.

8.20 To allow emergency services to extinguish a firthe spread of smoke must be stopped completely in thdirection of access to the incident. Therefore, therequired ventilation load may be higher than that givenin Table 8.1 and an increase of the design load may nto be considered, based on cost-benefit arguments.

Design Fire Loading for Structural Fire Protection

Vehicle Fire

8.21 Fire loads from single vehicles and theirassociated combustible contents are given in Table 8.Note that the values given are typical and there will bevariation in fire load between different vehicles withineach classification. A tunnel fire could involve thecombustion of components of its construction, but it cabe assumed that this contribution is small in comparisto that of the vehicles and their contents. The value fothe HGV is based on the assumption that it has a fullload of highly flammable material.

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8.22 The choice of fire load for tunnel protectiondesign will be dependant on the tunnel location and rtype. A maximum fire load of 100MW should be usedfires involving HGVs are reasonably probable withrespect to their numbers using the tunnel. Otherwisemaximum non-hazardous vehicle fire load can beassumed to be that of a lorry or coach, ie 20MW. Thefinal choice of fire load will depend on the cost-benefiof increased fire protection in comparison to increasereinstatement costs etc if a fire incident occurs.

Hazardous Goods Vehicle Fire

8.23 Incidents involving hazardous goods vehiclesmay result in the spillage of eg hydrocarbon fuel, eithin its gaseous or its liquid form. Leakage of liquidhydrocarbons, typically petrol, will result in pool firesupon ignition. However, the consequences of a relealiquified petroleum gas (LPG), due to its high volatilitywill be different to those of a petrol spill. Thecombustion events associated with gaseous releasesLPG vehicles are, in general, more intense and mayinclude jet fire, fireball and vapour cloud explosioneffects in addition to pool fires. The additionalconsequences of gaseous releases will need to beconsidered.

8.24 The heat output of a pool fire will depend on thliquid pool dimension which in turn depends on theleakage rate from the tanker. The total heat output frthe fire is calculated using a value of 43.7MJ/kg for thheat of petrol combustion.

8.25 The exact leakage rate from a damaged tankenot predictable, but it can be assumed that the reducsupply of air within a tunnel will limit the fire intensityto 100MW. As for vehicle fires, the final choice ofdesign fire load will depend on the cost-benefit of usinincreased fire protection in comparison to increasedreinstatement costs if a fire incident occurs. Proposadesign for 200MW (petrol tanker) and 300+MW(immersed tunnels) vehicle fire loads have been propoverseas.

8.26 Fire intensity is limited by supply of air withinthe tunnel rather than supply of fuel to the fire. The srate required to produce the maximum fire intensity o100MW will be higher when drainage is effective. Theeffect of drainage is to reduce the duration of a fire anot to reduce the maximum intensity.

Environmental Issues

8.27 In addition to the structural and life safetyimplications of a fire within a tunnel, there is also a

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potential threat to the environment. Particularconsideration shall be given to the effective dispersion osmoke and to the disposal of water used for fire fighting,both of which may contain significant concentrations oftoxic substances.

Active Fire Protection Requirements

Emergency Points in Tunnels

8.28 A typical layout for an emergency/distributionpanel point is given in Figure 8.3. Emergency pointsshall be positioned in accordance with Chapter 3 and asa minimum shall include:

i. Two portable fire extinguishers for all types offires, in suitable cabinets

ii. Hose reel (if required by fire brigade) connectedto a fire main, to extinguish non-electrical fires

iii. A telephone connected directly to the police ortraffic control centre

iv. Socket outlets on UPS for fire brigade powertools, see Chapter 11

v. Permanently illuminated emergency signs

vi. For longer tunnels, illuminated distance signs tocommunicate the distances to the nearest exits,upstream and downstream, are of benefit in anemergency eg installed signs at Mersey Tunnels.

8.29 Doors to hose reel and extinguisher cabinets shahave micro switches to give an alarm signal, to thepolice or traffic control centre, when a door is opened ora fire extinguisher is removed. A facility in the cabinetshall indicate to the road user that this alarm signal hasbeen received.

8.30 Emergency points (EPs) may be amalgamatedwith the electrical distribution panels to form emergency/distribution panels (EDPs). The electrical distributionsection shall be segregated. See Chapter 11.

Fire Extinguishers

8.31 Portable fire extinguisher types shall be to (13 A)fire ratings of BS EN 3 Part 1, either dry-powder, storedpressure type with a pressure gauge and coloured redwith a blue label, or AFFF (Aqueous Film FormingFoam) electrically tested, complete with CO

2 charge

container and coloured off-white for ease ofidentification.

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ose Reels

.32 Hoses shall be installed, in maximum sectionalngths of 30m of 19mm internal diameter hosessuming that emergency points are located at 50m

entres), to enable discharges from adjacent hoses toverlap. Water flow rate and pressure shall be to BSN671-1:1995. Hose reels may be fed from the tunnelre main and may need pressure reducing valves. Torevent hose reels from freezing in winter, they shall berovided with trace heated branches from the fire mainnd be installed in a closed compartment containing aw wattage electrical tube heater. Hose reels shallormally be of the swinging arm pattern, but physicalmitations in the tunnel may require a fixed pattern, with fairlead, to be used. The hose reel isolating valve shallot be accessible to the public and should be left in theN” position at all times. Drawing the hose off the reel

hall automatically start the flow of water into the hosend the nozzle valve shall control the water jet.

ire Main and Additional Hydrants

.33 One fire fighting supply main will normally berovided for each one way bore of a twin-bore tunnelne main on each side for a single-bore two waynnel). Mains shall comply with Local Water Authoritynd Fire Brigade requirements. To ensure security ofupply, each end of the fire main system shall, whereverossible, be supplied from an independent water sourcend be fitted with suitable isolating valves. The wateruthority may insist upon break tanks being installed. Aumped system would then be needed to achieve thequired fire fighting capacity. This would also applyhen water pressure could drop below minimumquirements. Water meters, if installed, are likely to be

ized for routine tunnel water requirements and so willot be adequate for the full emergency fire fighting flow.eter by-pass valves shall be installed and clearly and

ermanently marked to facilitate rapid by-passing of theeter during an emergency.

.34 Hydrants in the tunnel shall be horizontal, bibosed or oblique pattern landing valves to BS 5163,ranched off of the fire main and located atpproximately 750mm above the walkway or verge.ydrant numbers and locations shall be as agreed withe fire brigade and any not incorporated into emergencyoint cabinets be placed in individual, lockable, hydrantabinets. Where fire hydrants are required outside, in thennel approaches, they shall be of the underground typend located in the verge. The required flow of water, theinimum running pressure and the maximum designorking test pressure of the hose and hydrant systemnd the capacity of break tanks (where required) shall be

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to the requirements of BS 750, BS 5041:Part 1 and BS5306:Part 1, subject to any particular writtenrequirements of the Local Water Authority and FireBrigade.

8.35 Hydrants shall be suitable for use with hoses toBS 3169.

8.36 Pipe sizes are likely to range between 100mm to200mm, depending on pressure drop considerations.Pipe couplings used with steel pipes shall be of a typethat eliminate the need for pipe anchoring. Ductile ironpipe shall be provided with spigot and socket joints.These require to be anchored at changes in direction andgradients.

8.37 Fire mains shall be protected against freezing, inorder to ensure that a supply of water for fire fightingpurposes is always available for use by the Fire BrigadeDry mains shall be avoided, since the lengths ofpipework involved make the delay time required to fillthe pipe in emergency unacceptable.

8.38 Typical requirements for protection includethermal insulation of the main throughout the tunnel withtrace heating 50m in from each portal and at branches tothe hydrants. Outside the tunnel, no thermal protectionshould be necessary where the main is buried in groundat a depth of 1m or more.

8.39 When selecting the most appropriate type ofthermal insulation, the designer needs to considermechanical durability, rot and vermin protection andensure that the material selected shall not give off toxicfumes, if subject to fire.

8.40 Factory applied bitumen lining and bitumen outerwrapping will, in most cases, provide adequateprotection against corrosion of steel pipe. Corrosionprotection shall be applied, on site, to joints, valves andpipeline equipment to ensure continuity of protection.Similar treatment can apply to ductile iron pipe andfittings, with the addition of a polyethylene tubular filmprotective sleeving to BS 6076 where the pipework etc isburied in the ground.

8.41 Section isolating valves, normally at quarterpoints, shall be installed along the fire main within thetunnel for installation and maintenance purposes.

8.42 Automatic air release valves and drain downpoints shall be provided.

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ublic Emergency Roadside Telephones

43 Details of the emergency roadside telephones areven in Chapter 9.

ommunications

44 The emergency services communications systemse detailed in Chapter 9.

scape Routes: Cross-Connecting Passages and Doors

45 Cross passages are installed to assist in firehting and emergency egress/access, in accordance

ith the requirements of Chapter 3. A typical cross-nnecting passage door layout is shown in Figure 8.4

46 Each cross-passage shall be identified by aearly visible number (not shown in Figure 8.4) tosist with location in respect to an incident. The tunnelerating procedures shall clearly define the need to

inimise the risk of people using cross-passages anderging into the path of moving vehicles in theaffected bore. Where there is room not to impede thehicles of the emergency services during an incident,nsideration may be given to the provision ofmountable pedestrian barriers, opposite the doorsly, to prevent users of the cross-passage doors moving

to the live carriageway of the adjacent bore.

47 Cross passages shall be fitted with double-swing,lf-closing doors. Doors shall be a minimum of 914mm

ide and any associated stairway shall be at least12 m wide. Doors shall be of stainless steel, fitted withired glass vision panels, to enable users to be aware oe traffic conditions on the opposite side. The completeor assembly including doors, frames and fittings shall made from materials capable of two hour firesistance. Doors shall be of a good quality and fit suchat smoke does not pass when closed.

48 The opening of a cross passage door leading to ae carriageway shall activate suitable signals to warnivers approaching the tunnel of the possible presence pedestrians in the tunnel roadway.

49 Switches shall be fitted to indicate when doorse opened, they shall be of a type that do not giveurious signals when doors are subject to windovement due to passing traffic.

50 To assist the Fire Brigade, standard connections,ntained in stainless steel connector boxes, as shown in

Figures 8.5 and 8.6, shall be provided through the wallclose by the cross passage doors. A 50mm duct for a

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communications cable shall be provided as well as a fihose connector.

8.51 Fire hose connections shall have 65mminstantaneous couplings. A hand control valve shall beincorporated in the female coupling. The siting of theinlet and outlet shall be adjacent to the cross passagedoor jambs, 200mm to 600mm to the side, and betwee800mm to 1000mm from the verge. The connectionsshall be arranged so that they are effective from eithercarriageway. The female outlet shall always be to the lwhen passing through the cross-passage doors. The inand outlet shall be conspicuously labelled “FIREBRIGADE HOSE INLET” and “FIRE BRIGADEHOSE OUTLET”.

8.52 Recessed connections for breathing apparatus(BA) communications cable shall be provided togetherwith steel ring bolts approximately 80 to 100mm indiameter for use as BA guide line anchorage points, onon each side of the door in each bore and at agreedlocations along the tunnel walls, at a height of 1m abovthe verge.

8.53 The standards for these connections shall beagreed with the Fire Brigade(s) concerned, to ensurecompatibility of equipment.

Smoke Control Panels

8.54 For tunnels with mechanical ventilation, smokecontrol panels, normally located outside both portals oa bore, provide localised control of the ventilation by thFire Brigade. This is discussed in Chapter 5. Themethod of operating the ventilation system for smokecontrol shall be included in the Manual for Police andFire Services described in Chapter 13.

Automatic Fire Extinguishing Systems in Tunnels

8.55 Automatic fire extinguishing systems are notconsidered suitable for the traffic space. Total floodgaseous systems and foam systems are not practicalwhere people are present in vehicles. Water sprinklersystems may cool buoyant smoke causing immediatesmoke logging of the tunnel and producing potentiallyexplosive air/vapour mixes.

Passive Fire Protection

Tunnel Structure

8.56 The effects of fire on the tunnel structure andassociated ducts and shafts shall be carefully assesseaccording to the characteristics of the fire to be taken

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into account. Critical elements shall be identified anddesigned for the circumstances pertaining at individualsites. Additional guidance for tunnel structure (electricalcircuits and equipment, see below) is contained inreference, Fire in Road Tunnels: Protection for civilengineering structures, electrical circuits andequipments: WRA (PIARC) Routes/Roads, No 275, III:1991. The International Tunnelling Association (ITA) iscurrently undertaking further work in this field.

8.57 Depending on the design fire to be resisted,additional fire protection layers to structures may not berequired eg where the structure comprises cast ironsegments or where reinforced concrete with adequatecover is used, as these materials are inherently fireresisting. Some damage may occur in the event of a firewithout causing failure of the structure. Provision ofadditional mesh reinforcement may contain spalls ofreinforced concrete sections, particularly in morevulnerable upper walls and ceilings.

8.58 Where there is exposed structural steelwork inthe tunnel such as at ventilation shafts, two hours fireprotection of the steelwork is required to reduce the riskof collapse. This may be obtained by enclosure insuitable fire resisting materials or by coating/spraymethods.

Cabling

8.59 Low smoke zero halogen (LSOH) insulation andsheathing materials shall be used for all cables inside atunnel in order to minimise the hazards of smoke andtoxic fumes arising from burning cable insulation.Normal cable compounds such as PVC give off fumesand halogen gases which, when combined with moistureform toxic and corrosive acids. Where very short length(less than one metre) of low voltage communicationcables are required, engineering judgement shall be useto assess whether the potential risks are low enough fothe LSOH requirements to be relaxed.

8.60 All cables shall be enclosed in cable ducts. Thewalkway or verge ducts shall be designed to be two houfire resistant against a 2500C temperature, with thecovers in place. Smoke/fire barriers shall be installed atintervals of approximately 50m within each duct and atjunctions to prevent the unrestricted spread of fire orcombustion products.

8.61 The terminating chambers of equipment shallhave a minimum two hours fire resistance and care shabe taken to ensure that the fire resistant characteristicextends over the cable entry into equipment mounted onthe walkway, or verge ducts. If there is any possibility of

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combustible gases permeating unventilated ducts, cabchambers etc suitable provisions or prevention will neeto be made at the detail design stage.

Secondary Cladding

8.62 For tunnel structures provided with a separatesecondary cladding finish secured to a supportframework off of the main structure, fire stops shall beprovided within the void at approximately 30m intervalSee Appendix A.

8.63 Cladding shall be non-combustible and madefrom material that prevents toxic gases, or smoke beingenerated in the event of a tunnel fire. Any materialwhich satisfies the Category 1 compliance criteria forpanelling as given in Table 1 of BS 6853: 1987, may bconsidered. In the absence of any suitable Standard fothe testing of the products of combustion for toxicity,reference may be made to the Naval EngineeringStandard NES 713 Issue 3, March 1985, or latest.

Services Buildings and Plant Rooms

General

8.64 All buildings and ancillary structures shall bezoned and provided with one or more fire alarm systemto a suitable standard. Where such buildings or areasnot manned, automatic fire detectors shall be providedand monitored remotely, both for immediate detectionand location of the fire and for fault detection.

8.65 Means of escape, portable fire extinguishers,hose reels, hydrants, foam inlets and dry risers shall bprovided in buildings and structures in accordance witlocal fire regulations. Portable extinguisher types incluCO2

dry powder, foam, Aqueous Film Forming Foam(AFFF) or water. Suitable equipment shall be providedrelated to the potential risk.

8.66 Fixed fire fighting protection shall be installed toall drainage sumps and plant areas containing electricswitchgear, communications and control equipment angenerator plant.

Halon and Alternative Systems

8.67 The “Montreal Protocol on Substances thatDeplete the Ozone Layer” prohibits the use of Halon fiextinguishing systems in new installations (with very feexceptions) and production of Halons 1211 and 1301has ceased.

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8.68 Recycled halons continue to be available, butonly for use in existing installations employing Halon1301 (the only fire extinguishing Halon with a lowenough toxicity to be considered for this purpose).

8.69 Human exposure to Halon 1301, at aconcentration of 5% by volume, shall be limited to amaximum of 10 minutes. Five per cent concentration issufficient to extinguish most fires. Any undue exposureshall be avoided.

8.70 Effective monitoring, testing and servicingprocedures shall be used to minimise accidental releasof halon. Alternative simulation gases which areenvironmentally acceptable such as SulphurHexafluoride (SF6), or chlorodiflouromethane R22 shallbe used for testing halon systems.

8.71 A number of alternative chemical firesuppressants, claimed to be environmentally acceptabland capable of sustaining life, are available, many ofwhich are based on breathable mixtures of argon andnitrogen. Designers shall evaluate available options,considering performance, environmental and healthissues, availability and Fire Authority approvals, duringthe design stage.

Automatic Total Flooding Carbon Dioxide (CO2)

Systems

8.72 Carbon Dioxide systems are well proven, butrequire stringent safety precautions with regard tolocking off, signs, warnings and operating procedures.The potential hazard is asphyxiation, particularly asCO

2 is heavier than air.

8.73 A total flooding CO2 system comprises banks of

compressed gas storage cylinders with a system of fixedistribution pipework and discharge nozzles, installedover the areas of risk. Discharge shall be controlled froa fire panel operated by detectors, with a warning givenby a sounder distinctive in sound to that of the firealarms. Mechanical control, automatic by fusible link, omanually by pull release, may also be used.

8.74 An electro-mechanical lock-off, consisting of asolenoid operated catch operated by a key switch, whicwill prevent the automatic release of CO2

by theautomatic sensing units, shall be provided in all areaswhich are likely to be occupied (even for short periods)and are protected by total flooding CO

2 systems.

8.75 Complete room sealing is essential for gaseousextinguishers to be effective. Top up facilities shall beprovided for the interim period of repair if a leakagepath occurs.

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8.76 Rooms protected by such systems requireventilation equipment to be provided to clear the gasesfollowing discharge of CO

2 before the room is entered.

Sprinklers and Water Mist Systems

8.77 Sprinkler systems perform three functions; todetect a fire, to sound an audible signal and to contain extinguish the fire. Sprinklers contain and extinguish afire by a cooling action. They have the disadvantage ofcausing thermal shock and water damage to electricalequipment and, because they are automatic may createunacceptable damage if the water supply is not turnedoff once the fire has been extinguished.

8.78 Water mist systems, which generate a fine, densmist of water droplets may also be suitable for someapplications in service buildings, but require carefuldesign to ensure safety with the high operating pressurinvolved.

Drainage Sumps Connected to a Tunnel Carriageway

8.79 Fixed fire fighting protection shall be installed toall such drainage sumps. Sumps shall be provided withhydrocarbon gas and oxygen deficiency detectors to dewith the effects of a hazardous spillage. See alsoChapter 7.

8.80 Closed sumps shall have fixed nitrogen foamsystems, for fire protection or making inert.Additionally, a dry inlet shall be provided for the remoteapplication of foam by the fire brigade.

8.81 Sumps may contain an explosive and/orflammable atmosphere on occasions and electricalequipment shall be provided with a level of protection,see also Chapter 7.

Automatic Foam Systems

8.82 Foam concentrate shall be of the alcoholcompatible Fluoroprotein or AFFF type and shall beused for extinguishing fires in sumps. Foam applicationand expansion rates shall be in accordance with theappropriate standards.

8.83 A foam system may be initiated by detectors,fusible link, or manual release etc. Foam may also bedischarged upon detection of combustible gas.

8.84 Types of system include:

i. Premixed Foam System - this comprises thestorage of foam concentrate, premixed with

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water, and stored in tanks adjacent to the area tobe protected. Foam is ejected under pressureprovided by a bank of CO2 bottles.

i. Foam Generators - these operate by injection offoam concentrate into a water supply via aproportioning device. Water Authority approvalis necessary if a direct connection to a mainswater supply is required.

ii. Nitrogen Foam System - a system usingcompressed nitrogen can be more compact. Theuse of an inert gas has the advantage of making asump inert in the event of a combustibleatmosphere forming.

.85 Where foam is intended to be in place forrotecting a sump for a prolonged period, facilities shalle provided for the injection of additional foam to top up

he foam blanket by the Fire Brigade, as necessary.here such provision is made the designer and TOA

hall ensure that the foam used for the automatic systems compatible with any foam that may be used by theire Brigade.

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Road Tunnel Length/Type Equivalent Ventilation Design Load (MW)

Motorway Urban Major Rural Major B RouteRoute Route

Length > 2000m 50 50 20 20

Length < 2000m 50 20 20 20

Table 8.1 Equivalent Longitudinal Ventilation Design Fire Loads (minimum values)

Vehicle Classification Fire Load (MW)

Car 5

Van 15

Coach/Lorry 20

HGV, fully laden 30 –100

Table 8.2 Vehicle Fire Loads

Open Road Type Injury Accidents Deaths

Motorway 9 ??

Dual Carriageway * 10

Single Carriageway * 11

Urban Roads ** 30

* link rates, well clear of junctions

** lower limit taken

Table 8.3 Injury Accident And Death Rates On The Open Road (per 100 million vehicle kilometerestravelled)

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Specify VentilationDesign Fire Load

Calculate Fire ProtectionDesign Load

Calculate Fire Duration

Calculate Smoke ProductionRate and Smoke Layer Properties

Calculate Fire/Smoke Temperature Profile

Assess Effect of Ventilation onFire Temperature Profile

Fire Quantification Methodology

Assess Drainage Effects onFire Duration

Calculate Fire Size

Assess VentilationEffects on Fire Size

Assess Ventilation and GradientEffect on Smoke Layer Properties

Fire SizeFire Temperature ProfileFire Duration

Figure 8.1

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Specify VentilationDesign Fire Load

Calculate Fire Design Load

Quantify Fire Size,Temperature and Duration

Specify StructuralDesign Criterion

Calculate Heat Transferto Structure

Assess Options for Fire Protection tomeet Structural Design Criterion

VENTILATIONDESIGN,Chapter 5

Procedure for Design ofFire Protection in Road TunnelsFigure 8.2

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Typical Emergency / Distribution PanelFigure 8.3

IlluminatedEmergency Sign Telephone

Calling Lamp

EmergencyTelephone

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Walkway Level

Note: Doorto fire hose cabinetomitted for improved clarity

Comm'sCabinet

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Fire extinguisher Fire extinguisher

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Example Tunnel Cross Connection DoorsFigure 8.4

Edge of running lane

Edge marking (white line)

Kerbs

Face of tunnel lining

Door frame

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Telephone

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Edge of running lane

Fire brigadeconnectorbox

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Micro switches

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HAZARDFAST MOVING TRAFFIC

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BEHIND DOORS

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Detail of Fire Brigade Connectors on Side of Doorways(Section in Plan)

Secondary Lining

Connection Box

Female Coupler

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Partition Wall

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Detail of Fire Brigade Connectors(Section in Elevation)

65 Dia. piping(cast in)

Guideline anchor

Top of plinth

Male coupler

Door

Secondary lining

Connection box

50 Dia. uPVC cableduct (cast in)

Guideline

Top of plinth

Female

Door

Figure 8.6

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Chapter 9Traffic Control, Communications and Information Systems

General

9.1 This Chapter describes the provisions to be mafor the design and authorization of traffic control,communications and information systems for tunnels.Reference to tunnels includes the relevant approach aexit roads coming within the limits of the operatingregime for the tunnel that have been jointly agreedbetween the Design Organisation, the Police TrafficController and authorities responsible for maintenanceand operation.

9.2 Traffic management and communication systemensure the safety of tunnel users and personnel emploin tunnel maintenance and operation. A range ofelectronic equipment is deployed to monitor and controtraffic flow, transmit alarms, alert emergency andbreakdown services and maintain contact between trafcontrollers, tunnel operating authorities and relevantemergency services.

9.3 To provide appropriate levels of safety over thefull range of operating conditions, facilities for trafficmanagement and tunnel communication shall be fullyintegrated with the operation of systems installed tomonitor and control the tunnel environment, see Chapt10. Tunnel systems shall interface with standardcommunication and signalling systems used on theadjoining motorway or other trunk road networks.

9.4 System design will be related to the layout of thtunnel and its safety facilities eg emergency points andescape routes. The structural form of a tunnel willdetermine the space, beyond the traffic gauge, that isavailable for positioning the necessary equipment, seeChapter 2.

Communications for Motorways and Other Networks

9.5 Communication and signalling systems used tomonitor and control traffic for motorways and othertrunk roads shall be of a type approved, in writing,on behalf of the Secretary of State, or appropriateAuthority. In England and Wales, shall be to therequirements of the National MotorwaysCommunication System (NMCS), a computercontrolled network operating signals, telephones andother devices. In Scotland, a system utilising a

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combination of the National Driver Information andControl System (NADICS) and locally distributedcontrol offices shall be used. In Northern Ireland,signs and signals used for traffic control shall meetthe requirements of Traffic Signs Regulations (NI)1997, equipment shall have an approval issued onbehalf of the Department of Environment (NI), adviceon responsibilities/approval for signing/signallingshall be sought from Roads Service Headquarters.

9.6 Monitoring of traffic and other activities isachieved by combinations of closed circuit television(CCTV), CCTV alert and incident detection, andemergency telephones placed at regular, fully referencedintervals. Traffic is controlled by fixed signs, variableand enhanced message signs (VMS, EMS), matrixsignals and portal/lane control signs, according tospecific needs. When hazards arise, variable signalsdisplay appropriate warnings to slow or redirect trafficor warn of lane closures.

Control Centres

9.7 Police Traffic Control Centres (TCC) arenormally directly responsible for all matters concerningtraffic management and the initial response tobreakdowns, accidents and emergency situations thataffect a tunnel road user. Usually, the Police TCC willbe remote from the tunnel and a tunnel will have, inaddition, its own dedicated centre for the management otunnel systems. The latter is usually in a Tunnel ServiceBuilding (TSB) located in close proximity to the tunnel,or it can be at a location remote from the tunnelparticularly if the TSB is unmanned. A TunnelManagement Centre (TMC) is normally responsible fortraffic management involving maintenance operationssuch as temporary signing in accordance with Chapter 8of the Traffic Signs Manual. The TMC may also beparty to all aspects of traffic information communicationand signal control, provided appropriate procedures areagreed with the Police Controller on the understandingthat overall responsibility for initiation and control oftraffic signals remains with the Police.

9.8 Matrix Signals are set by the Police, in ControlOffices, via computer controlled systems. Such systemsautomatically calculate and set additional aspects onadjacent and nearby signals, in order to display a safesequence to the road user. Calculations may be comple

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where there is a high density of signals eg atinterchanges, elevated roads, long cuttings, tunnels orunderpasses or where the sequence passes through PoControl Office boundaries.

General Design Considerations

9.9 The location of equipment shall be designed sothat adequate safe and easy access is provided for themaintenance of all equipment.

9.10 The potential dangers from vehicle andequipment breakdowns and the difficulties of dealingwith emergencies within the confines of a tunnel,together with the problems of access may present thepolice, tunnel operators and emergency services withsevere operational difficulties, all practical andreasonable mitigation measures shall be consideredduring the design stage.

9.11 An integrated approach shall be used whendesigning communication systems, and in particular thecontrol centre equipment. The electrical power systemshall be designed to supply all of the control centrecommunications system requirements. As the systemscarry emergency service requirements they should beprovided with battery back up sufficient to ensure asuninterrupted supply.

9.12 Duplication of equipment at the control centreshall be considered. Typically, equipment working inmain and standby modes is often necessary to ensureoperational availability.

9.13 Of particular importance is the integration ofsystems so that the organisation responsible for day today operation of the tunnel is provided with a clearindication of the overall status of the tunnel operations.A custom-built layout is normally provided for thetraffic control room in the TCC, incorporating controldesks with facilities for dealing with emergency calls,alarms and radio calls, and for viewing traffic in andaround the tunnel by television monitors linked to theCCTV system. Control desk facilities will also includefor activated alarm identification of which emergencytelephone is calling, selection of CCTV camera input fordisplay on a particular monitor and for setting upvariable message signs etc.

9.14 The layout and provision of equipment for theorganisation responsible for the various activities areimportant factors to be agreed with the organisationsconcerned.

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.15 The communications equipment room(s) at theMC and the TCC (separate from the control room)hall be laid out so that maintenance staff can readilyccess the equipment for routine maintenance and repaork. All cables shall be terminated on a clearly labelledistribution frame with unrestricted access. Space within

he communication equipment room shall be allocatedor spares, system documentation, and maintenanceerminals if required.

.16 Full consideration shall be given to the equipmenoom environmental conditions eg temperature, humiditynd dust exclusion, to ensure correct equipmenterformance. Equipment room access security is alsoequired.

.17 For some tunnels, it may be necessary to providedditional equipment rooms and/or out stationedquipment cubicles. These should preferably be locatedutside of the tunnel. Similar design criteria are required

or these but the more hostile and vulnerablenvironment for any cubicles near or within tunnels shale taken into account.

.18 Where VMS, EMS and other signalling isnavoidably required within a tunnel then provision shale made for cabinets to house the signalling equipment

hese can conveniently be located at an Emergencyoint. For such cabinets a local power supply isolation

acility for maintenance purposes shall be provided.dequate facilities shall be made for all necessary powend communications cabling to the signs and signals,

rom power supply points and the main communicationabinets.

.19 Mechanical and electrical failure mode effectsnalysis is required to the relevant British and/oruropean Standards. The analysis shall include allspects of signal, face interlocking, signal interlockingnd signal driver interactions.

able Routes

.20 In relatively short tunnels (less than 1km inength) cable may be run straight through ducts to thequipment within the tunnel (telephone, camera, etc). In

onger tunnels, cable is usually run to a distribution boxhere the cable is terminated and distributed to thedjacent area. Space shall be allocated for such a box,hich shall be readily accessible for maintenanceurposes.

.21 Provision shall be made for routeing the multi-pair copper, fibre optic and associated communicationspower cables through or round a tunnel.

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Communications cables shall not be installed within0.5m of electricity supply cables, other than thosesupply cables associated solely with the communicationsystem.

Facilities in Tunnels

9.22 The following facilities are available fordeployment, according to the tunnel classificationdescribed in Chapter 3:

Telephones - General

9.23 In an emergency such as a vehicle breakdown orfire, tunnel users need to be provided with facilities tocommunicate readily with the appropriate authority.

9.24 Telephones located at emergency points shall beinstalled in such a manner that they can be readilyaccessed and used in safety away from the tunnel traffic

9.25 Emergency telephone installations shall consist othe following items, to be confirmed by the TDSCG:

i. Emergency telephone

ii. Maintenance telephone

iii. Smoke control telephone.

9.26 In addition, telephones shall be provided atTDSCG agreed locations, such as entrances/exits of thetunnel and adjacent laybys or locations where large orhazardous loads require special attention such asinspection or escort.

9.27 All line levels of the telephones shall becompliant with NMCS.

9.28 Telephones shall be installed at a height of 1.1mto the handset centre line, above finished ground level.

9.29 Heavy traffic vibrations, high ambient noiselevels, traffic fumes, as well as the nature of use, dictatethe standards to which the telephones and theirinstallation need to conform. See Chapter 2.

9.30 The adverse effects of the very high noise levelsin the tunnel on the use of telephones shall be minimisedby:

i. Dynamic side tone switching to provide acontrolled level of feedback from the mouth to theear of the user

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. Separate send and receive circuits to optimise thespeech paths to and from the TCC/TSB/TMC.Use of two or four wire circuits to be confirmed.

i. A telephone specially designed to reduce theeffects of background noise eg with a noisecancelling microphone, rather than use ofacoustic hoods.

mergency Telephones

.31 The telephones may be connected to NMCS,hich is to be approved on behalf of the Secretary of

tate) to provide direct links to the TCC. Telephoneshall utilise self diagnostic equipment with automaticult alarms. Lifting a handset shall raise an automaticlarm at the TCC and initiate a local flashing alarm ate point of use.

.32 Emergency telephones shall be able to receivealls from the TCC which, in addition to the normaludible ringing signal, shall initiate a local flashinglarm of the same cadence.

.33 When the telephones are connected to the NMCe responders for interface equipment shall be locatedoth ends of the tunnel, on opposite carriageways, orithin service buildings, unless otherwise agreed.

.34 If more than two responders are required toervice all the telephones within the tunnel andpproaches then they shall be located at both ends of thnnel so that an equal number of telephones is servedom each location/responder.

.35 To provide increased security of coverage withinnnels, alternate telephones shall be served fromsponders at different locations. Adjacent telephones

hall not be served from responders at the same locatior served from the same cable.

.36 Adequate signs within the tunnel shall berovided to allow road users in difficulties to locate anmergency telephone readily. Each telephone andssociated equipment shall be clearly identified withuitably designed signboards clearly signalling that suchlephones are intended for the use of the road user, ane locational reference number of the telephone.

aintenance Telephones

.37 Where required, the maintenance telephonesngineer’s or Service) shall be part of the emergency

oint installations and shall be connected to a Serviceelephone Network (STN).

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9.38 The STN shall link all plant rooms and otheroperational locations relevant to the operation andmaintenance of the tunnel and its various supportfacilities.

9.39 Such telephones may take the form of fulltelephones or jack socket connections.

Smoke Control Telephones

9.40 Where required in addition to the maintenancetelephones, the smoke control telephones shall be parthe emergency point installations and shall connect theuser directly to those in control of the ventilation asidentified and agreed by the TDSCG.

Closed Circuit Television (CCTV)

9.41 Where CCTV is to be provided, cameras shall binstalled inside the tunnel, outside of each portal and othe approaches/exits so as to provide as far as ispractical total, unobscured coverage.

9.42 The Design Organisation shall ensure that thewhole of both tunnel bores and the approach roads, tothe first upstream and downstream junctions or diversipoints, can be viewed from the TCC/TSB/TMC, asrequired. Cameras shall be positioned to ensure that tmaximum effective coverage is achieved with aminimum number of cameras.

9.43 It is appreciated that factors such as alignmentobstructions caused by tunnel equipment, etc mayprevent 100% coverage.

9.44 Cameras inside the tunnel shall be cornicemounted, those outside the tunnel shall be installed onmasts or gantries.

9.45 Potential invasion of privacy shall be mitigatedfor at all cameras sites and precautions taken byelectronic or physical blanking out, or the restriction oflens magnification.

9.46 All cameras shall be provided with pan, tilt andzoom (PTZ), screen wipers, washer bottles andweatherproof housings, as necessary.

9.47 To avoid damaging and safety monitoring hazaeffects from headlight dazzle, to reduce privacy invasioand to make use of red brake-lights as an additionalvisual traffic problem alarm, fixed position camerasshall not face the oncoming traffic. Image processing, used, also requires cameras to face to the rear of traff

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9.48 Provision shall be made for all necessary localcamera cabling and cable junction boxes, which canconveniently be housed at emergency points.

9.49 The design shall identify requirements forinterfaces with the traffic control system, whereappropriate (ie. NMCS2).

9.50 CCTV controllers shall be located at intervalswithin tunnels, and in positions that do not impede theaccess ways.

9.51 Consideration shall be given to providingmonitors that can sequentially scan the cameras on aregular basis. The technique is well proven and issatisfactory for routine operations.

CCTV Alert

9.52 CCTV Alert is a technique whereby traffic flowdata is collected by means of vehicle detectors andanalyzed using the HIOCC (High Incident Occupancy)algorithm. A pre-selected camera (or cameras) isfocused on the area which caused the HIOCC threshoto be exceeded. Perturbations in traffic flow, possiblycaused by a stranded vehicle, are then quickly broughthe attention of the TCC. The need for CCTV Alert shabe discussed by the TDSCG and if so recommendedshall be considered by the Overseeing Organisation foconfirmation of its use.

9.53 The recommended concentration of CCTVcameras in tunnels is such that it may be uneconomic provide video transmission circuits back to the TCC/TSB/TMC for all. Additionally, TCC accommodationrequirements would normally prohibit the provision of amonitor permanently allocated to each camera.

9.54 When CCTV Alert is provided, the fire point andcross connection passage door alarms shall be linkedinto the CCTV Alert system in order to focus a cameraon the area where the alarm originated or where thepedestrians may be situated. This enables the TCC toquickly assess the situation and take any necessarysafety measures required.

Fixed Signs, Variable Message Signs and Signals

9.55 Signs and signals used for traffic control shallmeet the requirements of the Traffic Signs Regulationsand General Directions and approval on behalf of theSecretary of State. Examples of tunnel signing are givin Figures 9.1 and 9.2.

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9.56 Responsibilities/approval for signing/signalling iEngland (items i. to iv.) are as follows:

i. Static signs - Driver Information and TrafficManagement (DITM), Department ofEnvironment, Transport and the Regions

ii. Variable Message (EMS & FT(fixed text)MS) -DITM and Highways Agency

iii. Signalling - Highways Agency (who will liaisewith DITM)

iv. Sign lighting (if required) - Highways Agency

v. Approval may also be granted by the OverseeinOrganisations, elsewhere.

9.57 Conventional motorway and trunk roadcommunication systems, such as NMCS2, are notdesigned nor maintained as Safety Critical or SafetyRelated systems. Safety Critical and Safety Relatedsystems shall be partitioned such that the Safety Criticor Safety Related element is clearly separated from thNMCS system. Partitioning systems in this way shouldalso minimise costs.

Emergency Exit Signs

9.58 Signing of escape routes for road users in theevent of an emergency shall be provided. At eachemergency point within the tunnel it is desirable toinclude the distance to the nearest emergency exit in edirection.

9.59 On uncontrolled escape routes permanentlyilluminated signs shall be used.

9.60 On controlled escape routes Variable MessageSigns or signs only legible when illuminated shall beused. These signs shall have a facility for switch on onwhen it has been verified that the route is safe to beused.

9.61 Special consideration shall be given to themaintenance and operation of Safety Critical Systemsensure the safety of road users and personnel ismaintained throughout the life of the system.

Variable Message Signing

9.62 Variable Message Signs (VMS) consist of eitheFixed Text Message Signs (FTMS) or EnhancedMessage Signs (EMS). Both of these sign types may bused to provide traffic management instructions forpredictable situations which affect traffic flow and tosign diversionary routes. For example, VMS displays

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may be appropriate where it is necessary to regulatetraffic in the event of routine maintenance or emergenctunnel closures.

9.63 FTMSs and EMSs may also be used to enhancsignalling during emergencies. Such VMS shall becontrolled and monitored from the TCC.

9.64 Where variable message signs and signals areused for maintenance procedures, FTMS type signs sbe employed, possibly in conjunction with EMS typesigns.

9.65 When considering VMS sites, the visual criteriafor siting normal signs shall be applied and they shallcomply with the relevant provisions of the Traffic SignsRegulations.

9.66 Where VMS units are required to have flashingamber lanterns, they shall be synchronised between aVMS units viewable from one location, and with anyflashing lanterns associated with motorway matrix typesignals viewable, within 100m, at the same time

9.67 A facility for local manual control of VMSs shallbe provided, but with suitable safeguards to ensureavoidance of the potential for displays to conflict withthe remotely controlled system requirements.

Portal/Lane Control Signals

9.68 Considerations shall be given to providing staticadvice signs describing what portal/lane control signsmean, as detailed in the Traffic Signs Regulations.

9.69 Signals to be sited in the tunnel shall be locatedcentrally over each lane. Care shall be taken to ensuresignal visibility and that signals and equipment do notencroach within the traffic gauge.

9.70 In circumstances where portal lane controlsignals cannot be mounted centrally above the runninglanes care shall be exercised to ensure that there is aunambiguous relationship between the displayed aspeand the lanes they apply to.

9.71 Matrix type signals should generally be provide(details are given in Schedule 6 of the Traffic SignsRegulations).

9.72 Portal/lane controls signals, capable of displayilane closed cross (red), lane open arrow (green) andblank (wig-wag), shall be provided where it is necessato separately control traffic in each running lane and toemploy contraflow working during maintenance etc, asthese type of signs can be safety interlocked.

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9.73 If contraflow is to be operated, then signals shallbe mounted at the entrance and exit of each bore alongwith loop detectors. Lane control signals within thetunnel should be mounted back to back.

9.74 Provisions for signs and signals shall beaccording to the type of tunnel:

i. All tunnels shall be equipped with portal/lanecontrols signals to enforce closures. SupportingVMS/EMS may be provided at the tunnel portalsto provide the road user with informationexplaining the reason for any closure egTUNNEL CLOSED with relevant textACCIDENT, FIRE, TRAFFIC FUMES etc

ii. For normal traffic conditions, two way and alldual carriageway and motorway tunnels shallhave lane control signals mounted centrally abovthe running lanes within the tunnel

iii. For dual carriageway and motorway tunnelsgantry mounted signals shall be providedupstream of the tunnel, before the last divergencepoint, to warn that the tunnel is restricted orclosed (ie the portal signals are in use) andprovide the road user with the opportunity to usea signed alterative route.

iv. Single carriageway tunnels shall be provided withupstream (lead in) signals to warn motorists as(iii).

9.75 For two way tunnels, care shall be taken insigning to discourage traffic from entering the tunnel onthe right hand side of the road.

Display Requirements

9.76 Consideration shall be given to provide for thealternative of not displaying the green arrow, on portal/lane control signals, but showing blank instead.

Face Interlocking

9.77 All VMS signs and signals potentially capable ofdisplaying conflicting information shall be interlockedby hardware, software or a combination of both.

9.78 Portal/lane control signals shall be hardwareinterlocked on site so as to ensure that lane open arrowcannot be displayed simultaneously on both forward an

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otorway Matrix Signals

.79 Motorway tunnels which require overhead laneignalling to be used regularly for contraflow, or wherehe approaches to tunnels will be subject to restrictedccess shall be provided with motorway matrix signals

n place of the wig-wag type signal.

.80 The normal rules for the provision of signals onotorways apply to tunnels and their approach roads.ecause alignments of tunnels and their approach roaay differ from open motorways, the Designrganisation shall ensure that the indicator legends an

heir flashing lanterns are legible at 300m and 500m,espectively. Signal siting shall also provide continuouisibility over a 500m range.

IDAS

.81 For motorway tunnels Motorway Incidentetection and Automatic Signal setting (MIDAS) maye required. The system processes data from vehicleetectors and applies HIOCC algorithms toutomatically set speed restriction signals on motorwaatrix signs. MIDAS may also be used to automaticalisplay messages on VMS signs.

.82 MIDAS shall be provided in the tunnel and onhe approach roads as far as the first upstream junctior diversion point or as far as queues may be expecte

orm, with the intention of protecting, from collision,ehicles in the tunnel, at the entrance/exit of the tunnend the rear end of traffic queues.

.83 The Overseeing Organisation shall be consulteegarding the deployment of MIDAS at non-motorwayunnels.

raffic Monitoring

utomatic Traffic Monitoring Vehicle Detection

.84 A system shall be provided to detect vehiclestopped in a tunnel so that CCTV camera(s) canutomatically view that area before an emergency

elephone conversation.

.85 Vehicle detection loops may be provided withinhe tunnel and beyond the exit of the tunnel for 100m.pacing of the loops is usually at 50m intervals. Alleather laser scanner types perform similar functions

and being gantry mounted do not involve disruptions tothe carriageway surface. Both systems are able to beused within vehicle classification systems at toll boothsetc.

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9.86 Above road detection systems (infra red,microwave and CCTV image processing) may be used.

Vehicle Counting

9.87 Vehicle counting shall be achieved by theinstallation of (2N-2) vehicle detection loop arrays in thecarriageway where N = Number of lanes including anyhard shoulder.

Vehicle Measuring

9.88 The need for provision of vehicle measuringequipment will be decided by the OverseeingOrganisation.

9.89 Measuring equipment shall be capable ofproviding:

i. A continuous count of the number of vehicles perhour in each lane in each of the following twocategories:

a) HGVs

b) Other vehicles

ii. A continuous count of the total number ofvehicles per hour in each direction, classified inspeed bands.

Traffic Census Equipment

9.90 The need for provision of traffic censusequipment will be decided by the OverseeingOrganisation. The location and numbers of traffic censussites to be provided shall be in accordance with therequirements of the Overseeing Organisation.

Overheight Vehicle Detection

9.91 Provision of over height vehicle detection is onlyrequired for tunnels whose headroom clearances do notmeet TD 27 (DMRB 6.1.2) and for limited facilitytunnels.

Toll Collection

9.92 The need for provision of toll collectionequipment will be decided by the OverseeingOrganisation.

Radio Rebroadcast Systems

9.93 Tunnels shall be provided with a means ofmaintaining radio communication with emergency

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hicles, emergency personnel and maintenance staff.nsideration may be given to digital trunked radio

stems to provide data as well as speech facilities,ere justified.

stem Requirements

4 All radio transmission systems within a tunnelquire approval of the Department of Trade andustry or, in the case of Home Office approvedergency services, shall comply with Home Officegulations.

5 Radio systems to be provided in new tunnels sha given priority in the order of Police, Fire Brigade,bulance Service, Tunnel Operating Authority ander services.

6 All radio operating Authorities are required totain their own licences for the use of the equipment.

7 Care shall be taken in the siting of any form ofrial within a tunnel to ensure good radio coverage andoid any interference with, or from, any other radio ornel equipment provided. Where more than one

diating cable is to be installed into one tunnel bore,n provision shall be made for eliminating or

nimising any interference between the cables, or anyer susceptible devices. Radio cable lengths into thenel and to any outside aerials shall be minimised.

8 Where ‘off air’ rebroadcasting systems are to beed, provision shall be made for external aerials inations that permit effective communication. Activeuipment shall be installed in a position that maximises ability to receive radio signals ‘off air’, and provideslear path and minimum distance for the feeder cablennecting it with the radiating cable.

9 At both the design and commissioning stages,verage performance shall be considered, to minimisey dual path propagation effects, from normal ‘off air’nals and signals from the radiating cable.

00 Any Overseeing Organisation contribution to theovision of the radio rebroadcast facilities for theergency services and Tunnel Operating Authority

all be agreed at an early stage of the tunnel design.

stem Performance

01 The performance of the radio rebroadcastuipment shall provide clear and intelligible receptionthe Police, Fire, Ambulance, Tunnel Operatingthorities, and Breakdown/Recovery Services mobiles

hand portable receivers.

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Chapter 9Traffic Control, Communications and Information Systems

9.102 For existing tunnels, it may be required to extendcoverage of emergency and maintenance servicesthroughout the tunnel. A general review may be found iTRRL Contractor Report 41, ‘Planning and designconsiderations for Road Tunnels: The Influence ofOperation and Maintenance’, in particular Table 10.

Police

9.103 Normally the Overseeing Organisation willprovide to the Police the radiating facility, some spacefor a rack of electronic equipment, a power supply and site for an external antenna. The Police, either directly through the Home Office, shall provide, install andmaintain the electronics. Frequencies used are in theUHF and VHF bands and the Home Office shall beconsulted for details.

Fire Brigade

9.104 The same situation as for the Police can apply,although the Overseeing Organisation may provide theentire package as the Fire Brigade take the view that thOverseeing Organisation should provide and fund anyequipment necessary for fire protection.

Ambulance Service

9.105 Normally the Overseeing Organisation willprovide all equipment to facilitate one VHF channelthroughout the tunnel, ie vehicle to base. In addition, thAmbulance Service will provide a link between medicalemergency teams working at the scene of an incident athe hospitals who would receive any injured.

Tunnel Operating Authority

9.106 Provision by the Overseeing Organisation of onespeech channel for use by the Tunnel OperatingAuthority in their normal work and when assisting theemergency services can normally be justified.

Broadcasting Radio and Mobile Telephones

9.107 When a road user enters a tunnel, the car radioand mobile phone will cease to function effectively. Anadditional re-broadcast system could be installed by theservice provider to maintain continuity of their service.Normally the Overseeing Organisation will not permitthe use of a road tunnel by third parties who may wishto have their networks carried through the tunnel. A re-broadcast system may be acceptable provided it does ninterfere with, or degrade, the emergency and operationfacilities described. The rebroadcasting company wouldthen be required to finance its installation andmaintenance. See Chapter 2.

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.108 The Overseeing Organisation shall be consulteegarding the issuing of any licences to the broadcastompanies for any service provision in a road tunnel.

.109 Any arrangements regarding access foraintenance shall be agreed with the Overseeingrganisation at an early stage of design.

ommunications Infrastructure and Cabling

.110 Communications infrastructure used in motorwunnels shall conform, as closely as possible, to thetandards and Specifications for NMCS.

.111 Communications infrastructure used in non-otorway tunnels may be to a lower level of provisionut shall use components which conform topecifications for NMCS.

.112 Where the facilities provided in a non-motorwaunnel are monitored and/or controlled from a motorwolice control office, the communications infrastructurehall comply with Standards and Specifications forMCS.

.113 Extra capacity, as required by the Overseeingrganisation, for the main communications cables shae provided to allow for future expansion.

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Chapter 9Traffic Control, Communications and Information Systems

TUNNEL CLOSEDALL TRAFFICFOLLOW LLL

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Central Reserve Matrix Signal

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Chapter 10Plant Monitoring and Control

10. PLANT MONITORING AND CONTROL

General

10.1 Tunnel lighting, ventilation, drainage, securitysystems etc benefit from programmable logic controller(PLC) based supervisory control and data acquisition(SCADA) facilities which process information receivedfrom instrumentation located in or close to the tunneland determine the optimum mode of operation. Correctprogramming will ensure that the specified performancerequirements and safety criteria are met, whilst avoidingunnecessary use of equipment and consequent wastageof energy etc. Under normal circumstances operationwill be fully automatic, with a facility for manualoverride by the Tunnel Operating Authority (TOA)operator in emergencies or for maintenance. Figures10.1, 10.2 and 10.3 show typical systems and networks.Figure 10.3 is based on NMCS2 (National MotorwayCommunication System 2) system architecture.

10.2 To enable the operator to be aware of any failuresof plant or equipment and to determine the extent of suchproblems, the status, consumption and performance ofprincipal items of mechanical and electrical plant iscontinuously monitored. Alarm signals are generated bycertain designated events and upon failure of individualitems of plant or complete systems and are gradedaccording to the urgency of response required.Monitoring of performance, plant condition and energyconsumption allows the operator to predict maintenancerequirements and future operating costs.

10.3 Operator terminals to receive the output data andsignals may be provided locally at the tunnel, and atremote locations via suitable data links. Terminals maybe programmed for mimic displays to provide completeor partial control and monitoring facilities, with theopportunity to cover a number of tunnels from a singlelocation. Interfaces with other systems, eg CCTV or theTunnel Traffic Controller (TTC), may be provided toprovide additional inputs and outputs for control of plantand to initiate automatic closure of the tunnel undercertain emergency conditions.

10.4 The TTC is closely linked to the SCADA systemand has the capability to interrogate the SCADA systemfor information relevant to its traffic control function. Asa result of traffic conditions, the TTC can make requestsfor operation of plant eg increase lighting, switch onfans etc through the SCADA system. An over-ride maybe necessary eg to initiate emergency procedures.

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stem Architecture

.5 For the automatic monitoring and control of thennel environment, a typical system should consist ofe following elements:

Central SCADA monitoring equipment,consisting of dual processors (on-line and hotstandby), together with watchdog link, statusindicator panel, interface equipment andsupporting hardware. A service engineer’sterminal comprising VDUs (CRT or touch screentype), keyboards, mice and printer shall beprovided, adjacent to the central processor, formaintenance and on-line testing purposes. TwoVDU and keyboard sets allow simultaneousviewing of system overview and detail pages.SCADA software shall provide the requireddegree of supervision and control whilstmaintaining a high degree of clarity and userfriendliness.

One or more local or remote terminals for use byTOA and Traffic Control Centre (TCC) staff,located as determined by operationalrequirements. Each terminal shall be equipped toreceive alarm and alert messages and to providemonitoring and control facilities as appropriate.It is normal for one such terminal to be located atthe Tunnel Services Building for use duringmaintenance activities and in emergencies, withadditional remote terminals at the TOAheadquarters and the TCC. These terminals arecommonly based on a PC with keyboard, mouseand printers.

Two printers, as follows:

a. An event log printer to provide a hard copy ofall events and commands issued, capable ofuse as a legal record if required

b. A service engineer’s printer for producing logsand reports as required by maintenance staff.

PLC based outstations at strategic locationsthroughout the tunnel installations, linked to eachother and to the central processor or monitoringequipment. Outstations will receiveenvironmental and performance data from

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instrumentation and monitoring equipment andgenerate control signals for switching lighting,ventilation fans, drainage pumps etc, as well asalarm and event data. Algorithms for lighting andventilation etc control will generally beprogrammed into the appropriate PLCoutstations, so that only data relating to alarmand monitoring signals and commands forupdating set points or for overriding automaticcontrols need to pass between the outstations andthe central processors.

v. Instrumentation for control of ventilation,positioned at suitable points within the tunnel tomeasure tunnel air velocity, external wind speedand direction, concentrations of carbonmonoxide, nitrogen dioxide (if required) andobscuration. See Chapter 5.

vi. Suitably mounted photometers to monitor lightconditions at the tunnel portals and thresholdzones. See Chapter 6.

vii. Water level sensors, oxygen depletion andhydrocarbon sensors for control of drainagepumping plant.

viii. Door switches and similar devices for statusinformation and alarm purposes.

Operational Aspects

10.6 To prevent system faults from causing adeterioration of the monitoring functionality, the systemshall be designed with a high degree of security orredundancy. Hot standby with auto-changeover systemsare required at unmanned tunnels and may also beappropriate when tunnels are manned.

10.7 Careful consideration shall be given to theeffects of fire or power failure on the security of thesystem and their mitigation eg the manual dischargeof foam systems or the switching of standby pumps. Itis important to undertake hazard analysis and riskassessments in line with the operating proceduresadopted.

10.8 The design of the system software andfirmware shall only permit off line softwareamendments, but shall allow control thresholds forplant and equipment to be adjusted on line. Passwordprotection shall be provided to restrict access to thesefacilities.

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0.9 Full system documentation including Operatingnd Maintenance manuals shall be provided. Seehapter l 3.

nvironment, Design Life

0.10 All equipment supplied shall be fit for purpose,uilt to withstand the rigours of the specific tunnelnvironment and shall comply with all relevanttandards. All components shall have a design life of aast ten years and shall be compatible with anyssociated electrical or mechanical plant.

ealth and Safety

0.11 Safety requirements for all programmablelectronic systems in safety critical applications muste satisfied. Any non-compliance shall be brought toe attention of the Design Organisation forsolution.

ystem Safety

0.12 All systems and control items shall be designeduch that any failure in the instrumentation or controlystem shall cause all associated plant and equipment go into, or remain in, a safe state.

0.13 Safety of any systems shall be agreed with theOA.

0.14 All equipment located within any hazardousrea shall be suitable to be certified as intrinsicallyafe or explosion proof by the appropriate authoritiesnd be clearly labelled as such.

ninterruptible Power Supply

0.15 An Uninterruptible Power Supply (UPS) shalle provided for PLCs and the SCADA monitor, toaintain monitoring of the plant when the mainower supply fails. Any associated field instrumentsat are required in monitoring the plant may also be

onnected to the UPS. See Chapter 11.

0.16 The UPS shall provide the SCADA monitor ands peripheral equipment with electrical power ofufficient quality to prevent malfunctions from voltageansients and other mains borne disturbances. Powerilures shall be logged as an alarm condition andmediately reported on the SCADA monitor.

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Plant Monitoring

10.17 To ensure that an appropriate response ismade to every fault or emergency situation it isimportant that the TOA has access to the operationalstatus of all principal items of tunnel equipment at alltimes and is alerted to any circumstances requiringspeedy action.

10.18 Typical parameters for monitoring include:

i. Plant status, eg RUNNING/STOPPED/OUT OFSERVICE/FAULT

ii. Operating state, eg HIGH/LOW, OPEN/CLOSED

iii. Hours run, energy consumed

iv. Control availability, eg LOCAL/REMOTE/OFF/AUTOMATIC

v. Lighting and ventilation levels.

10.19 Digital and analogue monitoring circuits shall beindependent of plant control or power circuits, withvolt-free on-off or changeover contacts being providedon the equipment as appropriate for interfaces withPLCs. Analogue circuits shall be suitable for 4 to 20mAoperation. Where necessary, safety isolation shall beprovided, eg by the use of optical couplers, orequivalent. Optical couplers allow different circuits to bconnected together but to remain isolated in operation.

Alarm Classification

10.20 Depending on the immediacy of the actionrequired, alarm signals from the monitoring systems wiusually be classified as follows:

i. Alarm signals classed as ‘URGENT’ include allevents or circumstances which involve an actualor potential hazard requiring immediate action.They may also include those which may lead tosevere disruption or which indicate a breach ofsecurity. These alarms are usually presentedaudibly and visually.

ii. Alarms classed as ‘ALERT’ do not requireimmediate action but will need to be assessed toestablish when investigative or remedial actionwill need to be taken. Further sub-classificationmay be desirable, eg to separate items which cabe left for a week from those which should beattended to the next day,

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iii. ‘RECORD’ alarms include such things as plantswitching events and the entry and exit ofpersonnel attending the Services Building.Although these require no action, they provide ahistorical record useful for fault investigation.

10.21 Software shall allow faults and alarms receivedto be acknowledged in any order. This allows the TOAto prioritise and quicken any response. All fault, alarmand event messages received from the monitoringequipment shall be stored magnetically for futurereference and analysis. Urgent messages shall be prinon the system printer.

10.22 The system software shall allowacknowledgement of faults in the order received, toenable the TOA to decide more easily on the order ofpriority.

10.23 Procedures for handling, storage anddown-loading of fault, alarm and event data shall bedetermined according to local requirements. Long termstorage of data should be kept to a minimum. A suitablsoftware search engine shall be provided to assist inassessment and analysis of fault records.

Plant Control

10.24 Except under emergency and maintenanceconditions, the operation of the plant shall normally becontrolled automatically by the PLC-based systemsreceiving control signals from the various monitors anddetectors in the tunnel.

10.25 By use of information derived from sensors andmonitors and other data sources automatic control of tfollowing shall be provided:

i. Lighting levels in the tunnel - switching on andoff successive stages of tunnel lighting to obtainthe correct graduation of light intensity. SeeChapter 6.

ii. Tunnel ventilation (where required) - control ofthe speed or number of fans in operation and thedirections of air flow in the tunnel to supply freshair, disperse exhaust fumes and any fire smoke maintain a safe and acceptable air quality in allparts of the tunnel. See section on SCADA andChapter 5.

iii. Pumping (where required) - because pumpingstations are usually localised, control systemswould normally serve individual sumps eg toswitch on pumps when the water level in the

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tunnel sumps exceeds a preset limit. Connectionto the SCADA system shall be for monitoring oroverride purposes only. See Chapter 7.

iv. Standby or backup equipment - in most cases,local control systems will automatically detectfailures of duty plant and switch to standby orbackup facilities. Connections to the SCADAsystem shall be for monitoring or overridepurposes only.

Programmable Logic Controllers (PLC’s)

10.26 The key functions of the PLC are:

i. Control of plant.

ii. Plant status monitoring (including alarms).

iii. Operator interface.

10.27 PLCs shall directly handle all inputs (egequipment status information, alarms, environmentaldata.) and all control outputs. They shall carry out allcontrol algorithms, sequence control functions and datagathering. It shall not be possible for the SCADAmonitor to control plant and equipment directly.

10.28 PLCs shall continuously monitor their ownoperation and report faults to the operator. All items ofplant affected by a fault condition shall be controlled tomove to a safe condition and any further changeinhibited until the fault has been cleared or an overridecommand is issued by an operator.

10.29 Each PLC shall have the following operationalfeatures:

i. Self-check on power-up of the PLC. Onsuccessful completion, the PLC will revert to thefully automatic mode.

ii. Automatic operation. This is the normaloperating state under which all PLCs and links tthe SCADA monitor will be active. In the eventof failure of any communications link, all PLCsshall continue functioning independently, usingeither the latest remote information, or defaultvalues as appropriate. The PLC may also berequired to store some historical data locally forlater transmission to the SCADA system.

iii. Manual operation, under which selected plantitems are placed under local manual control. Allsuch operations shall be the responsibility of theTOA.

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iv. Software editing facilities. Access to thesefacilities shall not be available to the operator.

v. Operator interface - each PLC shall be providedwith an interface for a portable terminal for useduring commissioning, testing, maintenance,program changing and editing.

vi. A printer shall not be permanently installed to aPLC.

vii. Safety and security requirements - passwordprotection shall be provided for all non-routineoperator instructions.

Location

10.30 Generally, each PLC shall be located close to tassociated plant or control item. For convenience, alimited number of non-related alarm sensors egemergency call point may use a PLC as their interface

SCADA (Supervisory Control And Data Acquisition)Systems

10.31 All executive and systems software shall beproprietary packages, fully proven for the intendedapplication. A SCADA specification is required whichsupports both outline and detailed requirements andfrom which the functional specification can be written.The SCADA system should provide 3 levels of control:

i. Fully automatic: driven by environmentalmonitoring and/or traffic level data

ii. Remote manual over-ride: from tunnel controlcentre

iii. Local manual control: in case of SCADA failureor for maintenance or test purposes.

10.32 A SCADA system provides a useful platform foentering, storing and accessing information relating totunnel events, costs and other relevant data as requireby BD53 (DMRB 3.1.6) The SCADA system shall becapable of use for this purpose.

10.33 A primary objective of the SCADA system is toensure a safe environment for tunnel users under a wivariety of operating conditions. For example, functionsfor ventilation include:

i. Operating tunnel plant automatically andefficiently, including the rapid clearance of airpollution

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ii. Providing a continuous plant monitoring facility,with alarms for abnormal conditions

iii. Providing operators with clear information ontunnel plant status

iv. Facilitating the manual operation of ventilationplant, under pre-determined conditions, for smokcontrol in a fire emergency and for maintenancework

v. Providing an interface to the traffic controlsystem for automatic signal setting in the event failure of any key plant.

10.34 The SCADA monitor shall be located in a tunneservices building, with facilities for local and remoteterminals.

Privileges and Modes

10.35 Privilege levels - there may be a number of usegroups with access to common data, but not able toaccess each others’ privileged information. Theminimum user groups to be provided for, include:

i. TOA/Maintaining Agent (Local Authority)

ii. Term Maintenance Contractor (Service Enginee

iii. Police

iv. TTC.

10.36 System user access levels (in order) to suitoperational needs could include:

i. Monitoring only (operator CANNOT issuecommands)

ii. Control (operator CAN issue commands)

iii. Configuration/editing/engineering (by ServiceEngineer)

iv. Operating system (from maintenance terminaland under off-line, controlled and testedconditions only).

10.37 To prevent unauthorised use if left unattended,access levels at any work station shall automaticallyrevert, in a safe manner, to the lowest level at apredetermined time after the last key stroke entered.

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Data Logging, Alarm Reports

10.38 All data logging, alarm reporting etc shall becarried out by a SCADA system capable of producingsite specific printed reports, on demand, at the TOA HQand TCC. The reports shall typically contain thefollowing:

For operation and maintenance:

i. Daily log of events

ii. Daily fault log

iii. Daily log of outstanding faults

iv. Monthly log of events

v. Monthly fault log.

For planning and monitoring:

i. Energy usage

ii. Plant running hours

iii. Air quality versus time

iv. Lighting and fan stages versus time

v. Weather data (eg wind speed, temperature,daylight illuminance).

10.39 The memory capacity of the system shall besufficient for storing records of all events over a threemonth period without loss.

Link from SCADA to Tunnel Traffic Controller (TTC)

10.40 Should it be required, the SCADA system shallassist the TTC in its traffic control and managementfunctions, by making available its plant andenvironmental data to the TTC. The TTC shall be ableto access the SCADA system to obtain whatever data isneeded for the requirements of a specific tunnel location.

10.41 The TTC shall also collate traffic flow data. SeeChapter 9.

10.42 Data may be available to the operator, via theSCADA system, through the NMCS2 Control OfficeBase System (COBS) Tunnel Subsystem or via the TTCin its stand alone mode. Where a tunnel is not equippedwith an NMCS2 system a TTC shall be used for thispurpose.

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0.43 It is important to minimise the energyemands of a tunnel and a significant contribution isequired through operating any ventilation fansccording to traffic flow. Fans shall start to clearehicle pollution as its concentration begins to rise,hus reducing the need to run fans at full power tolear high concentrations of pollutants.

0.44 Although traffic flow and speed data is notormally available to the SCADA system via the TTC

here could be significant benefits in arranging for theTC to assist the SCADA system to refine control

unctioning, for example by early prediction ofentilation needs from traffic data. A case shall be my the Design Organisation for agreement andonfirmation by the Overseeing Organisation.

0.45 TTC shall comply with the requirement of Safentegrity Level SIL 3 (as defined in Internationallectrotechnical Committee IEC 16508).

0.46 Communication between the SCADA system ahe TTC shall be controlled in an orderly fashion usinroven protocol. The protocol shall ensure all

ransmissions are received error free and without loshe preferred protocol is RS 485 Modbus Plus.essage content between systems shall be tightly

efined.

ower Supplies to Transmitters

0.47 Power supplies for field-mounted transmittershall be routed via the appropriate local control panend any associated PLC. A two-wire system where

ransmitters receive power from the signal circuit isreferred.

ransmission

0.48 Adequate provision shall be made for the secund high speed transmission of all necessary dataetween plant, equipment rooms, control offices,aintenance depots and all other locations associateith the tunnel. The requirement may require duplicaf essential equipment and provision of alternative

ransmission routes.

0.49 Systems shall incorporate modems for longistance data transmission and provide standard datonnectors (ports) for data transmission to local storaevices.

0.50 Data transfers shall take place at predeterminntervals and also whenever demanded by the operat

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Inspections

10.51 Daily visual inspections of the general conditionof the tunnel and all of its equipment together with thecomputer records of continuously monitored equipmentshall be undertaken to disclose the majority of faults.More detailed tests, inspections and data analysis shallbe carried out at regular intervals for diagnosticpurposes. See Chapter 14.

10.52 The SCADA system shall be regularly inspected.

10.53 The intervals for detailed examinations depend onthe operational circumstances and equipment provisionsof a particular tunnel. The SCADA system shall promptand remind the TOA when such inspections are due.

10.54 Inspection observations shall be recorded in aclear and simple a manner on forms designed forcomputer encoding into the SCADA system. To assist aninspector in identifying defects and remedial actions, theSCADA system shall present inspection results on aVDU and/or printer in a form which allows readycomparison with past data.

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10/7

CCTV Monitorand Controller

CCTV CameraController

Computer Terminal and Printer

Video MatrixController

Maintenance Unit

Radio orLandline CCTV

Transmission

Tunnel Control Room

CCTV CameraController

Video MatrixController

SCADA ComputerTerminal

and Printer

Surface Junction

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Inductive Loop Vehicle Detectorsfor UTC

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Tunnel ZoneEast and West

TunnelApproaches

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Video to PCC

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MaintenanceInterface

VariousInputs

IntruderAlarms

HosereelDoorsTelephone

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Legend

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11. ELECTRICAL POWER SUPPLY ANDDISTRIBUTION

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11.1 This Chapter describes the provision to be madfor the supply and distribution of electrical power for thtunnel equipment and services installed to provide safeconditions for the full range of operational requirementincluding emergencies. Requirements for earthing andcircuit breakers are important in reducing the risk ofelectrical fire.

11.2 Power is normally received at high voltage,typically 11kV, and is distributed to one or moresubstations along the line of the tunnel, where it istransformed down to 400 volts for final distribution toplant and equipment throughout the tunnel systems, vilow voltage main switchboard, which contains controland protection equipment for the numerous circuits.

11.3 Incoming supplies and key items of equipmentsuch as transformers and main distribution cables arefrequently duplicated, and appropriately sized so that ione is out of service, either because of a fault or formaintenance, service can be maintained via the other as long as necessary.

11.4 To maintain supplies to essential equipment in tevent of failure of the incoming supplies, standby poweis provided. This may take the form of uninterruptiblepower supply (UPS) equipment, which uses batterypower to maintain supplies without a break to connecteequipment for a limited period of time, or one or morediesel powered standby generators which will startautomatically when a mains failure is detected and runfor as long as fuel is available or until mains power isrestored. In the latter case, a limited amount of UPSprovision is needed to cover the short period required fthe standby generator to start and run up to speed, analso for the possibility of a failure to start. A stand-bygenerator will not normally be required, but may benecessary eg where there are essential loads, such aspumping, which exceed the practical capacity of theUPS or tunnel closure due to prolonged lightingreduction is not acceptable.

11.5 The provision of duplicate and standbyequipment can be very expensive in its own right andalso in terms of space requirements. It is important toestablish at a very early stage in the tunnel designexactly what level of security is required, and to balancthe cost of additional facilities against the consequenceof loss of supply eg tunnel closure.

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11.6 A wide range of electrical equipment is installedwithin a tunnel to keep the tunnel safe for road users.The main equipment comprises 11kV and 400Vswitchgear, transformers, distribution boards, fans,pumps, luminaires and associated equipment supporteby stand-by supplies. Most tunnels will use two sub-stations but in long tunnels 3 or 4 sub-stations may beneeded for adequate supply distribution.

Supply Requirements

11.7 Requirement for electricity shall be assessed foreach main area of demand (lighting, ventilation,pumping and the remainder of the installation), todetermine the total connected load in kVA and the likelymaximum demand. This will enable the supply capacityand the ratings of the plant (transformers, switchgearand cabling) to be established. Electricity supplyorganisations shall be consulted at the design stage abthe estimated installed load for all tunnel electricalequipment (lighting, pumps, fans etc). Information fordiscussion shall include sufficient predicted loadprofiles, plotted against time over typical 24 hourperiods and any seasonal variations as well as peakdemands during an emergency. This will then allow themost appropriate tariff of energy charges to bedetermined.

11.8 Maintaining a high power factor is necessary tominimise tariff penalties from the supply authority andto reduce electrical losses. Power factor correctionequipment shall be installed, where necessary, to achiea minimum overall power factor of 0.92.

Tunnel Electricity Supply System

11.9 The following description illustrates the mainfeatures of a typical tunnel electricity supply system,with two substations. See Figures 11.1, 11.2 and 11.3.

11.10 Two high voltage (HV) supplies, at 11kV andderived from separate sources, ensure maximum securof the power supplies. The cables associated with thesservices are separately routed for maximum security ofsupply. The HV is transformed to 400V and distributedvia the low voltage (LV) switchboards to distributionpanels mounted in the tunnel walls at road level. Eachpanel has two compartments, each houses final circuit

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distribution equipment fed from one of the two suppliesBy this means, power from each supply is separately aevenly distributed throughout a tunnel to supply tunnellighting jet fans, axial fans in inlet/outlet shafts etc.

11.11 Figure 11.1 shows an arrangement where HVsupplies 1 and 2 are provided at opposite ends of atunnel, Figure 11.2 shows both supplies at one end onand Figure 11.3 is as Figure 11.2 but with provision fostandby generation. Cabling associated with Supply Aand Supply B should be segregated to achieve maximsecurity of supply, including during a fire. Change-overconnections at HV may be provided, and at LV will beprovided, to give the maximum security of supply. Fornormal operation, circuit breakers 1 and 2 are opengiving two independent systems. The loss of a mainsupply feeder, A for example, shall be sensed and cauthe 11kV incoming circuit breaker on side A to open,and circuit breaker 1 to close, restoring a supply to theA side.

11.12 The change-over connection at the 400V side othe transformers, circuit breaker 2, allows for onetransformer to be out of commission and isolated, andall circuits to be connected to the functioningtransformer. Care shall be taken in the interlocking ofthe HV circuit breakers and the LV circuit breakers toprevent any paralleling of supplies.

11.13 In the tunnel, luminaire circuits are connectedalternately to the three phases of the A and B suppliesshown. Similarly the other electrical loads of the tunnewill be alternately connected to the A and B supplies, afar as is practical.

11.14 For security of essential loads an uninterruptiblpower supply (UPS) is provided. At some tunnels astandby generator may also be provided, connected tothird section C of the LV switchboard. In such cases thUPS and essential loads can also conveniently beconnected to C, see Figure 11.3.

11.15 If the 11kV supplies are provided one at each eof the tunnel (Figure 11.1) then an auxiliary 11kVinterconnector cable is required to achieve the samedegree of security of supply. In this case, interconnectiof the 400V supplies would not usually be undertakenbecause of the problem of excess cable size, and theUPS and/or stand-by generator would be connected toone side only of the LV supply board.

Security of Supply

11.16 Security of supply is paramount. Primarysupplies shall ideally be derived from two

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independent sections of the 11kV network which, inturn, should preferably be derived from differentpoints on the National Grid system. Carefulconsideration shall be given to establish if faults onone section of the system feeding one side can affectthe second supply.

11.17 It can be difficult to obtain two truly independenseparate supplies. They may be independent up to apoint but still be derived from a common 33kV gridsubstation. Failure of the supply at the 33kV level, eg damage to overhead lines, could lead to loss of bothincoming supplies and this possibility shall be taken intaccount when assessing standby supply requirements

11.18 A UPS with a 2 hour capacity will normally beprovided for essential loads (as discussed under UPS)and standby generators will not normally be used, seeearlier text.

11.19 A whole life costing approach to the provision ostandby power is valuable to balance the high costs ofinstalling and maintaining full UPS systems againstthose of partial UPS with standby generator plant.Standby generators have the potential to be used forpeak lopping locally and into the supply network,provided they are designed for the purpose and thenecessary additional equipment for control andsynchronisation is installed.

11.20 The method and degree of security of supplywhich can be negotiated with the electricity supplier wiconsiderably affect the HV design.

General: Design and Maintenance

11.21 Electrical equipment to supply and controlelectrical services in tunnels shall be designed to haveminimum 20 year service life. Its design requires specicare and attention to detail to ensure continuity ofsupply, safe working conditions, performance, properoperating sequences and physical measures to combahostile environment.

11.22 The maintenance philosophy to be adopted shabe taken fully into account in the initial design of thewhole of the electrical system. The system shall becapable of being safely maintained. Onerousmaintenance requirements may be reduced by specifythe most appropriate plant.

11.23 The cable layout and circuitry shall be designedwith maintenance in mind and particular attention paidas to how future electrical testing will be carried out anat what frequency. Ease of fault finding in the system

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shall also be taken into consideration together withprovision for removing and replacement of theinstallation at the end of its useful life.

11.24 Minimum standards for the design andinstallation shall be those given in BS 7671:Requirements for Electrical Installations. If theminimum standards included in the Standard are notacceptable and higher standards, or particularalternatives, are required, these shall be definedunder the relevant section of the project specification,with reference to other appropriate standards. Therequirements of relevant legislation such as EECDirectives and the Electricity at Work Regulations1989 must be met.

11.25 The tunnel environment is particularly aggressiveand the combination of road salt, soot and chemicalsubstances from vehicle exhausts and accumulated acidfrom tunnel washing detergents can be highly corrosive.Within this environment, equipment such as junctionboxes, cable trays and trunking, conduits andaccessories, brackets, channels and metal supports,shall, wherever possible, be made of a suitable highgrade stainless steel. All fixings, screws, nuts and bolts,washers and studs shall also be of stainless steel of acompatible grade. The grade of stainless steel in allinstances shall be chosen for the environmentalconditions, see Chapter 2. If carbon steel has to be usedwith the prior agreement of the Overseeing Organisationit shall be galvanised or epoxy painted to a highstandard. Mixed metal joints shall be avoided.

11.26 All materials shall be compatible one withanother. In those areas outside the tunnel where stainlessteel and IP65 enclosures are not required fixingmaterials, conduit systems including all accessories,cable trays, cable trunking and similar material shall behot dipped galvanised. There shall be no exposed baremetal surfaces where corrosion can occur.

11.27 All plant, equipment, fittings and any othercomponent of the permanent installation within thetunnel and other areas affected by the tunnelenvironment shall be protected to IEC Category IP65, orother suitable standard. Water jet velocities shall bestated.

High Voltage (HV) System

11.28 HV systems must only be operated by AuthorisedPersons (APs) with appropriate training andcertification. Not all TOAs have such staff available atall times, and the system design and operating

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rocedures shall allow for switching operations to beontracted out to others.

V Distribution

1.29 Each 11kV feeder shall terminate in a substationhere the supplies will be metered. The substation mayrm part of the services building provided for thennel. The consumer’s 11kV switchboard may bestalled in a separate 11kV switchroom within the

ervices building. However, to increase reliability, it isetter to negotiate common use of a single 11kV switchom with bus-bar connection between supplier and

ser. Each switchboard shall comprise two sections, And B, with a bus-section switch between the twoections. One supply feeder will be connected to eachection.

V Switchgear

1.30 Although other types may be considered, thecommended HV switchgear is the indoor single bus-

ar, metal enclosed, compartmented type, suitable for2kV continuous, 60kV or 75kV impulse levelepending on the system exposure. Vacuum or SF6ircuit breakers of suitable current rating and minimumult level of 250MVA shall be fitted and be of the

ertically isolated withdrawable type, spring operated,10V DC motor wound, with shunt trip and closing coilsnd manual reset. Earthing provision shall be built in.

1.31 Each HV switchboard shall have one 110Vattery for tripping duty and one 110V battery forlosing and spring winding. Nickel/cadmium batterieshall be provided and they shall float across chargersapable of both rapid and trickle charging.

1.32 The Design Organisation shall be aware that aeed may exist to coordinate the protection of HVircuits and certain LV circuits, such as transformerecondary outputs. HV relays shall be of the static type.

1.33 Sufficient controls and indicators shall berovided to allow safe operation by manual means.

1.34 Status and alarm monitoring of the switchgearhall be carried out both locally, by means of indicationmps on the switchgear, and remotely. Sufficient

ontacts shall be made available to enable the status toe monitored via the plant control system at remotecations. See Chapter 10.

1.35 The monitoring system shall be arranged to give visual alarm of loss of a power supply.

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Transformers

11.36 Each of the A and B power supplies shall beequipped with a transformer. The transformer shall be 11000/400V Dy11 type, with sufficient kVA rating toenable one transformer to carry the whole of the requirtunnel load without excessive temperature rise, althougload shedding may be implemented to disconnect non-essential loads. Restricted Earth Fault protection shall provided for the transformers.

11.37 Vector groups other than Dy11 may be moreappropriate where large inductive loads are connectedthe transformer.

11.38 Depending on earthing configuration andresistance, the neutral point of each transformer shall bearthed through an adequate link within the LVswitchboard.

Low Voltage (LV) System

11.39 The design of the low voltage system shall bebased on the following.

LV Distribution for Lighting, Electrical DistributionPanels

11.40 The LV switchboards shall provide separatecircuits for the various stages of lighting, (emergencylighting shall also be connected to the UPS equipment)

11.41 Electrical distribution panels (EDPs) are requirethroughout a tunnel. It may be convenient to incorporatthe electrical distribution points into the same cabinetsas those provided for emergency fire and telephoneservices where these occur at the required intervals, seChapter 8. The combined panels are referred to asemergency distribution panels EDPs. They shall beconstructed of stainless steel and to IEC category IP65

11.42 Within the EDPs two panel sections shall beprovided, one for the A supply and the second for the Bsupply, see Figures 11.1 to 11.3. The distribution paneshall incorporate final circuit fuses and/or miniaturecircuit breakers feeding the tunnel lighting. Eachdistribution panel shall have sufficient distributionboards to feed the various lighting stages and astandardised unitised layout.

11.43 Lighting circuits shall be so arranged that, as isfar as practical, adjacent luminaires are connected todifferent circuits or, where two incoming supplies areavailable, to separate sources. By interleaving lightingcircuits, failure of one will then only result in the loss of

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50% of the lighting in the affected area and reduce theneed to fall back on emergency lighting. Each lightingdistribution sub-section shall be fed by a cable dedicateto the particular stage of lighting and each sub-sectionshall, therefore, be a separate unit within the A and Bdistribution panel capable of being isolated and workedon without danger from other sub-sections in the samedistribution panel.

11.44 Special attention shall be given to the segregatioof supplies derived from the UPS systems.

11.45 Equipment within the EDPs shall be rated for thetemperature rise within the enclosures.

11.46 Particular care shall be taken in the design of thEDPs to ensure that adequate space is available for alequipment and connections. EDPs shall incorporateother electrical equipment such as connections forCCTV, communications, traffic loop detectors, controloutstations etc. Suitable socket outlets (110V AC) forthe TOA and special socket outlets for the use of theFire Brigade may be required.

11.47 Care shall be taken to provide adequateterminations and space to allow reasonable bending raof tails and outgoing cables.

11.48 Conduits for the final circuits from the EDPs toluminaires shall comply with IP65 and the use ofstainless steel conduits and accessories is required. Fincircuits shall be arranged to suit the characteristics ofthe lamps served (including starting currents).

11.49 BS7671 requires that the earthing bondingsystem from the services buildings shall be extended toeach EDP to ensure the integrity of the earthing systemby the provision of a separate circuit protectiveconductor (cpc) other than using the armouring of thesub-main cables. The cpc shall also be bonded toextraneous conductive parts.

LV Distribution for Ventilation

11.50 The electrical distribution, switchgear and controfacilities shall be developed to suit each tunnel. Thedesign shall recognise the need to ensure security ofsupply and the complete segregation of the electricalcircuits for the ventilation from other systems.

11.51 Where fans are used to provide longitudinalventilation along the length of a tunnel it is possible forthe associated starter equipment to be located either inthe LV switchrooms, or in panels local to the fans. It isusual to adopt the latter, except in short tunnels, withlocal control/starter panels, manufactured to a similar

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specification as the EDPs, being provided for a group fans. Cables between the LV switchrooms and the fancontrol panels shall be run to provide segregationbetween the fan supply cables and other systems, alsbetween A and B supplies for the fans.

LV Distribution in Services Buildings, etc.

11.52 In addition to the LV supplies for lighting andventilation, LV distribution is needed for the variousservices set out in Chapter 12. A “clean” supply may bneeded for computer systems.

11.53 Earthing systems to provide equipotentialbonding, frame earthing, neutral point earthing,computer system “clean” earths and general protectionshall be considered when designing Services BuildingsHigh quality copper systems shall be installed andallowance made for the testing facilities to be providedThe laying of earth electrode mats may be requiredbefore building superstructure work commences. Thebonding system may require to be extended to connecequipment outside the Services Building.

LV Switchboards

11.54 LV switchboards shall be suitable for operatingon a 400V, three phase, 4 wire, 50 Hz supply withingress protection to IEC IP31. They shall be fault ratefor 50KA for 1 second.

11.55 Switchboard enclosures shall be of cubicleconstruction, with units mounted in tiers within eachcubicle, assembled to form a flush fronted, floormounted, free standing, dust protected metal enclosurhaving 1 to 1.25m minimum access from the front, withbottom cable entries whenever possible. To allow forfuture requirements, a minimum of 25% spare waysshall be included. The maximum overall height of theswitchboards shall be 2.2 m to aid access and operatiwith the operating switches and dial reading instrumenat a maximum height of 2.0m, minimum height 0.45m,from the finished floor level. Switchboards shall bearranged with 2.5m free space at the front and back a2m at each end.

11.56 Each switchboard shall include all necessary acircuit breaker units with 110 volt (close) and 110 volt(trip) DC motor wound spring operated mechanisms,with provision for hand and remote closing and openinThe 110V DC supplies shall be derived from twinbattery systems similar to those described under HVSystem.

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11.57 The switchboard is normally divided into twobusbar sections (A and B) and interconnected througbusbar circuit breaker. Sections A and B would be fefrom each of the transformers, respectively. If requirea third Section C would be fed from the standbygenerator.

11.58 The neutral of each transformer shall be brouinto the LV Switchboard and fitted with a suitably rateneutral link to facilitate neutral isolation and earthcontinuity tests.

Protection Systems

11.59 All protection systems for the LV distributionshall be compatible. Certain HV protection circuits orcircuit breaker operations may require a response frothe related LV protection system.

11.60 When specifying any form of protection systemit is necessary to ensure that discrimination ismaintained throughout each circuit and sub-circuit, toprevent tripping of higher level circuits.

Interleaving of LV Supplied Equipment

11.61 To minimise the risk of a complete failure ofservices in any section of tunnel, in the event of a failof one of the primary supplies, equipment such asluminaires and jet fans shall be alternately connectedpower supplies derived from the A and B sources asshown in Figures 11.1, 11.2 and 11.3. Cables from thtwo supplies shall be routed separately to minimise thrisk of loss of both circuits simultaneously.

Uninterruptible Power Supply (UPS)

11.62 An uninterruptible power supply, withappropriate autonomy, is essential, in the event of amain electrical supply failure to maintain power tooperational and safety systems and permit use of thetunnel to continue. Failure of the normal suppliescausing sudden loss of tunnel lighting could lead tothe disorientation of a driver entering or already in atunnel. It is essential that some level of lighting ismaintained throughout the whole of the initial periodof supply failure.

11.63 Other systems essential to safety, such asemergency lighting, fire protection, communications,alarm and traffic control systems, shall be providedwith emergency battery backup power to ensure thatthe tunnel can be safely evacuated, and incidentsidentified and attended to, should an alternativepower supply also fail. Vital equipment such as data

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logging, CCTV, traffic control signs, emergencyservice communication systems, computers(particularly SCADA and control systems),equipment which cannot tolerate any interruptionduring switching operations or while any standbygenerator is starting up, and essential supportservices situated in the services buildings shall have aguaranteed secure electrical supply.

Emergency Lighting

11.64 Since failure of the normal power supply willresult in total loss of tunnel lighting unless standbyarrangements are made, careful consideration shall begiven at the planning stage to the probability of supplyfailure and the operational requirements in such anevent. Provision of a permanently available, independensecond mains supply will reduce this risk, but can be acostly option and cannot guarantee complete freedomfrom supply outages.

11.65 As a minimum requirement, one luminaire in tenof the Stage 1 lighting shall be designated as emergenclighting and maintained by a UPS. This will providesufficient light for safe evacuation of the tunnel, but notfor continued operation with traffic, and the tunnel shallthen be closed until full power is regained. Daylightpenetration and vehicle headlights may be of assistancbut cannot be relied upon.

11.66 Where tunnel closure is unacceptable, sufficientstandby lighting shall also be provided to permit the safpassage of traffic, with an appropriate signed speedrestriction. This may be achieved by maintaining thenormal daytime interior zone lighting (Stages 1 and 2)but switching off the boost lighting in the entrance andexit zones (Stages 3 and above). The standby lightingload is usually too large to be supported by a UPSsystem alone, and a standby generator shall be provideto power this and other essential loads. UPS capacitythen only needs to be sufficient to maintain continuity oflighting between the moment of supply failure andacceptance of the load by the standby generator.

Essential Service Loads for UPS

11.67 The essential loads shall be listed and quantifiedand sufficient UPS power shall be provided to allowsuch services to be maintained until either any mainstandby generating equipment is brought into operationor a predetermined tunnel evacuation and diversion oftraffic is achieved if no standby generator provision or ithe event of a failure of standby generation to start.

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1.68 The essential loads shall be permanentlyonnected to the UPS equipment so that in the event oains failure their supply is maintained.

1.69 Components of the essential load shall include

. Approximately 10% of the Stage 1 lighting, asdescribed

i. Computer control and fault indication systems

ii. Sub-surface communications systems includingCCTV

v. Radio Systems

. Tunnel portal signals/signs

i. Fire Brigade power tool sockets (if required byFire Brigade)

ii. Other relevant components unique to the tunnelunder consideration.

ype of UPS

1.70 Static type systems with a no-break reversion tohe mains supply on failure are adequate for tunnelpplications using appropriate battery capacity. Rotary

ypes may be considered.

PS Design Parameters

1.71 Each UPS system design shall take account of ollowing factors:

. The type of load to be fed and the characteristic(eg p.f and current inrush) of the load

i. Acceptable limits of harmonics fed back into thepower supply network, particularly where astandby generator is installed

ii. Compatibility with standby generator plant,where provided

v. The minimum period of time the UPS is requiredto operate under full load after mains supplyfailure (normally two hours)

. Operational and physical compatibility with otherelectrical equipment

i. Recharging times after discharge. Batteries shalbe capable of being fully recharged, from the75% discharge state, in seven hours,automatically

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vii. Control equipment to be provided.

Standby Generating Equipment

11.72 Where it is likely that drainage pumps orventilation plant will need to be operated under mainsfailure conditions to maintain the security of the tunnelsystems and structure, such loads will be beyond thecapacity of a UPS. For such cases, automatic startstandby generating equipment shall be considered.

11.73 Separate accommodation, with 4 hours fireprotected enclosure, shall be provided for the standbygenerating equipment, fuel tanks etc.

11.74 As an alternative to permanently installedstandby generating plant, consideration may be given tothe provision of suitable connecting points for the use ofmobile generators. The availability of a suitablegenerator shall be carefully assessed, particularly takinginto account competing demands that may be made foruse of such plant and the likely time required to bring themobile generator to the tunnel site.

Essential Service Loads For Standby GeneratingEquipment

11.75 shall be rated to provide adequate power,including starting currents, for the essential loads listedfor the UPS plus the requisite pumping system loads,including fire main pressure pumps, if installed. Ifsurplus power is available, additional loads may beconnected in the following order of priority:

i. Essential ventilation plant

ii. Lighting and HVAC equipment in ServicesBuildings

iii. Limited tunnel lighting (normally Stages 1 and 2)according to the design requirements.

Standby Generator Design Considerations

11.76 A standby generator, where required, may bespecified to accept load in two stages, the first notexceeding 60%, and the system design shall allow forthis.

11.77 Output shall be connected to the LV switchboardSection C, see Figure 11.3. In the event of a powersupply failure of the primary supplies, the system shallautomatically bring the standby generators intooperation and isolate Sections A and B of the LVswitchboard.

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1.78 Fuel storage tanks, shall store sufficient fuel foeven days running at full load. A dump tank shall berovided external to the diesel set room to take theontents of the day service fuel tank which will emptyutomatically should a fire occur in the diesel room. Tump tank shall be provided with pumps to empty it.

1.79 Separate accommodation shall be provided fore standby generating equipment, fuel tanks etc.

1.80 Provision shall be made to generate from, andansmit to, the tunnel site all necessary signals andontrols to and from the standby generator sets.

abling

1.81 Cable fire protection shall be in accordance wie requirements of Chapter 8. Design of cabling shallso be based on the following.

ervices in the Tunnel

1.82 Cables feeding services in the tunnel shall be ro far as is possible, in the verge ducts on either sidee bore. Preference shall be given to lighting sub-maeing run in the verge duct adjacent to the left handarriageway side. Where ventilation using jet fans ismployed, cables feeding these fans shall be located e verge opposite to that containing the lighting cable

1.83 Fixings for cables, if they are cleated, shall berovided at intervals not greater than those stated in B671.

ervices Below Ground (Outside the Tunnel)

1.84 Where cables are to be buried in the ground, thepths of cable trenches shall be defined so that thereo ambiguity regarding the depth required. For examp may be specified that an LV cable shall be laid at ainimum depth of 450mm on a bed of sand 150mm de. a trench depth of 600mm). Cable tiles or markerpe shall be provided over the installed cables.

1.85 Where cables are housed in glazed or plastic dipes, it shall be arranged, where economically practir only one cable to be installed in each pipe. At leas5% spare ducts shall be provided, above the initialssessment, to allow for future requirements.

ervices in Switchrooms and Services Buildings

1.86 The design of switchrooms and service buildinghall allow for adequate space for known and possibleture cable routes beneath floors. See Chapter 12. In

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switchrooms, floors shall be of the suspended type witapproximately 1m of space below them, and shallconform with the Building Regulations and LocalAuthority requirements. Fire partitioning and barriers toaid system segregation shall be incorporated.

11.87 In switchrooms or similar locations, cable traysshall be designed and erected so that they do not sagwhen the cable installation is completed. All fixings andaccessories shall be of stainless steel, or, when notexposed to the tunnel environment, hot dippedgalvanised materials may be used. Wall or ceilingmounted support systems to the cabling may be requirSuch systems need to be purpose designed for eachproject.

11.88 Entries to equipment shall be arranged to giveaccess to cables approaching from below. In the case major short interconnections (eg. between the LVterminals of a transformer and a main LV switchboard)consideration may be given to the use of bus ductconnections rather than cable, but care needs to be tain the physical layout of the equipment to ensuremaximum economy.

11.89 Cables shall not be run beneath the floor inbattery rooms.

Cable Design Requirements

11.90 Cables shall have copper cores. Cable cores sbe stranded (except for MICC cables) where used onany part of the lighting, power distribution, final circuitand control systems. Care is required in the selection ocable entry glanding materials suitable for a road tunnenvironment, see Chapter 2.

11.91 All HV cables shall be manufactured to suitablestandards and shall be XLPE insulated, steel wirearmoured and red LSOH sheathed.

11.92 All LV cables for general purpose use outside thtunnel shall be to the Manual of Contract Documents fHighway Works.

11.93 Low Smoke Zero Halogen (LSOH) insulationand sheathing materials, with an emission of HCl of nogreater than 0.5%, shall be used for all cables partiallyor completely inside the tunnel and its substations. Theshall conform to one of the following specifications:

i. LSOH/SWA/LSOH (Cu) construction,.Armouring shall be round galvanised steel wirewith a black LSOH oversheath, suitable forpermanent immersion in water. The cable to berated at 600/1000V.

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ii. LSOH/LSOH (Cu) LSOH insulated, LSOHsheathed overall, stranded copper conductorpower cables suitable for use on an earthedsystem at rated voltage of 600/1000V.

iii. LSOH insulated copper conductor wiring cablesrated at 450/750V installed in heavy gaugeconduit.

iv. MICC/LSOH Mineral insulated copperconductors, with a LSOH outer sheathed overalrated at voltage of 600/1000V, generally used fofire alarms (with a red sheath) and otherapplications where resistance to hightemperatures is required.

LV Cable Sizing

11.94 Long route lengths may require the use of cablehaving large core sections to meet the voltage drop,disconnection time requirements and the powercorrection factors for groups of cables. Cableterminations shall be sized to suit these requirements.

11.95 As the distance between the low voltageswitchboard and the furthest fan or luminaire increasecable sizes may need to be increased to compensate the drop in voltage along the cables. Voltage drop in thLV cable system may be reduced by the provision ofmore frequent sources of supply, through the extensionof the HV system to additional substations. In tunnelslonger than 400m, more than one transformer substatiwill probably be needed to avoid undesirably long lowvoltage circuits.

11.96 A cost benefit analysis shall be undertaken toassess the benefits of providing such additionalsubstations compared to the provision of larger crosssection LV power cables.

Other Cables

11.97 Other types of cables to the relevantspecifications may be used for other tunnel purposes ainclude:

i. General purpose cables outside of the tunnel

ii. Heating appliance cables

iii. Industrial heavy duty cables

iv. Multipair communication cables

v. Radiating co-axial cables

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vi. Optical fibre cables

vii. Intruder alarm and fire alarm cables.

Cable and Termination Identification

11.98 A system of identification for cables, and cablecores in terminations, shall be established and recorde

11.99 Except where buried in the ground or in encloseducts, all cables shall be identified externally bystandard cable markers, fixed over the external sheathat intervals not exceeding 25 metres. All cables shallhave the same identification provided at each cabletermination, at each change of direction and wherepassing through barriers.

11.100 Cable cores and terminations shall be identifiewith a previously agreed code of alphabetic andnumerical symbols, by means of pre-engraved indentecircular markers closely fitted to the core insulation ofeach constituent core. Cores not utilised shall beidentified as ‘spare’ and shall be terminated in a spareterminal arrangement of the same pattern as that usedfor the ‘in use’ cores.

11.101 Cable voltage ranges shall be indicated by thecolour of the outer sheath, eg red sheath for HV, blacksheath for LV and the sheath for control cables to be osome other distinguishing colour.

Cable Segregation

11.102 Throughout an installation, strict segregationshall be maintained between services derived fromdifferent sources, or operating at different voltages, orwhose operating characteristics may interfere with thesatisfactory operation of other cables or services.

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Typical Tunnel Power Supply SystemHV Supply at Each End of Tunnel

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Supplyphase

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Distributionpoints

Figure 11.1

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= LV Switchgear

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= LV Supply Sections

(Note:Electrical loads are shared as equally as possible between LV supply sections A,B,C,D)

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Typical Tunnel Power Supply SystemHV Supply at One End of TunnelFigure 11.2

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= Normally Open Circuit BreakerN/O

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Typical Tunnel Power Supply Systemwith Standby Generator

XX

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Figure 11.3

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X = Circuit breaker

= LV Switchgear

= Normally Open Circuit BreakerN/O

1,2 = Incoming HV Supplies

= LV Supply Sections

(Note:Electrical loads are shared as equally as possible between LV supply sections A,B)

= LV Standby Generator

= Interlocking

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12. SERVICES BUILDINGS AND PLANT ROOMS

General

12.1 Tunnel Services Buildings and Plant Roomshouse the main electricity substation, plant rooms andtemporary control centre for a tunnel. Additionalstructures may be required for substations and plantrooms at other locations adjacent to the tunnel. Plantrooms shall be sized not only to accommodate the plantand associated systems to be installed initially at thetunnel, but also to provide for any foreseeable futurerequirements.

12.2 Building layout shall facilitate effectivemanagement of operations and maintenance and fullyreflect the system of tunnel management to be adoptedeg manned or unmanned tunnels. If the ServicesBuildings are normally unmanned, they shall be suitablefor occasional use as a temporary control facility duringmaintenance and emergency operations.

12.3 The siting and requirements of the ServiceBuildings are discussed in Chapter 2.

12.4 Tunnel complexes including Services Buildingsshall comply with the requirements of the BuildingRegulations and water bye-laws etc.

12.5 In addition to the facilities required for the tunnelequipment and systems, maintenance workshops, storemessing and toilet facilities may be required foroperational, maintenance and contractors’ staff. Outsidethe main building a vehicle hard standing is requiredwith access for fire fighting vehicles, equipment andpersonnel. A helicopter landing pad may need to beconsidered at major tunnels.

12.6 Access to the Services Buildings shall be strictlycontrolled and access facilities managed to preventunauthorised entry and operation of plant. Adequatesecurity arrangements shall be provided to protect allmaterials and equipment.

12.7 As well as normal lighting,the provision ofemergency lighting (for escape under mains failureconditions) and standby lighting (to permit continued useof selected areas if normal power fails) shall beprovided.

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pace and Provision Requirements

2.8 A layout of an example services building for aad tunnel is shown at Figure 12.1.

2.9 Space and suitable cable access may be requirr each of the following:

Electricity Supply Authority intake and metering

. ll kV switchgear

i. Transformer pens

. Diesel generator, fuel tanks and dump tank

. UPS and battery equipment

i. LV switchgear including control and interfacepanels for lighting and ventilation systems

ii. Fire protection systems

iii. HVAC plant

. Drainage pumping equipment and associatedelectrical equipment

. Computer, control systems and peripherals

i. Radio and telephone communications equipmen(possibly also a secure area for police network)

ii. Protected mains sockets for portable tools andtest equipment.

2.10 Adequate space shall be provided for opening oabinet doors and access to switchgear. Allowance shae made for cable runs and bend radii.

able and Equipment Separation

2.11 To minimise the risk of radiated interferenceommunications equipment and cables shall be locateds far as possible from high voltage and low voltagewitchgear and cabling and generator plant.

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Heating and Ventilation

12.12 Heating will be required in all rooms, to preventcondensation. Rooms containing LV switchgear, UPSplant and batteries and electronic equipment may requirair conditioning to maintain an acceptable operatingtemperature for the equipment. Most types of commonlyused batteries can evolve hydrogen gas under certainconditions and ventilation shall be provided to preventany dangerous build-up of gas.

Floors

12.13 Floor loadings of all electrical equipment shall becalculated and taken into account for in the civilengineering design. The requirement for providing falsefloors for cabling is described in Chapter 11.

12.14 Cables shall not be run beneath the floor inbattery rooms. The floors in the battery rooms shall beof solid construction and finished with a dust and alkaliresistant surface. The floor shall have drainage outlets tallow for electrolyte and cleaning water removal. Theseoutlets may be connected to the sink drain within theroom.

Earthing and Cabling

12.15 See Chapter 11 for cabling and earthingrequirements in Services Buildings and Switchrooms.

Lightning Protection

12.16 An assessment of the need for lightningprotection for the Services Buildings shall be carried outas described in BS 6651:1992 and a suitable lightningprotection system installed if necessary, in accordancewith the same Standard.

Building Security and Fire Protection

Intruder Alarm System

12.17 The Service Buildings shall be provided with anintruder alarm system comprising magnetic doorswitches and break glass window contacts on allexternal doors and windows. Where necessary internalareas (eg the roof space) may be additionally protectedby passive infra-red (PIR) or microwave movementdetectors. In the case of roof voids, consideration shall

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be given to the risk of false alarms which may be causif birds etc can gain access.

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2.18 Operation of a mortice type door key switch ate Services Buildings shall initiate a “Staff on Duty”

ignal for logging by the SCADA system. Forced entryrough any of the outside doors or windows will breakn electrical contact and trigger an alarm conditionhich will then activate an external alarm bell andansmit an alarm signal to the operator and/ or theolice via the SCADA system. See Chapter 10.

2.19 An external self-contained alarm bell shall berovided with its own battery unit and internal relays soat in the event of the wires being severed or the bellmoved, it shall be instantly activated.

ire Alarm and Extinguishing Systems

2.20 A fire alarm and automatic fire extinguishingystem shall always be provided in the Serviceuildings. See Chapter 8.

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Note: LV Switch Room, Communications Room & Control Room typically have suspended floors

LV Switchroom

LV Panels

HV Switchroom

HV Panels

U.P.S. Room

FireSecurityPanel

Communications RoomControl Room

ControlDesk

ControlDesk

ToiletLobby

Mess Room

Bulk FuelTank

DieselOil

Storage

DayTank

Store

DieselGenerator

GeneratorSet

OutletAlternator

Silencer

Transformer Transformer

Transformer Compound

ResistiveLoadBank

InductiveLoadBank

ControlPanel

Battery Room

Rooms with High VoltageElectical Hazard

Rooms protected byCO2 Fire Extinguishing System

Figure 12.1

CO2 Bottles

InletAlternator

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13. TUNNEL COMMISSIONING, HANDOVER ANDOPERATIONAL DOCUMENTATION

Chapter 13Tunnel Commissioning, Handover and Operational Documentation

General

13.1 Adequate tunnel documentation is essential toprovide a record of the ‘as built’ installation, equipmenttest results including those for statutory purposes,operating and maintenance procedures and emergencydrill for all the authorities who respond to incidents. Theease of understanding and ready availability of essentiinformation from the relevant documents is essential tomaintain traffic flow, ensure efficient working of staffand equipment, and continued provision of safeconditions.

13.2 Detailed technical specification requirements forroad tunnel equipment may be found in the Manual ofContract Documents for Highway Works: Volume 5:Section 7: Mechanical and Electrical Installations inRoad Tunnels, Movable Bridges and Bridge AccessGantries.

13.3 To ensure that the documents are correctlycompiled and well presented, they shall be written bycompetent technical authors to form a single, coherentcross-referenced package.

13.4 The documentation supplied shall be designed tmeet the needs of the tunnel operator for specific day-tday safe operating needs, as well as the needs of perioinspection and planned and emergency maintenance. Tinformation shall be prepared in the form of indexedhard copy manuals, but consideration should be given specifying that manuals and drawings shall also beprepared to an agreed electronic format which wouldoffer significant benefits in ease of retrieval,transmission and updating of information as well asreduced storage space. The storage of indexedinformation on CD-ROM, or latest equivalent, withhypertext links may be particularly convenient.

13.5 Of special importance is the documentationprepared to assist the police and emergency servicesresponding to tunnel incidents and emergencies. Thisshall present clear and concise information andaccurately reflect the agreements reached between theparties of the TDSCG.

13.6 All drawings, test certificates and calculationsshall be produced by the Contractor and signed asapproved by the Design Organisation.

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SUMMARY OF RECORDS REQUIRED

13.7 A summary of the documentation required for anew or refurbished road tunnel is as follows. Adescription of the various documentation is given later inthis Chapter. Typical contents are listed in Appendix C.

13.8 The Contractor is required to provide thefollowing documentation with timeliness, clarity andcomprehensiveness:

i. Tunnel Commissioning Records

ii. Certificate of Practical Completion, Handover

iii. As Built Records

iv. Operator’s Guide

v. Operation and Maintenance Manual

vi. Inspection Check List

vii. Computerised Data Recording Forms.

13.9 The Design Organisation is required toprovide the following documentation with timeliness,clarity and comprehensiveness:

i. Report of the TDSCG (see Chapter One)

ii. Manual for Police and Fire Services.

13.10 The police, fire and ambulance services arerequired to provide the following documentation, asappropriate, with timeliness, clarity andcomprehensiveness:

i. Emergency Services’ Operational Manuals

ii Police Control Centre Operator’s Manual.

TUNNEL COMMISSIONING RECORDS

13.11 The commissioning phase of a road tunnel projecis to ensure that the complete installation of M&E plantand equipment functions properly and is certified fit forits intended purpose, before handover to the tunneloperator.

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13.12 The outline design of M&E functions of a roadtunnel will be undertaken by the Design Organisation.Much of the detailed design and selection of plant andmaterials rests with the Contractor through his appointemanufacturers and specialist subcontractors. Documenrelating to design information and the commissioningprocess will need to be provided for record, handoverand warranty purposes and shall include:

i. Records comprising relevant letters relating tospecific equipment, agreements and minutes ofmeetings.

ii. Alert Notices and Field Service Reportscomprising the list of any faults which aroseduring inspection, and the remedial actions,adjustments and modifications carried out.

iii. Works Test Certificates covering general matterssuch as electrical continuity, insulation andenclosure checks, and specific performancechecks, such as fan or pump volumetric tests orphotometric tests for lighting. See the Manual ofContract Documents for Highway Works:Volume 5: Section 7: Mechanical and ElectricalInstallations in Road Tunnels, Movable Bridgesand Bridge Access Gantries.

iv. Site Test Certificates verifying the performanceof all equipment and systems after installation onsite, with full test results, signed andcountersigned.

CERTIFICATE OF PRACTICAL COMPLETION,HANDOVER

13.13 Towards the end of the construction period, whenall the equipment has been tested and found to be inaccordance with the specifications and in good workingorder, a Certificate of Practical Completion, orequivalent, shall be issued, certifying the date on whichthe tunnel was substantially complete. Issue of thiscertificate marks the date of handover to the MaintainingAgent (acting on behalf of the Overseeing Organisation)commencement of the 12 months defects liability periodand of full payment, apart from any retention, of allmonies due for the works. For DBFO projects the sameprocedure shall be followed. It shall be noted that the 12months period referred to shall not be confused with anymanufacturer’s warranty period starting from the date osupply for particular pieces of equipment.

13.14 Since at handover, the Maintaining Agent isrequired to accept responsibility under the relevantHealth and Safety legislation for the safe operation of

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he tunnel, it is imperative that no representative of theverseeing Organisation should sign the Certificate ofractical Completion until complete operating andaintenance documentation is available. For DBFOrojects the same principles shall apply. It is veryeneficial if the Maintaining Agent, or equivalent, staffan witness the final commissioning and testing stages,or familiarisation purposes. The contract documentsill contain the requirements for training that is to berovided, see Manual of Contract Documents forighway Works: Volume 5: Section 7: Part 2: 7015:echanical and Electrical Installations in Road Tunnelsovable Bridges and Bridge Access Gantries.

3.15 To enable the operating and maintenanceocumentation to be considered for approval by theverseeing Organisation, in time for handover, finalrafts of the manuals and drawings shall be submitted

or approval to the Overseeing Organisation 6 weeks indvance of the target date for practical completion.

3.16 After practical completion and at handover, all ofhe documents listed in this Chapter shall be boundogether in separate volumes, and retained by the tunneaintaining Agent (or DBFO Contractor) for future

eference such as during inspections and maintenance unnel equipment. The Maintaining Agent (or DBFOontractor) shall also be responsible for updating theocuments (except for those from the emergencyervices), as necessary, to record changes in thenstallations or procedures.

andover Certificate

3.17 When all performance tests have been completeatisfactorily, and in accordance with the Specification, Certificate of Practical Completion will be issued, toertify the date on which the tunnel was contractuallyompleted and handed over to the Overseeingrganisation.

S BUILT RECORDS

3.18 A full record of the entire road tunnel installation,s built, shall be provided to the tunnel operator at the

ime of acceptance of responsibility for maintenance.his shall include site plans, and tunnel layouts showingccess provisions and facilities for the emergency andaintenance services, together with plans andescriptions of buildings for tunnel services andssociated ancillary structures such as sub stations,umps etc. See BD53 (DMRB 3.1.6).

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OPERATOR’S GUIDE

13.19 The Operator’s Guide for the tunnel and itsequipment should include all the drawings andspecifications for the equipment provided, and thegeneral procedures for its day to day operation andmaintenance.

OPERATION AND MAINTENANCE MANUAL

13.20 The Operation and Maintenance Manual shallinclude all the detailed manufacturer’s operating andmaintenance instructions and recommendations for theequipment, spare parts lists etc. The information shallalso be supplied on a computer readable source eg CDROM. Any spare parts recommended shall have aconfirmed availability for the working life of theequipment or at least 10 years. The Tunnel Operatormay either rely on storage and provision of spares by toriginal manufacturer or consider entering into anagreement with a spares provision agency.

INSPECTION CHECK LIST

13.21 To facilitate planned maintenance, inspectioncheck lists shall be provided for the inspection andmaintenance operations required to be carried out foreach item of equipment, at specified intervals. The chelist shall be designed to simplify the entry of record datinto a tunnel maintenance database.

COMPUTERISED DATA RECORDING

13.22 Operation and Maintenance (O&M) databasesystems (see Appendix C for content details) shall beprovided in order to enable improved organisation,improved operational reliability, logical sectioning ofwork and identification of cost sources for cost control.Software shall be compatible with systems, if any, of thOverseeing Organisation. Work sheets, in logicalgroupings, for scheduled maintenance shall be generatby software. Data entry forms shall be provided, listingall tunnel equipment, with the relevant computer datarecording system entry code for group and individualentry. Compatible software and instructions shall beprovided for accessing, by maintenance and inspectionstaff, comparative data and trends for the equipmentprovided. The forms should not need to be retained aftelectronic data has been entered and processed. SCAD(see Chapter 10) is to supply a proportion of the incideand record data required by BD53 (DMRB 3.1.6).

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13.23 A computerised register shall be provided forrecording inspectors’ electronic signatures on compleof the scheduled inspections. Parameters shall beprovided which ensure that adverse data records arereported.

13.24 An option shall be available to allow for the dabase to be reset, if necessary, following majorrefurbishment work, this function should not beaccessible to the inspection staff.

13.25 Data review would be undertaken only byauthorised personnel, and an alarm should be arrangto inform the Tunnel Manager when reviews becomesdue. A hard (printed) copy of the review should beretained and used to record long term trends ofequipment performance.

REPORT OF THE TDSCG

13.26 The decisions effecting the design and operaticonfirmed and agreed at TDSCG meetings must beformally recorded into a finalised Report of the TDSCand accepted as an agreed addenda to the ApprovalPrinciple (AIP) document required by BD2 (DMRB1.1). See Chapter 1.

MANUAL FOR POLICE AND FIRE SERVICES

13.27 A manual shall be produced for the guidance ostaff at the local police and fire stations and controlrooms. The manual should briefly describe the principfeatures of the tunnel, including operational procedureand detail the facilities available to assist the police afire services in dealing effectively with incidents andemergencies in the tunnel. It should be clear and simp

EMERGENCY SERVICES’ OPERATIONALMANUALS

13.28 Police and fire services’ operational manuals fthe particular road tunnel are to be prepared separatby the relevant organisations concerned, fully taking iaccount the agreements of the TDSCG, and includingthe requirements of the ambulance service. Procedurgeneric to the force or service need not be repeated isuch documents. The text should identify who doeswhat, where and when, communication channels andequipment needs for the particular circumstances of troad tunnel in question. Typical contents of police andfire services operational manuals are given at AppendC. Guidelines for emergency (major incidents)operations are given at Appendix D. Together with the

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relevant information included from Chapter 14: TunnOperation, such guidance will form the basis for thedetailed Emergency Services and Police Control CenOperational Manuals for the operational circumstancrelevant to a particular tunnel. Such manuals shall bregularly updated, at least every 3 years, and incorpany changes to procedures and the findings from anemergency drills to BD53 (DMRB 3.1.6).

POLICE CONTROL CENTRE OPERATOR’SMANUAL

13.29 A separate manual relating to tunnel emergenoperation to assist the Duty Officer at the Police ConCentre shall be prepared by the police.

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14. TUNNEL OPERATION AND MAINTENANCE

Chapter 14Tunnel Operation and Maintenance

General

14.1 Road tunnels involve high capital investmenevery effort needs to be made to optimise theirproductivity in terms of continuous availability fortraffic throughput. This must be kept in mind whendevising maintenance procedures and measures toappropriate levels of operational safety. The tunnelbe designed and operated as an integral part of thehighway and not as a potential bottleneck within thenetwork. A road tunnel is usually an important link the highway system and is often located where thefew, if any, viable alternative traffic routes.

14.2 The overall framework set up to operate eactunnel on a day-to-day basis, execute plannedmaintenance, control tunnel traffic and respond to temergencies will depend on local circumstances andeal with a wide range of issues affecting safety aneconomy. The proposed framework will have influethe initial risk assessment.

14.3 The Tunnel Operating Authority (TOA) is thecompetent body, providing a nucleus of trained staare fully familiar with the operation, inspection andmaintenance requirements of the tunnel functions,together with the necessary maintenance plant andequipment, which is responsible for the tunnel operand whose staff are also capable of providing advicassistance to the police and emergency services.

14.4 As described in Chapter 2 certain tunnels reon site permanent staff dedicated to their operationMore generally, tunnels will be designed to operateautomatically, with remote supervision, and areunattended. However, there must still be a rapidresponse in the event of equipment failure or otheremergencies.

14.5 Such staff shall provide emergency cover onhour basis, with a schedule of agreed response timattend to equipment faults and emergencies and shrequired to oversee any maintenance work that iscontracted out (eg cleaning walls, bulk re-lamping eThey shall also, where necessary, include qualifiedauthorised personnel to comply with statutory safetprocedures such as permit-to-work systems relatinhigh voltage equipment and confined spaces.

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14.6 The relative emphasis that needs to be given tothe above considerations shall be clearly defined in theoperational manuals to be prepared as tunneldocumentation.

Operational Organisation: Division ofResponsibilities

14.7 Tunnel operational organisation has three mainareas of responsibility: routine traffic management;equipment operation and its maintenance; rapid andcoordinated emergency response. The details will depenon the individual tunnel and whether it is manned orunmanned. In manned tunnels, staff dedicated to workon tunnel equipment will be available, but manyunmanned tunnels depend on traffic police operators toinitiate action in connection with tunnel equipment,amongst their other duties.

14.8 The basis of tunnel organisation is shown inChapter 2, Figure 2.4.

14.9 For each tunnel there shall be clear proceduresand clearly defined responsibilities agreed and laiddown, with respect to traffic management and tunnelequipment, to ensure rapid and coordinated responseto emergencies.

Tunnel Traffic Management

14.10 The police Traffic Division will be responsiblefor the safe and efficient movement of the traffic throughthe tunnel, dealing with vehicle break-downs, trafficcongestion and tidal flow (if used), escorting dangerousloads (if required) and managing traffic during tunnelmaintenance (see Chapter 9).

Tunnel Equipment

14.11 The TOA will be responsible for the tunnelequipment, to maintain a safe environment for the tunneusers and maintaining such equipment in good workingorder (see Chapter 10).

Emergencies

14.12 An emergency will normally be detected byTraffic Control Centre from the CCTV monitors, trafficloops, incident detector alarms or the emergencyroadside telephones. Traffic Control Centre are then

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responsible for: the immediate summoning of thenecessary emergency services; the immediate controltraffic entering the tunnel; alerting the TOA to providenecessary control of lighting, ventilation and pumping required, and the setting up of diversions, trafficclearance measures and the issue of traffic informatioto minimise the effects of approach road congestion, iparticular for dealing with the emergency.

14.13 Those responsible for the control of trafficpassing through a tunnel will need to be aware of anychanges in levels (status) of output from the equipmeninstalled to control the tunnel environment, that is likelto lead to the development of an emergency conditionThey will be responsible for responding to alarms thatare raised at emergency points within the tunnel andwithin the tunnel services buildings. To undertake theirespective responsibilities, the police, emergencyservices and TOA need a reliable supply of informatioand data. See below and Chapters 9, 10 and 13.

Information Systems

14.14 The Traffic Control Centre needs information adata to assess and respond to emergency conditionswithin the tunnel which will have an effect on traffic (egalarm states for equipment and power), alarms raisedtunnel users at the emergency points (telephones, firecabinets, micro-switches), routine traffic conditionswithin the tunnel or on its approaches, the needs of themergency services, and overall security (eg tunnelservices buildings).

14.15 The emergency services need information: toimplement the agreed operating procedures in responto incidents and emergencies; on tunnel accessarrangements (traffic control measures enforced bypolice); on the coordinated response between emergeservices (before the emergency drill); on details ofescape facilities, provisions made for them in plant anequipment (eg ventilation override), surveillance(CCTV), and communications with emergency serviceHQs (headquarters) and local facilities from the tunnesite.

14.16 The TOA needs data on ambient conditionsconcerning wind, luminance and general weatherconditions, and the status of the equipment installed tocontrol the tunnel environment (day-to-day demands,usage and running costs). It also needs information onperiodic inspection and maintenance requirements;factors that influence the optimum use of the tunnelinstallation and any corrective maintenance required (systems analysis); the support to be given to emergen

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authorities (fire, breakdown, spillage); resourcemanagement (eg for energy conservation). See alsoChapter 13.

Basis of Tunnel Operation

14.17 The day to day operation for traffic passingthrough a tunnel, or group of tunnels, will beadministered from a Traffic Control Centre, which maybe located at the tunnel or remotely.

14.18 A Traffic Control Supervisor or Duty Officerwill normally be in charge of all operations and must beadvised of any change in traffic or tunnel equipmentoperating conditions, by means of traffic surveillanceand plant monitoring equipment. Most of this equipmenwill operate under localised automatic control and/or thtelemetry system, and be monitored in the control roomThe main functions to be carried out are to monitor,control and coordinate the traffic system, and to controthe approach lighting, tunnel lighting, tunnel ventilationand any other equipment, as required.

14.19 In the event of ALARMS the Duty Officer mustalert the staff concerned, up date any mimic, andgenerally monitor the status of all tunnel equipment andin the event of a fire or traffic incident, take the requiredaction, as laid down in the Police Control CentreOperators’ Manual.

14.20 Support functions will be the responsibility of theTOA and include: tunnel cleaning and maintenance;clearance after Traffic Control Division have removedincident vehicles; repair and renewal of the technicaloperating equipment; maintenance repair and renewal structural elements.

Normal Conditions (Free Flow)

14.21 In normal circumstances, traffic will be able topass through a tunnel without stopping. However, tominimise incidents, reduce danger and ensure the bestuse of a tunnel, traffic may be controlled at times ofpeak flow. Any traffic stop signals provided shalloperate automatically, under the control of road loops,and the phasing of the signals shall be set to becompatible with the general traffic flow. Where there is tidal flow system, computer software shall be providedto assist in the correct sequencing of traffic signs at flowchangeovers.

14.22 Normal traffic may include hazardous andabnormal loads. Any appropriate action such asescorting such loads is part of normal tunnel operation.

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14.23 Tunnel ventilation fans are automaticallycontrolled, as required by the levels of CO or visibilitymonitored by the appropriate sensors, and operated viathe control system.

14.24 The tunnel lighting system is automaticallycontrolled by a dawn/dusk timer and photo-electric cellsas described in Chapter 6.

Emergency Conditions (Minor Incidents)

14.25 The majority of incidents, such as vehiclebreakdowns, shunt accidents etc can be classed as“minor” and do not require more than the attendance ofa “Traffic Officer” and a breakdown recovery vehicle.Traffic signing to close effected lanes and traffic controlto deal with any build up of traffic congestiondownstream will be required.

Emergency Conditions (Major Incidents)

14.26 A major incident may require a greater response,in terms of resources, than the normal response provideby the standard emergency procedures, and will involvethe possibility of severe personal injury or loss of life,the risk of a serious fire or serious damage to propertyand serious disruption to the traffic flow with consequentexceptional delay. This subject is discussed in moredetail in Appendix D.

14.27 During a major incident, the police have overallresponsibility for the necessary intervention, under thecontrol of the most senior police officer present. If a fireis involved, the fire aspects of the incident are theresponsibility of the fire brigade under the control of themost senior fire officer present. Tunnel equipmentshould be operated by tunnel personnel, if available, whoare familiar with the tunnel and its plant, under thedirection of the police or fire incident officer, asappropriate.

Traffic Control

14.28 On receipt of an incident report, or theobservation, say, of an incident on the CCTV monitors,which is considered to be a major incident then thefollowing emergency procedures shall be put into action:

i. Set traffic system to ALL TRAFFIC STOP toprevent traffic entering the tunnel(s).

ii. Telephone all relevant emergency services andinform them of the type and likely severity of theincident. Advise if Fire and Ambulances serviceswill be required.

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. Telephone to inform Police HQ, local to tunnelportals, and any Motorway Control Centreswhich may need to be involved.

entilation Control

4.29 The ventilation plant shall be first switched toanual, then fan and damper settings changed for smo

learance to the predetermined regime appropriate to tcation of the fire.

4.30 If fan settings are subsequently changed again quest from the Incident Fire Officer, details of time ofquest, revised fan settings and name of requesting

fficer shall be entered into the Control Point Log.

4.31 These actions shall be accommodatedutomatically by the data logging system described inhapter 10.

ighting Control

4.32 All the lighting stages of illumination would bewitched to manual control to enhance the tunnelhting, as necessary, and give all possible assistancee emergency services, particularly in smoke condition

4.33 In the case of electrical power supply failure, aystem of emergency lighting comprising approximatelyne in ten twin lamp luminaires, would be switched onom an Uninterruptible Power Supply (UPS). The UPSupply comprising batteries lasts for approximately twoours.

dditional Actions

4.34 Additional Actions to be taken during andllowing a major incident are set out in Appendix D.

perational Staff Resources

4.35 Resources required by the Tunnel Operatinguthority should differentiate between normal andmergency situations. Tunnel staff employed by theOA should carry a dual responsibility ie for normalperating conditions, and for the additionalsponsibilities under emergency conditions.ppropriately trained and qualified staff shall beesignated special responsibilities in the case ofmergencies. Special responsibilities could includeaffic control duties, emergency services call out,ontrol of ventilation plant and power supplies and usef breakdown and recovery equipment.

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14.36 Sometimes the operation of a road tunnel iscarried out on a shared responsibility basis. Normallythis responsibility will be divided between the LocalHighway Authority who will take care of all work inconnection with the roads and their maintenance and thOverseeing Organisation who will have responsibilityfor the tunnel structure and its equipment. Such adivision of responsibility would occur when it is noteconomically feasible to provide a dedicated tunneloperating force. Irrespective of the shared roles, normaand emergency operating procedures will also need to bcovered by the respective parties.

Safety Officer

14.37 A single member of staff shall be appointed asSafety Officer, responsible for all aspects of tunnelsafety, with authority to obtain implementation of SafetyRecommendations either directly, or immediatelythrough the Tunnel Manager. The Safety Officer shall bresponsible for the requirements of the Health and Safeat Work Act and the regulations made under its powerssuch as the Control of Substances Hazardous to HealtRegulations 1988. Responsibilities for safety supervisioand its observance in the tunnel workplace must beaccepted and applied by the whole of the workforce.

14.38 The Safety Officer shall be responsible for co-ordinating all aspects of handling emergency situationsand traffic incidents including the effects and exposurelimits of known pollutants and the effect of fire onmaterials which are likely to be transported through thetunnel. The Safety Officer shall have responsibilities formonitoring all arrangements for abnormal working ofthe tunnel and the performance of equipment to be useunder emergency conditions.

14.39 The Safety Officer shall ensure that wherepotentially confined spaces such as ducts, service waysumps etc could be at risk from hazardous gases, liquispills or seepage, there shall be a “gas free” check andpermit to work issued, if safe, before any maintenancestaff enter the space. Standard procedures on safeworking practice shall be enforced and training providedto assist rescue from, and avoidance of, such potentialdangerous situations.

Authorised Staff

14.40 TOA maintenance staff shall comply with theElectricity at Work Regulations 1989, Health and Safetyat Work Act 1974, the current IEE Regulations and anyother relevant procedures issued by the TOA. A “permito work” system shall be implemented for maintenance

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n all electrical equipment. This allows only authorisedunnel staff, or outside contracting personnel, to repairr maintain plant and equipment, when it has beenlocked” off electrically. HV systems must only beperated by Authorised Persons (APs) with appropriat

raining and certification, see Chapter 11.

unnel Maintenance

4.41 Maintenance will be carried out under the generrovisions of the agreement with the Overseeinguthority. A tunnel shall be maintained and cleaned toigh standards, during the short periods of lowest traffi

low. Lifetime expired equipment will need to beeplaced at periodic intervals, and may require severaleeks of continuing work. Tunnel lighting, for example,ill require major work at the end of the selected burn-

ife of each set of lamps eg fluorescent lamps, at 50%urn on equal duty cycle, will require such work every5 to 22 months (6000 - 8000 operating hours). Major

unnel refurbishments may be needed every 15 years oore and will require extensive planning andreparation.

4.42 This section shall be read in conjunction with theafety requirements of Chapter 2 and other Chaptersescribing particular specialist topics.

4.43 Whether maintenance is carried out by tunneltaff or term contractors, it is necessary to establish anpecify, the levels of need and the quality of workequired for the various types of maintenance to bearried out. It is most important to carry out the rightaintenance at the right time and which minimisesisruption to the travelling public. A whole life costpproach shall be used which avoids short term savingt the expense of higher longer term costs. Aaintenance strategy shall be put in place by the TOAeet such needs and which anticipates the likely extenf requirements, lane closure times available, noise an

ight pollution restraints, identification of any weak andulnerable links in the system, need for contingencylanning, availability of funding, relationships withanufacturers and term contractors, police etc.

4.44 The strategy should consider needs for flexibilityo meet the unexpected and make changes in the light xperience, concentration of work into locational zonesnd specialist trades, expected times to complete each

ask, breaking down large tasks into smaller ones on aogical basis, concentration on repeated or extensiveaults and their elimination, switching of items in-serviceo even out wear and tear, equipment component lifexpectancy, spares, specialist tools and equipment, ne

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of access, communications, inspections, feedback, traffimanagement etc. Obsolescence should be considered,particularly in the case of electronic equipment. Newerequipment may be cheaper to install and more reliablethan old, even if the older equipment is still functioningbut is difficult to maintain, as specialists disappear andsuppliers cease trading or product support. It may alsoprove cost effective to replace complex equipment withsimpler equipment that has either less chance of failureor has a fail safe facility.

14.45 From the strategy established, maintenanceplanning objectives for the short, medium and long termcan help in the decisions as to which items can bemaintained on a daily, weekly, monthly, yearly, urgent orroutine basis. Control of the maintenance process is byprioritisation, inspection, and recording.

14.46 The broad categories of road tunnel maintenanceand inspection are as follows:

i. Corrective Maintenance,

objectives: Continuity of system operation,keeping the tunnel open and safe to use eg if aCO sensor fails and is not repaired the ventilationfans may not run, if a jet fan falls because itsfixing bolts have vibrated loose, then the tunnelwill be closed whilst all the remaining fixings areinspected.

by: Permanent or standby staff undertakingsupervisory and overall inspection roles.

ii. Planned, Preventative Maintenance,

objectives: Preservation of investment,prevention of unscheduled closures, possibly forlengthy periods.

by: Term contractors, manufacturers’ staffundertaking roles of regular specialist inspection,performance testing of equipment, calibration andcleaning. Overhauls will be to manufacturer’sinstructions. Systems testing of safety criticalitems (regular testing, auto diagnostics,continuous monitoring) eg traffic management,programmable logic controllers (data processing),communication systems.

iii. Technical Inspections, Special Inspections,

objectives: To ensure preservation of investment,planned and funded maintenance works and thecontinued safety of operation for the travellingpublic.

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c by: TOA coordinating the input of termcontractors, manufacturers and other specialists,in accordance with BD53 (DMRB 3.1.6), IEEWiring Regulations etc. Work is normallyundertaken during a series of plannedmaintenance closures. Principal Inspectionsidentify what works may be needed for the next3/6 years.

. Major Overhaul and Refurbishment of the TunnelEquipment and Tunnel Fabric,

objectives: To ensure long term preservation ofinvestment by acting on the agreedrecommendations of the Principal Inspectionreports.

by: Specialist design consultants, contractors andmanufacturers. Advantage will be taken of longeror more frequent closures periods, to replace inone go many items that have proved difficult todeal with during short term lane closures. ATDSCG will normally need to be set up for suchworks.

4.47 Prior to tunnel opening, a regular schedule foraintenance shall be established together with a planf limited closures of the tunnel for planned minoraintenance.

leaning and Maintenance Schedules

4.48 Within the tunnel, walls, carriageways andrainage systems will all need to be cleaned regularly.ir ducts for tunnel ventilation and the entrances to freshir supply ducts shall also be cleaned at regulartervals. Collections of tunnel dust can be a potential

re hazard and may contain heavy metals, asbestos andther pollutants from vehicles. Personal protectivequipment is essential. Specialised and articulated,echanical rotating brush and spray jet equipment isvailable or can be manufactured to suit particularnnel geometries. Care is needed that over-vigorous

leaning does not remove the protective systems ofquipment against corrosion.

4.49 Cleaning and maintenance shall be carried out atast once per week. A typical tunnel maintenance

chedule is shown in Figure 14.1.

4.50 Manuals (specified in Chapter 13) will have beenrepared for the instruction and guidance of the Tunnelperation Authority in carrying out specificaintenance functions within the tunnel.

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Inspection and Testing

14.51 An inspection and testing programme shall beestablished which will include examination of the tunnelstructure, quantitative measurements of light output,vibration of rotating machinery, and failure rate againsthours run etc, all logged on a regular basis, as describedin Chapter 10. BD53 (DMRB 3.1.6) gives details ofinspection types and reporting records. The inspectiontypes are purposely intended to lead to no surprises andconsequent unplanned closures for emergency repairs.

14.52 Isolated items of equipment may often fail in theirvery early life. These items will be replaced within theMaintenance Period. Certain items will need to beinspected to meet the timing requirements of eg IEE,other items which prove to be troublesome will needincreased frequencies of inspection, or whole scalereplacement. For items which are large in number orpresent difficulties from the point of view of availabletime to access them, such as items behind secondarycladding panels, then the number of items to inspect oveeach year can be estimated from the normal distributioncurve (NDC), see Figure 14.2. If the mean time tofailure (MTF) of an item is taken to be 3 standarddeviations (SD) then from time zero (new) all items mustbe inspected at increasing numbers per year so that all(100%) are inspected by the time the MTF year isreached. For example, if MTF is 9 years, then 4.28%,27.46% and 68.26% of items must be inspected, on arandom basis, in each of the respective three 3 yearperiods from time zero. This method allows resources tobe concentrated into the latter years when proportionallymore failures could be expected to occur.

Lane Closures

14.53 Lane closures and use of cross overs may berequired when carrying out maintenance and inspectionwithin a tunnel. Lane closures etc by means of gantrysignals shall be supplemented by additional signing,cones etc in accordance with Chapter 8 of the TrafficSigns Manual. PIARC C5 Report: Brussels 1987: I.2 -Signing in the Case of Work Inside Tunnels givesillustrations of sign and cone layouts for fixed,alternated and mobile worksites. Police assistance maybe invaluable during the onerous and dangeroustemporary signing process in assisting to reducing thedanger from traffic at lane closing/opening stages and in“enforcing” speed limits. Automatic lane closure barriers(by progressive unfolding in conjunction with signals)are used successfully in Europe but are believed not tobe legal under the current Highways Act. Animatedretroreflective dummys waving red flags at potentialdanger spots have also been successfully used Oversea

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lans shall include sufficient time for the set up/putay times for traffic management and the effect onailable productive maintenance working times.

.54 The TOA will normally need to arrange laneosures in liaison with the affected Local Highwayuthorities and include for alternative routes. A websitetailing lane closures is available at http//ww.highways.gov.uk/. Local media may also need to informed. The relevant Traffic Orders shall be in

ace for carriageway closures.

affic Control During Maintenance

.55 The maintenance workforce shall be protectedm the traffic and the traffic from the works.affic Control Supervisors or Duty Officers willquire minimum disturbance to traffic duringriods of maintenance. Such requirements lead to

e creation of special traffic conditions duringaintenance works, involving single lane restrictions closures, depending upon the scale of the work ande layout of the tunnel. The equipment used directly control the traffic shall include the lane controlgnals and lane segregation signs on overheadntries, working in conjunction with Variableessage Signing, as provided.

.56 Traffic within a tunnel can produce noise levels excess of 95dB(A). Traffic also produces turbulent anditions, greater than the open air, which with positivd negative (suction) pressures and other air speedzards can unbalance those on foot or working atight. Projections from vehicles can hit workers orbalance working platforms etc. The workforce mayt be sufficiently protected, when working in a closed

ne of a bore, if vehicle speeds are not physicallystricted in the remaining running lanes. A system ofatooning, by grouping vehicles together and guidingem through the tunnel at slow speed (say 15 mph) wlead vehicle, will enable air velocities to be limited anlow maintenance to be carried out safely whilstaintaining at least some traffic flow through the bore.n angled temporary concrete barrier, or equivalentield (traffic management) vehicle (unoccupied andm minimum from workers) placed just inside of thelevant portals can protect against vehicle drivers whoay still attempt to enter a closed tunnel bore or lane, ror. It shall be recognised that some safety items ma temporarily out of operation during the maintenance

orks. It is preferable to work on equipment inorkshops away from the tunnel.

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Radio communications

14.57 Radio communications allow rapid coordinationand response in the event of an incident, withcommunications direct to the Traffic Control Centre.

Equipment Settings During Maintenance

14.58 During maintenance conditions, the lighting andventilation may have to be enhanced so that staff canwork in safety and efficiently. Pollution levels will behigher if any traffic is permitted to stop/start. It is usualto provide maximum approach/tunnel lighting duringmaintenance works.

14.59 Where conditions warrant, the ventilation plantshall be switched to manual. The lighting shall beswitched to manual control and extra stages of lightingused to increase the lighting levels. The usage ofluminaires shall be arranged to give continuity oflighting throughout the length of the tunnel.

Access and Safety Procedures

14.60 All staff and contractors involved with enteringthe tunnel shall be issued with, and abide by, the rulesand procedures of tunnel operations, including lane antunnel closures - all of which shall be clearly stated andbe expressed simply. All shall be familiarised with thetunnel site layout. A system of recorded signatures forreceiving such information is advisable. The workingroute of an inspector (as with all persons working in atunnel) shall be recorded and a system provided to verreturn. If access is required to an enclosure a secondman shall be present. A driver will be needed for transithrough an operational tunnel.

14.61 Maintenance Staff shall notify the appointedTunnel Controller before entering and immediately afteleaving the tunnel environs and provide details of anywork which may affect the traffic or tunnel services.Tunnels with mechanical ventilation can purge the tunnbores etc of vehicle pollution prior to entry by staff.Tunnels with natural ventilation may need time to clearand readings of CO, NO

2 etc shall be taken using

personal gas monitors prior to entry of any section of thtunnel.

14.62 Services Building entry doors will normally beprotected by Intruder Alarm Systems. Maintenance stawill therefore need to switch off the alarm system onentering the building and re-activate it on leaving.

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14.63 Maintenance staff will notify the TunnelController before entering a halon or Co

2 protected room

and “lock off” the fire extinguishing system. They shallreverse the procedure on leaving.

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FIGURE 14.1: Typical Maintenance Schedule

Item Equipment Cleaning Frequencies Maintenance Frequencies

1 Lamps 1 - 2 months 8 - 36 months

2 Lighting controls 12 months 12 months

3 Jet fan overhaul 48 months

4 Axial flow fans and auxiliary equipment Minor: 4000 hoursMajor: 25000 hours

5 Obscuration meters 1 month Minor: 1 monthMajor: 12 months

6 CO monitors 3 months 3 - 12 months

7 Anemometers 6 months

8 Ventilation computer 1 month 1 month

9 Ventilation switch gear 24 months 12 months

10 Remote control system 6 months

11 Lights 1 week - 3 months 6 months

12 Variable message signs 6 months 12 months

13 Safety barriers 6 months

14 Movable barriers 6 months

15 Traffic recording/induction loops 3 - 12 months

16 Traffic computer 6 months 1 month

17 Peripheral units 6 months 6 months

18 Emergency phones 1 month 3 months

19 Fire Hydrants in tunnel recesses 6 months 6 months

20 Hand fire extinguishers 6 months 12 months

21 Fire hydrant main 6 months

Chapter 14Tunnel Operation and Maintenance

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Item Equipment Cleaning Frequencies Maintenance Frequencies

22 Automatic fire alarm system 3 months

23 CCTV cameras and equipment 1 month 1 month

24 Public address loudspeaker system 6 months

25 Radio system 12 months 6 months

26 Overheight vehicle detectors 6 months

27 Escape doors and tunnel walls See Chapter 6 6 months

28 Transformers 12 months

29 HV switch gear 12 months 12 months

30 LV switch gear 24 months 12 months

31 Emergency switch gear and UPS systems 12 - 24 months 1 - 3 months

32 Batteries 1 week 1 - 12 months

33 Gulleys 1 month

34 Sumps 1 month

35 Foul sumps 1 - 3 months

36 Oil and petrol separators 1 month

37 Pumps 1 week 1 month

38 Pump controls 1 week 1 month

39 Valve actuators 1 week 1 month

40 Road Surfacing 1 week Minor: 1 monthMedium: 12 monthsMajor: 7-10 years

Chapter 14Tunnel Operation and Maintenance

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aintenance

z = -3 z = -2 z = -1 z = 0 z = 1 z = 2 z = 3

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Time

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(iii) Resources concentrated into latteryears when more failures can be expected

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15. REFERENCES AND GLOSSARY

Chapter 15References and Glossary

General

15.1 This Chapter provides, in chapter order, a list oreferences and a glossary of common abbreviations.Unless specifically referred to within the other Chapterand Appendices of this Standard or a publisheddocument of the Overseeing Organisation such referendocuments are intended for information and guidanceonly and may not be taken to reflect the current policy the Overseeing Organisations. Documents will from timto time be updated or superseded and DesignOrganisations shall ensure that they are working to themost current versions. See also Appendix E.

15.2 Departmental Standards of the DMRB (DesignManual for Roads and Bridges) and Manual of ContraDocuments for Highway Works are published by theHighways Agency and may be obtained from theStationary Office Publications Centre, PO Box 276,LONDON SW8 5DT, United Kingdom (GeneralEnquiries: telephone +44 (0)171 873 0011, +44 (0)171873 8247 fax).

15.3 World Road Association PIARC documents mabe obtained from British PIARC Secretariat, Room 4/79, St Christopher House, Southwark Street, LONDOSE1 0TE, United Kingdom ( telephone +44 (0)171 9214349, +44 (0)171 921 4505 fax).

15.4 Publications and reports of TRL (TransportResearch Laboratory) may be obtained from TRLLibrary Services, Old Wokingham Road, Crowthorne,Berkshire, RG45 6AU, United Kingdom (telephone +44(0)1344 770783/4, +44 (0)1344 770193 fax).

15.5 Publications of the Health and Safety Executivemay be obtained from HSE Books, PO Box 1999,Sudbury, Suffolk CO10 6FS, United Kingdom(telephone +44 (0)1787 881165, +44 (0)1787 313995fax).

15.6 Publications of the British Standards Institutionmay be obtained by writing to BSI, Lindford Wood,Milton Keynes, MK14 6LE, United Kingdom.

15.7 Publications of CIRIA (Construction IndustryResearch and Information Association) may be obtainefrom CIRIA, 6 Storey’s Gate, Westminster. LONDONSW1P 3AU, United Kingdom (telephone +44 (0)171222 8891, +44 (0)171 222 1708 fax,

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15.8 REFERENCES

Chapter 1. Introduction

Overseeing Organisation Publications

i. Manual of Contract Documents for HighwayWorks: Volume 5 Contract Documents forSpecialist Activities: Section 7 Mechanical andElectrical Installations in Road Tunnels, MovableBridges and Bridge Access Gantries.

Other publications

i. The First Road Tunnel: PIARC Committee onRoad Tunnels: 1995.

ii. Tunnel Vision?: The Future Role of Tunnels inTransport Infrastructure: ParliamentaryOffice of Science and Technology: January 1997ISBN 1 897941 36 6.

Chapter 2. Planning, Safety, General DesignConsiderations

Overseeing Organisation Publications

i. Departmental Standard BD2 (DMRB 1.1) PartIII - The Technical Approval of HighwayStructures on Motorways and Other TrunkRoads: Procedures for Tunnels

ii. Departmental Standard BD21 (DMRB 3.4.3) -The Assessment of Highway Bridges andStructures

iii. Departmental Standard BD31 (DMRB 2.2) -Buried Concrete Box Type Structures

iv. Departmental Standard BD37 (DMRB 1.3) -Loads for Highway Bridges

v. Departmental Standard BD42 (DMRB 2.1.2) -Design of Embedded Retaining Walls and BridgeAbutments (Unpropped or Propped at the Top)

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vi. Departmental Standard BD43 (DMRB 2.4) -Criteria and Materials for the Impregnation ofHighway Structures

vii. Departmental Standard BD47 (DMRB 2.3.4) -Waterproofing and Surfacing of Concrete BridgDecks

viii. Departmental Standard BD53 (DMRB 3.1.6) -Inspection and Records for Road Tunnels

ix. Departmental Advice Note BA80 (DMRB 2.1.7)- Design of Rock Bolts

x. Departmental Standard HD13 (DMRB 4.1) -Documentation Requirements for GroundInvestigation Contracts

xi. Departmental Standard HD22 (DMRB 4.1.2) -Ground Investigation and Earthworks Procedurfor Geotechnical Certification

xii. Departmental Advice Note HA34 (DMRB 4.1) -Ground Investigation Procedure

xiii. Departmental Advice Note HA73 (DMRB 4.1.7)- Site Investigation for Highway Works onContaminated Land

xiv. Departmental Standard HD19 (DMRB 5.2.2) -Road Safety Audits

xv. Departmental Advice Note HA42 (DMRB 5.2.3)- Road Safety Audits

xvi. Departmental Standard TD20 (DMRB 5.1) -Traffic Flows and Carriageway WidthAssessment

xvii. Departmental Advice Note TA46 (DMRB 5.1.3)- Traffic Flows and Carriageway WidthAssessment for Rural Roads

xviii. HA Health and Safety Notices, Volume 1: StaffSite Safety Manual. Notice No.9 - Working inConfined Spaces

xix. HA Health and Safety Notices, Volume 1: StaffSite Safety Manual. Notice No.10 - Working inTunnels

xx. HA Health and Safety Notices, Volume 1: StaffSite Safety Manual. Notice No.11 - StaffWorking with Lighting Equipment and ElectricalServices on Roads and in Tunnels.

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British Standards

i. BS 1449, Part 2: 1983 - Specification forStainless and Heat-resisting Steel Plate, Sheetand Strip

ii. BS 5266, Part.1: 1975 - Code of Practice for theEmergency Lighting of Premises other thanCinemas and Certain other Specified Premisesused for Entertainment

iii. BS 5400 - Steel, Concrete and CompositeBridges, All Parts but in particular, Part 1: 1988- General Statement; Part 2: 1978 - Specificationfor Loads; Part 3: 1982 - Code of Practice forDesign of Steel Bridges; Part 4: 1990 - Code ofPractice for Design of Concrete Bridges; Part 5:1979 - Code of Practice for Design of CompositeBridges. All as implemented by respectiveseparate documents of the DMRB (DesignManual for Roads and Bridges).

iv. BS 5839 - Fire Detection and Alarm Systems forBuildings, Part 1: 1988 - Code of Practice forSystem Design, Installation and Servicing

v. BS 6164: 1990 - Code of Practice for Safety inTunnelling in the Construction Industry

vi. BS 7671: 1992 - Requirements for ElectricalInstallations, IEE Wiring Regulations, SixteenthEdition.

TRL (Transport Research Laboratory) ContractorReports

i. CR41: Planning and Design Considerations forRoad Tunnels: The Influence of Operation andMaintenance. S T Jones, G Fudger

ii. CR51: Some Considerations Affecting theSelection of Tunnelling Methods. I W Farmer

iii. CR63: A Study of the Operating Costs of RoadTunnels in the United Kingdom. A M Rossell,B R Pursall

iv. CR124: Comparison of Predicted and MeasuredPerformance of the Retaining Walls of the BellCommon Tunnel. K G Higgins, D M Potts,I F Symons

v. CR139: Risk Assessments of the Transportationof Hazardous Substances Through Road Tunnelsin the United Kingdom. M Considine, S T Parry,K Blything

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vi. CR252: Study of Costs of Cut and Cover TunnConstruction. A R Umney, D Miller

vii. CR265: Finite Element Analyses of SettlementAbove a Tunnel in Soft Ground. R J Mair,D W Hight, D M Potts.

TRL Laboratory Reports

i. LR326: A Preliminary Study of the Cost ofTunnel Construction. G Margason, R G Pococ

ii. LR714: The Particle Size Distributions of DebriProduced During Tunnelling Trials. A F ToombR A Snowdon, M P O’Reilly

iii. LR740: A Guide to Site Investigation Procedurefor Tunnels. M J Dumbleton, G West

TRL Published Papers

i. Prospects of Urban Highways in Tunnels.M P O’Reilly, A P Munton. ICE TransportationEngineering Conference, pp 43-53, 1972

ii. Sub City Tunnels. M P O’Reilly. CivilEngineering, Oct 1975

iii. Transport Tunnels in Urban Areas.M P O’Reilly. Journal Institution HighwayEngineers, Jan 1976

iv. Cost Factors for Cut and Cover Tunnels.A R Umney, D Miller, D R Carder. Tunnelling’91, Institution of Mining and Metallurgy,London, pp 313-327, 1991.

v. Tunnelling Induced Ground Movements:Predicting their Magnitude and Effects.B M New, M P O’Reilly. InternationalConference on Ground Movement andStructures, Cardiff, Vol 4, pp 671-697, July 199

vi. Ground Vibrations Caused by the Constructionand Operation of Transport Systems. G I CrabB M New, D M Hiller. Proceedings 3rdInternational Symposium on Field Measuremenin Geomechanics, Oslo, pp 443-454, 1991

vii. Environmental Impacts of Tunnel Construction.D M Hiller, K H Bowers. Proceedings of TheChartered Institution of Water and EnvironmenManagement, South Western Branch, CentenaSymposium, Tunnelling In The Water Industry.

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TRL Supplementary Report

i. SR335: A Review of Tunnel Lining Practice inthe United Kingdom. R N Craig, A M MuirWood.

TRL Project Reports

i. PR89: The Design, Construction andInstrumentation of The Pen-Y-Clip Section ofThe A55, North Wales Coast Road. K C Brady,D A Barratt and P J Selley

ii. FEHRL 2: Analysis of The Submerged, FloatingTunnel Concept

iii. PR280: Ground classification systems in tunnelconstruction. G I Crabb

iv. TRL Report 379: Performance duringconstruction of a cut-and-cover tunnel founded inLondon Clay at Edmonton (A406 Fore StreetTunnel). D R Carder, K J Barker, M R Easton.

Other Documents

i. CIRIA Report 44 - Medical Code of Practice forWork in Compressed Air: 1982

ii. CIRIA Report 81 - Tunnel Waterproofing(withdrawn)

iii. Statutory Instrument 1958 No. 61 - Work inCompressed Air Special Regulations

iv. Statutory Instrument 1989 No. 635, Health andSafety - Electricity at Work Regulations

v. Health and Safety Executive, Guidance NoteEH40: Occupational Exposure Limits. (Updatedannually).

vi. DISC PD2000-1:1996 - A Definition of Year2000 Conformity Requirements (BSI)

vii. Research on Tunnels at the Transport and RoadResearch Laboratory. M P O’Reilly.Underground Services, Vol 3, No 4, 1975

viii. Recent Research in the United Kingdom on theOperation of Road Tunnels. M P O’Reilly,G R Fellowes. Tunnel Management: Economics,Environment and Safety, Lugano, Switzerland,Seminar RT2, Nov 1990

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ix. TRL Working Paper No.14: Tunnelling Researchin the UK. Hudson.

x. Road Safety in Tunnels: PIARC Committee onRoad Tunnels: 1995

Chapter 3. Operational Classification of SafetyFacilities for the Road User

World Roads Association PIARC

i. PIARC XVIIIth World Road Congress, Brussels1987. Technical Committee Report No. 5 - RoadTunnels, Section 1.1.1 - Safety Equipment

ii. PIARC XXth World Road Congress, Montreal1995. PIARC Committee on Road Tunnels:Supplementary Paper on Classification ofTunnels, Existing Guidelines and Experiences,Recommendations.

Overseeing Organisation Publications

i. Departmental Report MCH 1745 A, Issue 03:August 1994. Hazards of Traffic Managementwithin Tunnels

ii. The Value for Money Manual, HighwaysAgency, June 1996.

Chapter 4. Tunnel Geometric Design for Traffic

Overseeing Organisation Publications

i. Departmental Standard TD9 (DMRB 6.1.1) -Highway Link Design

ii. Departmental Standard TD20 (DMRB 5.1) -Traffic Flows and Carriageway WidthAssessment

iii. Departmental Standard TD27 (DMRB 6.1.2) -Cross Sections and Headrooms

iv. Traffic Appraisal of Roads Schemes (DMRB12.1) - The Traffic Appraisal Manual (TAM),August 1996.

TRL Supplementary Report

i. SR455: Speed/Flow Relationships in RoadTunnels. A P Bampfylde, G J D Porter,S D Priest.

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hapter 5. Ventilation

. Permanent International Association of RoadCongresses (PIARC), XXth World RoadCongress, Montreal, Sept. 1995. Report ofCommittee C5 on Road Tunnels, Part II -Pollution, Environment, Ventilation

i. Permanent International Association of RoadCongresses (PIARC) Technical Paper: RoadTunnels - Emissions, Ventilation, Environment,1995

ii. World Health Organisation (WHO). Air QualityGuidelines for Europe, WHO RegionalPublications, European Series No. 23, 1988

v. Health and Safety Executive Guidance NoteEH40: Occupational Exposure Limits. (Updatedannually)

. Department of Transport, Vehicle Standards anEngineering Division. Fact Sheet No. 1, Issue 3Sept. 1995: In-Use Vehicle Emissions StandardApplicable from September 1995

i. Department of Transport, Vehicle Standards anEngineering Division. Fact Sheet No. 2, Issue 3Sept. 1995: In-Use Vehicle Emissions StandardSupplementary Requirements Applicable from 1January 1996

ii. Road Vehicles (Construction and Use)Regulations 1986, Regulation 61 (“First Use”requirements for new vehicles) andSupplementary Instruments

iii. TRL Contractor Report 136: Vehicle EmissionExperimental Study. J F L Lowndes, A West,P J Martin

x. TRL Laboratory Report 477: A Review ofMethods of Ventilating Road Tunnels.H J Hignett, L Hogbin

. World Roads Association, PIARC Committee oRoad Tunnels: Fire and Smoke Control in RoadTunnels, 1999

i. DMRB (11.3.1) Environmental Assessment: AirQuality.

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Chapter 6. Lighting

British Standards

i. BS5489, Part 7: 1992 - Code of Practice for theLighting of Tunnels and Underpasses

ii. BS5266, Part.1: 1975 - Code of Practice for theEmergency Lighting of Premises other thanCinemas and Certain other Specified premisesused for Entertainment

Commission International d’Eclairage (CIE)Publications

i. CIE30.2:1982 - Calculation and Measurement oLuminance and Illuminance in Road Lighting

ii. CIE66:1984 - Road Surfaces and Lighting (JointTechnical Report CIE/PIARC).

Chapter 7. Drainage

i. Highways Act 1980. London : HMSO, 1980.(In Scotland: Roads (Scotland) 1984)

ii. Health and Safety at Work etc Act 1974.London : HMSO, 1974

iii. Public Health Act 1936. London : HMSO, 1936

iv. Design and Analysis of Urban Drainage:Wallingford Procedure, Volume 4 ModifiedRational Method. London, National WaterCouncil, 1981

v. A Guide for Engineers to the Design of StormSewer Systems. Department of the EnvironmentRoad Note 35, 2nd Edition. London, HMSO,1976

vi. Russam, K. Hydraulic Efficiency and Spacing ofBS Road Gulleys TRRL Report LR277.Crowthorne, TRRL 1969

vii. The Drainage Capacity of BS Road Gullies and Procedure for Estimating their Spacing. TRRLCR2 “Hydraulics Research Station ReportEX1118” Crowthorne TRRL 1984

viii. BS 5345 : Part 2 : 1983. Code of Practice forSelection, Installation and Maintenance ofElectrical Apparatus for use in PotentiallyExplosive Atmospheres (other than miningapplications or explosive processing andmanufacture) : Part 2 Classification ofHazardous Areas.

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Overseeing Organisation Publications

i. Departmental Advice Note HA71 (DMRB 4.2.1)- The Effects of Highway Construction on FloodPlains

ii. Departmental Standard HD33 (DMRB 4.2.3) -Surface and Sub-surface Drainage Systems forHighways

iii. Departmental Standard BD2 (DMRB 1.1) PartIII - The Technical Approval of HighwayStructures on Motorways and Other TrunkRoads: Procedures for Tunnels.

Additional Information

i. Water Practice Manual. IWE&S.

ii. Meteorological Office Records (Precipitation).

Chapter 8. Fire Safety Engineering

i. Home Office Technical Bulletin 1/1993:Operational Incidents in Tunnels andUnderground Structures: HMSO (now SO).

ii. Fire Risk Assessment: Complying with the FirePrecautions (Workplace) Regulations 1997: FireIndustry Council

iii. BS 476 1970 Fire Tests on Building Materialsand Structures Part 4 - Non Combustibility Testfor Materials. London: BSI. BS Standards(various) for flammability and fire testing.

iv. The Building Regulations 1991 ApprovedDocument Part B Fire, Safety. London : HMSO,1992, ISBN 0 11 7523135

v. Montreal Protocol on Substances that Deplete tOzone Layer

vi. Studies of Fire and Smoke Behaviour Relevant Tunnels. Heselden, A.J.M. Paper J1, SecondInternational Symposium on the Aerodynamicsand Ventilation of Vehicle Tunnels. Cranfield :BHRA, 1976.

vii. Major Hazard Aspects of the Transport ofDangerous Substances: Advisory Committee onDangerous Substances: Health & SafetyCommission: 1991, HMSO (now SO). Appendix13 covers emergency planning.

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viii. Fire in Road Tunnels: Protection for civilengineering structures, electrical circuits andequipments: WRA (PIARC) Routes/Roads,No 275, III: 1991.

ix. Road Safety in Tunnels: PIARC Committee onRoad Tunnels: 1995

x. British Standards, or equivalent, where relevanto road tunnels and service buildings:

BS AU 169: Burning behaviour of road vehicles(internal materials) etc.BS EN 671-1: Fixed fire fighting systems. Hosesystems.BS ISO 10294: Fire resistance tests. Firedampers for air distribution systems.BS 5041: Fire hydrant systems equipment.BS 5306: Fire extinguishing installations andequipment on premises.BS 5588: Fire precautions in the design,construction and use of buildings.BS 5810: Code of Practice for access for thedisabled to buildings.BS 7273: Code of Practice for the operation offire protection measuresBS 7346: Components for smoke and heatcontrol systems.

DD 233: Code of Practice for gaseous firefighting systems.DD 240: Fire safety engineering in buildings.

xi. See also Chapters 10, 11 & 12 references.

TRL Contractor Reports

i. TRL Contractor Report No.28: MathematicalModelling of Fire in Road Tunnels - Validation oJasmine. S Kumar, G Cox

ii. CR101: Mathematical Modelling of Fire in RoadTunnels - Effects of Radiant Heat and SurfaceRoughness. S Kumar, G Cox.

Chapter 9. Traffic Control, Communications andInformation Systems

Overseeing Organisation Publications

i. Departmental Standard BD2 (DMRB 1.1) - TheTechnical Approval of Highway Structures forMotorways and other Trunk Roads - Part IIITunnels.

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i. Manual of Contract Documents for HighwayWorks: Volume 5 Contract Documents forSpecialist Activities: Section 7 Mechanical andElectrical Installations in Road Tunnels, MovableBridges and Bridge Access Gantries

ii. MCE 2108 - 620 Cabinets for BT Interfaces

iii. MCE 2122 - Active Infra Red Above GroundVehicle Detectors

iv. MCF 2336 - Tunnel Sub System

v. MCH 1745 - Hazards of Traffic Managementwithin Tunnels

vi. TR 2029 - Inductive Loop Cable for VehicleDetection Systems

vii. TR 2031 - Armoured Feeder Cable for InductiveLoop System

viii. TR 2095 - NMCS2 Variable Message SignDriver

ix. TR 2124 - (Draft) Specification for AutomaticIncident Detection Systems Outline SystemSpecification

x. TR 2125 - Specification for Automatic IncidentDetection Systems Outline Instation Specificatio

xi. TR 2136 - Functional Specification forContinuous or Discontinuous VMS

xii. TR 2144 - NMCS2 MIDAS SubsystemSpecification

xiv. TR 2147 - Microwave Vehicle Detectionequipment for Portable Vehicle Actuated TrafficSignals

xv. TR 2148 - Outline Specification for CCTV AlertSystem

xvi. TR 2166 - NMCS2 Traffic Counting SubsystemSpecification

xvii. TR 2174 - NMCS2 MIDAS System PerformanceSpecification

xviii. TR2177 - NMCS2 MIDAS Outstation AlgorithmSpecification

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ixx. TR 2178 - NMCS2 MIDAS InterfaceSpecification.

Other Documents

i. The Traffic Signs and General DirectionsRegulations HMSO

ii. Planning and Design Considerations for RoadTunnels: The Influence of Operation andMaintenance. Crowthorne: TRRL ContractorReport 41

iii. European Community Directive 89/376/EEC

iv. International Electrotechnical Commission -IEC - 1508

v. International Electrotechnical Commission -IEC - 332-2

vi. International Electrotechnical Commission -IEC - 332-3

vii. Institute of Electrical and Electronic EngineeringIEEE - 383

viii. Radio Communications Agency PublicationRA 133

ix. Radio Communications Agency PublicationMPT 1367

x. Radio Communications Agency PublicationMPT 1510.

Chapter 10. Plant Monitoring and Control

i. Departmental Standard BD53 (DMRB 3.1.6) -Inspection and Records for Road Tunnels

ii. TRL Supplementary Report No.833: TheApplication of Microelectronics to the Control ofHighway Tunnels. H J Bennett, M F Chudleigh,M P Halbert, G K A Oswald.

iii. BS EN 60695: Fire hazard testing

Chapter 11. Electrical Power Supply andDistribution

i. BS7671:1992 - Requirements for ElectricalInstallations, IEE Wiring Regulations, SixteenthEdition

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i. Statutory Instrument 1989 No. 635, Health andSafety - Electricity at Work Regulations.

ii. Guidance Note 4 of IEE Wiring Regulations onprotection against fire.

. BS 4066: Tests on electric cables under fireconditions.

. BS 6425: Tests on gases evolved during thecombustion of materials from cables.

. BS 6387: Specification for performancerequirement for cables required to maintaincircuit integrity under fire conditions (< 750volts).

hapter 12. Services Buildings and Plant Rooms

. The Building Regulations 1985. London: HMSOSI 1985 No.1065,1985

i. BS6651:1992 - Code of Practice for theProtection of Structures Against Lightning.

ii. See Chapter 8, 10 & 11 references.

hapter 13. Tunnel Commissioning, Handover andunnel Documentation

. Manual of Contract Documents for HighwayWorks: Volume 5 Contract Documents forSpecialist Activities: Section 7 Mechanical andElectrical Installations in Road Tunnels, MovableBridges and Bridge Access Gantries

i. Departmental Standard BD53 (DMRB 3.1.6) -Inspection and Records for Road Tunnels.

hapter 14. Tunnel Operation and Maintenance

. Health and Safety at Work Act 1974

i. Electricity at Work Regulations 1989

ii. The Control of Substances Hazardous to Health(COSHH) Regulations 1988

. Planning and Design Consideration for RoadTunnels : The Influence of Operation andMaintenance S. T. Jones & G. Fudger,Department of Transport, TRRL, CR41 (1988)

. Guidelines to Set Up Instructions in Case of Firein Road Tunnels. PIARC Technical Committeeon Road Tunnels, Working Group Operation -Maintenance - Management, 15 March 1990.

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vi. Dartford Tunnel Controllers Manual, Vol. 2:Emergency Procedures, Mott Hay and Anderson

vii. M25 Holmesdale Tunnels, Operation Manual(Metropolitan Police), Mott, Hay and Anderson.

Chapter 15. References and Glossary

No additional references.

Appendix A - Secondary Cladding

No references.

Appendix B - Durability and Materials

i. BS 5493:1977 - Code of Practice for ProtectiveCoating of Iron and Steel Structures AgainstCorrosion

ii. Specification for Protection of Highway Works,Series l900 6th Edition, and Notes for Guidance

iii. BS Code of Practice 1021 for CathodicProtection.

Appendix C - Tunnel Documentation:TypicalContents

No references.

Appendix D - Guidelines for Major IncidentOperations and Fire Tests

Additional Information

i. Guidelines to Set up Instructions in the Case ofFire in Road Tunnels, PIARC TechnicalCommittee on Road Tunnels, Working GroupOperation - Maintenance - Management,15 March 1990.

ii. Heselden, A.J.M., Studies of Fire and SmokeBehaviour Relevant to Tunnels. Paper Jl, SecondInternational Symposium on the Aerodynamicsand Ventilation of Vehicle Tunnels. Cranfield:BHRA, 1976.

iii. Home Office Technical Bulletin 1/1993:Operational Incidents in Tunnels andUnderground Structures: HMSO (now SO).

iv. Major hazard aspects of the transport ofdangerous substances: Advisory Committee onDangerous Substances: Health & SafetyCommission: 1991, HMSO (now SO). Appendix13 covers emergency planning.

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o additional references.

ppendix F - Tunnel Design and Safety Consultationroup (TDSCG) Requirements

See Appendix D references.

BD2 (DMRB 1.1): Technical Approval ofHighway Structures on Motorways and OtherTrunk Roads: Part III: Procedures for Tunnels.

. BD53 (DMRB 3.1.6): Inspection and Recordsfor Road Tunnels.

ppendix G - Life Expectancy of Tunnel Equipment

o references.

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15.9 GLOSSARY OF TERMS

TERM/ABBREVIATION MEANING

AADT Annual Average Daily Traffic

ACB Air circuit breaker

AFFF Aqueous Film Forming Foam

AIP Approval In Principle document

ASTA Association of Short Circuit Testing Authorities

AWA Aluminium Wire Armoured

BA Bridges Advisory, Similarly HA (Highways), TA (Traffic)

BBC British Broadcasting Corporation

BD Bridges Directive, Similarly HD (Highways), TD (Traffic)

BS British Standard

BSI British Standards Institution

Cavitation A physical combination of vapour (and liquid) forming on the blades of amoving impeller causing noise and poor pumping ability

CCTV Closed circuit television

CFC Chlorofluorocarbon

CFD Computational Fluid Dynamics

CIBSE Chartered Institute of Building Services Engineers

Coaxial cable Type of cable consisting of two concentric conductors separated by insulation,used to transmit high frequency (eg television) signals

Chapter 15References and Glossary

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TERM/ABBREVIATION MEANING

Conductor Set of wires, or conductors, which together form a power supply or datacommunication cable.

COBS Control Office Base System

CP British Standard Code of Practice

CPU Central Processing Unit

dB decibel

dB(A) decibel related to sound level

DC Direct Current

DIN A German standard

DMRB Design Manual for Roads and Bridges

DP Double pole

Duct Pipe or conduit for access to and mechanical protection of cables

Earth Any zero-voltage point

Earth electrode A conductor or group of conductors providing a sound electrical connectionwith the earth (soil or ground)

Earth leakage current A stray current which flows to earth, in a circuit which is electrically sound

EDP Emergency Distribution Panel

EHO Environmental Health Office/Officer

EMS Electronic Message Sign

EN European Standard (or Euronorm)

Chapter 15References and Glossary

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TERM/ABBREVIATION MEANING

EPROM Erasable programmable read only memory

FOSD Full Overtaking Sight Distance

Fuse Protective device which operates and causes current flow to cease underovercurrent or fault current conditions

Glanded off Cable fitted with a proprietary termination device or sleeve, employed to presspacking tight on or around it, and the action of fitting such a device

GRP Glass reinforced plastic

HGV Heavy (or large) Goods Vehicle

HRC High rupturing capacity

HTHW High temperature hot water

HVAC Heating, ventilating and air conditioning

High voltage (HV) Voltage exceeding 1,000 volts AC or 1,500 volts DC between conductors,or 600 volts AC or 900 volts DC between conductors and earth

HSE Health and Safety Executive

IBA Independent Broadcasting Authorities

IEC International Electrotechnical Committee

IEE The Institution of Electrical Engineers

Impedance A measure of the response of an electric circuit to an alternating current(resistance, inductance and capacitance)

Inductance The property of an electrical circuit by which a voltage is generated by achange in the current

Chapter 15References and Glossary

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TERM/ABBREVIATION MEANING

IP Ingress Protection

I/O Input /Output. The term is used to refer to those operations, devices anddata-bearing media that are used to pass information into or out of a computer

ISMC International Society for Measurement and Control (Formerly InstrumentSociety of America)

ISO International Organisation for Standardization

kVAr Kilovoltamperes Reactive

LCD Liquid crystal display

LED Light emitting diode

LSOH Low smoke zero halogen

LTHW Low temperature hot water

Low voltage (LV) Voltage not exceeding 1,000 volts AC or 1,500 DC between conductors, or600 volts AC or 900 volts DC between conductors and earth

LSF Low smoke and fume

M&E Mechanical and Electrical

MCB Miniature circuit breaker

MCCB Moulded case circuit breaker

MCC Motor Control Centre

MCHW Manual of Contract Documents for Highway Works

MICC Mineral Insulated Copper Covered

Chapter 15References and Glossary

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TERM/ABBREVIATION MEANING

MICS Mineral Insulated Copper Sheathed

MIDAS Motorway Incident Detection and Automatic Signalling

MIS Management Information System

MTBF Mean Time Before Failure

MTHW Medium temperature hot water

MTTR Mean Time to Repair

NMCS National Motorway Communications Systems

OECD Organisation for Economic and Cooperative Development

‘On Snore’ The ability of a pump to run for a limited amount of time whilst cavitating

PIARC World Roads Association PIARC (Permanent International Association ofRoad Congresses)

PID Proportional integral derivative

PLC Programmable Logic Controller/Programmable Controller

PSTN Public switched telephone network

PVC Polyvinyl Chloride

QWERTY Standard UK keyboard arrangement

Chapter 15References and Glossary

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RCD Residual current device (earth leakage circuit breaker)

RFAC Royal Fine Art Commission

RF Radio frequency

RFI Radio frequency interference

RH Relative Humidity

RMS Root mean square value of voltage

ROM Read only memory

RTD Resistance Temperature Device

SCADA Supervisory Control and Data Acquisition

Screen To surround or encase a circuit with metal in order to reduce the effect ofelectric or magnetic fields

SELV Safety extra low voltage system which is electrically separated from earth andfrom other systems in such a way that a single fault cannot give rise to the riskof electric shock

Short circuit A deliberate or accidental low resistance connection, on an electrical circuit.(Its effect is to equalise voltages at two points and allow current to flow)

SP&N Single pole and neutral

SSD Sight Stopping Distance

SWA Steel wired armoured. A cable type

Switchfuse Fuse incorporating a switch or isolator, thereby enabling the power supply ordevices fed from it, to be turned off

Chapter 15References and Glossary

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TAA Technical Approval Authority

TDSCG Tunnel Design and Safety Consultation Group

Telemetry The measurement of events at a distance. Transducers are used to measurephysical activities and to convert these to signals that reflect the measurement

TOA Tunnel Operating Authority

TP Triple pole

TP&N Triple pole and neutral

Transit system A system of intumescent compressible blocks within metal frames to sealcables and pipes where they pass through walls

Twisted pair A cable consisting of a pair of conductors twisted around each other, inorder to reduce interference

UPS Uninterruptible power supply

VDU Visual Display Unit

VMS Variable message sign

XL Cross linked

XLPE Cross-linked Polyethylene

Chapter 15References and Glossary

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16. ENQUIRIES

Approval of this document for publication is given by the undersigned:

Quality Services DirectorThe Highways AgencySt Christopher HouseSouthwark StreetLondon J KERMANSE1 0TE Quality Services Director

Director, Road Network Managementand Maintenance DivisionThe Scottish Executive Development DepartmentVictoria Quay N B MACKENZIEEdinburgh Director, Road Network ManagementEH6 6QQ and Maintenance Division

Director of HighwaysThe National Assembly for WalesCynulliad Cenedlaethol CymruHighways DirectorateGovernment BuildingsCathays Park K THOMASCardiff CF1 3NQ Director of Highways

Director of EngineeringDepartment of the Environment forNorthern IrelandRoads Service HeadquartersClarence Court10-18 Adelaide Street V CRAWFORDBelfast BT2 8GB Director of Engineering

All technical enquiries or comments on this document should be sent in writing as appropriate to the above.

Chapter 16Enquiries

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APPENDIX A - SECONDARY CLADDING

Appendix ASecondary Cladding

General

A.1 Where the finish of the main tunnel structuralsupport elements is not able to achieve sufficientsmoothness for tunnel light reflectivity, easy cleaningand lack of dirt retention then a secondary cladding (wlining) may be considered for achieving such objectivesSecondary cladding is also used to improve theappearance of a tunnel to the road user and to prevenany future water leakage from appearing on the roaduser side. Cladding has additional benefits in reducingdrag losses for the tunnel ventilation system, insulationagainst freezing and reduction of tunnel noise. ThisStandard does not cover the use of eg epoxide paintsystems for in-situ finishes to concrete or cast ironlinings etc.

A.2 Secondary cladding surfaces are directly exposto the tunnel environment and shall be designedaccordingly, taking into account the tunnel size andshape, available space, tunnel use and the nature of aresidual water ingress which it may be one of thefunctions of the cladding to intercept. See Chapter 2.

A.3 The needs of minimal maintenance withdurability shall be designed into the secondary liningsystem. When maintenance or replacement of parts dobecome necessary, this shall be capable of beingaccomplished by non-skilled personnel, in time periodswhich minimise lane closure and traffic disruption.

A.4 Particular attention needs to be given to thedesign of details at panel joints and at the interfacesbetween panels and tunnel equipment, as these are thzones most vulnerable to the disfiguring effects of anyseepages. Experience shows that seepage tends to bemore able to circumvent a joint detail than unskilleddesign is able to prevent.

A.5 A generalised list of desired secondary claddingcharacteristics is as follows:

i. Resistant to tunnel environment, withoutcorrosion

ii. Resistant to impact, abrasion, chipping by stone(particularly at lower levels), water, salt sprayand cleaning chemicals

iii. High light reflectance, diffuse not specularproperties as described in Chapter 6

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iv. Non-combustibility, resistance to flame spreadwith non-production of noxious fumes, seeChapter 8 on Fire Safety Engineering

v. Easily and quickly demountable and replaceablin units

vi. Resistant to applied traffic gust loading, fatigueand vibration, see Chapter 2

vii. Economy of cost of installation, maintenance anreplacement

viii. Not attractive to dirt, over design life

ix. Easily cleanable and resistant to loads applied cleaning apparatus

x. Neat, tidy, long term attractive appearance,without any quilting effect

xi. Accommodates, and co-ordinates with, tunnelfurniture

xii. Ability to conform to shape imposed by tunnelalignment and cross section within spaceconstraints

xiii. Sound reduction and insulating properties, asrequired.

Materials

A.6 Several materials are commercially available fouse as secondary tunnel cladding. These have beendeveloped principally as cladding materials forbuildings. A road tunnel environment is notoriouslyharsh and materials (or coatings) which appear topossess the correct properties, on the basis of laborattests, or long term performance as building cladding cexhibit particular weaknesses when exposed to such aenvironment, even for short periods. Different tunnels,because of differences in size, shape, internal layout otraffic composition and volume may expose suchmaterials to environmental conditions of varying degreof severity.

A.7 A panelling system will usually need a supportinframework of ribs or rails (the grounds) to impartstiffness and impose the required longitudinal and

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transverse shape. The grounds together with the panelneed to resist, without excessive deformation, thetransient gust and suction loadings caused by thepassage of traffic, and of withstanding, withoutwidespread collapse, a vehicle impact load, whichproximity to passing traffic may make likely. Thegrounds will be hidden and inaccessible for routineinspection and maintenance, and they may be exposedseepages and the aggressive environment within a roadtunnel. Therefore, confidence in the durability of thegrounds, panels and their fixings, without continualmaintenance, is required.

A.8 A surface finish of vitreous enamel, in the senseof its capacity to resist the harshest of tunnelenvironments, is generally acknowledged to be the bestmaterial. It is durable, impact resistant, not inflammableeasy to clean, and chemically inert but combination witha flat steel substrate leads to a product which may berelatively expensive in terms of initial cost. Paintcoatings or forms of coated board possess lesserqualities but are less expensive in initial cost. The aimshould be to match the properties of possible secondarcladding systems with the expected in-service conditionwithin each particular tunnel and compare the whole lifecosts.

Fire Properties of Secondary Cladding Materials

A.9 To distinguish between the various possiblematerials used for secondary cladding it is convenient tsub-divide materials into those which do, and thosewhich do not, require a coating for corrosion protectionand decorative purposes within a tunnel environment.The coating may affect fire propagation and its effects.See also Chapter 8.

A.10 Materials not requiring a coating but suitable foruse in tunnels:

i. Stainless Steel

Stainless steel does not support combustion. SeChapter 2 for suitable grades.

ii . Glass Reinforced Concrete (GRC)

GRC is non-combustible and not easily ignitable.It tends to need thick sections and is easilystainable. It can be susceptible to failure fromfatigue.

A.11 Materials not requiring a coating but unsuitablefor use in tunnels are:

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. Glass Reinforced Plastic(GRP)

GRP can be formulated to possess a limitedflame spread performance and smoke emissiobut the production of acidic fumes during burnis unavoidable.

i. Polyvinyl Chloride (PVC) Sheets

PVC does not support combustion, but whenPVC based materials are burnt by continuedexposure to a source of ignition the products ocombustion include hydrogen chloride from thePVC and hydrogen cyanide from otherconstituents of the material. This is consideredbe an unacceptable hazard which could alsoinitiate the corrosion of metallic elements in thevicinity.

.12 Materials requiring a coating are which may beuitable for use in tunnels:

. Aluminium Sheet

Aluminium is generally considered to benon-combustible. However, in the rare event osuccessful ignition, it generates considerable hThe protective coating proposed would be animportant consideration in judging its potentialfire hazard. Corrosion may quickly set in oncethe protective coating suffers local damage. It a low resistance to impact damage.

i. Building Boards

Cementations, fibre reinforced or wood particleboards coated on one side have been developfrom uncoated versions and are used forinsulation or fire resistance. They will burn wheexposed to fire and so the manufacturer’s FireTest report issued by an accredited testing stashall be checked for the fire resistant propertybefore the proposed board is considered foracceptance. Some boards are very brittle andeasily shattered.

ii. Mild Steel

Mild Steel does not itself support combustionbut, as with aluminum, its coating should becarefully chosen to avoid a potential fire hazarA very high standard of corrosion protection isrequired. Corrosion may quickly set in once theprotective coating suffers local damage.

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iv. Composite Cladding Panels

Structures of metal composite panels usingpolymeric cores do not provide any standard offire resistance. However a specific degree of fireresistance can be achieved by the use of suitabinternal linings.

Design Life

A.13 Whatever materials are chosen for a secondarycladding system the minimum design life in service shabe 20 years. Inert and non-corrosive materials arecapable of far longer design lives, subject to carefulmaintenance and not being damaged by vehicle impacA design life for a particular system shall be specifiedwhich is a suitable multiple of 20 years, so that thesecondary cladding systems may be renewed, asnecessary, at the time which coincides with extensivetunnel equipment refurbishment.

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APPENDIX B - DURABILITY AND MATERIALS

Appendix BDurability and Materials

General

B.1 This Appendix gives further guidance on thematerials and corrosion prevention finishes for tunnelequipment. Equipment must be protected against thehostile environmental conditions within tunnels to securecontinuous operation, safeguards against structuralfailure, economy in maintenance and economic life spanSee Chapter 2.

B.2 Extensive refurbishment has had to be undertakein recent years because of water ingress through thetunnel structure. Watertightness should, therefore, be aprime design and construction requirement. See Chapt2.

B.3 BS 5493 gives guidance on how to specify achosen protective system. It also recommends specificmethods of corrosion protection for steel structures inmost environments. Preparation and application methodare also covered. The Specification for Highway WorksSeries 1900 and Notes for Guidance shall be used toselect an appropriate finish system for external tunnelworks.

B.4 If there is any doubt as to the coating required, itis preferable to specify the operating conditions andobtain a binding guarantee from a specialist in protectivsystems.

B.5 Equally important as the specification of thecoating system, is the monitoring of the quality of itsapplication, from initial surface preparation to the finalcoat.

B.6 Some manufacturers, eg for electrical motors,provide a “standard manufacturer’s finish”. Any othertype of coating may be prohibitively expensive andinvolve long delivery times. Where it is impractical tochange the standard finish, the solution may be toovercoat on site with a compatible system giving therequired performance.

B.7 Care shall be taken with rotating machinery, toensure that bare steel shafts have suitable corrosionprotection.

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B.8 Consideration shall be given to the possibilityelectrolytic corrosion. This can occur between fixingjoints of dissimilar materials and even between simil

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aterials eg some stainless steels where moisture is alsoresent. To prevent electrolytic action in the tunnelnvironment, all equipment shall be bonded to prevent

nteraction, or equivalent special methods applied.here cathodic protection is to be provided it shall be

nstalled in accordance with BS Code of Practice 1021,r equivalent.

esign Life of Tunnel Equipment

.9 Most equipment has an expected working life inhe order of 20 to 25 years. See Appendix G. Therefore,he associated metallic components, plus theirrotection, shall achieve a similar life. For example,

uminaires have an effective life of about 20 years and itollows that racking should last this length of time sohat it may be replaced with the luminaires.

.10 Jet fans may require shop maintenance afterbout 10 years, when they could also be repaintedelatively easily.

.11 Electronic equipment has an expected workingife of 10 years. See Chapter 11 for electrical equipment.

unnel Environment

.12 Products of combustion of hydrocarbon fuelsdiesel smoke, benzenes, CO2

, CO, NO and waterapour) and road dirt which contains corrosive elements,oad salt, road chippings and cleaning chemicals,ogether with a damp atmosphere, groundwater seepageeat from engines and exhausts, and temperatures fallingelow dew point, combine to form a particularlyggressive environment for mechanical and electricalquipment. This may be further aggravated by chemicalsnd salts in the surrounding ground, groundwater and by marine atmosphere in a coastal area. See also Chapte.

.13 All equipment, plant, cables, materials andncorporated components shall be designed and installedo operate satisfactorily in such an environment for theiresign lives, with an ambient temperature range of -15oC

o +35oC and relative humidity of up to 100%. Vibrationffects due to traffic shall also be taken into account

s orar

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Protective Measures

Cleaning

B.14 Regular cleaning is essential to good“housekeeping” of a tunnel and as an aid to encouragcomponent maintenance. See Chapter 14.

B.15 Dust from the ventilation system and vehicleemissions will contribute to a build-up of dirt on thetunnel internal surfaces. Regular cleaning of the surfawill remove this dirt and prevent corrosion from settingin. Dust left to build into thick layers can be asignificant fire hazard.

B.16 Cleaning of the tunnel light fittings and the wallsurfaces is important for the safety aspect of theoperation. If dirt is allowed to build up on lighting theluminance deteriorates, as discussed in Chapter 6.

B.17 Normal cleaning procedure is to use a specialtunnel cleaning machine to wash the tunnel with a strodetergent followed by some form of scrubbing action tremove adhered dirt and then a clean water rinse. It isimportant that the toxicity of the detergent is acceptabto the tunnel drainage system (see Chapter 7) andsuitable protective equipment is provided for thecleaning personnel.

B.18 Dirt which accumulates in false ceilings orbehind drip sheds or on high level crawlways maycontain deleterious substances such as asbestos andconcentrations of heavy metals. Adequate access forcleaners with protective clothing, extraction equipmenand sealed rubbish containers may be necessary.

Design

B.19 Consideration shall be given to additional aspeof corrosion protection such as:

i. The possibility of incorporatingcorrosion-resistant materials or coatings in thedesign, eg. plastics (non-toxic in a fire types, ifused in significant quantities), carbon fibre,stainless steel, vitreous enamel etc

ii. Possible damage to the coating system duringtransit and erection, and whether applied duringfabrication

iii. The maintainability of the coating system, asinstalled, without major dismantling

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iv. The reliability of the system, ie its track record insimilar environments

v. The possible effect of repair work on the coating

vi. The effect of fire on the coating, creating apossible smoke or toxic emission hazarddangerous to fire fighting personnel in sufficientquantities

vii. Elimination of water/dirt traps and crevices bycareful design of components

viii. Provision of corrosion resistant fixings andsupports and not just for the supported item.

B.20 Potentially aggressive ground water infiltrationrequires special consideration being given toconstruction materials suitable for such groundconditions eg the possibility of chloride and sulphateattack on concrete and reinforcement, eg methods ofconstruction adopted for sub aqueous tunnels.

B.21 Finishes inside tunnels requiring the leastmaintenance are likely to last longest and provide betteappearance. Attention paid to surface finishes from theearly stages of tunnel design invariably proves costeffective in the long run, since labour costs formaintenance continue to rise.

B.22 All surfaces require cleaning, which is arelatively unskilled process. Paintwork will requirepreparation work and re-coating at certain intervals anrequires skilled manpower. It is disruptive and timeconsuming.

B.23 Care shall be taken in the design of equipmentinstallations to allow sufficient access for maintenanceof tunnel surfaces.

Mechanical Protection

B.24 Protection, in the form of a surface coating, canbe achieved either by paint, plating, metal spray or acombination of these. Surface coatings for steel arenumerous and the initial cost must be consideredtogether with the frequency and extent of subsequentmaintenance requirements.

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Examples of Tunnel Materials and Finishes

Item Material & Finish

Emergency Point Cabinets Stainless steel or vitreous(see Chapters 8, 11) enamel

Electrical switchboards Painted steel(see Chapter 11)

Crash barriers Galvanised steel

Handrails Galvanised and paintedsteel, stainless steel orvitreous enamel

Secondary cladding Coated aluminium,precast segment lined or vitreous enamelledtunnels or cladding steel sheeting onof diaphragm walls aluminium or stainless

steel framing

Fire hydrants, hose Steel or ductile ironreels and other fire pipework, gunmetal orfighting equipment brass fittings

Fans Generally painted steelbodies, aluminium or steelrotors, specified electricmotors, stainless steelaccessories

Luminaires Epoxy powder coatedaluminium alloy bodies,stainless steel accessories

Racking, hangers, cable Galvanised steel ortrunking, conduits stainless steeland fixings.

Tunnel Refurbishments

B.25 Tunnel refurbishment may need to be consideredwhen the tunnel design has become outdated, or thetunnel structure and finishes require remedial work.There may be no alternative to major refurbishment if asystem requires updating, but early remedial work toavoid corrosion problems will prolong the life of thestructure and its equipment.

B.26 It is mainly the M&E services and secondarylining systems of a tunnel that will be subject torefurbishment, as there is usually little that can, or needsto be done, to refurbish a tunnel structure. Much tunnel

eqsyprexsmca

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uipment such as switchgear, controls and monitoringstems is overtaken by advancing technology. Fireecautions also develop with time requiring, forample, improved ventilation systems to give betteroke control and the replacement of PVC insulatedble with LSOH insulated.

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APPENDIX C - TUNNEL DOCUMENTATION: TYPICALCONTENTS

General

C.1 Requirements for tunnel documentation arediscussed in Chapter 13. This Appendix lists typicalcontents of such documentation for guidance purposesonly. It is not necessarily exhaustive.

Tunnel Commissioning Documentation

C.2 Specific documents should be provided oncompletion of the commissioning of tunnel equipment forecord, handover and warranty purposes, including:

History Records

These would be in the form of relevant letters relating tospecific equipment, agreements and minutes of meetingA systematic numbering system is required.

Alert Notices and Field Service Reports

A historical record comprising the list of faults notedduring inspection and actions taken, adjustments andmodifications either completed or to be carried out.

Works Test Certificates

These would cover rotational and electrical continuityand enclosure checks in case of electric motors, switchgear, panel assemblies, annunciator alarm system, etc.

In the case of fans, pumps etc volumetric test reportswould be required.

Photometric, insulation and enclosure test certificateswould be required for lighting units for both prototypesand production units.

Site Test Certificates

All equipment and systems will be tested to verify theirperformance after installation on site. Test results will bedocumented, signed and countersigned for recordpurposes.

Test certificates would normally be required forindividual equipments such as:

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. Ventilation fans

i. Drainage pumps

ii. Switch gear

. Diesel generator sets.

erformance test certificates should also be provided fohe following systems:

. Ventilation control system

i. Drainage control system

i. Lighting

. Fire detection and extinguishing system

. Traffic surveillance system

i. Electrical cable system

ii. Communication system

iii. Computer control and data logging system.

here more than one piece of equipment of a given typs installed test certificates should be provided for eachnit.

tatutory Documentation

his will include insurance inspection certificates for

. Lifting equipment

i. Pressure vessels such as compressor air receive

ii. Boiler plant, if relevant.

unnel Operator’s Guide

.3 The Tunnel Operators Guide should meet theequirements of Chapters 13 and 14. It should refer toanufacturers’ operation and maintenance manuals for

etailed instructions on equipment. The document shouontain some or all of the following information:

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General

i. Glossary of terms

ii. Schedule of drawings

iii. Useful telephone numbers

iv. Tunnel design and operation philosophy

v. Equipment automatic controls.

Operating Procedures

i. Traffic control procedures

ii. Traffic plan

iii. Description of control console, operatorskeyboard, VDU and printer facilities, togetherwith details of any manual and police controls

iv. Security systems

v. Safety procedures

vi. Emergency facilities

vii. Emergency procedures.

Control System

i. Data acquisition and monitoring

ii. Control and command facilities and terminallocation

iii. Air quality and visibility monitoring

iv. Control room equipment

v. Data of outstation location and equipment

vi. Tables of VDU and printer out-turn, commandsPolice messages, codes.

Electrical and Mechanical Safety Regulations

These should be stated in detail together with theprocedure for authority to work on electrical ormechanical plant.

Schedule of Equipment

i. All mechanical and electrical equipment installe

ii. Drawings with respect to identifying operatinglocations.

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Electrical Supplies, Standby Supplies, Earthing Syste

i. High voltage distribution system

ii. Low voltage distribution system

iii. Transformers

iv. Inverters and batteries, where provided

v. Remote alarms and indications

vi. Earthing systems

vii. See also Standby Electrical Supplies item.

Tunnel Lighting

i. Description of the lighting system

ii. Description of the lighting system controls, autoand manual

iii. Description of the lighting distribution system

iv. Description of the lighting transfer, auto tomanual

v. Description of the lighting for any contra flowworking

vi. Description of the emergency lighting system

vii. Description of other details specific to the tunnelighting design

viii. Details of remote indication and alarms

ix. Tables of luminaire arrangement, settings andelectrical load.

Tunnel Ventilation

i. General description of the ventilation system

ii. Ventilation electrical distribution system

iii. Ventilation control system - auto

iv. Ventilation control system - manual - with controeither via keyboard or hand switch

v. Tables giving CO, NOx and visibility operationallevels

vi. Tables giving fan group setting, change overprocedure.

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Pumping, Valves, Gas Sensors

i. Pumps and pumping stations

ii. Pumping duty and changeover sequence

iii. Gas sensors and emergency sump entryrequirements.

Standby Electrical Supplies

i. Uninterruptible Power Supplies (UPS)

ii. Standby Emergency Diesel Generation

iii. Changeover switching procedure.

Fire Alarm, Fire Mains and Other Fire ExtinguishingSystems

i. Fire alarm and extinguisher system includingtunnel service buildings

ii. Portable extinguisher equipment

iii. Hose reels

iv. Fire pump system where installed

v. Fire mains and relevant isolating valves

vi. Fire zones.

Tunnel Structure and Secondary Linings

i. Ground water control

ii. Stability of slopes, particularly over portal areas

iii. Convergence monitoring

iv Wall painting

v. Wall cleaning

vi. Cladding cleaning, removal and replacement forinspection

vii Waterproofing

viii Pavement surfacings, markings

ix Anchorage monitoring, equipment supports

x Long term settlement monitoring

xi Fire protection.

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Building Services and Security

i. Heating and ventilation system

ii. Water and drainage

iii. Lighting and power

iv. Alarm system.

Traffic Signs and Signals

i. Equipment details

ii. Operation procedures.

Communications

i. Service telephones

ii. Emergency telephones

iii. Radio system and block diagram.

Schedule of Drawings

i. Local area map

ii. Road layouts

iii. Traffic flow layouts

iv. Main services and buildings

v. Zones of control where applicable

vi. Radio net

vii. Equipment drawings.

Equipment Operation and Maintenance Manual

C.4 The Equipment Operation and MaintenanceManual should meet the requirements of Chapter 13. Itshall contain all necessary information in a form suitablefor a proprietary computerised maintenance system:

i. General description of each item of plant andequipment and asset register. For each asset (egiii. to xiv.) the following information is required:

a. Location within tunnel site

b. Details of manufacture including contactinformation

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c. Technical specification: including functionahierarchies, state variables and safetytolerance boundaries, rule based preventamaintenance requirements and help files

d. Parts, specialist tools list

e. Maintenance schedule, in a diary formsuitable to show work due, work completed(with automatic entry into item e.) and workoverdue including status queries on selectefields

f. Maintenance and operational history facilityincluding in-service duty hours recording.

ii. Relevant design information, includingsummaries of design calculations, performancdata and equipment general specifications.

iii. Cable, circuit and equipment schedules, genearrangement and schematic drawings.

iv. Control system:

a. Main equipment

b. Traffic surveillance and control

v. Tunnel ventilation

vi. Tunnel lighting

vii. Emergency telephones

viii. Operator telephones

ix. Radio Service Buildings

x. Emergency/Distribution Panels (EDPs)

xi. Smoke control panels

xii. Gantry structures

xiii. Tunnel carriageway drainage and outfall

xiv. Pumps, pipework and valves

Inspection Check List

C.5 An inspection check list will typically contain aset of instructions as follows:

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i. All equipment and carriageways should beinspected daily and any abnormal operatingcondition reported.

ii. Daily performance of equipment should berecorded, from visual checks on instrumentationreadings which show values outside those to beexpected, and from direct viewing of thecarriageway and of lighting performance andcondition of emergency services facilities. Thedata should be reviewed and all fault indicationsreported.

iii. Routine equipment inspections should be made atsuch intervals as are recommended by the varioussuppliers, when the equipment should beinspected in detail. The equipment operationshould be checked against the design standard foboth automatic and manual control.

iv. Alarms should be checked with response ofequipment to variations in priorities and in the setpoint and range settings of alarm parameters.

v. The performance of automatic control equipmentshould be monitored against variations in thecontrolled parameters.

vi. Records should be made of vibration and noiselevels of relevant equipment.

vii. The response of all Emergency Services shouldbe checked and their combined response tosimulated incidents should be regularlymonitored, together with that of staff.

viii. All recorded data should be reviewed andrecommendations for actions should be reportedagainst long term trends, hard copies beingretained to record such trends.

ix. When major equipment maintenance is necessaryrecords should be made of equipment condition tosupplement the computerised data for equipmentperformance.

Manual for Police and Fire Services

C.6 The Manual for Police and Fire Services willtypically contain a set of guidance, as follows:

Location and Access

Tunnel location with access provision for emergency andmaintenance services should be shown on a map and/ordiagram.

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Structures

The tunnel and associated buildings should be brieflydescribed and illustrated by detailed diagrams andsketches. The location and layout of emergency servicand details of equipment should be included andillustrated. Any items which are unusual or special to tparticular tunnel should be emphasised.

Electricity Supplies

The source of electricity supplies should be statedtogether with means of providing any uninterruptible anstandby supplies, with limitations and arrangements foemergency operation.

Security

All automatic controls and alarms should be listed withoperational consequences and action required by thepolice or fire services.

Communications

The various communications systems provided in thetunnel complex should be fully described together withprocedures particular to the tunnel and any testprocedure actions required. A telephone directory forany internal telephone system should be providedtogether with BT (British Telecom) telephone numbersand brief details of provision made for operation of radsystems in the tunnel

Drainage and Pumping, Fire Hoses

All drainage systems, sumps and pumping equipmentshould be briefly described and sumps and pumpslocated, together with action required in the event of analarm and any other police/fire action envisaged.Provision for control of the spillage of hazardous liquidshould be covered in detail and operationalresponsibilities defined. The location and any specialoperating conditions for permanent fire hoses should bfully defined.

Lighting

The automatic main and emergency lightingarrangements should be described together with anypolice procedure for provision of standby powersupplies. Any provision for police manual control shoube detailed together with any limitations and adescription of any additional control available to themaintenance staff.

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Ventilation

The ventilation plant normal operating arrangementshould be described and any automatic control actiondefined. Any provision for police/fire service manualcontrol should be detailed, including any reason for, aeffect of, manual controls, any limitations, and adescription of any additional controls available to themaintenance staff. Any police/fire action necessary inresponse to fault alarms should be detailed.

Plant Monitoring

A description should be given of all automatic controlsystem (computer) originated messages, together withthe required response, similarly for printer messages(where a printer is installed) and alarm signals. It isimportant that all information provided is free ofambiguity particularly where interpretation may be bynon technical personnel working under stress inducedany emergency. All prescribed alarm messages shoullisted, together with the police/fire response required.

Traffic Surveillance

A description should be given of any traffic surveillancsystem.

Abnormal Situations

The expected alarm response to any system failureshould be stated and the required response defined. Tpossible consequences of any failure to act should alsbe stated.

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Appendix DGuidelines for Major Incidents Operations and Fire Tests

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APPENDIX D - GUIDELINES FOR MAJOR INCIDENTSOPERATIONS AND FIRE TESTS

General

D.1 The basic operating procedures and supportingdocumentation for dealing with major incidents intunnels is set out in Chapters 8, 13, 14 and AppendixThis Appendix adds some guidance for emergency maincident operations, particularly in relation to planningsuitable response to fire.

D.2 Major incidents, whether or not involving fire,have common features in that immediate response isneeded to facilitate rapid access of the emergencyservices to the site of the incident, evacuation ofcasualties and restoration of traffic flow as soon aspractical.

Initial Response and Traffic Control

D.3 The quality of the decisions and resultingresponse made in the first ten minutes after an incidenoccurs is vital. The initial response, on detection of amajor incident, shall be to stop all traffic entering thetunnel in both directions, followed immediately bysummoning the emergency services appropriate to theincident. Traffic downstream of the incident and in anyunaffected bores shall be allowed to proceed out of thtunnel, leaving clear access for emergency services. Tinitial alarm will trigger the initial response. During theinitial response time (which should be known fairlyaccurately for given conditions) the tunnel control centwill pass as much information (nature, seriousness, sitraffic, casualties, evacuation progress, best directionapproach etc) to the emergency services so that the meffective deployment can be made onward from arrivaat the rendezvous points. An Initial Response andTraffic Control Plan will have been already prepared bthe TDSCG. This shall include for:

i. Normal approach routes

ii. Alternative approach routes to be used if normaapproach routes are congested

iii. Agreed rendezvous points, as near as possiblethe tunnel portals

iv. Agreed initial mobilisation levels/resources.

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D.4 Occupants may be reluctant to leave theirvehicles unless a uniformed member of the police oremergency services is directing them. Any tunnel staff the scene early in the incident should use their bestendeavours to communicate directions to the public,before handing over on arrival of the emergencyservices.

D.5 Once the unaffected bore is clear of traffic, thenany necessary action can be taken, for example, byilluminating escape route signs, to evacuate vehicleoccupants through the cross passages into the adjacebore.

D.6 In the event of fire in a single-bore two waytunnel, vehicle occupants shall first be evacuated fromthe side of the fire to be used for smoke clearance andbefore operating the smoke control fans. Reversible fashall be first checked to ensure that they are set tooperate in the intended smoke clearance direction.

D.7 Shorter, naturally ventilated tunnels, withoutmechanical ventilation, allow vehicle occupants toescape quickly via the short distances to reach the tunportals and cross passages. Emergency services shoube aware of possible smoke direction reversals, as windirections change, or chimney effects for tunnels built oa gradient.

Smoke Control (in the event of a fire)

D.8 If an incident involves fire, the ventilation fansshould be stopped and switched to manual control. Assoon as traffic has ceased moving in the tunnel anassessment should be made of the location of the fire the fans switched to the operating mode best suited tothe particular conditions. For example, in a one-waybore with longitudinal ventilation, once traffic hascleared and the CCTV shows that there are no peopledownstream of the fire, the fans can be switched on topush the smoke and hot gases in that direction. Smallefires may not generate sufficient heat for stratification osmoke layers in the tunnel ceiling to occur. For suchcases, lower level smoke logging will occur and fanspeeds shall be adjusted to levels sufficient to clear thesmoke logging. Changes to fan operation shall only bemade with the agreement of the fire officer in charge.

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D.9 In a two-way tunnel smoke control is moredifficult, as traffic will probably be backed up both sideof a fire. In still air, the heat and products of combustiwill rise and spread along the ceiling of the tunnel. Anyapplication of forced ventilation in a longitudinal systemwill increase the rate of spreading in one direction (anreduce it in the other). So, the fans should remainswitched off until it is verified that no persons remaindownstream of the intended direction of smokeclearance. It will normally be quickest to clear thevehicle occupants in the lanes where the distance fromthe incident position to the nearest portal is the shorte

D.10 Where a fully transverse ventilation system isinstalled the fans should be switched to full extract assoon as a fire is detected. For semi transverse andcombination systems, the above principles for thelongitudinal flow component apply.

D.11 The emergency operating procedures for smokcontrol shall be drafted taking into account the above,the results of at least one full scale emergency drill anpreferably the results of a practical fire test.

Additional Actions to be Taken During and Followinga Major Incident

D.12 In addition to the basic actions set out in Chap14, additional actions listed in this section may benecessary. Their need and order of priority will dependon the type of incident and whether or not there is fire

During the Incident

i. Ensure investigating personnel proceed into thetunnel in the direction of the traffic flow or smokclearance direction (two way tunnels) and notinto the path of dense smoke.

ii. Ensure that no persons proceed into the tunnelwithout first receiving confirmed information, viathe Traffic Control Centre, regarding traffic andsmoke.

iii. Establish a Control Point Area and keep the arclear except for personnel involved in operationfor the incident.

iv. Sound klaxon, where provided, in the ControlPoint Area. A klaxon is effective in alerting roadusers that the emergency is real eg installation Clyde Tunnel.

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v. Instruct the Portal Control Points staff tomaintain a “clearway” including cross over lanesfor possible contra flow of emergency vehicles.

vi. The Traffic Controller will monitor the incidenton CCTV and assess the nature and seriousnesof the incident, taking further action asappropriate.

vii. Arrange for any necessary additional uniformedand maintenance staff to report for duty.

viii. Advise relevant managements and the media.

ix. Arrange additional canteen facilities to beavailable for the duration of the emergency.

x. The Traffic Controller should instruct staff toassist in the evacuation of persons in the tunnel.

xi. Advise staff to ensure that ignition keys are left ithe ignition switches of abandoned vehicles, theidoors closed but left unlocked.

xii. If appropriate and system available, broadcast“evacuate tunnel” message.

xiii. Depending on the nature and the scale of theincident the following facilities may be requiredby the emergency services:

a. Casualty collection point

b. Evacuation assembly point

c. Mortuary collection point.

xiv. Maintain liaison with emergency services toassist in dealing with any injured persons.

xv. NB: a major incident may overloadcommunication channels with enquiries. It isadvisable to have a separate public enquirytelephone system set up and staffed by a suitabtrained person/s. Automatic switchboards shouldbe set to manual and lines reserved for outgoingcalls.

xvi. It is important to know at all stages the locationsof all staff.

xvii. The availability of keys for normally lockeddoors and gates requires regular monitoring.Combination locks or keypad systems can beeffective. Codes may be radioed/phoned to staffas necessary, and codes regularly changed forsecurity reasons.

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After the Incident is Over

i. Broadcast, by radio, an internal fire alarm clearcode to Traffic Officers. Guide drivers andpassengers to abandoned cars at the scene of thincident.

ii. Establish tidal-flow in unaffected lane orcontra-flow in the unaffected tunnel bore, asappropriate.

iii. Allow in the pre-arranged emergency call outcontractors to undertake their works such asvehicle removal, vital equipment replacement,pumping and sludge removal etc.

iv. As and when circumstances permit, progressivelyreturn to normal traffic flow.

v. Enter details in Control Point Log.

vi. Prepare and submit a full report.

Fire Tests

D.13 It is recommended that for tunnels withmechanical ventilation, full scale fire tests are carriedout, prior to opening a tunnel, to verify the emergencyprocedures, including fire detection and alarm, trafficcontrol, emergency services response time and the smocontrol system.

D.14 This section discusses the tests to verify smokecontrol procedures.

Test Method

D.15 Tests should be conducted using the draftemergency operating procedure for the tunnel, whichwill include appointing a person with overallresponsibility for coordination.

D.16 Firemen should be prepared to control the fireusing the equipment available at the tunnel emergencypoints. A fire appliance should also be in attendance incase of any failure of the tunnel equipment orprocedures.

D.17 Instrumentation should include air velocity anddirection measurement, temperature measurement at 510m, 20m, 50m, and 100m from the fire in bothdirections at the road level, at 1.5m above the road andat the level of lighting cables or other vulnerableequipment in the top 3m of the tunnel cross-section.Ambient temperature and air velocity should be

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easured before and after the test. Temperature data ahe output from the tunnel’s normal CO, smoke and airelocity measuring equipment should be continuouslyecorded during the test. Photographic, video or otherecording of the smoke development should be made.

eat and Smoke Sources

.18 Cold smoke generators are not suitable sources,s the smoke does not have the correct buoyancy. Auitable fire can be produced by burning a mixture of 25itres of petrol, 5 litres of gas oil and pieces of car tyre,n a 4m³ steel tank placed above a heat insulated androtected road surface, burning a steel fire tray of oilithin a large skip insulated from the road, or byurning an old car. Experience shows that fires of thisize are unlikely to damage the tunnel if carefully sitedn relation to vulnerable equipment. Hot smokeenerators are currently under investigation.

seful Precautions

.19 To protect the carriageway the fire should belaced on corrugated iron sheets or a 20cm thick bed oand or on blocks, with the carriageway watered duringhe test.

.20 The test should be carried out before the tunneleiling or vault is painted or any acoustic treatmentpplied. Fire experience suggests that the test firesecommended above will not damage the ceiling etc,rovided the ventilation is operated. However, a larger

ire, equivalent to an HGV, could be expected to damagehe ceiling etc. Side-wall equipment is not likely to beffected, but plaster plates covering the sidewalls for a

ength of 8m, the lighting for 10m and cables for 20mould be used as a precaution. Use of an insulating firelanket, attached to the adjacent tunnel walls and ceilingbove will also ensure protection of any finishes.

.21 If an old car is used the petrol tank must bemptied of petrol and filled with water to preventxplosion, any tyres shall have their valves removedrior to burning. The burnt car shell must be handledarefully after use and some components can becomeoxic after exposure to fire

est Report

.22 The test report should record the attendingersonnel, the objectives, conditions and method of theests, the initial condition, instrumentation, description ohe development of the fire including the smoke

ovement, measured data and analysis, evaluation of tire intensity and lessons to be drawn and acted upon.

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Appendix ERecent Research by the Highways Agency

APPENDIX E - RECENT RESEARCH BY THEHIGHWAYS AGENCY

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General

E.1 The Highways Agency of the Department ofEnvironment, Transport and Regions (formerly theseparate Departments of Environment and Transphas undertaken a comprehensive programme of rework in road tunnel subjects. A summary is providethe more recent, but as yet unpublished, reports apapers relevant to the planning, design and equipproad tunnels.

E.2 Unless specifically referred to within theChapters of this Standard such reference documeintended for information and guidance only and mabe taken to reflect the current policy of the Oversee

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Organisations. Documents will from time to time beupdated or superseded and designers shall ensure thathey are working to the most current versions. See alsChapter 15.

E.3 Development work on New Austrian TunnellingMethod (NATM), the Observational Method in TunnelsLimited Facility Tunnels, Road Tunnel Maintenance anCivils Specifications for the Construction andMaintenance of Road Tunnels will be published inDepartmental Standards and Specifications currentlyunder development.

E.4 Copies of reports may only be obtained with theprior approval of the Highways Agency.

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PROJECT REPORTS

E.5 The following unpublished reports may exist only in draft form:

Report No. Title Summary

PR/CE/42/94 Computer Models To Determine The The study is in two parts, namely the predictionDistributions And Effects Of ground movements arising from tunnelling activitieTunnelling Induced Ground soft ground and the prediction of damage to strucMovements. due to ground movements. It describes theR Andrews mathematical basis of calculation methods and

illustrates the capabilities of computer software toperform calculations in each of these areas.

PR/CE/66/94 Construction Impacts At the The report considers the effects of construction wPen-Y-Clip Tunnel. at the Pen-y-Clip tunnel and provides a case studyD M Hiller against which future schemes may be appraised an

any objections may be judged.

PR/CE/128/95 The Application of a Service Tunnel The report investigates the application of separain the Design of Highway Tunnels in service tunnels in the design of highway tunnels. the UK. seeks to highlight the benefits to the planning,R J F Goodfellow, P J Astle and construction and long term maintenance of the tuD M Hiller and to demonstrate the conditions where the benefit

outweigh any additional construction costs.

PR/CE/163/95 Review of Single Pass Tunnel Linings The report contains a review of single pass tunnFor United Kingdom Highway lining techniques, based on case histories ofTunnels. construction projects worldwide, in relation to theirP N Groves and T W Mellors applicability to highway tunnels in the United

Kingdom. It starts with a review of tunnel constructiopractice, in terms of primary and secondary linings,leading to a review of single pass lining methods.

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Report No. Title Summary

PR/CE/164/95 The Prediction of Ground Movements The reports review and provide guidance on thePR/CE/195/96 Caused By Tunnelling. prediction of ground movements caused by tunnelling

B M New works. The guidance is applicable to the predicting thepotential impacts of tunnelling schemes and to theassessment of the effects.

PR/CE/169/95 Design Criteria and Concrete Mix The report reviews the current design recommendatioRequirements for Below Ground and concrete mix requirements for structuresConstruction constructed below ground and in particular criteria forA J Powderham, J Forbes, controlling early age thermal cracks. The reviewH B Shanghavi and N R Buenfeld highlights the importance of empiricism, describes

ambiguities in current design criteria, and gives costcomparisons for changes in design criteria.

PR/CE/12/96 Design Fire Loading For Major A report on the fire rating and duration times thatHighway and Limited Facility Tunnels could be used for road tunnel design including limitedR D Andrews facility tunnels which admit only cars and vans.

PR/CE/37/96 Ground Classification Systems in A review of the current methods of classification of theTunnel Construction ground for tunnel support and an approach to groundG I Crabb classification which will assist in setting up cost

effective contracts for new tunnelling works.

PR/CE/110/96 A Review Of The New Austrian The report reviews issues arising from the recentTunnelling Method. experiences of NATM in the UK and gives guidanceK Bowers on the potential future application of the system.

PR/CE/144/96 The Potential Application of Risk The report reviews the range of current risk assessmeAnalysis to Highway Tunnel practices in the UK with special reference to how theyConstruction. may be applied to road tunnel schemes. The nature ofJ J Conway, R J F Goodfellow, risk is discussed with particular attention to those riskD M Hiller and K H Bowers factors which may heavily influence the success of

such projects.

PR/CE/151/96 CFD Modelling of Fires In The The report describes the application of the CFD fireMemorial Tunnel. model TUNFIRE to the task of modelling a series ofS D Miles and S Kumar (BRE) fire tests performed within the Memorial Tunnel, USA.

PR/CE/152/96 Assessment of HSE Tunnel Fire The report briefly describes tests representing a truckTests. fire occurring on board a heavy goods vehicle shuttleR D Andrews train in the Channel Tunnel. The main aim was to

investigate the manner in which forced ventilationcould control combustion products and ensure a safeenvironment for truck drivers travelling in the amenityrail coaches. A further objective was to provideexperimental data to compare with computational fluiddynamics (CFD) predictions.

PR/CE/153/96 Environmental Considerations The report seeks to define and identify the relevantFor Highway Tunnels - Status Report. environmental impacts associated with the constructioJ Cloke and R D Andrews and operation of road tunnels.

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Appendix ERecent Research by the Highways Agency

Report No. Title Summary

PR/CE/174/96 A Review of Lining Design Practice The report provides an overview of the tunnel desigfor Bored Highway Tunnels. process, outlining the approaches currently adoptedN A Moss tunnel lining design. The report presents the elements

required for the design of a tunnel lining, focusing onthe analytical and numerical analysis of the groundstructure interaction problem.

PR/CE/203/96 The Prediction and Mitigation of Building on previous work, this report concentratesTunnelling Induced Ground relating the predicted ground movements to the natuMovement Damage to Structures. and magnitude of their likely adverse impacts onD M Hiller, K H Bowers, overlying structures. Additionally means of mitigatingJ D Redgers, J M Reid and G Clark the adverse effects of tunnelling induced ground

movement have also been investigated.

PR/CE/50/97 Prospects For Single-Pass Sprayed The development of sprayed concrete linings forConcrete Linings in Highway Tunnels. highway tunnels offers the potential for considerableG I Crabb construction cost savings by eliminating the need for a

waterproof membrane or a cast concrete final lining.However, there are considerable reservations over sucaspects as the watertightness, durability and surfacefinish achievable. The report addresses such concerns

PR/CE/56/97 Environmental Considerations For The report includes discussions on air quality, noisHighway Tunnels. vibration, geology and soils, ground movements,R D Andrews and J Cloke hydrogeology and drainage, ecology, landscape,

archaeology and the built heritage, severance,underwater tunnels, driver perceptions and anti-roadprotest action. Appropriate assessment methodologiesare outlined and, where available, methods formitigating the major disbenefits are proposed.

PR/CE/109/97 A Review of Factors Influencing the Four particular areas of tunnel design and construDesign and Construction of Highway are considered to update and expand informationTunnels. previously presented, namely: Environmental effects oD M Hiller & J D Redgers the construction works, the application of service

tunnels to highway tunnels, ground classificationmethods and application of risk analysis techniques tohighway tunnels.

PR/CE/148/97 Review of Tunnel Lighting Levels The lighting levels required by BS 5489:Pt.7 have bin BS 5489. questioned as to being too high and inappropriate forS Bird the traffic speeds actually achieved. An interim report

reviews tunnel lighting levels and identifies areaswhere economies might be possible.

PR/CE/159/97 Value Engineering of Tunnel An interim report reviews the methods available forEquipment. applying value engineering to tunnel equipment, usingJ Potter data from the A55 North Wales tunnels. The report

introduces the subject of value engineering for roadtunnels and proposes the development of a whole lifecosting model.

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August 1999

Report No. Title Summary

PR/CE/183/97 Limited Facility Tunnels and Bridges. The report brings together advice on design, operatioK Bowers, D Hiller & R Evans and maintenance of limited facility underpasses, sought

from a number of agencies, and provides acommentary on the content, adequacy and suggestedamendments to HA Standard TD 43/95 (draft),together with a revised draft of the Standard.

PR/CE/195/97 Highway Tunnel Ventilation - The report describes the purpose of tunnel ventilation,Status Report. available types of ventilation and control mechanismsDr Robin Andrews and their performance. Areas of tunnels design

improvement which could lead to more efficientventilation performance are outlined and maintenanceissues briefly discussed. Results of field experimentson portable emergency ventilation equipment arepresented.

PR/CE/201/97 Specification, Notes for Guidance & The document consists of a review and appropriateMethod of Measurement for Highway development of the British Tunnelling Society ModelTunnel Construction and Maintenance Specification for Tunnelling. Areas for further study in(Phases 1 and 2). Phase 3 are to be identified.S Bird

PR/CE/31/98 Maintenance of Highway Tunnels. The report reviews factors to determine the necessarS Bird scope of a draft Advice Note on the Maintenance of

Road Tunnels: namely the scope of advice necessary;the connection between maintenance and design,equipping and operation; and requirements of users ofthe advice.

PR/CE/57/98 Review of Forms in BD53 A review of the content and adequacy of the formsS Bird contained in BD53 (DMRB 3.1.6) and proposals for

changes to permit its use with a computerisedrecording system.

PR/CE/73/98 The Prediction of Tunnelling Induced The report presents an approach to the prediction ofGround Movement: Prediction and ground movement arising from a range of tunnellingConsequences. activities in various ground conditions. Guidance isK Bowers given on the choice of appropriate analysis and

parameters for commonly encountered situations.

PR/CE/80/98 Value Management and Engineering Records a Value Management and EngineeringWorkshop. workshop arranged to re-examine the present level ofG Clarke provision of equipment provided in highway tunnels, to

seek areas where economies could be made withoutcompromising safety or increasing congestion.

PR/CE/143/98 Single Pass Tunnel Linings Final The report focuses on the problems and subsequentReport. development of sprayed concrete technology. ItR H Dimmock describes the current state of the art in its technology

and associated material performance characteristicsachieved using the wet mix application process. Thereport also assesses the benefit of steel andpolypropylene fibre reinforcement.

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Appendix FTunnel Design and Safety Consultation Group (TDSCG) Requirements

APPENDIX F - TUNNEL DESIGN AND SAFETYCONSULTATION GROUP (TDSCG) REQUIREMENTS

General

F.1 The Tunnel Design and Safety ConsultationGroup (TDSCG) is required to discuss and agree roadtunnel design and refurbishment proposals affectingoperational requirements in the context of the topicslisted below, where applicable to the tunnel underconsideration. See Chapter 1. The list shall be regardedas the minimum requirement and is not intended to beexhaustive. Individual tunnels or groups of tunnels mayhave certain additional features which have a directbearing on operational safety. Such features shall beadded to the list.

Topic List

F.2 The minimum list of topics for discussion andagreement by the TDSCG are presented in the order ofthe relevant Chapters, as follows:

Chapters 2 and 14

i. Safety and operational effectiveness of the overasystem proposed for the tunnel

ii. Identification of emergency incident and hazardscenarios to be effectively dealt with

iii. Requirements for the passage of hazardous good

iv. Contribution of TDSCG Report to Road SafetyAudit

v. Personal safety equipment provision, trainingneeds.

Chapter 3

i. Any unusual features of the tunnel which maygive rise to particular hazards

ii. The level of provision of emergency points,stopping lanes, walkways and refuges and escaproutes for emergency use

iii. The level of provision of communications andfire fighting equipment.

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. The siting of signs and gantries

i. The general layout in terms of standby areas atportals, vehicle recovery and cross-over andcontraflow arrangements for emergency andmaintenance purposes

ii. Access for Police and Emergency Services

. Considerations for tunnel users making use ofemergency points/escape facilities.

hapter 5

. The adequacy of the ventilation system (whereprovided) to maintain an acceptable air qualityduring all normal operation and tunnelmaintenance scenarios

i. Any restrictions that may need to be imposed ontraffic or maintenance operations due tolimitations of the ventilation system

ii. The performance and operation of the ventilationsystem in all foreseeable fire or emergencysituations, including plans for automatic andmanual ventilation control.

hapter 6

. Cleaning and maintenance regimes and relatedtunnel closures and traffic orders

i. Exit lighting design in terms of trafficmanagement for special and emergency operatingconditions

ii. Security of supply, use of UPS and need forstand by generators.

hapter 7

. The operational assumptions of the inflow ratesupon which the design of the drainage system isbased

i. The possible results and hazards of abnormalstorm conditions exceeding the design criteria.

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iii. The ability of the drainage system to accept andsafely contain a hazardous spillage

iv. The acceptability of arrangements to dischargestorm water and polluted water (eg from tunnelcleaning operations or spillages)

v. The proposed means of disposing of hazardous other substances which cannot be dischargednormally

vi. Arrangements and procedures for inspecting andcleaning pipework and sumps, includingprocedures for any confined spaces.

Chapter 8

i. The initial response by the Police, EmergencyServices and Tunnel Operating Authority of theMaintaining Agent, in terms of the facilitiesdeployed in accordance with this Chapter.Consider advice contained in Home OfficeTechnical Bulletin 1/1993: Operational Incidentsin Tunnels and Underground Structures: HMSO.

ii. Coordination of operating procedures andcontingency plans of the Police and EmergencyServices attending an emergency. Considerationof partial or full loss of any facilities due to firedamage or explosion.

iii. The satisfactory review and necessary follow-upactions resulting from the outcome of the plannedmandatory emergency incident drill as requiredby BD53 (DMRB 3.1.6) and carried out duringthe commissioning of the tunnel prior to openingor re-opening. The drill shall involve extensiveuse of the active fire protection, communication,coordination and response provisions and the fulparticipation of the Police and EmergencyServices.

Chapter 9

i. Communications and control systems, CCTVAlert

ii. The automatic, static and temporary signing to bprovided, in advance of and at the tunnel, fornormal, maintenance and emergency trafficoperations for the tunnel

iii. The requirements for and siting of telephones

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v. The requirements and provision of equipment fothe radio rebroadcast facilities of the emergencservices

. Provisions for removing broken down vehiclesetc from within the tunnel.

hapter 11

. Possible hazardous consequences of failure ofincoming mains supply or a section of the tunneinternal power distribution network.

i. Security of supplies to essential equipmentrequired to continue operating under mains powfailure conditions, including durationrequirements.

ii. The effect on tunnel operation and safety ofdisconnection or removal of key items ofequipment, eg transformers or circuit breakers,for maintenance or repair.

hapter 13 and Appendix C

. Tunnel documentation requirements.

ppendix D

. Guidelines for major incident operations and firetests.

i. An Initial Response and Traffic Control Planshall be prepared by the TDSCG.

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Appendix GLife Expectancy of Tunnel Equipment

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APPENDIX G - LIFE EXPECTANCY OF TUNNELEQUIPMENT

G.1 Road tunnel whole life costs are determined noonly by construction, operating and maintenance costsbut also by the cost of renewing equipment andinstallations which have a service life far less than thaof the tunnel structure.

G.2 Service life is defined here as the period of dutyafter which replacement, rather than continued use, isanticipated to be justifiable on an economic oroperational basis, either due to a greater risk of failureor to an unacceptable increase in unreliability, operatinand maintenance costs.

G.3 Precise estimates of service life are not possiblsince external influences (such as traffic changes,legislation changes, obsolescence, technology advancetc) may have a significant impact on the achievable liof tunnel equipment. The service life figures given shabe considered as guidance for typical values of currenUK road tunnel equipment. Values need to be adjustedaccording to local conditions, better or worse than theaverage. Similarly, predictions of remaining serviceupon handback to the Overseeing Organisation ofprojects procured under Design Build Finance andOperate (DBFO) may be estimated on a project specifbasis.

G.4 Examples of factors that may affect the servicelife of equipment or installations are given. Mitigation osuch factors will increase the potential for reaching theintended service lives or longer.

Corrosive influences (see also Appendix B):

i. Concentration and content of exhaust emissions

ii. Ratio of HGVs to lighter vehicles

iii. Cleaning agents, methods and frequencies

iv. Use of road salt rather than acetates

v. A marine environment

vi. Weather conditions (ie prevalence of rain, wind,humidity snow, ice etc)

vii. Impact of stones and debris

viii. Water seepage or flooding

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ix. Non compatibility of materials in contact

x. Fire damage of protective coatings

xi. Stray current and field corrosion.

Intensity of Use:

i. Traffic density and daily flow profile

ii. Plant control methods, switching levels andfrequencies

iii. Weather conditions (eg number of sunny days forlighting, prevailing wind for ventilation)

Other Factors:

i. Vibration

ii. Thermal movement

iii. Ambient Temperature

iv. Ease of access for inspection or repair

v. Fire or vehicle impact

vi. Maintenance policy.

G.5 Because of the inherent difficulties in gainingaccess to tunnel equipment for maintenance orreplacement, optimum whole life costs are oftenachieved by the selection of equipment having a longerservice life or which has lower operating andmaintenance costs. Service life values given are based those normally achievable with high quality products,correctly maintained at the recommended intervals. Insome instances subsidiary components may have aservice life less than that of the main part of theequipment, and in such cases these have been listedseparately.

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Page 187: British Standards Tunnel

Volume 2 Section 2Part 9 BD 78/99

August 1999

Appendix GLife Expectancy of Tunnel Equipment

G1/2

Mechanical Plant

Ventilation

Jet Fans 18 yearsAxial Fans 30 yearsElectrostatic filters 10 years (estimated)

Drainage

Pumps 15 yearsWater level detectors 10 years.

Fire Fighting

Hand Extinguishers 7 yearsHydrants 28 yearsHose reels 20 yearsFire main pipework 30 yearsSprinkler Systems 20 yearsFire detectors (Services Building) 10 yearsAutomatic Gas Discharge Systems 20 years.

Electrical Equipment

Power Supply and Distribution

Switchgear 20 yearsTransformers 30 yearsCables HV 50 yearsCables LV, comms 40 years.

Standby Supplies

Diesel generators 20 yearsUPS sets 15 yearsBatteries:

- valve regulated lead acid 5 years- vented nickel cadmium 20 years.

Lighting

Luminaires 18 yearsBallasts and control gear:

- conventional 20 years- electronic 10 years

Lamps Refer to Chapter 6Guide lighting (emergency) 10 years.

Control Systems

CO, NO2 sensors 13 years

Visibility Monitors 15 yearsAnemometers 20 years

Photometers 15 yearsComputer and PLC systems 18 years (but may be

obsolescent earlier).

CCTV Systems

Cameras 15 years (but may beobsolescent earlier)

Monitors 10 years (but may beobsolescent earlier)

Control equipment 20 years (but may beobsolescent earlier)

Cables 20 years.

Traffic Monitoring and Control Systems

Inductive loop systems 13 yearsSigns and signals 14 years (but may be

obsolescent earlier)Control equipment 15 years (but may be

obsolescent earlier)Closure gates 15 years (13 years if

automatic type)Height detector 15 years.

Communications

Telephones 15 yearsTelephone cabinet 20 yearsSwitch equipment 20 years (but may be

obsolescent earlier)Radio antenna cables 15 yearsTransmitter/receiver equipment 15 years (but may be

obsolescent earlier).

Fire Alarm and Detection systems

Detectors- in tunnel 5 years- elsewhere 20 years

Control Equipment 20 years.

Tunnel Panels

Enclosure cabinets (stainless steel) 35 yearsDistribution Boards 20 yearsFire fighting equipment See above.

Fixings and support systems

Stainless steel 100 yearsHot-dip galvanised steel 15 years.

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