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M4 Corridor around Newport

PUBLIC INQUIRY DOCUMENT

REFERENCE NO. : ID/223

RAISED BY: Matthew Jones DATE: 13/03/18

RESPONDED BY: DATE:

SUBJECT: Reclassification of the existing M4 – Summary of strategy, design and risk

This file note reviews the proposed reclassification of the existing M4 around Newport, to be provided if a new section of motorway south of Newport is built. It considers the strategy for the reclassification, the physical measures proposed and the assessment of potential changes in risk profile arising from the change in use of the road.

Please Note: This is Additional information to supplement the statement in PID 202.

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C:\Users\AnnLas\Documents\OBJ letters pdf\M4CaN-DJV-HGN-ZX_GEN-FN-CH-0010 Ben Sibert.docx Page 1 of 26

Project title M4 Corridor around Newport

cc File reference

M4CaN-DJV-HGN-ZX_GEN-FN-CH-0010 Rev P04

Prepared by Simon Lawrence / Matt Jones

Date

12 March 2018

Subject i

M4 Reclassification – Summary of Strategy, Design and Risk

1. Introduction

This file note reviews the proposed reclassification of the existing M4 around Newport, to be provided if a new section of motorway south of Newport is built. It considers the strategy for the reclassification, the physical measures proposed and the assessment of potential changes in risk profile arising from the change in use of the road.

The file note is set out with the following sections:

1. Introduction

2. Reclassification Strategy

3. Proposed changes to existing infrastructure including risk

4. Changes in Driver / User Class / Vehicle Characteristics including risk

5. Evaluation of Residual Risks

6. Conclusions

7. Declaration of Independence

Appendix 1: Design Development Documents and Supporting Information

Appendix 2: Base Year & Opening Year: Total Forecast Traffic Flows & HGV Flows

This note provides evidence that the Designer has given proper, holistic consideration to the safety of the road under its proposed future operating condition including assessment of risk.

2. Reclassification Strategy

The 2010‐2012 M4 Corridor Enhancement Measures Programme1 investigated works to the existing M4 to enhance capacity and improve safety. Over 100 options were considered in developing a solution to the problems associated with the existing M4 around Newport. Through involvement of diverse stakeholders, including the emergency services and local authorities, it was determined that options involving online widening performed poorly against Welsh Government’s social, environmental and economic objectives.

A 2013 Strategic Environmental Assessment2 further considered options and the strategy for the M4 Corridor around Newport was set in the Plan3 adopted in 2014. Adoption of the Plan in 2014 was accompanied by publication of the Preferred Route. The 2014 Plan determined that a new section of

1 http://m4cem.com/ 2010 - 2012 2 M4 Corridor Around Newport, Strategic Environmental Assessment (SEA) Environmental Report, Welsh Government, 2013, WG19741 3 M4 Corridor around Newport, The Plan, Welsh Government, 2014, ISBN: 978-1-4734-1790-8

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motorway was required plus reclassification of the existing M4 around Newport to an All Purpose Trunk Road (APTR). Reclassification was considered necessary to avoid Newport being enclosed within a ‘motorway box’ and to ‘enable traffic management, safety and revised access measures‘. This decision was successfully confirmed by Judicial Review in 20154.

In March 2015, Costain/Vinci Joint Venture was appointed to develop the proposals up to and through the statutory process and, dependent on the outcome of that process, to design and build the Scheme. Engineering, technical and environmental support has been provided to the contractor by Arup‐Atkins Joint Venture and RPS respectively.

The Project has been developed through engagement, integration and collaboration with a wide range of stakeholders and in March 2016 the draft Orders for the Scheme were published, alongside a body of supporting documents.

The M4 Corridor Around Newport Public Local Inquiry commenced in February 2017 and is ongoing.

The existing motorway layout was designed and constructed in accordance with the standards prevailing at the time (over 50 years ago). The layout has been modified subsequently.

The geometry of the existing road and the frequent high levels of congestion were key factors in determining the need for the new road and associated reclassification.

Historically, the accident frequency rate (AFR) on the existing M4 has been substantially poorer than the UK motorway average. Implementation of the Variable Speed Limit (VSL) system has significantly improved safety, however investigation has concluded that vehicle speeds are not the main factor in accidents on the route, even during off‐peak periods when the VSL system does not typically restrict speeds and the default national speed limit applies. A traffic modelling assessment identified that over 300 accidents would be saved holistically on the network as a result of the M4 Project.

Since adoption of the strategic 2014 Plan, the Atkins Arup Joint Venture (AAJV – the designers) developed further detail of the reclassification works as summarised and reviewed in this note.

The Reclassification Design and Options Report5 identified the following strategic parameters:

a. All works must occur within the existing highway boundary – Increased land‐take would result in increased costs plus significant negative social and environmental impacts.

b. Amendments to existing pavements and amendment or reconstruction of existing structures must be avoided [wherever possible] – [to avoid]: increased construction costs; service diversions; additional land‐take; increased traffic disruption; and a greater environmental impact.

A strategic decision has been made that the National Speed Limit would apply to the Reclassified M4 except for the section between junctions 25 and 26, where a permanent 60mph speed limit would apply.

The strategy of the M4 Project including reclassification, provides a collective package of measures which, overall, provide a safe route for road users. The strategy will avoid Newport being contained in a ‘motorway box’; reduce congestion and weaving along the existing M4; and reduce both the absolute volume and proportion of HGVs using the existing highway corridor.

It is acknowledged that reclassification as an APTR alters the risk profile of the existing road. This, beneficially, includes lower expectations about the physical characteristics of the road [compared with that

4 M4 Corridor around Newport, Public Local Inquiry Library – Document Ref. 4.5.45 http://m4-newport.persona-pi.com/4-scheme-development-and-alternatives 5 Refer to Appendix 1: M4 Corridor around Newport, Reclassification of the M4 and A48(M): Design and Options Report

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of a motorway] as well as an anticipation of other classes of both vehicle and road user that a driver may encounter. It is important that the risk assessment considers all of these factors.

The collective package of measures comprising the strategy for the M4 Project and set out in the Plan, is currently being scrutinised at the M4 Corridor around Newport (M4CaN) Public Local Inquiry (PLI) before a final decision is made on whether to proceed with the entire M4 Project.

3. Proposed Changes to Existing Infrastructure including Risk

This section describes the principal changes and discusses the assessment of associated risk and mitigation.

The principal physical changes proposed to the existing infrastructure are:

a. Reduction in number of lanes [from 3 to 2] in some sections b. Physical and operational changes to junctions 25 and 25A c. Improvements to existing merge and diverge layouts d. Changes to road‐side furniture such as signs

As previously noted, this section of highway was constructed many years ago and design standards have changed significantly in the meantime. There is no requirement to check retrospectively all the situations that become non‐compliant as a result of the introduction of new standards: that would be impractical. The proposed reclassification however introduces a need to reassess. The designers have identified 124 Departures from Standard at discrete locations on the existing M4, within the overall length of the proposed reclassification. These comprise existing retained, existing modified and new Departures. At the same discrete locations, the designers have identified 153 Departures if the existing highway (without reclassification measures) was assessed to current standards. The quantified reduction of at least 29 Departures, from 153 to 124, arises as a consequence of layout changes to the mainline and junctions that are enabled as a direct result of reclassification from motorway to ‘A’ class road. This notable immediate reduction would be reflected in a road user safety benefit due to the lower expectations a driver would have of an ‘A’ road as opposed to a motorway.

There are numerous other locations along the existing M4 (between J23 and J29) where existing Departures from standard would be eliminated completely by the proposed reclassification works. A full technical assessment has not been undertaken at these locations to determine the exact number of existing Departures removed however, an estimate of between 200 and 300 extant Departures has been made. This implies a conservative reduction of at least 76 Departures (200 – 124), almost all of which arise from physical layout changes to the mainline and junctions. There are extremely few Departures which are eliminated purely as a consequence of reclassification from motorway to APTR status.

Albeit, risk consideration needs to factor in the associated change in permitted users of the road. Each principal change is described and a discussion on risk presented below.

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3.1. Reduction in Number of Lanes

3.1.1 Proposals

Based on the traffic model and future forecast traffic flows, approximately 50% of existing traffic flow will divert onto the new road south of Newport. The reduction in traffic volume on the existing M4 presents the opportunity to reassign existing road space to achieve closer compliance with current DMRB6 highway design standards and prescribed junction layouts. The proposed reduction in the number of lanes [from 3 to 2] in some sections, forms part of this strategy.

This proposal introduces a change to the infrastructure and the way that it will operate. The sections/junctions affected by the proposed reduction in the number of lanes are shown in Table 1.

Where traffic volumes and / or existing highway gradients (vertical alignment) require the provision of 3 traffic lanes in accordance with design standards, 3 lanes have been retained.

Table 1: Schedule of Existing / Proposed Lane provision by location.

Existing Proposed Comment

Section/Junction Westbound Eastbound Westbound Eastbound

J23 3 3 Proposed is assessed with new corridor. 23‐23A 3 3

Magor J23A 2 2 2 2

23A‐24 3 3 2 2

Coldra J24 2 2 2 2

24‐25 3 3 2 2 + 1

EB climbing lane from J24 merges with auxiliary diverge to J25

St. Julians/Caerleon J25 3 3 2 2

25‐25A 3 3 2 2

E Brynglas J25A 2 2 2 2

25A‐26 2 2 2 2

W Brynglas/Malpas J26 2 2 2 2

26‐27 3 3 3 3

High Cross J27 3 3 3 3

27‐28 3 3 3 3

Tredegar Park J28 3 3 2 2

28‐29 3 3 3 3

Castleton J29 3 3

Proposed is assessed with new corridor.

Cell colour shading demonstrates the reduced variability in carriageway cross‐section in the proposed scenario.

6 Design Manual for Roads and Bridges, The Stationery Office Ltd.

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Where it is proposed to reduce the number of traffic lanes from 3 to 2, it is Lane 1 that would be removed from normal use. In all cases, the reduction in number of lanes is proposed by road markings (hatching) and not by physical removal of the highway pavement.

Areas of the existing carriageway removed from normal use remain available to provide emergency refuge to broken‐down vehicles and for incident management by Police and Traffic Safety Officers. Non‐operational paved areas also afford space to manage traffic and facilitate the safer delivery of future maintenance of the existing corridor.

3.1.2 Risk Discussion

With fewer running‐lanes, the proposed future highway would present a more open appearance to road users. All proposed road markings would be in accordance with the Traffic Signs Regulations & General Directions (TSRGD) and the Traffic Signs Manual (TSM) and would not therefore present road users with any unusual features. The reduction in the number of lanes would permit the removal of existing features of the highway that are not in accordance with current standards, a recurring example being the junction diverge and merge arrangements. This would reduce the risk to road users.

In summary, the changes to the lane provision for the reclassification proposals are considered to reduce risk compared with the existing configuration. The changes respond to the forecast traffic flows as a result of the proposed Scheme. The proposed changes offer further opportunity, at detailed design stage, to correct some more marginally non‐compliant features such as lane widths and forward visibility issues arising from the horizontal and vertical alignment.

3.2. Traffic Speed

3.2.1 Forecasts

With reduced traffic volumes and reduced traffic congestion, it is forecast that the traffic speed profile would change. By way of example, the 2037 AM and PM peak flows on the Reclassified M4 are forecast to be similar to the current inter‐peak average flows. There will therefore be longer periods in the future where traffic is subject to the default National Speed Limit (or other permanent limit in respect of the J25‐J26 section) and not subject to VSL traffic speed / flow control.

An important point to note here is that the proposed reclassification to APTR reduces the National Speed Limit for a number of user classes such that in the future, the majority of user classes would be subject to a maximum speed of 60mph. This is shown in Table 2.

Due to the legal differences between motorways (Special Roads) and APTRs, it is proposed that the existing VSL signage would become advisory following reclassification.

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Table 2: National Speed Limit (mph) by Vehicle Type

Type of vehicle / User Class Motorway Dual carriageway (APTR)

Cars, motorcycles, car-derived vans and dual-purpose vehicles

70 70

Cars, motorcycles, car-derived vans and dual-purpose vehicles when towing caravans or trailers 60 60

Motorhomes or motor caravans (not more than 3.05 tonnes maximum unladen weight) 70 70

Motorhomes or motor caravans (more than 3.05 tonnes maximum unladen weight) 70 60

Buses, coaches and minibuses (not more than 12 metres overall length) 70 60

Buses, coaches and minibuses (more than 12 metres overall length) 60 60

Goods vehicles (not more than 7.5 tonnes maximum laden weight)

70 (60 if articulated or towing a trailer)

60

Goods vehicles (more than 7.5 tonnes maximum laden weight) in England and Wales 60 60


Now, considering the speed limit strategy, it is useful to look at actual observed and generic forecast AFRs.

The historical records permit a general comparison between pre and post‐VSL commissioning AFRs. This is shown in Table 3 and demonstrates that VSL commissioning has been accompanied by reduction in the AFR reduction on all sections of the existing M4 between J23A and J29.

Table 3: M4 Historical Collision Rates

Section Average Collision Rate (per million veh km)

Pre VSL (2003‐2008) Post VSL (2011‐2015)

J23A – J24 0.0395 0.0310

J24 – J25 0.1154 0.0536

J25 – J26 0.1828 0.0408

J26 – J27 0.1536 0.0664

J27 – J28 0.0660 0.0412

J28 – J29 0.0443 0.0394

More detailed accident records post‐VSL commissioning offer a breakdown by time period. This is shown in Table 4. The period experiencing the highest accident rate for a particular section of road is set out in red.

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Table 4: M4 Accident Frequency Rates by Time Period (per million vehicle km), July 2011‐December 2015

Section AM Peak PM Peak Inter-peak Off Peak Weekend

J23A-J24

J24-J25

J25-J26

J26-J27

J27-J28

J28-J29

0.039

0.054

0.072

0.085

0.015

0.018

0.015

0.123

0

0.198

0.029

0.053

0.027

0.016

0.121

0.044

0.019

0.051

0.044

0.072

0.103

0.051

0

0.010

0.026

0.043

0.069

0.009

0.044

0.020

Full Length 0.044 0.076 0.036 0.043 0.030

The data in Table 3 and 4 shows variability of accident rates by time period and different motorway sections which makes it difficult to draw clear inferences or trends regarding accident rates both for the existing situation or the future Reclassified M4.

The PM Peak period experienced the highest AFR, while the rate in the AM Peak was very similar to the Off Peak period. The lowest rates occurred at the weekend and in the weekday inter‐peak period.

In general, the periods with the highest traffic volumes showed the highest accident frequency rates, although the relatively high rate in the off peak appears to go against this trend. While this rate may be influenced by higher vehicles speeds, it is impossible to draw this as a firm conclusion; it is complicated by the fact that most accidents in this period occur during the hours of darkness and there are therefore several other possible contributory factors including driver fatigue and reduced visibility. It is also noteworthy that, in the AM and PM Peak periods, the two sections outside the VSL area (J23A‐J24 and J28‐J29) ‐ where speeds would be expected to be higher than those within the VSL ‐ show accident rates that are lower than the average for the full length, suggesting that vehicle speeds are not the main determining factor in the accident rates.

Cobalt 37 data (Table 5) show the predicted AFR values based on experience from the UK‐wide network. These figures do not include any experience of APTRs equipped with VSL.

Table 5: Data Extract from Cobalt 3 AFR data (2009 unadjusted figures)

Road Classification AFR (mVkm)

D2M / D3M 0.063

Old D2AP 0.077

Modern D2AP (speed >40) 0.077

Modern D2AP with H/Strip 0.059

Old D3AP 0.101

Modern D3AP with H/Strip (speed >40) 0.101

From the data presented in Tables 4 and 5, it can be seen that the current inter‐peak, off‐peak and weekend incident rates are generally lower than the typical rate for a D2M road, while the PM peak period in particular exhibits a poorer accident record than the typical average for a UK D2M road.

One important feature of the overall assessment of accident causation, is that seven of the nine observed accident clusters occur during peak periods. The observed factual evidence from the existing highway

7 Department for Transport – WebTAG Databook

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operation leads to the broad conclusion, that accident and incident rates appear to increase during times of increased traffic flow / traffic congestion and by implication, times of lower speed.

It is also noted that, although perhaps not statistically significant, speed is not identified as a contributory factor in any of the accident reports of the three reported fatal collisions.

Design Year (2037) peak period traffic flows on the reclassified corridor are forecast to be broadly in line with current inter‐peak traffic volumes. The current inter‐peak AFR for the whole length of the existing M4 is approximately half of the Cobalt predicted AFR for a D2M or D3M road.

For the above reasons, the anticipated change in the vehicle speed profile on the reclassified highway and the proposed change in the application of the VSL system from mandatory to advisory is not considered to present any significant increase in risk to road users.

3.3. Physical and Operational Changes to Junctions 25 and 25A 3.3.1 Proposals

Of all the proposed M4 Reclassification works, the most significant physical infrastructure change would take place at J25/J25A viz:

a. The existing eastbound merge slip road (J25A) is to be stopped up and replaced by a new eastbound diverge slip to J25

b. The existing westbound diverge slip road (J25A) is to be stopped up and replaced by a new westbound merge slip from J25

c. In conjunction with the above slip road changes, the existing westbound diverge slip road (to J25) would be widened to 2 lanes and the J25 roundabout is proposed to be signalised (full‐time signals).

d. Traffic which currently uses the J25A slip roads to connect between the M4 and the A4042 (Heidenheim Drive) would in future make this connection via the traffic‐signal controlled J25 gyratory.

In summary, J25A is effectively removed and J25 has its full‐movement capability reinstated; as the junction was originally conceived and constructed. These proposed changes simplify the existing network by removing two successive, closely spaced eastbound merges and westbound diverges. The proposed highway layout is considered to present drivers with a more logical and therefore safer sequence of decision making and consequently is considered to reduce the risk to road users. Refer to Reclassification Layout Drawings8.

Furthermore, the restoration of full‐movement capability at J25 will respond better to the modelled local trip demand and is therefore expected to reduce both driver stress generally and rat‐running on the local highway network. Both aspects are considered to reduce risk to road users.

3.3.2 Risk Discussion – New road layout

It is acknowledged that changes to existing highway layouts may lead to short term increased risks for established, experienced drivers; those who have driven around the existing layout frequently and who are familiar with the existing situation (habitual drivers). This problem is typical of all highway modifications and is not due to any inherently unsafe aspect of the proposed layout. The proposed ‘standard’ mitigation

8 Appendix 1 – Drawing series – M4CaN-DJV-HGN-ZX_GEN-DR-H-0001 to 0014

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‐ signage that will be familiar to most drivers ‐ is the deployment of temporary ‘New Road Layout’ warning signs (TSRGD Diag. 7014) for 3‐6 months after works completion. Risk levels would be expected to return to ‘normal’ after a period of a few months.

3.3.3 Risk Discussion – Weaving Length and Speed Limit

The proposed reconfiguration of the slip roads at J25 / J25A reintroduces the opportunity for vehicles to join the corridor at J25 and exit at J26 and vice versa. This infrastructure change generates a traffic weaving movement which potentially extends through the Brynglas Tunnels.

The design standard minimum weaving length is 1000m. The provided weaving lengths are 752m eastbound and 763m westbound. In both cases this includes the highway length within the Brynglas Tunnels. Departures from standard have been investigated by the designers for both carriageways.

Lane‐changing within the Brynglas tunnels is currently ‘prohibited’ both east and westbound, by the single [unbroken] white line; this is a non‐prescribed marking (not in the TSRGD). The weaving lengths indicated above assume that lane changes are permitted within the tunnels in the future.

The operational risks to road users have been considered, including the change in user classes and vehicle types permitted by the change from motorway to APTR. A risk assessment identified risks associated with the physical change in infrastructure, change in operation and specifically the short weaving lengths. All identified risks can be mitigated such that they are assessed to be ‘Low’ following mitigation.

Proposed mitigation measures have been considered for the Departures from standards and include:

User classes – Non‐motorised users will be prohibited from using the Brynglas Tunnels (this prohibition would be consistent throughout the existing M4 corridor between J23 and J29).

Signs and Lines – It is proposed that signs and markings will be used to improve lane discipline and reduce the incidences of weaving. Lane indication signs and markings will encourage appropriate lane choice for drivers approaching the weaving section and may include:

a. Advance Lane Designation signs placed on the approaches to the weaving area to improve lane discipline;

b. Hazard Warning Line Markings (diagram 1004.1) to be used on carriageway; c. [Subject to tunnel constraints] Countdown warning signs (diagrams 823, 824 and 825) to be

used on approach to diverges; d. Map type advance direction signs to be placed at edges of carriageway at appropriate

locations subject to other physical constraints; e. Rectangular merge warning signs to be used on mainline carriageway at an appropriate

distance upstream of the Caerleon Junction westbound merge and the Malpas Junction eastbound merge.

Speed Limit – The speed limit strategy considers this section of the network [J25 – J26 and immediate environs] particularly carefully and advocates that between junctions 25 and 26, a permanent 60mph speed limit would be applied, due to the combination of existing substandard elements. These substandard elements include the adjacent weaving lengths, highway cross section through the tunnels (no hard shoulder or hard strip) and other facets of the geometry, such as curvature and visibility, which are below the required standard. It is considered that the presence of the tunnel heightens the risks in this section, primarily due to the user perceived effect of enclosed space and change in lighting conditions. Also, a permanent speed limit reduction would be beneficial to reducing the accident potential for this part of the existing M4.

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It is therefore considered appropriate to apply a permanent speed limit of 60mph in this region alone [J25 – J26 and immediate environs]. This, together with the other measures described above, comprises the mitigation proposed to address the risks identified in this section of the Reclassified M4.

3.4. Improvements to Existing Diverge and Merge Layouts

3.4.1 Proposals

The existing M4 exhibits a diverse range of junction merge and diverge layouts between J23 and J29. Most junction layouts have been adapted and modified (since original construction) in response to increasing traffic flows over time. None of the existing junctions would be fully compliant if assessed to current standards for traffic flow and geometric layout. Road users currently experience a very inconsistent series of junction layouts and geometries over a relatively short distance. This road user experience impacts on all drivers due to the multiple lane drops / lane gains on the mainline; it is not restricted to the users of individual junctions.

As reported above, the transfer of traffic to the new road to the south of Newport and consequent reduction in traffic volume on the existing highway, creates the opportunity to reduce the number of traffic lanes on the existing mainline.

The proposed lane reduction vacates space in the highway paved area which can be reallocated and removes a number of existing lane drop / lane gain arrangements. The existing highway geometry and physical highway boundary constraints preclude revised junction layouts which comply fully with current design standards. With appropriate design of road markings and relatively limited physical reconstruction, it is feasible to provide junction diverge and merge layouts which respond to the forecast traffic flows and align more closely with the DMRB derived layouts. Mainline and junction flows are expected to be smoother as a consequence of these changes. This reduces driver stress and reduces the risk to all road users.

Lane reduction and junction layout revisions have been looked at in particular detail between J24 and J25 due to the combination of gradient and horizontal curvature. Climbing lanes and auxiliary diverge lanes have been found to be the most appropriate solution in this region.


The Reclassification Design and Options Report presents detailed assessments of the options considered for each individual slip road at each junction and compares the potential advantages and disadvantages of each.

In the case of all existing junctions, it is the Designer’s view that the proposed reclassification works remove some Departures and reduce the magnitude of others.

The complete elimination of Departures is impractical due to physical constraints and associated costs [additional land requirements]. Moreover, the physical disruption that would be entailed by works to widen the corridor would present significant additional (albeit short term) risks to road users, the disbenefits of which are considered to outweigh the existing risks associated with the proposed retained / modified Departures.

The reclassification proposals reduce overall risks to road users by delivering a suite of junction layouts that are as close as reasonably practicable to the DMRB Layouts derived from the forecast traffic flows. The

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proposed layouts represent a substantial improvement in design compliance compared with the existing M4 motorway.

3.5. Changes to Roadside Furniture

3.5.1 Proposals

The M4 Reclassification proposals involve minimal changes to roadside furniture. The proposed changes will replace equipment on a like‐for‐like basis.

Features to be replaced will include motorway signage which would be replaced with trunk road signage. Sign locations are expected to be unchanged.

Features to be retained will include: cabinets and gantries associated with the VSL system; emergency telephones and street lighting.

Features that require modification include safety barriers which are likely to require reassessment in respect of set‐back distance and working width.


In all cases, if roadside furniture is currently in a safe protected position, then there is no expectation that any associated existing risk would increase. Indeed, taking an overview of the existing physical infrastructure, the proposed reclassification amendments to lane and junction layouts are expected to reduce risks attached to individual items of roadside furniture.

To conclude, while very little change to roadside furniture is proposed, the assessment of risks in the context of an APTR compared with a motorway class road would suggest an overall reduction in risk to road users.

4. Changes to User Classes / Vehicle Characteristics and Road-space Utilisation

The proposed reclassification of the existing motorway to APTR could open the road up to user classes that are currently prohibited by virtue of the motorway designation. This would include inter alia, all non‐motorised user categories, agricultural and construction vehicles, learner drivers. It would also permit a change of use whereby HGVs could use the lane adjacent to the central median from which they are presently excluded.

The potential risks associated with increased speeds on the reclassified highway have been considered previously. The potential for risks associated with differential vehicle speeds on the reclassified corridor has also been raised as a matter of concern. These include:

a) New user classes may include slower vehicles; b) Will there be a greater speed differential between user classes? c) Will the future situation differ materially from the current where slow moving HGVs frequently

occupy Lane 1?

The implications of the additional road user classes (that could be permitted to use the existing M4 corridor following the proposed reclassification) are considered below.

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The physical differences between motorways and APTRs are relatively minor in respect of the physical horizontal and vertical geometry. There are also only limited differences in the national speed limits applicable to the two road classifications and those differences that exist, relate only to certain vehicle classes (refer to Section 3, Table 2,). As such, little difference in driving style would be anticipated between the two road classifications.

It is noted here that there is no general legal minimum speed limit for vehicles on UK motorways. For vehicles to be permitted to use motorways, they must be capable of a sustained speed of 25mph but signed legal minimum speeds are rare on UK highways.

4.1. Changes to Driver / User Class

4.1.1 Additional / Increased Users

New (potentially slower moving) user types would automatically gain access to the existing road after the proposed reclassification of the existing M4 to an APTR in the absence of any specific Traffic Regulation Orders. The reclassification would automatically open the route to the following new user classes:

a) Provisional licence holders (Learner Drivers). b) Motorcycles under 50cc. c) Agricultural vehicles. d) Vehicles carrying oversized loads (however these could have been permitted on the motorway

subject to advance planning) e) Mobility scooters. f) Pedestrians. g) Cyclists. h) Horse riders.

Vehicle types a) and b) should be anticipated to use the reclassified route. The urban ‘bypass’ nature of the corridor in particular between existing junctions 24 and 28, may give rise to a higher proportion of vehicle types a) and b) than the UK average for APTR.

Provisional licence holders are, by definition, less experienced and therefore potentially slower drivers. However, this user class is legally entitled to use the APTR network and does so in and around many other urban centres throughout the UK without leading to statistically significant incident numbers. There is no evidence to suggest that the interaction between provisional licence holders and other drivers would be any different on the reclassified road compared with anywhere else on the APTR network.

Motorcycles under 50cc are low powered motor vehicles and would be expected to be travelling slowly relative to many other power road users. Like provisional licence holders, riders of these vehicles are legally permitted to use the APTR network and do so elsewhere without statistically significant incident rates. The location at which these vehicles and users may be considered to be most vulnerable is the Brynglas Tunnels. Here, the recent tunnel lighting replacement and proposed future [after reclassification] 60mph speed limit are considered to offer appropriate hazard mitigation for this user class.

Generally, the prevalence of vehicle type c) agricultural vehicles, would be expected to be lower than the UK average for APTR given the general urban nature of the corridor. The exception to this may perhaps be the section between existing junctions 23A and 24 where the existing motorway is bordered by agricultural land. This section of the existing road offers some of the better geometric standards where agricultural vehicles would not be expected to encounter nor present any particular difficulties.

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Vehicle type d) abnormal and oversized loads are, by their nature, infrequent events that could also be encountered on the existing motorway subject to appropriate movement planning and permissions. The proposed reclassification is not seen as a likely trigger for a substantial increase in such vehicle movements. This vehicle type and the potential change in the numbers using the reclassified road, is considered to be insignificant to this assessment.

Vehicle type e) mobility scooters, would be legally entitled to use the reclassified route however, notwithstanding the ‘bypass’ nature of the road, the actual likelihood of drivers choosing to use the corridor is considered to be low. This conclusion is reached based on the presence of alternative, potentially more desirable established routes. Given the particularly slow nature of these vehicles, if concerns remain, then it may be appropriate to investigate the number of such vehicles present in a typical neighbourhood and the potential for the reclassification to unlock a latent user demand.

The later three user types f) – h), all fall under the umbrella heading of Non‐Motorised Users (NMU). Previous work including a Non‐Motorised User Audit9 and Road Safety Audit10, has concluded that NMUs should not be permitted to use the reclassified road at any point. This conclusion is founded on safety concerns and the recognition that alternative, potentially more desirable routes exist for these user classes.

4.1.2 Reduced Users

While it is recognised that new user classes and potentially slower vehicles would gain access to the existing road following reclassification, it is also important to consider the forecast overall reduction in traffic volumes and then specifically the forecast reduction in the number of vehicles from existing ‘slower’ HGV classes. Appendix 2 presents the base year and opening year total forecast traffic flows and HGV forecast traffic flows derived from the Traffic Model, broken down by corridor route section (between existing junctions). Using eastbound flows as an example, in summary, total traffic flows are forecast to be reduced by between 31% and 72% with an average of about 45% at Opening Year compared with the Do Minimum solution. The corresponding HGV traffic reduction is forecast to be between 52% and 76% with an average of about 62%.

With such a significant transfer of HGV traffic away from the existing route, it is forecast that there would be a material reduction in the proportion of potentially slow moving vehicles even after the introduction of the new user classes


Reclassification would permit new potentially slower user classes to access the highway. However, the likelihood of the slowest vehicles actually choosing to use the route is considered to be low. In terms of absolute vehicle numbers, those new user classes that do use the route are likely to be offset by a general reduction in the proportion of HGV traffic in the traffic flow. The result is likely to show an overall reduction in the proportion of potentially slower moving motorised vehicles in the traffic flow.

9 Appendix 1 – Stage 1 NMU Audit Report for Reclassified M4 – M4CaN-DJV-HGN-ZX_GEN-RP-TR-0001

10 Appendix 1 - Stage 1 Road Safety Audit - M4 Reclassification – Response Report, M4CaN-DJV-GEN-ZX_GEN-RP-CH-0001

File Note


Risk assessment has identified concerns with the absence of safe refuge areas, particularly in the section west of the Brynglas Tunnels where a D3AP cross‐section is to be maintained. The risk assessment also highlighted the potential for conflict between higher speed vehicles and low speed NMUs at merges and diverges for grade separated junctions. It is therefore proposed that all non‐motorised user classes should be prohibited from using the reclassified road.

The presence of alternative, parallel routes which are more desirable to non‐motorised users was a consideration/mitigation in arriving at this decision and the strategic 2014 Plan took consideration of wider enhancement of non‐motorised user routes.

4.2. Changes to Manner of Use (Road position)

4.2.1 Proposals

The proposed reclassification to APTR permits the use of Lane 3 by HGVs where it is present. This differs from the current 3 lane motorway, where HGVs are excluded from Lane 3.

Potential risks associated with the changes to permitted lane use and the physical vehicle positions within the reclassified corridor have been raised as a concern. The implications for each section of the reclassified corridor are considered in turn here.

As a general principle, narrow lanes are not permitted within the design standard on motorways or APTRs and they are not proposed for the reclassified corridor.

The existing and post‐reclassification proposed lane configurations are set out in Table 1. The following reclassification proposals will lead to less weaving and lane changing on approaches to junctions with a correspondingly smoother traffic flow:

a. removing all of the existing Lane 1 for much of the route to the east of the Brynglas Tunnels b. reconfiguration of junction layouts and c. associated removal of lain drop / gain arrangements.

J23A (Magor)

The existing dual two‐lane arrangement through the Magor junction would be retained. HGV traffic is currently permitted to use Lane 2 nearest to the central median and this arrangement is not proposed to be changed.

Existing hard shoulders will be reduced in width with white lining to delineate the new back of hard strip.

In the Opening Year (2022), total traffic volume is forecast to be 49% less and HGV traffic 72% less than the [2014] Base Year.

Other than the traffic volume reduction, there are considered to be no other material operational changes to the use of the road.

J23A – J24 (Magor – Coldra)

The existing Lane 1 and discontinuous hard shoulder is to be taken out of operation and replaced with a continuous hard strip.

File Note


HGV traffic will be permitted to use the lane adjacent to the central median for the first time.



HGV traffic will use Lane 2 on occasions, however the highway horizontal geometry of this section is relatively benign and forward visibility is not generally compromised for users. HGV drivers have an elevated driving position which generally mitigates the effect of tight horizontal alignments and any consequent obstruction of forward visibility.

J24 (Coldra)

The existing dual two‐lane arrangement through the Coldra junction would be retained. HGV traffic is currently permitted to use Lane 2 nearest to the central median and this arrangement is not proposed to be changed.

Existing white line road markings will be modified to delineate the new back of hard strip.


J24 – J25 (Coldra - Caerleon)

The existing westbound Lane 1 and discontinuous hard shoulder is to be taken out of operation and replaced with a continuous hard strip. A climbing lane / auxiliary diverge lane will be retained eastbound over the total distance between junctions.




The highway geometry of this section is horizontally and vertically poor, particularly in the vicinity of St. Julian’s / Christchurch Hill. HGV use of Lane 2 is expected to be low due to the steep gradients and lower corresponding vehicle speeds. However, in the event that HGVs do enter Lane 2, the HGV driver’s elevated driving position generally mitigates the effect of tight horizontal alignments and any consequent obstruction of forward visibility.

J25 (Caerleon)

The existing dual three‐lane arrangement without hard shoulders through Caerleon junction would be reduced to a dual two‐lane carriageway with hard strips.



File Note



The highway geometry of this section is poor horizontally and vertically. HGV drivers’ elevated driving positions generally mitigate the effect of tight horizontal alignments and any consequent obstruction of forward visibility. Further mitigation is provided by the proposed 60mph speed limit between J25 and J26 (and immediate approaches).

J25 – J26 (Caerleon – Malpas)

This section of the existing highway will experience the greatest physical changes. The carriageway cross section will be reduced to dual two‐lane with hard strips where there are currently 3 lanes in places. The reprovision of the J25 west‐facing slip roads and associated closure of J25A will also assist in providing a smoother dual two‐lane approach to / exit from the Brynglas Tunnels.

Through the two‐lane tunnels, HGV traffic is currently permitted to use Lane 2 nearest to the central median and this arrangement is not proposed to be changed.


Appropriate lane destination signing and the proposed 60mph speed limit in this section will mitigate the effects of the short separation between J25 and J26 and the substandard weaving length.

J26 (Malpas)

The existing dual two‐lane arrangement through the Malpas junction would be retained. HGV traffic is currently permitted to use Lane 2 nearest to the central median and this arrangement is not proposed to be changed.


J26 – J27 (Malpas – High Cross)

Forecast traffic volumes to the west of the Brynglas Tunnels are high enough to warrant the retention of a dual three‐lane carriageway. The currently discontinuous hard shoulder would be replaced with a hard strip where it is physically possible to achieve this. The new hard strip would be delineated with white lining.

With the reclassification to APTR, HGV traffic will be permitted to use the lane adjacent to the central median for the first time. However, in practice, with the three‐lane cross section retained and the steep gradients leading to lower vehicle speeds, HGV use of Lane 3 is expected to be low.


The highway geometry of this section is horizontally and vertically poor. HGV use of Lane 3 is expected to be relatively low due to the steep gradients and lower corresponding vehicle speeds. However, in the

File Note


event that HGVs do enter Lane 3, the HGV driver’s elevated driving position generally mitigates the effect of tight horizontal alignments and any consequent obstruction of forward visibility.

J27 (High Cross)

The existing dual three‐lane arrangement without hard shoulders through High Cross junction would be retained. Hard strips will be provided where physically possible, delineated with white lining.

HGV traffic will be permitted to use the lane adjacent to the central median for the first time. However, in practice, with the three‐lane cross section retained and the steep gradients leading to lower vehicle speeds, HGV use of Lane 3 is expected to be low


The highway geometry of this section is poor both horizontally and vertically. HGV drivers’ elevated driving positions generally mitigate the effect of tight horizontal alignments and any consequent obstruction of forward visibility.

J27 – J28 (High Cross – Tredegar Park)

The existing dual three‐lane arrangement without hard shoulders would be retained. Hard strips will be provided where physically possible, delineated with white lining.

HGV traffic will be permitted to use the lane adjacent to the central median for the first time. However, in practice, with the three‐lane cross section retained and the steep gradients leading to lower vehicle speeds, HGV use of Lane 3 is expected to be low


The highway geometry of this section is poor horizontally and vertically. HGV drivers’ elevated driving positions generally mitigate the effect of tight horizontal alignments and any consequent obstruction of forward visibility.

J28 (Tredegar Park)

The existing dual three‐lane arrangement without hard shoulders through Tredegar Park junction would be reduced to a dual two‐lane carriageway with a lane drop / gain arrangement either side of the junction. This proposed arrangement offers a much closer alignment with DMRB junction layout standards based on the forecast traffic flows when compared to the existing condition.




File Note


The highway geometry of this section is relatively good. HGV traffic would not be expected to encounter any difficulties in using Lane 2.

J28 – J29 (Tredegar Park – Castleton)

The existing dual three‐lane arrangement would be retained. Discontinuous hard shoulders would be replaced by hard strips where physically possible, delineated with white lining.

HGV traffic will be permitted to use the lane adjacent to the central median (Lane 3) for the first time. However, the anticipated use of Lane 3 by HGVs is expected to be low in the westbound direction because of the steep gradient leading to lower vehicle speeds.


The highway geometry of this section is relatively good. HGV traffic would not be expected to encounter any difficulties in using Lane 3.


The future use of Lane 3 by HGVs would place them in a running location where they would experience reduced forward visibility [to low objects] at locations where they would not presently (e.g. right hand bends in either direction). It is not possible to address this lack of forward visibility in the design proposals, since it would require land outside the highway boundary.

To the west of the Brynglas Tunnels, the retention of the D3AP carriageway is likely to lead to only limited use of Lane 3 by HGVs. This would be compounded by the relatively steep vertical alignment gradients leading to slower moving HGVs and less propensity to perform overtaking manoeuvres. The effect of steep gradients and correspondingly slower vehicle speed would also be seen at Christchurch Hill / St. Julians to the east of the Brynglas Tunnels. The anticipated use of the lane adjacent to the central median barrier is anticipated to be low in the regions where the vertical alignment is steepest, which happens to coincide with those areas which exhibit some of the tightest horizontal radii.

While acknowledging that horizontal geometry is substandard, tight horizontal radii and consequent reduced forward visibility past the central median barrier is not necessarily a problem for HGV drivers, given the elevated driving position and drivers’ visibility over the barrier.

The risk presented by HGVs using the lane nearest to the median barrier is considered to be negligible to slight, based on the anticipated low numbers and generally acceptable forward visibility for those vehicles that do arrive in that lane.

The risk presented by differential vehicle speed has also been considered. It is proposed to retain a D3AP cross section where forecast traffic volume justifies the provision and a climbing lane is provided where the vertical alignment justifies this [e.g. eastbound between Caerleon and the Coldra]. Consequently, the potential risk presented by slower moving vehicles is mitigated by the provision of appropriate carriageway space at the relevant locations. Differential vehicle speeds are not assessed to present an increased risk to road users.

The risk presented by traffic weaving has been considered. The proposed lane number reductions and associated junction layout reconfigurations, enabled by the overall reduction in traffic volumes post

File Note


scheme implementation, will have a significant beneficial impact on traffic flow. The elimination of the need to switch lanes to avoid junction lane drops will have a significant smoothing effect on traffic flow and the elimination of potential vehicle conflicts.

5. Evaluation of Current and Future Residual Risks

DMRB Vol.0 Para 2.2.3 requires that:

the Designer must ensure that any submitted departure application has fully assessed the risks, impacts and benefits in terms of safety, technical, programme, economic, maintenance and environmental issues.

Para 2.2.4 goes on to advise that:

The Designer must be able to confirm that the residual risks are as low as reasonably practicable and that the benefits outweigh the disbenefits.

The design team’s assessments acknowledge that, whilst the reclassification strategy and design seeks to remove or reduce risks, there would remain residual risks present on the reclassified road. Mitigation measures have been integrated to manage risks to as low as reasonably practicable. Numerous and extensive studies have demonstrated that further physical works to the road (for example straighten) are impracticable for economic, social and environmental reasons.

A broad assessment of the current and possible future risks is presented in Table 6 below in consideration of which the following facts should be borne in mind.

a. The existing motorway, despite many non‐compliances with current design standards, operates in a broadly safe manner albeit with increasing levels of congestion.

b. In a Do Minimum situation, with no new motorway, travel conditions on the existing motorway would be expected to get worse with time because of traffic growth and further increased congestion. This would be expected to include an increase in accident levels even with the retention of a mandatory VSL.

c. Implementation of the new section of motorway to the south of Newport will reduce traffic volumes and hence reduce congestion on the existing motorway. This should improve driving conditions for users of the existing highway; however, the benefit may be partially offset by the current proposed change from mandatory to advisory VSL.

File Note


Table 6: Existing Corridor Quantitative Risk Assessment

Description Existing Motorway in 2014 (Base Case)

Existing Motorway in 2022 (Do Minimum)

Reclassified Trunk Road in 2022 (Do Something)

Eastbound AADT 33,773 to 52,878 39,409 to 60,310 16,692 to 34,203

Westbound AADT 34,585 to 52,458 39,190 to 58,895 22,713 to 37,056

Risk re Traffic Congestion Medium High Low

Eastbound HGVs (AADT) 4,580 to 5,649 4,678 to 5,981 1,541 to 2,427

Eastbound HGVs (%) 13.6 to 10.7 11.9 to 9.9 9.2 to 7.1

Westbound HGVs (AADT) 4,333 to 5,388 4,666 to 5,531 1,422 to 2,163

Eastbound HGVs (%) 12.5 to 10.3 11.9 to 9.4 6.2 to 5.8

Risk due to HGV volume High High Medium / Low

Accident Frequency Rate / Collision Rate (per million veh. km) Post VSL 2011 – 2015

0.0454 (J23 – J29 mean)

Observation – AFR is anticipated to increase

Observation – significantly reduced traffic flows and improvement of some junctions anticipated to reduce AFR.

Accident Frequency by time of day (per million veh. km) Post VSL 2011 – 2015 (J23 – J29 mean)

0.030 (weekend) to 0.076 (pm Peak)

Observation – AFR is anticipated to increase

VSL Operation Mandatory VSL Mandatory VSL Advisory VSL (in conjunction with:) Significant traffic volume reduction. Junction layout improvements (junction layouts better matched to forecast traffic flows). Highway cross section improvements (cross section better matched to forecast traffic flows).

Accident / Collision risk Medium High Low

WebTAG Cobalt 3 forecast AFR per million veh. km (2009 Source year) *

D2M/D3M = 0.063 D2M/D3M = 0.063 ** Old D2AP = 0.077 Modern D2AP with H/Strip = 0.059

Observations Mandatory VSL would be expected to reduce the AFR.

Benefit of Mandatory VSL could reduce with increasing congestion. Travel conditions would deteriorate generally and AFR could rise despite the general Cobalt prediction of AFR reduction over time **.

Significantly reduced traffic volume removes the dominant effect of congestion on the AFR. Cobalt predicted AFR reduction with time leads to future year AFR of the order of 0.040. Advisory VSL could lead to upward drift in AFR.

Accident risk Low High Medium

File Note


Description Existing Motorway in 2014 (Base Case)

Existing Motorway in 2022 (Do Minimum)

Reclassified Trunk Road in 2022 (Do Something)

Departures from Standard 153 *** 153 *** 124

Departure Risk Observation – Medium because current situation.

Observation – High because risk could increase due to increasing congestion.

Observation – Low due to removal of some departures.

* Cobalt default rates are determined from UK-wide statistics and are therefore averages.

** Cobalt forecasts a reduction in accident rates over time based on anticipated improvements in vehicle safety technology. However, accident rates on the Existing M4 are thought to be dominated by traffic volume / congestion which is forecast to deteriorate further over time in the Do Minimum scenario.

*** 153 existing Departures from Standard have been identified at the discrete locations on the existing M4 where new Departure applications are proposed in conjunction with the M4 Reclassification. Other Departures are known to exist currently at other locations between J23 and J29 where future Departures are not required.

The immediate benefit of accepting the Departures is that it will facilitate the implementation of the M4 Project. This would transfer around half the existing traffic to the new road with higher standards, therefore holistically improving the safety of the network with the number of accidents saved, conservatively, assessed as over 30011.

An additional means of further mitigating residual risks has been considered, namely a further reduction in speed limits along the reclassified route. However, this has been considered and has been assessed on balance to have significant economic and social disbenefits due to the large associated drop in economic efficiency and productivity of the route with associated disbenefits for communities and businesses to the north of Newport and the Valleys. Furthermore, informal consultation with Gwent Police has indicated that they would have concerns on enforceability of and compliance with a lower speed limit on the route. For these reasons, the benefits of the proposed Scheme are considered to significantly outweigh the disbenefits of the residual risks of the Departures.

11Traffic Expert Witness – Inquiry Proof of Evidence http://bailey.persona-pi.com/Public-Inquiries/M4-Newport/C%20-%20Core%20Documents/1.%20Proofs/1.2.6%20%20Bryan%20Whittaker%20-%20Revised%20PoE%201.2.1%20Rev%20A.pdf

File Note


6. Conclusions

The reclassification design process undertaken by the designers has identified:

a. existing Departures that would be eliminated

b. existing Departures that are improved

c. existing Departures proposed to be retained and

d. new Departures.

The latter three categories account for the 124 Departures from Standard (from the current DMRB) identified by the designers that are to be submitted to the Technical Review Panel.

Each departure from standard is accompanied by a risk assessment which collectively demonstrate an overall reduction in risk to road users after the mitigations appropriate to each departure have been implemented.

The changes to the highway layout proposed for the Reclassified M412, would address a substantial number of the substandard highway geometry aspects of the existing road. This is delivered typically by a closer alignment of the future forecast traffic flows with the proposed numbers of lanes, junction diverge / merge layouts and carriageway cross section required by the current DMRB standards.

The M4 Reclassification proposals have been subject to a Stage 1 Road Safety Audit. The Road Safety Audit made 20 Recommendations, all of which are accepted by the Designer13 and no Exceptions were required.

Consideration has been given to additional mitigation measures (i.e. further speed limit reductions) but the disbenefits of this far outweigh the benefits and therefore render these further mitigation measures inappropriate.

Collectively, the reduction in existing Departures and appropriate mitigation of remaining / new Departures would provide a safer route for road travellers.

7. Declaration of Independence

Simon Lawrence is a Chartered Civil Engineer (MICE, MCIHT) and an Associate of Arup. He is familiar with the M4CaN Project having been involved with the project’s evolution at various times during the past 24 years. He has had no involvement with the current KS4 PLI stage of the project or any of the associated design development work and as such, has had no involvement with the development of the M4 Reclassification proposals.

12 Appendix 1 – Drawing series – M4CaN-DJV-HGN-ZX_GEN-DR-CH-0001 to 0014 13 Appendix 1 – Stage 1 Road Safety Audit - M4 Reclassification – Response Report, M4CaN-DJV-GEN-ZX_GEN-RP-CH-0001

File Note


Appendix 1: Design Development Documents and Supporting Information

Further details are available in the following documents:

1.

Drawings M4CaN‐DJV‐HGN‐ZX_GEN‐DR‐CH‐0001 to 0014.

M4 Reclassification Proposal Layout Drawings. Refer to Design and Options Report.

2. Stage 1 Road Safety Audit ‐ M4 Reclassification – Response Report (WG Report), November 2016

Document Reference – M4CaN‐DJV‐GEN‐ZX_GEN‐RP‐CH‐0001

The auditor made 20 recommendations in the Road Safety Audit Stage 1 – Reclassified M4. All 20 of the audit recommendations have been accepted by the Designer and no exceptions are required. 3.

Reclassification of the M4 and A48(M): Design and Options Report, March 2016

Document Reference ‐ M4CaN‐DJV‐HGN‐ZX_GEN‐RP‐CH‐0002

This report presents a detailed account of the design decisions and [significant] alternative options considered for the mainline, interchanges and junctions. The following elements were considered when reviewing options: • Engineering – to include (where applicable) appraisals of geometry, NMU impacts, structures, Network

Rail interfaces and construction issues; • Environmental – to include appraisals of any notable environmental impacts; • Traffic – to include appraisals of any notable traffic impacts; • Safety – to include appraisal of any notable safety impacts; and • Cost – an assessment of cost impacts of providing differing options. The report advises that the following constraints relate to the project strategy and have been considered in the assessment of reclassification options: • All works must occur within the existing highway boundary – … Increased land‐take would result in

increased costs and a greater environmental impact. • Amendments to existing pavements must be avoided … • Amendment to or reconstruction of existing structures should be avoided wherever possible … 4.

ITS Strategy on Reclassified Existing M4 (File Note), November 2015

Document Reference – M4CaN‐DJV‐HGN‐ZX_GEN‐FN‐TE‐0001

… discusses the options and proposes a strategy to make best use of the legacy investment in technology along the route of the existing M4 Motorway when it is re‐classified to a dual carriageway APTR to provide ITS that supports safety, efficiency, reduced environmental impact and journey time reliability and follows the best practice and standards set by the Welsh Government.

File Note


5.

Stage 1 NMU Audit Report for Reclassified M4 (WG Report), September 2016

Document Reference – M4CaN‐DJV‐HGN‐ZX_GEN‐RP‐TR‐0001

File Note


Appendix 2: Base Year & Opening Year: Total Forecast Traffic Flows & HGV Flows

EASTBOUND

Total Traffic (vehs) HGVs (vehs)

Base Year Do Min Do

Something Base Year Do Min Do

Something

No Tolls No Tolls No Tolls No Tolls

2014 2022 2022 2014 2022 2022

J24‐J23A AM 3,317 4,278 1,892 380 398 168

IP 2,434 3,285 928 400 410 97

PM 2,771 3,487 1,264 287 277 100

AADT 36,638 47,973 16,692 4,934 5,031 1,541

J25‐J24 AM 4,180 4,845 2,826 389 389 180

IP 3,038 3,776 1,672 467 497 186

PM 3,707 4,315 2,182 338 334 158

AADT 46,655 55,904 27,857 5,591 5,788 2,388

J26‐J25 AM 2,887 3,262 2,079 293 283 104

IP 2,326 2,782 1,434 403 424 135

PM 2,552 2,941 1,763 260 253 87

AADT 33,773 39,409 22,411 4,580 4,678 1,553

J27‐J26 AM 4,352 4,798 3,305 342 333 131

IP 3,207 3,792 1,966 455 476 172

PM 4,273 4,647 3,033 284 273 98

AADT 50,211 56,930 34,203 5,186 5,264 1,933

J28‐J27 AM 4,299 4,843 3,159 337 328 126

IP 3,168 3,690 1,896 454 474 169

PM 4,551 4,788 3,232 288 274 99

AADT 50,670 56,826 33,881 5,172 5,241 1,901

J29‐J28 AM 4,853 5,317 3,273 407 442 210

IP 3,219 3,748 1,844 478 512 185

PM 4,565 5,264 3,271 313 308 143

AADT 52,878 60,310 34,021 5,649 5,981 2,427

File Note


WESTBOUND

Total Traffic (vehs) HGVs (vehs)

Base Year Do

Minimum Do

Something Base Year Do

Minimum Do

Something

No Tolls No Tolls No Tolls No Tolls

2014 2022 2022 2014 2022 2022

J23A‐J24 AM 3,000 4,004 1,864 427 490 176

IP 2,190 3,024 1,414 302 365 90

PM 3,596 4,708 2,163 262 310 119

AADT 36,570 49,207 22,860 4,333 5,130 1,584

J24‐J25 AM 4,007 4,548 2,641 518 555 230

IP 2,821 3,476 1,913 391 425 158

PM 4,352 4,897 2,725 283 300 121

AADT 46,667 54,732 30,669 5,314 5,721 2,236

J25‐J26 AM 2,935 3,179 1,940 374 399 108

IP 2,084 2,505 1,575 345 371 119

PM 3,275 3,551 1,694 236 246 77

AADT 34,585 39,190 22,713 4,374 4,666 1,422

J26‐J27 AM 4,718 5,019 3,525 435 460 149

IP 3,049 3,584 2,228 398 423 160

PM 4,935 5,164 3,132 258 260 83

AADT 52,458 57,880 37,056 5,011 5,272 1,863

J27‐J28 AM 5,275 5,376 3,837 442 462 149

IP 2,905 3,363 1,935 390 414 147

PM 4,665 4,666 2,522 251 251 74

AADT 52,413 55,913 34,087 4,951 5,185 1,748

J28‐J29 AM 4,508 5,121 3,158 511 545 222

IP 3,137 3,643 2,043 418 447 175

PM 4,780 5,250 2,622 255 202 70

AADT 51,876 58,895 32,932 5,388 5,531 2,163

DOCUMENT CHECKING

Prepared by Checked by Approved by

Name Simon Lawrence / Matt Jones

Ben Sibert Gary Davies

Signature

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