ERTMS/ETCS National Values - jonroma.net · 2017. 2. 9. · for the ETCS onboard to use when the...

Rail Industry StandardRIS-0708-CCSIssue: OneDate: September 2017

ERTMS/ETCS NationalValues

Synopsis

This document contains requirements andguidance for a process to determine orrevise a set of values of ERTMS/ETCSNational Values.

Copyright in the Railway Group documents is owned by RailSafety and Standards Board Limited. All rights are herebyreserved. No Railway Group document (in whole or in part)may be reproduced, stored in a retrieval system, ortransmitted, in any form or means, without the prior writtenpermission of Rail Safety and Standards Board Limited, or asexpressly permitted by law.

RSSB members are granted copyright licence in accordancewith the Constitution Agreement relating to Rail Safety andStandards Board Limited.

In circumstances where Rail Safety and Standards BoardLimited has granted a particular person or organisationpermission to copy extracts from Railway Group documents,Rail Safety and Standards Board Limited accepts noresponsibility for, nor any liability in connection with, the useof such extracts, or any claims arising therefrom. Thisdisclaimer applies to all forms of media in which extractsfrom Railway Group documents may be reproduced.

Published by RSSB

© Copyright 2017Rail Safety and Standards Board Limited

Uncontrolled when printed Document supersedes GERT8408 Iss 1 and GEGN8608 Iss 1 with effect from 02/09/2017

Issue Record

Issue Date Comments

One 02/09/2017 Original document. To include additional National Values fromERTMS Baseline 3

This document will be updated when necessary by distribution of a complete replacement.

Superseded Documents

The following Railway Group documents are superseded, either in whole or in part as indicated:

Superseded documents Sections superseded Date whensections aresuperseded

GERT8408 issue one ERTMS/ETCSNational Values

All 02/09/2017

GEGN8608 issue one Guidance onERTMS/ETCS National Values

All 02/09/2017

Supply

The authoritative version of this document is available at www.rssb.co.uk/railway-group-standards. Enquirieson this document can be forwarded to [email protected].


ERTMS/ETCS National Values

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http://www.rssb.co.uk/railway-group-standardsmailto:[email protected]

Contents

Part 1 Purpose and Introduction 7

1.1 Purpose 71.2 Context 71.3 Application of this document 81.4 Health and safety responsibilities 81.5 Structure of this document 81.6 Approval and Authorisation 8

Part 2 Requirements for ERTMS/ETCS National Values 9

2.1 Proposal of a set of ERTMS/ETCS National Values 92.2 Consultation on the proposed ERTMS/ETCS National Values 92.3 Consultation response on the proposed ERTMS/ETCS National Values 102.4 Optimising National Values 102.5 Publishing National Values 10

Appendices 11Appendix A 11

Definitions 68References 74

ERTMS/ETCS National Values Rail Industry StandardRIS-0708-CCSIssue: OneDate: September 2017

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List of Figures

Figure 1: Confidence interval of a ETCS fitted train 33

Figure 2: Chart demonstrating, by simplifying the curves as straight lines as an example, the shape ofthe resultant Permitted speed curve 35

Figure 3: High level schematic diagram of the processing of braking curves 36

Figure 4: Schematic diagram of how braking curves are derived 38

Figure 5: Comparison of where the 'hook' is shown if GUI curve is enabled. 41

Figure 6: Comparison of the position of the 'hook' if Q_NVSBFBPERM is enabled 42

Figure 7: Comparison of the position of the 'hook' if Q_NVINHSMICPERM is enabled 44

Figure 8: Demonstration of how A_NVMAXREDADH derates EBD and increases braking distance 46

Figure 9: DMI with TI initiated 47

Figure 10: DMI with TTI initiated 48

Figure 11: An example of a four steps Kv_int 58

Figure 12: Four steps Kv_int models 58

Figure 13: Process of extracting Kv_int 61

Figure 14: An example of a set of M_KRINT correction factors with five steps 65



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List of Tables

Table 1: Q_NVDRIVER_ADHES 11

Table 2: V_NVSHUNT 13

Table 3: V_NVSTFF 13

Table 4: V_NVONSIGHT 14

Table 5: V_NVSUPOVTRP 14

Table 6: V_NVUNFIT 17

Table 7: V_NVLIMSUPERV 18

Table 8: V_NVREL 19

Table 9: D_NVROLL 20

Table 10: V_NVALLOWOVTRP 22

Table 11: D_NVOVTRP 23

Table 12: T_NVOVTRP 24

Table 13: M_NVDERUN 26

Table 14: M_NVCONTACT 27

Table 15: T_NVCONTACT 27

Table 16: D_NVPOTRP 29

Table 17: D_NVSTFF 31

Table 18: Q_NVLOCACC 32

Table 19: Q_NVGUIPERM 40

Table 20: Q_NVSBFBPERM 41

Table 21: Q_NVINHSMICPERM 43

Table 22: A_NVMAXREDADH1/2/3 45

Table 23: Q_NVSRBKTRG 49

Table 24: Q_NVSBTSMPERM 50

Table 25: Q_NVEMRRLS 50

Table 26: M_NVEBCL 52

Table 27: M_NVAVADH 54


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Table 28: V_NVKVINT 56

Table 29: Q_NVKVINTSET 56

Table 30: M_NVKVINT 57

Table 31: A_NVP12 59

Table 32: A_NVP23 60

Table 33: Comparison of how A_NVP12, A_NVP23, Kv_int_x_a and Kv_int_x_b affects the outcome(all values are in relative terms) 62

Table 34: L_NVKRINT 63

Table 35: M_NVKRINT 64

Table 36: M_NVKTINT 66



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Part 1 Purpose and Introduction

1.1 Purpose

1.1.1 This document is a standard on ERTMS/ETCS National Values, for members of RSSB to use if they sochoose.

1.1.2 This document contains requirements for a process to determine or revise European Rail TrafficManagement System (ERTMS) / European Train Control System (ETCS) National Values within a set.

1.1.3 Guidance is provided as a series of sequentially numbered clauses prefixed ‘G’ immediately beloweach requirement. Where there is no guidance, this is stated.

1.1.4 The process set out in this document is applicable to ETCS fitted infrastructure irrespective of whetheror not ERTMS-fitted trains operate on that infrastructure.

1.1.5 ERTMS/ETCS National Values, determined in accordance with the process set out in this document,describes asset characteristics that are relevant to compatibility between ERTMS-fitted trains and tracksideinfrastructure.

1.1.6 This standard is applicable to all three ETCS Baselines legal at the time of publication: Baseline 2,Baseline 3 Maintenance Release 1, and Baseline 3 Release 2, as specified in the Control Command andSignalling Technical Specification for Interoperability (CCS TSI).

1.1.7 Details on all the ERTMS/ETCS National Values are set out in the Appendix.

1.2 Context

1.2.1 ERTMS/ETCS National Values are parameters in the ETCS system, described in ERTMS subset-026,Systems Requirements Specification (SRS).

1.2.2 A set of ERTMS/ETCS National Values applies to a ‘National Area’. A National Area is a geographicregion and does not necessarily align to political borders. ‘National’ in this context means determined atthe national level, not necessarily applying throughout a whole nation.

1.2.3 The values are set as part of the infrastructure design to configure the behaviour of an ERTMS/ETCSapplication to be compatible with the operational and technical practices of a particular geographic region,for example, the maximum speeds permitted under different modes of operation.

1.2.4 National Values are configured by the infrastructure manager (IM) and coded within the tracksideinfrastructure, that is, Eurobalises and Radio Block Centres (RBCs). The values are sent to trains operating inthe geographic region to which they apply and they cause the ETCS onboard to function in a way consistentwith the infrastructure.

1.2.5 The SRS describes the National Values and details the range of values, it also specifies a default valuefor the ETCS onboard to use when the National Values for the geographic region that it is operating in arenot available. This information is replicated in the Appendix.

1.2.6 Because the ERTMS/ETCS National Values are part of the trackside design, an IM needs to determinea set of values that are suitable for a geographic region. By the nature of National Values, this will affectthe performance of ETCS fitted trains operating on that infrastructure. Therefore, it is consideredadvantageous to have an industry-agreed method of proposing, evaluating, agreeing and making availablenew sets, or revising existing sets, of National Values. This standard fulfils that purpose.


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1.2.7 This standard requires the IM who is introducing or revising the National Values to engage inconsultation with neighbouring IMs and RUs who may be affected by the new National Values. Theobjective is to achieve harmonised operational practices across geographic regions.

1.2.8 This standard does not recommend specific values as National Values, but it does provideinformation to assist in determining a set of values, or evaluating the impact of a set of values.

1.2.9 In determining or revising a set of values, an IM will need to apply its own processes to managesafety and this will need to consider trains operating with the default set of values when the correct set forthe geographic region is not available. Processes such as the Common Safety Method for Risk Evaluationand Assessment (CSM RA) will likely apply and the guidance in this standard will support these processes.

1.2.10 The CCS TSI requires that ETCS onboard equipment is compatible with any specific value of aNational Value within the permitted range; once placed into service it is possible that the train may receiveany permitted value of National Value during its lifetime.

1.3 Application of this document

1.3.1 Compliance requirements and dates have not been specified since these will be the subject of internalprocedures or contract conditions.

1.3.2 The Standards Manual and the Railway Group Standards (RGS) Code do not currently provide aformal process for deviating from a Rail Industry Standard (RIS). However, a member of RSSB, havingadopted a RIS and wishing to deviate from its requirements, may request a Standards Committee toprovide opinions and comments on their proposed alternative to the requirement in the RIS. Requests foropinions and comments should be submitted to RSSB by e-mail to [email protected]. Whenformulating a request, consideration should be given to the advice set out in the ‘Guidance to applicantsand members of Standards Committee on deviation applications’, available from RSSB’s website.

1.4 Health and safety responsibilities

1.4.1 Users of documents published by RSSB are reminded of the need to consider their own responsibilitiesto ensure health and safety at work and their own duties under health and safety legislation. RSSB does notwarrant that compliance with all or any documents published by RSSB as sufficient in itself to ensure safesystems of work or operation or to satisfy such responsibilities or duties.

1.5 Structure of this document

1.5.1 This document sets out a series of requirements that are sequentially numbered.

1.5.2 This document also sets out the rationale for the requirement. The rationale explains why therequirement is needed and its purpose. Rationale clauses are prefixed by the letter 'G'.

1.5.3 Where relevant, guidance supporting the requirement is also set out in this document by a series ofsequentially numbered clauses and is identified by the letter 'G'.

1.6 Approval and Authorisation

1.6.1 The content of this document was approved by the Control Command and Signalling StandardsCommittee on 13 April 2017.

1.6.2 This document was authorised by RSSB on 26 July 2017.



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Part 2 Requirements for ERTMS/ETCS National Values

2.1 Proposal of a set of ERTMS/ETCS National Values

2.1.1 For a National Area under its responsibility, the IM shall propose a set of values of ERTMS/ETCSNational Values, including the rationale for the determination of each value.

Rationale

G 2.1.2 As ERTMS/ETCS National Values are part of CCS trackside, the IM is responsible for deriving a set ofERTMS/ETCS National Values to enable trains to operate acceptably.

Guidance

G 2.1.3 Appendix A of this document gives guidance on determining the ERTMS/ETCS National Values.

G 2.1.4 This requirement allows the IM to propose more than one set of ERTMS/ETCS National Valueswithin a National Area as there are operational situations where the provision of a different set of ERTMS/ETCS National Values can provide safety or performance benefits. Examples of these operational situationsinclude, but are not limited to:

a) Changing the setting of M_NVCONTACT during data radio failures, orb) Adjusting a mode related ceiling speed on the approach to the border with another NID_C area, orc) Increasing the reverse movement limit for trains such as rail grinders or snow ploughs.

G 2.1.5 Where more than one set of ERTMS/ETCS National Values can be applied within a National Area,the risks of trains having differing operational constraints have to be managed.

G 2.1.6 The values for the ERTMS/ETCS parameter NID_C, which define National Areas, are limited. Whendetermining a set of ERTMS/ETCS National Values, if the set has the same values as other National Areaswhich are under the responsibility of the same IM, consideration should be given to extending the NationalArea, instead of creating a new National Area. National Areas do not necessarily have to share a commonboundary.

G 2.1.7 Complexity in operational rules and the potential of ETCS intervention are reduced if the set ofERTMS/ETCS National Values is the same in bordering National Areas.

2.2 Consultation on the proposed ERTMS/ETCS National Values

2.2.1 The IM proposing any set of ERTMS/ETCS National Values shall consult with all affected IMs andrailway undertakings (RUs) about the proposed values.

Rationale

G 2.2.2 Affected RUs and IMs are consulted to check that the impact on safety and performance isacceptable.

Guidance

G 2.2.3 Affected IMs are those that have National Areas that border the National Area for which a set ofvalues is being proposed.


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G 2.2.4 Affected IMs can also include those that have similar sets of ERTMS/ETCS National Values. In orderto avoid increasing the number of National Areas, an existing National Area which has a similar set ofvalues can be extended (see G 2.1.1.4).

G 2.2.5 Affected RUs include those that have track access agreements for the National Area.

G 2.2.6 Some ERTMS/ETCS National Values continue to have an effect on ERTMS/ETCS fitted trains inareas that are not fitted with ERTMS/ETCS trackside equipment. Normally, when operating on lines notfitted with ERTMS/ETCS trackside equipment, ERTMS/ETCS fitted trains use the last set of ERTMS/ETCSNational Values received. Affected IMs and RUs should take this into account when assessing the impact ofa proposed set of ERTMS/ETCS National Values.

G 2.2.7 Appendix A of this document gives guidance to affected IMs and RUs on assessing the impact ofthe proposed set of ERTMS/ETCS National Values.

2.3 Consultation response on the proposed ERTMS/ETCS National Values

2.3.1 Affected IMs and RUs shall respond, explaining their opinions in relation to the proposed ERTMS/ETCS National Values, in a timely manner.

Rationale

G 2.3.2 Timely receipt of comments from affected IMs and RUs will enable optimisation of the proposedset of ERTMS/ETCS National Values to be achieved.

2.4 Optimising National Values

2.4.1 The IM proposing a set of values of ERTMS/ETCS National Values shall determine an optimal set ofvalues for a National Area, taking into consideration the responses from the affected IMs and RUs.

Guidance

G 2.4.2 Appendix A of this document gives guidance on the factors to be considered when determining theoptimal ERTMS/ETCS National Values.

2.5 Publishing National Values

2.5.1 The IM proposing a set of ERTMS/ETCS National Values shall publish the new or revised ERTMS/ETCSNational Values for the affected National Area.

Rationale

G 2.5.2 When national values are created or revised it is important that those affected are advised in atimely manner by the IM proposing the change, in order that they can prepare for the impact of thechange, if required.



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Appendices

Appendix A

A.1 Introduction

A.1.1 This document does not set out ERTMS/ETCS National Values.

A.1.2 Research project T093 was conducted between 2003 and 2004, on behalf of the National ERTMSProgramme. T093 specifically covered ERTMS/ETCS National Values for Baseline 2, some of which is alsoapplicable to Baseline 3. Each description of ERTMS/ETCS National Values will indicate the applicableERTMS/ETCS subset.

A.1.3 During the development of this document, reports from the ERTMS national programme BrakingAspect Working Group were used as an input to derive guidance on the brake related ERTMS/ETCS NationalValues, as defined in Baseline 3.

A.1.4 This appendix provides general guidance. For application in a specific National Area, considerationshould be given to the characteristics of the particular area when determining the suitability of anyindividual value.

A.1.5 Default values are applied only if ERTMS/ETCS National Values are not available or there is amismatch between the values onboard and the country or region identifier (NID_C) read from a balisegroup when compared to the corresponding identifier stored onboard.

A.1.6 The set of ERTMS/ETCS National Values is stored by the ERTMS/ETCS onboard equipment, evenwhen the ERTMS/ETCS onboard equipment is switched off (NP), and re-used when powered on.

A.1.7 When assessing the impact of values on driving behaviour, RUs will need to consider the informationpresented on the driver machine interface (DMI).

A.1.8 The ERTMS/ETCS National Values are set out in the following properties' tables and address Baseline2 and Baseline 3 variables, as appropriate.

A.2 Q_NVDRIVER_ADHES

A.2.1 Summary

Name Q_NVDRIVER_ADHES - Qualifier for the modification of tracksideadhesion factor by driver

Subset-026 values 0 - Not allowed ; 1 - Allowed

Subset-026 Default value Not allowed

Resolution Either 0 or 1

ETCS Baseline Baseline 2 Baseline 3

Used in modes UN, SR, OS, FS and SH UN, SN, SR, OS, FS, LS and SH

Used in levels 0, 1, 2 and 3 0, NTC, 1, 2 and 3

Table 1: Q_NVDRIVER_ADHES


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A.2.1.1 The ERTMS/ETCS onboard braking model can be modified to take into account low adhesion byextending the calculated braking distance based on the maximum rate of deceleration set by ERTMS/ETCSNational Value, A_NVMAXREDADH. This can be selected either:

a) As commanded by trackside, orb) By the driver, if permitted, using the low adhesion function via the slippery rail ON/OFF control on the

DMI.

A.2.1.2 Q_NVDRIVER_ADHES specifies whether the driver is allowed to select the use of the modifiedbraking model. Irrespective of the Q_NVDRIVER_ADHES value, the trackside can command the ERTMS/ETCS onboard equipment to modify the adhesion factor (as set out in Subset-026 and RSSB-ERTMS-OC).

A.2.2 Safety considerations

A.2.2.1 ERTMS/ETCS can be configured to increase the calculated braking distance in low adhesion areasusing the low adhesion functionality. Whether this functionality is used or not, is outside the scope of thisdocument. If this functionality is used, it is possible to allow the driver to switch it on or off using theSlippery Rail controls on the ERTMS/ETCS DMI, that is, to either increase the calculated braking distance orrevert to the normal braking distance.

A.2.2.2 The effect on the braking curves of switching the low adhesion function on is dependent on thevalues of A_NVMAXREDADH1/2/3 (see also A.19 A_NVMAXREDADH1, A_NVMAXREDADH2,A_NVMAXREDADH3 on page 45). If A_NVMAXREDAD1/2/3 are set to any of the three special values andthe low adhesion function is switched on, the Slippery Rail indication will be displayed on the ERTMS/ETCSDMI, but the braking curves are not modified. In practice, adhesion varies widely across the infrastructurewith both location and time. This variation is significant, even in areas where the adhesion is acknowledgedto be low, and the modifications imposed on the braking curves if A_NVMAXREDADH1/2/3 are not set tothe special values cannot be guaranteed to accurately reflect the actual braking conditions.

A.2.2.3 Regardless of whether the low adhesion function is switched on by the driver or commanded by theERTMS/ETCS trackside, the information presented on the DMI may lead a driver to falsely believe that byfollowing the information on the DMI the train can always be stopped before the end of its movementauthority in any low adhesion condition. That said, where a driver becomes aware of low adhesionconditions (which may well be very localised), this potentially safety-critical information should be utilisedas quickly and as widely as possible. On this basis, it could be appropriate to allow a driver to use theadhesion factor as an aid to driving the train more cautiously regardless of whether the braking curve ismodified or not.

A.2.3 Performance considerations

A.2.3.1 Applying a limiting deceleration factor, ERTMS/ETCS National Value A_NVMAXREDADH, has theeffect of extending the braking distance calculated by the ERTMS/ETCS onboard equipment, whichincreases journey times; hence increases headway times and therefore reduces the line capacity.

A.2.4 Discussion

A.2.4.1 A factor that may influence on whether to allow drivers to toggle the low adhesion function maybe the ownership of responsibility in deciding where/when to apply the low adhesion function, or not toapply it at all. Regardless of who owns the responsibility to toggle the low adhesion function, there will stillbe a requirement for drivers to modify their behaviour in response to the available adhesion if safety andoptimum performance are to be achieved. This is especially true when stopping a train where the stop is notsupervised by ERTMS/ETCS, for example at station stops.

A.2.4.2 The advantages of permitting drivers to switch on/off the low adhesion function include:

a) Allowing immediate local responses to patches of low adhesion.b) Providing a reminder to drivers of the need to take into account adhesion conditions in their behaviour

where the reminder is not provided by the trackside.

A.2.4.3 The disadvantages include:



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a) The additional driver training required in determining the conditions under which this Slippery Railfunction should be used.

b) The possible misunderstandings by drivers on the limitations of the low adhesion function, with thepotential for driving behaviour which is inappropriate for the conditions.

c) Incorrect use of this function, either leaving it switched on when not required with consequentialperformance implications, or failing to switch it on in low adhesion conditions, thus missing theopportunity to reduce risk.

d) Additional workload for the driver.

A.2.4.4 Further details on the setting of A_NVMAXREDADH are set out in A.19 A_NVMAXREDADH1,A_NVMAXREDADH2, A_NVMAXREDADH3 on page 45. There are other parameters, set out in section3.13.10.4 of Subset-026, that affect the ETCS braking model. While these have some similarities with othervariables in this document, these are not part of the ERTMS/ETCS National Values set and are outside thescope of this document.

A.3 V_NVSHUNT, V_NVSTFF, V_NVONSIGHT, V_NVSUPOVTRP

A.3.1 Summary

A.3.1.1 The four following ERTMS/ETCS National Values are all related to mode speed limits and aretherefore considered together in this section.

Name V_NVSHUNT - Shunting mode (permitted) speed limit

Subset-026 Minimum value 0 km/h

Subset-026 Maximum value 600 km/h

Subset-026 Default value 30 km/h

Resolution 5 km/h


Used in modes SH SH

Used in levels 0, 1, 2 and 3 0, NTC, 1, 2 and 3

Table 2: V_NVSHUNT

A.3.1.2 V_NVSHUNT specifies a maximum speed to which the train is supervised when the ERTMS/ETCSonboard equipment is operating in the SH mode (see also RSSB-ERTMS-OC). When providing a movementauthority with SH mode profile, the trackside also has the possibility of overriding the ERTMS/ETCS NationalValue via the V_MAMODE parameter within the mode profile packet.

Name V_NVSTFF - Staff Responsible mode (permitted) speed limit




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Name V_NVSTFF - Staff Responsible mode (permitted) speed limit


Resolution 5 km/h


Used in modes SR SR

Used in levels 1, 2 and 3 1, 2 and 3

Table 3: V_NVSTFF

A.3.1.3 V_NVSTFF specifies a mode-related speed restriction applicable to trains operating in SR mode.Other speed restrictions can also be supervised while in SR mode, as set out in Subset-026 section 4.5.

Name V_NVONSIGHT - On Sight mode (permitted) speed limit




Resolution 5 km/h


Used in modes OS OS


Table 4: V_NVONSIGHT

A.3.1.4 V_NVONSIGHT specifies a mode-related speed restriction applicable to trains operating in OSmode. Other speed restrictions are also supervised while in OS mode. When providing a movement authoritywith OS mode profile, the trackside also has the possibility of overriding the ERTMS/ETCS National Value viathe V_MAMODE parameter within the mode profile packet.

Name V_NVSUPOVTRP - Permitted speed limit to be supervised when the'override EoA' function is active





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Name V_NVSUPOVTRP - Permitted speed limit to be supervised when the'override EoA' function is active


Resolution 5 km/h


Used in modes SR, SH, SN, SE and UN SR, SH and UN

Used in levels 0, STM, 1, 2 and 3 0, 1, 2 and 3

Table 5: V_NVSUPOVTRP

A.3.1.5 V_NVSUPOVTRP specifies the ceiling speed to which the train is supervised while the overridefunction is active. Closely related to this national variable are D_NVOVTRP and T_NVOVTRP.


A.3.2.1 V_NVSHUNT - While the ERTMS/ETCS onboard equipment is operating in SH, only ceiling speedsupervision is provided, with no distance supervision. In addition, there is no guarantee regarding the stateof occupancy of the section in which the train is moving and, unlike FS or OS, SH does not necessarilyprovide any assurance of route protection from the interlocking. Inherently, shunting is an activity that islikely to involve movements up to other vehicles or within a possession. The responsibility for avoidingcollisions (with vehicles, buffer stops or people on the track) resides with the person controlling themovement and the driver, and their compliance with appropriate working practices is crucial. In SH mode,the train needs to be controlled to stop short of an obstruction or at the end of the movement authority.The value for V_NVSHUNT should be set low enough to enable observation of the line so that the train canbe stopped safely and short of any obstruction.

A.3.2.2 V_NVSTFF - When the ERTMS/ETCS onboard equipment is in SR, the ERTMS/ETCS onboardequipment has insufficient information to fully supervise the train movement. The driver is responsible fornot exceeding the distance which the train is authorised to move, which will be marked by an ETCS stopmarker. For example, it may be that the line ahead is occupied by another train or obstructed by some otherobstacle, the Radio Block Centre (RBC) is unable to determine the location of the train or whether the trainis the only train in the section (especially at start of mission). The value for V_NVSTFF should be set lowenough to enable the driver to observe the line so that the train can be stopped safely and short of anyobstruction. Otherwise there is the potential for a tripped train to exceed the overrun distance available.

A.3.2.3 Setting V_NVSTFF to be high would increase performance, but the distance which a train couldtravel in SR is limited by D_NVSTFF, see section (A.13 D_NVSTFF on page 31). Having a high V_NVSTFFand a short D_NVSTFF may not be an ideal combination as drivers may interpret a high speed to meanthey have a longer distance to cover, which may not be the case. Trains operating in SR mode will be trippedby balise message ‘Stop if in Staff Responsible’. If a train is tripped while travelling close to a high ceilingspeed, it will stop further beyond the trip location compared with a train that is limited to a lower ceilingspeed.

A.3.2.4 V_NVONSIGHT - While the ERTMS/ETCS onboard equipment is operating in OS, the train receivesa lesser degree of protection in comparison with FS. In particular, no guarantee regarding the occupationstatus of the sections through which the train is authorised to proceed is provided. Therefore, the primaryprotection against collision with obstacles resides with the driver of the train. From a safety perspective thevalue for V_NVONSIGHT should be set at a very low speed so that, by default, trains would travel at speedsfrom which they could stop within any sighting distance that would be encountered.


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A.3.2.5 V_NVSUPOVTRP - While the override function is active, the level of protection provided to a train byERTMS/ETCS is reduced, because the event that would otherwise cause a train trip will not trip the train. Inparticular, the system will not enforce compliance with signals at danger in Level 1 and, similarly, themovement of trains without a movement authority in Level 2 will not be prevented. Consequently, theERTMS/ETCS system does not provide any guarantee to the driver of a train with an active override that thetrack sections through which they are driving are unoccupied, nor that the points are set appropriately. Thedriver takes responsibility for the safety of their train (which may be in conjunction with the signaller if awritten order has been issued) and the primary protection against collision and derailment is provided bythe driver (this applies while override procedure is active, see Subset-026, section 5.8.4, and while operatingin SR or SH). In order to ensure that the train can stop if any obstacle or inappropriately set points areencountered, the speed of the train should always be low enough that it can be stopped within sightingdistance.

A.3.2.6 V_NVSHUNT, V_NVSTFF, V_NVONSIGHT and V_NVSUPOVTRP are maximum supervised speeds,they are not necessarily target or line speeds.


A.3.3.1 The actual impact on performance made by the value of V_NVONSIGHT depends upon thedifference between it and the line speed. From a performance perspective, the optimum value is the largestspeed within the constraint of safety. This is true for V_NVSTFF, V_NVSHUNT and V_NVSUPOVTRP.

A.3.3.2 If the value of V_NVSUPOVTRP is greater than or equal to that of V_NVSHUNT, V_NVSTFF andV_NVUNFIT it will have no impact on performance, as these would be used to derive the ceiling speed towhich the train is supervised instead.

A.3.3.3 If permitted by operational rules, the driver can adjust the value of the SR ceiling speed supervision,irrespective of the value of V_NVSTFF.

A.3.4 Discussion

A.3.4.1 V_NVSHUNT, V_NVSTFF, V_NVONSIGHT and V_NVSUPOVTRP are ceiling speeds and not targetspeeds, and drivers should be trained to concentrate on driving at a speed appropriate to the conditions andactivity. The value of V_NVSHUNT, V_NVSTFF, and V_NVONSIGHT can be shown on the DMI as the 'BasicSpeed Hook' in their respective mode, but only when the driver toggles it on, as the default setting is off(not displayed).

A.3.4.2 In SH or OS mode, the trackside has the capability to send a Movement Authority to the ETCSonboard, which contains the SH or OS mode profile, along with a V_MAMODE; when accepted, speedproposed by V_MAMODE will override V_NVSHUNT or V_NVONSIGHT. This also applies to V_NVLIMSUPERV see section A.5.4.2 on page 19.

A.3.4.3 Safety and operational considerations suggest that the value for all four parameters is themaximum speed from which any train could be brought to a standstill within the available sightingdistance. However, the available sighting distance differs between locations, weather and, potentially, varieswith time. Driving at an appropriate speed remains the driver's responsibility; ETCS provides a mechanismto reduce the risk associated with overspeed through the selection of appropriate values for V_NVSHUNT,V_NVSTFF, V_NVONSIGHT and V_NVSUPOVTRP.

A.3.4.4 The risk for the four speeds may be different, depending on the circumstances in which the mode isapplied. Independent risk assessments should be taken for each speed. The specific values used woulddepend upon the specific circumstance within the National Area. The DMI only displays the maximumsupervised speed in OS and SR on request from the driver.

A.3.4.5 If different values for the respective speed variables are used, the trackside application designshould consider the implications of a different value for V_NVSTFF compared to V_NVONSIGHT when atrain is running in SR and transitions to OS as a precursor to FS. If V_NVSTFF has a higher value thanV_NVONSIGHT, an intervention could result (this is also true if the driver has selected an SR speed valuegreater than V_NVONSIGHT).



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A.4 V_NVUNFIT

A.4.1 Summary

Name V_NVUNFIT - Unfitted mode (permitted) speed limit




Resolution 5 km/h


Used in modes UN UN

Used in levels 0 0

Table 6: V_NVUNFIT

A.4.1.1 V_NVUNFIT specifies a ceiling speed to which the train is supervised while the ERTMS/ETCSonboard equipment is in UN; other speed restrictions might also be supervised while in UN (see subset-026section 4.5).

A.4.1.2 Unfitted mode is used to allow train movements in areas either:

a) That are equipped neither with ERTMS/ETCS trackside equipment nor with a national train controlsystem(s), or

b) That are equipped with ERTMS/ETCS trackside equipment and/or a national train control system(s), butoperation under their supervision is currently not possible.

A.4.1.3 The Class 158s and 97s that operate in Level 2 on the Cambrian Line are ETCS Baseline 2 and havebeen configured to operate in Level 0 UN elsewhere.


A.4.2.1 When an ERTMS/ETCS fitted train is operating in UN in Baseline 3, it is driven with no tracksidetrain protection system, including Class B systems such as AWS/TPWS; whereas in Baseline 2, UN can beused in conjunction with these national train protection systems to control overspeed and/or enforcemovement authorities.

A.4.2.2 In UN mode in Baseline 3 the safe movement of a train is reliant on operational procedures. Thebest contribution to safety that ERTMS/ETCS can make is to supervise the train speed to the value that ispermitted under the procedures applicable while operating with no train protection system.

A.4.2.3 For Baseline 2 trains, V_NVUNFIT is not providing a safety function, as this is provided by Class Bsystems. V_NVUNFIT therefore has to be set to accommodate the highest permissible speed in theNational Area.

A.4.2.4 A TSR sent by a balise group will override V_NVUNFIT and reduce the speed of the train in UNmode, to cope with specific situations such as engineering works.


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A.4.3.1 From a performance perspective, the optimum value, in Baseline 3, for the parameter V_NVUNFITis a value that allows the train to move at a speed that is permitted by operational procedures while there isno train protection system.

A.4.3.2 In Baseline 2, because UN can be used in conjunction with Class B systems, V_NVUNFIT should beset at the highest permissible speed in the National Area.

A.4.4 Discussion

A.4.4.1 The UN mode has different applications depending on whether Baseline 2 or 3 is implemented atthe trackside. When setting V_NVUNFIT the IM has to consider the available train protection system(s)and the level of protection that it provides. In the absence of protection systems, V_NVUNFIT has to be setlow enough to enable drivers to control the train to a safe stop.

A.5 V_NVLIMSUPERV

A.5.1 Summary

Name V_NVLIMSUPERV - Limited Supervision mode (permitted) speed limit




Resolution 5 km/h


Used in modes N/A LS

Used in levels N/A Level 1, 2 and 3

Table 7: V_NVLIMSUPERV

A.5.1.1 V_ NVLIMSUPERV specifies a mode-related speed restriction applicable to trains operating in LSmode. Other speed restrictions are also supervised while in LS mode. When providing a movement authoritywith LS mode profile, the trackside also has the possibility of overriding the ERTMS/ETCS National Value viathe V_MAMODE parameter within the mode profile packet.


A.5.2.1 When an ERTMS/ETCS fitted train is operating in LS, some signalling information for the drivercomes from sources other than ERTMS/ETCS.

A.5.2.2 V_NVLIMSUPERV may be different to the line speed. Drivers may misinterpret V_NVLIMSUPERV asthe line speed. Safe operation depends on some form of signalling system that is independent of ERTMS/ETCS and on the associated operational practices. For example, safe operation may depend on the driverobeying lineside signals and line speed restriction indicators, possibly supported by warning and / orprotection systems.


A.5.3.1 From a performance perspective, the optimum value for the parameter V_NVLIMSUPERV is theleast restrictive one.



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A.5.4 Discussion

A.5.4.1 Whatever the maximum allowed speed values apply for Class-B trackside signalling systems, thatmaximum speed could be also the value for V_NVLIMSUPERV. Given that ERTMS/ETCS fitted trains will beexpected to operate without restriction on these other systems at today's speeds, the value ofV_NVLIMSUPERV should not be less than the maximum allowed for those systems.

A.5.4.2 In LS mode, the trackside has the capability to send Movement Authorities to the ERTMS/ETCSonboard. The speed variable V_MAMODE parameter when sent together with the relevant MA replaces theERTMS/ETCS National Value for V_NVLIMSUPERV. This also applies to V_NVSHUNT or V_NVONSIGHT (seesection A.3.4.2 on page 16).

A.6 V_NVREL

A.6.1 Summary

Name V_NVREL - Release Speed (permitted) speed limit




Resolution 5 km/h


Used in modes FS, OS and LS FS, OS and LS

Used in levels Levels 1, 2 and 3 Levels 1, 2 and 3

Table 8: V_NVREL

A.6.1.1 V_NVREL specifies the ERTMS/ETCS National Value of the release speed. V_NVREL is only usedwhen commanded from the trackside. In general, a release speed can be used where a close approach tothe End of Authority (EoA) is required.


A.6.2.1 Where V_NVREL is used as the release speed, the train is only guaranteed to stop before reachingthe supervised location in the event of a train trip when an appropriately restrictive value is used. The valueshould be such that the fitted train with the poorest deceleration is able to stop within the distance thatseparates the EoA and supervised location, at the location on the infrastructure where this distance isshortest and the down-hill gradient is steepest.

A.6.2.2 When setting V_NVREL, how a driver interprets the release speed may need to be considered. Arelease speed which satisfies A.6.2.1 on page 19, but is still relatively high, could be mistakenly interpretedby the driver as an MA extension, leading to the train passing the EoA and being tripped, resulting insecondary hazards such as passenger slips, trips and falls or traction and braking shocks.


A.6.3.1 In general, the larger the value of the release speed used, the lower the impact on performance, asa driver will be able to make an approach to the EoA/LoA at a higher speed. However, the faster theapproach to the EoA/LoA, the more likely a train trip is. Train trips will have a significant impact uponoperational performance, as recovery action will be required. The highest release speed that allows a train


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to make reasonable progress towards the EoA/LoA, while being sufficiently low to reduce the likelihood of atrain trip occurring, is probably the optimum value from the perspective of performance.

A.6.4 Discussion

A.6.4.1 V_NVREL is relevant if the ERTMS/ETCS trackside instructs the ERTMS/ETCS onboard to use theERTMS/ETCS National Value when approaching an EoA, or on expiry of a section timer. It is also possible forthe trackside to define a value to be used by the ETCS on-board as the release speed or to instruct the ETCSon-board to calculate its release speed for the on-board to use when approaching an EoA.

A.6.4.2 V_NVREL is set by the IM to control the likelihood of passing the SvL at location(s) where V_NVRELis not superseded by release speed values calculated by ETCS onboard or one that is associated with aparticular danger point. When setting the value for V_NVREL, the IM should consider reduced adhesion ordegraded mode of the rolling stock.

A.6.4.3 Setting V_NVREL to be very low might be difficult from a drivability point of view on specific traintypes.

A.7 D_NVROLL

A.7.1 Summary

Name D_NVROLL - Roll away distance limit

Subset-026 Minimum values 0 cm

Subset-026 Maximum values 327.660 km or ∞

Subset-026 Default value 2 m

Resolution 10 cm, 1 m, or 10 m depends on Q_SCALE


Used in modes FS, OS, PT, RV, SB, SH, SR, UN FS, OS, PT, RV, SB, SH, SR, UN

Used in levels 0, 1, 2 and 3 0, 1, 2 and 3

Table 9: D_NVROLL

A.7.1.1 D_NVROLL defines the maximum distance that a train can travel before the ETCS onboardinitiates a brake command as part of the Roll Away Protection, Reverse Movement Protection, or StandstillSupervision functions, see Subset-026 section 3.14.2, 3.14.3, 3.14.4.


A.7.2.1 The movement of a train in an unexpected direction (or an unexpected train movement)represents a potential hazard. A potential hazard could arise, for example, where a train has been stoppednear to a set of points, at a platform to allow passenger movement, near another train, near buffer stops orin the vicinity of trackside workers.

A.7.2.2 No value of D_NVROLL can ensure roll away protection, reverse movement protection, or standstillprotection is effective. Even a zero D_NVROLL value could allow some movement if the measurement ofmovement is subject to non-zero error.



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A.7.2.3 The smaller the D_NVROLL value used, the shorter the distance that a train will move and the lowerthe speed attained, before the brakes are commanded. Thus, while collisions could still occur, theconsequences associated with a collision would be limited.

A.7.2.4 Train brake failure might cause a train to roll away, but in these circumstances ETCS protectionmight be ineffective as it could be relying on applying protection through the defective braking system.

A.7.2.5 In a situation where a rolling train moves into a position where it could foul other train movementson the infrastructure, its speed has less relevance than its specific location. In general, even in this situation,low values of D_NVROLL of the order of small numbers of metres will present low levels of risk, as sometolerance is incorporated into the design of the signalling infrastructure.

A.7.2.6 In the case of coupling / uncoupling movements (see A.7.3.3 on page 21), the value ofD_NVROLL is not considered to have an impact on the safety of personnel involved in supporting couplingand uncoupling, as the rules controlling this activity expressly forbid staff from going between the vehiclesduring 'ease-up' movements unless they are absolutely sure that the vehicles cannot move.


A.7.3.1 The use of a small value for D_NVROLL could result in emergency brake applications being made inresponse to small movements with no potential impact on safety or in response to an odometry error. Inthat event, depending upon the implementation of the train's braking system, the driver might not be ableto release the brake and move the train for some time even after acknowledging the application. This couldintroduce a significant impact on performance.

A.7.3.2 In addition, the use of too small a value of D_NVROLL could introduce operational difficulties insituations where the stationary locomotive of a freight train attempts to commence an uphill movement. Itis possible that, in this case, the locomotive may be dragged downhill by the weight of the train as thetrain's brakes are released and before it has the opportunity to develop sufficient power and traction tomove in the desired direction. This downhill movement would result in the train's brakes being applied if thedownhill movement of the locomotive exceeded the value of D_NVROLL.

A.7.3.3 A non-zero value of D_NVROLL can be exploited to facilitate coupling and uncoupling operations inSB, thus avoiding the need for start of mission activities. This might have operational advantages in caseswhere the driving cabs being used to support the coupling or uncoupling movement are not those that thetrain will be driven from immediately before or after the coupling / uncoupling movement.

A.7.4 Discussion

A.7.4.1 The value for D_NVROLL from both the safety and performance perspectives is one that is smallenough to restrict the risk presented by inappropriate train movement to an acceptable level, while beinglarge enough to reduce instances of undesired brake application to an acceptable level.

A.7.4.2 In general, specifying a low value for D_NVROLL would ensure that, in most such cases, collisionsbetween trains caused by roll away or unexpected train movements would be avoided or would occur atvery low speeds. However, setting the value too low may potentially cause problems where a level of rollback is inevitable, for example, where a heavy freight train is undertaking a hill start on a rising gradient.

A.7.4.3 RSSB document ERTMS National Values-D_NVROLL records previous research carried out on theselection of the value for D_NVROLL.

A.7.4.4 Train management systems independent of ERTMS/ETCS may provide similar roll away, standstilland reverse movement protection. The parameters that configure these existing systems may help informthe process of the selection of the value of D_NVROLL. There may be implications on train operation if thetrain management systems independent to ERTMS/ETCS use different values.

A.7.4.5 In practice, for low values of D_NVROLL, roll away, reverse movement and, in particular, standstillprotection will be limited by the precision and sensitivity of the odometry system.


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A.8 V_NVALLOWOVTRP

A.8.1 Summary

Name V_NVALLOWOVTRP - Maximum speed limit allowing the driver toselect the 'override EoA' function




Resolution 5 km/h


Used in modes FS, OS, PT, SB, SE, SH, SN, SR, UN FS, LS, OS, PT, SB, SH, SN, SR, UN

Used in levels 0, STM, 1, 2 and 3 0, NTC, 1, 2 and 3

Table 10: V_NVALLOWOVTRP

A.8.1.1 V_NVALLOWOVTRP specifies the maximum train speed above which the driver's request forinitiation of the train trip override function will be rejected.

A.8.1.2 An override may be required where, for example:

• Either:

a) In Level 2, a train is stopped without an (MA) and no MA extension can be received (for example,after having received an emergency message, or after a train trip).

b) In Level 2, a train is stopped at the border between two adjacent RBCs (for example, the interfacebetween RBCs is unavailable).

c) In Level 2, a train is stopped after having passed the border between two adjacent RBCs (forexample, the connection to the accepting RBC cannot be established).

d) In Level 2, the RBC is unable to give a permission to run (for example, lost connection with theinterlocking).

e) In Level 1, a signal cannot show a proceed aspect (for example, signal failure, route cannot be set).• Or:

a) In Level 1, a train is stopped without an MA (for example, after the MA has been shortened due to atime out).

b) In Level 0, Level STM, or Level NTC when transitioning into a Level 1 or Level 2 area and an MA is notavailable.

A.8.1.3 Override procedure avoids a train trip, for example, when passing an EoA and when passing abalise group containing the following message(s):

a) Transmitting 'stop in SR'.b) Not contained in the list of expected balises in SR.c) Transmitting 'stop in SH'.d) Not contained in the list of expected balises in SH.e) Overpassing the SR distance (see also D_NVSTFF).



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A.8.1.4 The trainborne equipment does not permit a request for an override if the train speed is greaterthan the value of the parameter V_NVALLOWOVTRP. Activation of the override places the train in SR,unless the train is in SH, in which case its mode will not change (see also Subset-026 section 4.6.2 ModeTransitions) or unless the train is in SN or UN, in which case the train remains in SN or UN until a transitionborder is passed when it then switches to SR.


A.8.2.1 While the override is active, responsibility for the subsequent movement of the train past the pointwhere, otherwise, the train would have tripped, rests with the driver. In order to discharge this responsibility,the driver has to establish the reason why the override is required and the conditions that apply. ERTMS/ETCS specifications assume that a driver would only request such an override once, and after having beenprovided with the required information.

A.8.2.2 If the driver requests override on the move, the driver may mistakenly proceed beyond the intendedlimit of the movement, which may result in harm.


A.8.3.1 From a performance perspective, the optimum value is one that places no additional restriction onthe movement of a train. In practice, it is anticipated that the request for an override would be made from aposition close to the location where the train trip would otherwise occur (certainly within D_NVOVTRP)where the permitted speed would be low in any case, in anticipation of the requirement to stop.

A.8.4 Discussion

A.8.4.1 It is unusual for a train to need to request an override unless it is stationary, although it is possiblethat a higher speed could be tolerated, particularly for certain degraded mode operations such as workingby pilotman or for operation of trains in engineering possessions.

A.8.4.2 It may be difficult for the driver to judge where to select override while the train is travelling atspeed, and being within the distance (D_NVOVTRP) and time (T_NVOVTRP) windows during which overrideremains available. Therefore, the driver may request override too early causing the override to expire tooearly, resulting in the train being tripped.

A.8.4.3 Possible values could be determined using a similar logic as for the values of V_NVSHUNT,V_NVONSIGHT, V_NVSUPOVTRP and V_NVSTFF (see A.3 V_NVSHUNT, V_NVSTFF, V_NVONSIGHT,V_NVSUPOVTRP on page 13). This could apply in the case of working in possessions or temporary blockworking.

A.8.4.4 Generally, it is probable that a request for an override will be made when the train is at standstill,irrespective of the value of V_NVALLOWTRP (requesting an override might require a written order for whichthe train should be at standstill).

A.9 D_NVOVTRP, T_NVOVTRP

A.9.1 Summary

Name D_NVOVTRP - Maximum distance for overriding the train trip

Subset-026 Minimum value 0 cm

Subset-026 Maximum value 327.670 km


Resolution 10 cm, 1 m or 10 m depending on Q_SCALE


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Name D_NVOVTRP - Maximum distance for overriding the train trip


Used in modes SE, SH,SN, SR and UN SH, SN, SR and UN


Table 11: D_NVOVTRP

A.9.1.1 D_NVOVTRP defines the maximum distance for which the train trip function may be disabled afterthe override function has been invoked.

Name T_NVOVTRP - Maximum time for overriding the train trip

Subset-026 Minimum value 0 s

Subset-026 Maximum value 255 s

Subset-026 Default value 60 s

Resolution 1 s


Used in modes SH, SN, SR and UN SH, SN, SR and UN


Table 12: T_NVOVTRP

A.9.1.2 T_NVOVTRP is an ERTMS/ETCS National Value that specifies the maximum time that the train maytravel with the train trip function disabled after the override function has been invoked.

A.9.1.3 The override function remains active until (the full list of events which terminate override functionis set out in SRS 5.8.4.1):

a) Time T_NVOVTRP since the override function was activated has expired; orb) The train has travelled a distance D_NVOVTRP from where the override function was activated; orc) A trip event is overridden; ord) A further MA has been given to the train to pass beyond the location where it would have tripped the

train if override was not activated.

A.9.1.4 Both parameters are closely related to V_NVSUPOVTRP, which defines the maximum speed atwhich the train is permitted to travel while the train trip function is disabled after the override function hasbeen invoked. This parameter was set out in A.3 V_NVSHUNT, V_NVSTFF, V_NVONSIGHT, V_NVSUPOVTRPon page 13.


A.9.2.1 The train trip function provides a safety control to bring a train to a stand before a point ofconflict. The inhibition of the trip function overrides this safety control and therefore has potentially



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adverse safety implications if it is active when it should not be. The inhibition of the train trip functiontherefore should be kept to as short a period as possible, commensurate with the achievement of theoperational activity for which the override was requested.

A.9.2.2 Consequently, the preferred value of D_NVOVTRP is one that restricts the override as closely aspossible to that specific location where the train trip would otherwise occur. In principle, passing the pointat which the train trip would occur should terminate the override. In practice, in Level 1 or Level 2, therecould be failure modes whereby, for example, a balise that is expected to enforce a train trip, for somereason may not. For this reason, from a safety perspective, the optimum values of D_NVOVTRP andT_NVOVTRP are ones that are as small as possible, commensurate with the achievement of the operationalrequirement in support of which the override has been requested.

A.9.2.3 Consideration is needed on the safety implications of enabling trains to proceed with the train tripfunction inhibited, and the rules, restrictions and training that will be needed to fully mitigate that risk(while the override is active, the train will not respond to train trips).


A.9.3.1 Although these two ERTMS/ETCS National Values are closely associated with one another,D_NVOVTRP is considered to be the dominant factor when setting the values. After setting D_NVOVTRP,T_NVOVTRP can then be set by considering the time needed for a slow accelerating train setting off fromrest to cover a distance of D_NVOVTRP. The aim is to decrease the probability of a slow accelerating trainfrom being tripped because T_NVOVTRP expires before the train reaches the point where the override isrequired.

A.9.3.2 As set out above, the inhibition of the train trip function has safety implications and thereforeshould be kept to as short a distance and time as possible, commensurate with the achievement of theoperational activity for which the override was requested.

A.9.3.3 The value of T_NVOVTRP would have a significant impact upon performance if it is too small toallow the train to reach the point where no disruptive performance impact can occur. If it is too small, theneither an unwanted train trip will occur or it will be necessary to invoke the override function again.Potentially, either event is disruptive.

A.9.3.4 From a performance perspective, the values used for both parameters should be large enough toensure that no problems occur in practice; any further increase in the value confers no benefit. However,there are safety considerations of providing the ability for a train to proceed with the train trip functioninhibited.

A.9.4 Discussion

A.9.4.1 As set out above, when considering the train trip function and its override, location and distanceare more relevant than time and duration.

A.9.4.2 The preferred value of D_NVOVTRP is one that restricts the override as closely as possible to thatspecific location where the train trip would otherwise occur.

A.9.4.3 Significant performance impact would be experienced where T_NVOVTRP presented a driver withinsufficient time to commence the movement and pass the tripping location before the override functiontimed out.

A.9.4.4 It is therefore proposed that the extent of the override be limited by selection of the appropriatevalue of D_NVOVTRP, and that T_NVOVTRP should be given a value that ensures that it has the minimumrestrictive impact on performance.


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A.10 M_NVDERUN

A.10.1 Summary

Name M_NVDERUN - Enter of Driver ID permitted while running

Subset-026 values 0 - no; 1 - yes

Subset-026 Default value 1 - yes

Resolution N/A


Used in modes FS, NL, OS, SR, SB, UN, PT, SE andSN

FS, LS, NL, OS, SR, SB, UN, PT, SNand SH

Used in levels Levels 0, STM, 1, 2 and 3 Levels 0, STM, 1, 2 and 3

Table 13: M_NVDERUN

A.10.1.1 M_NVDERUN specifies whether a driver ID can be entered into the DMI while the train is moving.

A.10.1.2 The driver ID is a number of up to eight digits, which is entered and validated as a part of theERTMS/ETCS start of mission procedure. This procedure is invoked when the driving desk is opened.

A.10.1.3 If the parameter M_NVDERUN has the value 'yes', then it is possible to change the driver ID whenthe train is moving; if the value is 'no', then it is possible to change the driver ID only while the train isstationary.


A.10.2.1 The purpose of the driver ID is not, primarily, a safety related one. Therefore, if there is amismatch between the identity of a driver and the driver ID held by the ERTMS/ETCS onboard equipment,then the consequences are not safety critical. Entering a driver ID while the train is moving carries with it alevel of risk, because this data entry task could distract the driver from the primary function of driving thetrain.


A.10.3.1 The impact on performance of not allowing a driver to enter the driver ID while the train ismoving depends upon the action that is expected of the driver when the discrepancy arises. The impactcould be significant if the driver is required to bring the train to a standstill at the earliest safe opportunityand to enter the correct driver ID. This could result from driver relief in traffic at an intermediate stationwhere rapid changeovers are required.

A.10.4 Discussion

A.10.4.1 There are situations in which it would be undesirable for the driver to enter the driver ID while thetrain is in motion. This could be mitigated by the application of operational procedures, professional drivingpolicies or other associated governance methods. This is done in some cases, with instructions and trainingfor entering alphanumerical data into equipment such as train management systems or train radio systems.If permitted by M_NVDERUN, the driver decides when it is appropriate to enter the driver ID while on themove.



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A.11 M_NVCONTACT, T_NVCONTACT

A.11.1 Summary

Name M_NVCONTACT - Onboard reaction when T_NVCONTACT expires

Subset-026 Values 00 - Train trip; 01 - Service brake application; 10 - No reaction; 11 -Spare

Subset-026 Default value 10 - No reaction

Resolution N/A


Used in modes FS and OS FS, OS, and LS

Used in levels 2 and 3 2 and 3

Table 14: M_NVCONTACT

A.11.1.1 M_NVCONTACT defines the action that is to be taken if the ETRMS/ETCS onboard equipmentremains out of contact with the RBC equipment for a period defined by T_NVCONTACT.

Name T_NVCONTACT - Maximum time without new 'safe' message.

Subset-026 Minimum value 0 s

Subset-026 Maximum value 254 s or ∞

Subset-026 Default value ∞

Resolution 1 s (between 0 s and 254 s)


Used in modes FS and OS FS, OS, and LS

Used in levels Levels 2 and 3 Levels 2 and 3

Table 15: T_NVCONTACT

A.11.1.2 T_NVCONTACT defines the critical time for which the ERTMS/ETCS onboard equipment canremain out of contact with the RBC before the ERTMS/ETCS onboard equipment takes the action definedby M_NVCONTACT.


A.11.2.1 While the ERTMS/ETCS onboard equipment is out of communication with the RBC, it is notpossible for the ERTMS/ETCS onboard equipment to receive and respond to a safety-critical ERTMS/ ETCSmessage, for example, an emergency stop command. If the value of the parameter M_NVCONTACT is 'No


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reaction', then any train that is out of communication with the RBC equipment is able to continue until itreaches the end of its MA or until communication is re-established, no matter how long these take.

A.11.2.2 From a safety perspective this may be suboptimal, but the actual impact on safety will dependupon the frequency and extent of radio gaps, holes or interruptions, the extent of movement authoritytypically maintained ahead of trains, and the topography and features of the route. Another critical factoris the probability that a safety-related need will arise to withdraw or reduce any movement authority once ithas been provided.

A.11.2.3 In a system based on radio communication, relatively frequent confirmation that it is still safe toproceed is a possibility in most locations. However, there could be safety implications requiring location-specific assessment, where a train may be brought to a stand in an unsuitable location or may be caused todecelerate rapidly.

A.11.2.4 From a safety perspective, the smaller the value of T_NVCONTACT the better, because theexposure to the risk from not being able to implement an ETCS emergency stop will be shorter. The shortestpracticable time should not be less than the minimum period between the receipt of two consecutivetrackside messages, as this will result in the reaction defined by M_NVCONTACT.


A.11.3.1 From a performance perspective, the optimum value of the parameter M_NVCONTACT is 'Noreaction', because this allows the train to continue to the end of the currently held movement authority,even if the ERTMS/ETCS onboard equipment is out of contact with the RBC equipment. If, as set out above,the value 'No reaction' is undesirable, the use of the value 'Service brake' has less of a performance impactthan that of 'Train trip' because the receipt of a new message before the train is at a stand will release thebrakes and allow the train to continue.

A.11.3.2 From a performance perspective, the optimum value of T_NVCONTACT is the largest possiblevalue, because this will make railway operation more tolerant of communication failures. The actualperformance benefit arising from large values of T_NVCONTACT depends on, amongst other things, theextent of the movement authority that ERTMS/ETCS maintains ahead of trains. No additional performancebenefit is achieved by using values of T_NVCONTACT greater than the time at which the movementauthority is otherwise removed (for example, the time at which the train reaches the EoA/LoA or the time atwhich the MA times out, if at all).

A.11.3.3 At the other extreme, using a value of T_NVCONTACT that is less than the expected periodbetween 'safe' messages might have a significant effect on performance, because the action defined byM_NVCONTACT would be implemented before the receipt of each such message. Performance might beespecially adversely affected if M_NVCONTACT is 'Train trip' or 'Service brake'.

A.11.3.4 The values of T_NVCONTACT and M_NVCONTACT potentially affect the probability of operatingin a degraded mode when recovering from the action specified by M_NVCONTACT. Degraded modeoperation will have an impact on performance.

A.11.4 Discussion

A.11.4.1 M_NVCONTACT and T_NVCONTACT are closely linked, and the impact of the value selected foreach of them will depend, to some extent, upon the value of the other. The settings of these ERTMS/ETCSNational Values may depend on the design of the railway’s wider system and its operational concept. Ifthe system has been designed to tolerate temporary unannounced radio holes/gaps/interruptions, and issupported by the operational concept and training, then it may be argued that no braking reaction isrequired, thus the consideration of the time element is irrelevant.

A.11.4.2 Using 'No reaction' value for M_NVCONTACT in implementations is generally based upon theassumption that the frequency of coincidental radio disruption and the need to withdraw or reduce MA heldby the train will be very low. The following are factors for consideration when intending to use ‘No reaction’option for the parameter M_NVCONTACT:



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a) Depending upon the extent of the MA set ahead of the train and the extent of the radio disruption, thetrain may be allowed to proceed for a significant extent without the opportunity to affect its progress.

b) Although, in case of Emergency Stops (see Subset-026 section 3.10), the ERTMS may not rely entirely onsending Emergency Stop messages but also on the use of the Global System for Mobile Communications- Railway (GSM-R) voice communication (Emergency calls), a common mode failure in the radio systemor reception may lead to a loss of both data and voice communications.

A.11.4.3 The choice of the value ('Train trip', 'Service brake', 'No reaction') could differ for differentcategories of line, as there are marked differences between risks associated with high-speed main lines andrural routes, including the arrangements for recovering from the reaction defined by M_NVCONTACT.

A.11.4.4 In the case of an area with radio disturbance, the impact on performance depends on both theduration and the spatial extent of the disturbance. A potentially significant impact on performance ariseswhere a localised failure, such as the failure of a radio mast, results in the creation of a 'radio-hole'. If thevalue of T_NVCONTACT is insufficient to allow a train to cross the 'hole', then the train is trapped until thefailed equipment is repaired or the train is able to leave the 'hole' with the ERTMS/ETCS onboardequipment in an appropriate mode.

A.11.4.5 Regarding T_NVCONTACT, from a safety perspective, the smaller the value the better. However,the impact on performance is reduced as the value used increases. In the extreme, where the value ofT_NVCONTACT exceeds the time likely to be required to reach the extent of the MA provided (or exceedsthe extent time-out normally provided with MAs), there will be no impact on performance.

A.11.4.6 The reaction of the RBC and interlocking to a loss of contact should be considered. If both theseassume that an MA once issued remains with the train until the train reports otherwise, then systemintegrity can be maintained. If either use time-out logic, then this might need to be replicated on the train.The value of T_NVCONTACT would be chosen such that:

a) It is greater than the expected period between the ERTMS/ETCS onboard equipment receivingsuccessive 'safety' messages.

b) It is greater than the period required to recover from a radio drop-out.c) It is greater than the time required to cross 'radio holes' caused by failures of a single radio mast or a

single base transceiver station.d) It is not significantly greater than the typical time required to reach the EoA/LoA.

A.11.4.7 The above is for un-planned radio holes/gaps/interruptions. In case of an area with inadequateradio coverage, the infrastructure can be designed so that a train can be instructed, via 'Packet Number 68:Track Condition' to stop supervising T_NVCONTACT for a defined geographical extent in order to allow atrain to progress through a known radio hole.

A.11.4.8 V_NVREL is set by the IM to control the risk of passing the SvL at location(s) where V_NVREL isnot superseded by release speed values calculated by ETCS onboard or one that is associated with aparticular danger point. When setting the value for V_NVREL, the IM should consider reduced adhesion ordegraded mode of the rolling stock.

A.12 D_NVPOTRP

A.12.1 Summary

Name D_NVPOTRP - Maximum distance for reversing in Post Trip mode


Subset-026 Maximum value 327.670 km



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Name D_NVPOTRP - Maximum distance for reversing in Post Trip mode

Resolution 10 cm, 1 m or 10 m depends on Q_SCALE


Used in modes PT PT

Used in levels Levels 1, 2 and 3 Levels 1, 2 and 3

Table 16: D_NVPOTRP

A.12.1.1 D_NVPOTRP specifies the maximum distance for which a train may reverse while the ERTMS/ETCS onboard equipment is in PT. In PT, the ERTMS/ETCS onboard equipment allows train movement onlyin the reverse direction. If the distance travelled by the train exceeds that given by D_NVPOTRP, theERTMS/ETCS onboard equipment initiates a service brake application so as to limit any further reversemovement. The train trip is inhibited during the reversing movement.


A.12.2.1 A train trip is used to try to maintain the safety of railway operation when a potentiallydangerous situation has been detected. The use of the train trip is based on the assumption that, when thepotential danger has been detected, stopping the train as quickly as possible minimises the probability thatthe potential danger will become an actual danger and / or reduces the consequence of such a danger.

A.12.2.2 There may be scenarios where the ability to move the train following a train trip may actuallyreduce the risk. For example, a train suffers low adhesion and passes a signal at danger and the onboardequipment invokes a train trip. Eventually, the train would come to rest at a position that cannot becontrolled by the driver, possibly in the path of another train in a conflicting route. Such movements arealways subject to authorisation by the signaller, in accordance with the Rule Book.


A.12.3.1 The only performance benefit offered by the parameter D_NVPOTRP is the ability to make areversing movement more quickly following a train trip, because the movement can start without a changein operating mode, that is, the movement can be made while the ERTMS/ETCS onboard equipment is still inPT.

A.12.3.2 This performance benefit would be fully realised only if the value of D_NVPOTRP is sufficient forany train to complete the required reverse movement. If the distance that the train is required to reverse isgreater than D_NVPOTRP, then the movement cannot be completed without invoking a (service)application of the brakes and, ultimately, without a mode change; such a situation is likely to negate theapparent advantage.

A.12.4 Discussion

A.12.4.1 As set out in A.12.2 Safety considerations on page 30, train drivers are only permitted to reversewhen authorised to do so by the signaller, in accordance with the Rule Book.

A.12.4.2 If reverse movement in PT mode is not permitted, that is, the national value is set to 0 m, anyoperational need for the train to reverse following a train trip would require a change in driving cab andcompletion of the Start of Mission procedure, or a mode change. Depending on the implementation, themode change, for example to shunting mode, may additionally require authorisation by the signaller.

A.12.4.3 Permitting reversing in PT mode may deliver the operational flexibility to perform authorisedreverse movements without requiring a mode change, but its use can only be controlled procedurally. There



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is no technical means to prevent a driver reversing a train in PT mode if the value is non-zero, only to limitthe extent of the move through the implementation of the required value.

A.13 D_NVSTFF

A.13.1 Summary

Name D_NVSTFF - Maximum distance for running in Staff Responsible mode


Subset-026 Maximum value 327.660 km or ∞

Subset-026 Default value ∞

Resolution 10 cm, 1 m or 10 m depends on Q_SCALE


Used in modes SR SR


Table 17: D_NVSTFF

A.13.1.1 D_NVSTFF specifies the maximum distance for travelling in SR in the absence of a distancereceived from the RBC or entered by the driver.


A.13.2.1 When the ERTMS/ETCS onboard equipment is in SR, the ERTMS/ETCS onboard equipment hasinsufficient information to fully supervise the train movement. The risk associated with movement in thismode is mitigated by the application of operational procedures and the supervision of the train to a ceilingspeed (the ERTMS/ETCS National Value V_NVSTFF by default).

A.13.2.2 In practice, since the ERTMS/ETCS onboard equipment will leave SR as soon as conditions allow,there is no obvious safety risk associated with specifying a value for D_NVSTFF that exceeds that requiredto achieve the specific operational objective that is being addressed. Similarly, specifying a value that isinsufficient to allow a train to achieve the specific operational objective has no direct safety impact since,once the train had been brought to a standstill, the distance that could be travelled could (and presumablywould) be extended in any case. However, there could be safety implications due to the location where atrain is brought to a stand or the way in which a train is brought to a stand, especially if this is as a result ofrapid deceleration.

A.13.2.3 Depending on the specific circumstances, the ERTMS/ETCS onboard equipment might not be ableto leave SR (for example, if it is due to GSM-R or RBC failure). Allowing the train to continue for longdistances (for example, exceeding that required by the operational objective) without any means ofintervention is a potential safety risk, particularly in conditions of limited visibility. The SR movement couldbe constrained in the trackside application design by placing balise groups containing 'Stop if in SR'information (ERTMS/ETCS packet 137) at key locations which could allow a higher value of D_NVSTFF.


A.13.3.1 While the onboard ERTMS/ETCS equipment is operating in SR it is constrained to travel below aceiling speed that is:

a) V_NVSTFF (by default); or


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b) A value specified within the SR authorisation sent by the RBC (applies to Level 2 or Level 3 only); orc) A value entered by the driver (if permitted by operational rules).

A.13.3.2 Where this SR ceiling speed is significantly lower than the most restrictive speed limit that wouldotherwise be applied, there will be a significant performance impact associated with operating in SR,especially if it is expected that the train has to travel for a long distance. However, while D_NVSTFFspecifies the maximum distance a train can progress in SR, the value of D_NVSTFF is not necessarily thelimiting factor of the extent of the train's journey. A train will continue with its ERTMS/ETCS onboardequipment in SR until either the operational conditions ensure that it makes a transition to a morerestrictive mode, or the maximum distance that it is allowed to progress in this mode is reached. In thelatter case, it is anticipated that this maximum distance would be extended (either by the driver or by amessage from the trackside) since operational recovery could not, in general, be achieved otherwise.

A.13.3.3 Thus, the specification of a value for D_NVSTFF that corresponds to a distance that exceeds thatrequired to achieve the specific operational objective that is being addressed will introduce no adverseimpact on performance. However, if the values specified correspond to a distance that is less than thatrequired to achieve the specific operational objective, then, potentially, there could be a significant adverseimpact on performance, as an extension to the maximum distance that can be travelled in this mode wouldbe required.

A.13.4 Discussion

A.13.4.1 The value of D_NVSTFF has little or no impact on safety, because the speed (with V_NVSTFF)and the distance (with D_NVSTFF) are limited through design application rules. The distance set byD_NVSTFF should be long enough to cover the distance which the train has to travel while supervision fromthe lineside signalling system is unavailable. With a short D_NVSTFF, the driver may need to keep re-entering / revalidating SR to cover the same distance. In combination with ERTMS/ETCS National ValueV_NVALLOWOVTRP, if the latter is set to permit selection of override on the move, then there are potentialdistraction issues at the time when the driver should be particularly vigilant. If V_NVALLOWOVTRP requiresthe selection of override to be undertaken at a stand, then there would be performance issues (see A.8 V_NVALLOWOVTRP on page 22).

A.13.4.2 The distance which a train can travel in SR, while not exceeding D_NVSTFF, is also limited throughapplication rules for the use of the 'Stop if in SR' messages in balise groups placed strategically. The onlyimpact on performance will be an adverse one in situations where the value corresponds to a distance thatis less than that required to achieve the specific operational objective that is being addressed.

A.14 Q_NVLOCACC

A.14.1 Summary

Name Q_NVLOCACC - Default accuracy of the balise location

Subset-026 Minimum value 0 m

Subset-026 Maximum value 63 m


Resolution 1 m


Used in modes N/A FS, LS and OS



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Name Q_NVLOCACC - Default accuracy of the balise location

Used in levels N/A 1, 2 and 3

Table 18: Q_NVLOCACC

A.14.1.1 Q_NVLOCACC defines the accuracy of a balise location, and is used in the calculation of theconfidence interval (maximum / minimum-safe-front-end of the train), when linking information, andtherefore Q_LOCACC, is not available.

A.14.1.2 The ERTMS/ETCS onboard calculates a confidence interval, within which it assumes the train islocated. The confidence interval takes account of worst case acceptable tolerances of the odometersubsystem and the expected location accuracy of the balise group from which the distance is measured, asshown in Figure 1 Confidence interval of a ETCS fitted train on page 33.

Figure 1: Confidence interval of a ETCS fitted train

A.14.1.3 The maximum permissible over / under-reading amount is 5 m + 5% of distance travelled sincethe last reference point.

A.14.1.4 The confidence interval is the over-reading amount + the under-reading amount + 2 x Q_LOCACC.

A.14.1.5 The two parts of the confidence interval equation set out above, are to account for two types ofinaccuracy: dynamic and static. The over-reading amount and under-reading amount is to account for thedynamic inaccuracy of the odometry system on the rolling stock; and the Q_LOCACC/Q_NVLOCACC is toaccount for the balise installation inaccuracy.


A.14.2.1 Q_NVLOCACC is only used when linking information is not available. If the value of Q_NVLOCACCis less than the permissible installati

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