vision and potential for future signalling stratergies

8/6/2019 Vision and Potential for Future Signalling Stratergies

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VISION AND POTENTIAL FOR FUTURESIGNALLING STRATEGIES

A Paper to Discuss the Relationships betweenETCS Systems and the Business Needs of EC

Railways by Addressing:

Performance / Costs

Effective Application of ETCS and Migration

Open Architectures for Control and Signalling

The Translation of New Technologies into Future TrafficControl The Rle of the Euro-Interlocking Project Phase 2.

Version: 0.7 Amd MPCreated: 27 September 06

Amended 27/09/06

Saved: 27.09.06 13:59

Total Number of Pages: 52


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UIC Signalling Strategy v0.7.doc 27/09/06 Page 2 of 52

Document Data Sheet

Filing nameUIC SignallingStrategyv0.7.doc

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Amended27/09/06 Last saved byPope

LanguagesTitle of Document

VISION AND POTENTIAL FOR FUTURESIGNALLING STRATEGIES

Original

English

Translations

Pages Figures TablesSubject

52

PriceAuthor(s)Martin E Pope

Ian Harman

Document Right of Use

Open

Performing Body

UIC Signalling Panel of Experts

Sponsoring Body

UICApproved by Performing Body Approved by Sponsoring Body Availability of Document

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Application UsedMicrosoft Office

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Template Name Last Printed27 Sept. 06

Date of Publication

Abstract

A Paper to Discuss the Relationships between ETCS Systems and the BusinessNeeds of Railways.

This document was prepared for review of ERTMS practices for interfaces andtrackside equipment by the UIC Signalling Panel of Experts .


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Table of Contents

Document Data Sheet .............................................................................................................................2Table of Contents ...................................................................................................................................3

1. Abbreviations .................................................................................................................................5

2. References to Cited Texts:..............................................................................................................6

3. Introduction....................................................................................................................................7

4. Purpose...........................................................................................................................................8

5. Rationale .........................................................................................................................................8

5.1 Operational.............................................................................................................................8

5.2 Design Strategy ....................................................................................................................11

5.3 The Business Case................................................................................................................12

5.4 Asset Utilisation Under ERTMS..........................................................................................15

5.5 Benefits of ETCS Fitment ....................................................................................................16

5.6 Headway Concepts ...................................................................................................................17

6. Proposed Methodologies for Migration........................................................................................17

6.1 Past Efforts ...........................................................................................................................17

6.2 The Suppliers ........................................................................................................................186.3 The Current Situation...........................................................................................................19

7. Task Identification........................................................................................................................19

7.1 System Type Identification...................................................................................................19

7.2 Operational Scenarios...........................................................................................................20

7.3 Migration Planning...............................................................................................................217.3.1 Fallback and Degraded Modes ............................................................................................22

8. Interoperability & System Relationships......................................................................................24

8.1 The Signaller and the TCCS.................................................................................................249. Signalling Principles and Requirements.......................................................................................25

10. Important Guidelines ................................................................................................................26

11. Technical Solutions ..................................................................................................................27

11.1 The Basics ............................................................................................................................27

12. Architectural Strategy...............................................................................................................33

13. Interface Requirements.............................................................................................................34

14. Migration Strategy....................................................................................................................35

14.1 Existing Railway Signalling Architecture............................................................................36

15. Node Handling..........................................................................................................................36


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16. Interlocking Hierarchy..............................................................................................................37

17. Proposals & Recommendations................................................................................................39

17.1 Recommendation 1 ...............................................................................................................39

17.2 Recommendation 2 ...............................................................................................................39

17.3 Recommendation 3 ...............................................................................................................4017.4 Recommendation 4 ...............................................................................................................40

17.5 Recommendation 5 ...............................................................................................................40

17.6 Recommendation 6 ...............................................................................................................40

17.7 Recommendation 7 ...............................................................................................................41

17.8 Recommendation 8 ...............................................................................................................41

17.9 Recommendation 9 ...............................................................................................................41

17.10 Recommendation 10 .........................................................................................................41

17.11 Recommendation 11 .........................................................................................................41

Appendices ...........................................................................................................................................42

18. The TEN Routes ...................................................................................................................42

19. ERTMS Current Projects..........................................................................................................43

20. Portugal Interlocking Distribution............................................................................................43

21. Denmark Major Interlocking Types .........................................................................................45

22. DB Netz Interlocking Distribution (TEN)................................................................................47

Amendment Sheet ................................................................................................................................52


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1. Abbreviations

AEIF Association Europen Pour L`nteroperabilit Ferroviare

ATP Automatic Train Protection

CBA Cost Benefit Analysis

CER Community of European Railway & Infrastructure Companies

CTRL Channel Tunnel Rail Link

BDK BaneDanemark

DB Die Bahn

EC European Commission

EIM European Infrastructure Managers

ERA European Railway AgencyERIG Eirene Radio Implementation Group

ERTMS European Rail Transport Management System

ESIS European Signalling Interface Standards (UIC)

ERTMS European Train Control System

EU European Union

GENERIS Generic Requirements for Interlocking Systems (UIC)

GSM-R Global Systems Mobile Railways

GWML Great Western Main Line (UK)

HMI Human Machine Interface

IRSE Institution of Railway Signalling Engineers

MA Movement Authority

PPI Point Position Indicator

RBC Radio Block Controller

RIS Radio Interlocking System

TCCS Traffic Control & Command SystemTEN Trans European Network

TSI Technical Specification for Interoperability

UIC Union International des Chemins de Fer

UNISIG Union of International Signalling Supply Companies

UNIFE Association of European Railway Industries


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2. References to Cited Texts:

a) The UIC ESIS Project Feasibility Study version 2.0b) ERTMS Users Group Technical Specifications

c) AEIF Technical Specification for Interoperability.

d) Euro-Interlocking Business Case version 2.0 (December 2000)

e) EC ERTMS Memorandum o f Understanding (17 March 2005)

f) ERTMS FRS v4.29

g) ERTMS Regional FRS v3.0

h) ERTMS SRS v2.2.2


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3. Introduction

It is clear that the burdens in developing ETCS thus far have largely fallen onthe supply industry, but there may not have been commensurate effort on the part of

the railway administrations to make their requirements for the system clear, or indeeda perception of the need for them to do so, particularly where life-cycle costs andbenefits post deployment are considered.

It is perceived that this lack of engagement has contributed to some of theunexpected, sub-optimal outcomes and extended implementation timescales of pilotschemes and shortfalls in their performance, with the consequent risk of underminingconfidence in what ETCS and ERTMS are setti ng out to do.

It is argued in this paper that the lack of engagement over user requirementsfor the system is one of the key root cause drivers of costs, both capital and revenue,

and which costs, in turn are producing the main obstacles to the implementation ofthe TSIs on the defined routes throughout Europe.

This paper acknowledges that the TSIs produced to date are a summation ofcommon operating and technical factors employed in the railways as they existtoday. It accepts that the TSIs are highest common factor specifications thatdescribe the railways of today and the struggle to make these specificationsbusiness oriented is well documented. The only exception may be the CCS TSI thatprescribes the new system ERTMS. The cost-effective implementation of the CCSTSI into an operating railway environment, and the associated interface issues can,however, pose a number of economic and political challenges for railway

administrations and industry alike. Any misunderstanding of these by the railwayadministrations and industry is likely to lead to unexpected outcomes detracting fromthe overall system benefits of ERTMS.

Now that numerous rail links within the EC, and some without, have beennominated as corridors as a part of the strategy for the implementation ofInteroperability, it is therefore critical that the operational needs of these lines, as wellas the technical issues involved in the migration to ERTMS / ETCS, be discussed.Indeed this discussion particularly needs to focus on the needs of those linesscheduled for renewal but not designated as corridors, and how facilitating futuremigration to ETCS might be funded in the current technical and political environment

This paper explores these issues, sets out a vision for a possible structure ofETCS from the users point of view and makes recommendations for work streams toenable convergence between that vision and the needs of both industry and railwayadministrations, particularly aimed at migration, but also at whole-life cycle costsissues.

It is believed that through this approach there will be a better understandingbetween all parties concerned in the deployment of the TSIs, and, if thatunderstanding can be achieved, will contribute to a win-win situation for all parties

involved which will be for the benefit of rail transportation in Europe as a whole.This paper acknowledges and reinforces the ongoing need to ensure that the

railway supply industry is not left on the sidelines in any discussion of this nature. It is


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essential that all parties recognise that a planned approach to supply side issues isabsolutely necessary if all sides are to profit from the exercise. To date, the AEIF hasvirtually completed its mandated work, and handed over to the EC most of the TSIs ithad been working on in 2005. The remaining activities of the group relate to thesupport of these through Article 21 Committee discussions. During its winding upprocess, the AEIF produced a lessons learned document, (which was also sent tothe EC). It is useful as it highlights how the AEIF (gradually through hard wonexperience) became more proficient at TSI development. It also outlines thesuccessful key processes.

4. Purpose

Given the foregoing, this document has been written to open up the discussionon migration and operational issues and to introduce some hypotheses concerningsolutions for the implementation of ERTMS at the trackside level both in themigrating railway environment, and in that of newly constructed lines. The subjecthas been addressed in terms of the following subsets, all of which must beaddressed, and not necessarily individually:

1) Rationale

2) Business Case

3) Asset Utilisation

4) Benefits of ETCS

5) Proposed Methodologies for Migration to ETCS

5. Rationale

5.1 Operational

Considering that railways in general have reflected national political diversity overthe last 150 years or so rather than any form of international integration, it is oftendifficult to see a common way forwards in the current climate. Whilst a harmonisedapproach is required in order to address the Corridor issues, with interlocking andtrain control systems matched to the operators requirements over those lines, thereremain all the lines that seem to fall outside the scope of the TSIs. Furthermore, inthe short term, it is likely that will there be few dedicated lines (including the corridorlines) solely operated by trains fitted with ETCS. Most lines (including the corridors)seem at least to need to provide for mixed-mode operation with ETCS forinteroperable trains, and conventional national signalling systems for non-

interoperable trains. It is also unclear currently to what extent some administrationsfeel it appropriate to fit ETCS at major traffic nodes or hubs.


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Whilst dual fitment of either trains or infrastructure will lead in the short term toan undesirable increase in equipment populations, and therefore an associateddecrease in reliability, the costs and timescales involved in fitting such lines and thetrains running over them with so that ETCS can be used exclusively are likely beprotracted, if they are feasible. In order to achieve a cohesive and orderly change toETCS, a linear rollout of systems is required, and the effects of these systems intheir environment must be understood clearly from an operational standpoint. As analternative, an island approach might be considered that gradually erodes the gapsbetween islands of ETCS installation. This would mean that once an adequatepopulation of rolling stock has been suitably equipped and as signalling installationsbecome life-expired, they would be replaced with ETCS, the trains swappingbetween ETCS and conventional signalling at boundaries between ETCS andconventional signalling as necessary.

Furthermore, where ETCS is in use, there could be the ability to obtain a degreeof operational benefit by permitting trains with ETCS to exploit shorter block sectionsthan provided for in the conventional national signalling system. However, providingthe necessary coherence of information from the signalling system to ETCS-fittedand non-ETCS fitted trains is also likely to lead to more complex solutions than trainsconforming to one system or the other, and this complexity and the impact onreliability will inevitably need to feature in any railway administrations business casefor deploying ERTMS. It also suggests that ETCS needs to be made as flexible aspossible, and have the potential to work in conjunction with existing nationalsignalling systems, rather than requiring wholesale change-out of signalling systemsto secure implementation of ETCS.

Without such an approach, provision of a financial justification for deployingERTMS/ETCS exclusively is likely to remain a distinct challenge for railwayadministrations. Consider for example, the Great Western Mainline (GWML) corridorin the UK which uses a signalling control strategy from six signalling control centresalong the first 140km of its 500km length each with distributed interlockings attrackside controlled remotely from the control centres. This operational strategy forGWML is very different from the German railways perspective, where the Emmerich Basel corridor (although three times longer) is operated using an assortment ofmajor control centres and local signal boxes (STW). The operational context, and theproblems associated with migration are therefore completely different between eachrailway and each corridor.


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STW B STW C

Line BlockLine Block

STW A

InterlockingB

InterlockingC

Track CircuitBlock

Track CircuitBlock

InterlockingA

GWR ML Signalling Centree.g. Slough

Schedule ManagementCentre e.g. Mannheim

Figure 1: Control Area Configuration Differences

From a traffic standpoint, the two lines are quite similar in their use. The GWMLis designated as a High Speed TEN, but in reality, the traffic using it both now, andunder ETCS in the future will include both High Speed (up to 200kmh), conventionaland non-interoperable domestic services at differing speeds (up to 160kmh), andincluding freight running at up to 90Km/h, some of which freight may be international.Other than the international freight trains, the line is only used by domestic trainsoperating entirely within the borders of the UK, and therefore those trains could notbe considered to be truly interoperable. With such a variety of uses, there can be nosimple way to segregate ETCS trains from non-ETCS trains without building newlines and infrastructure, the feasibility of which is impossible to envisage in even thelong term. The challenge in migrating to ETCS/ERTMS on such a route, given the

long term need for mixed (i.e. ETCS and non-ETCS fitted) traffic, becomesimmediately apparent.

Other conventional and high speed TEN routes in the UK also suffer the sameconstraints, with even the UKs truly High Speed Line the 300Km/h CTRL about tobe used for domestic traffic (up to 230Km/h) as well as interoperable internationaltraffic, and also having potential for international and other freight trains, not unlikethe Mannheim Basel section of the Rotterdam Milan corridor which operatesmixed traffic over 200Kph lines (where signalling has been installed that permits thisspeed)

As can be seen from the foregoing, the derivation of harmonised operating rulesover these types of corridor will be further difficult problem to overcome, and must bea contributing factor to the requirements for a harmonised European operatingstrategy for the ERTMS railway. The rule set must be flexible enough to provide


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guidance to operators as to how ERTMS is intended to operate, e.g. a set of corerules, whilst allowing operators to build around these ERTMS core rules necessaryapplication rules to cover the interface with the national signalling system, includingwhether the national system operates concurrently with ERTMS, or abuts ERTMS.

To achieve the foregoing, it is clear that development of a harmonised set of

signalling and train control requirements is highly desirable for ERTMS at all levels.This activity must be completed concurrently with, and complemented by, the set ofERTMS rules referred to above in order to cement the development process to a firmfoundation. If this is not done soon, the European Rail industry stands a good chanceof running into the same situation as occurred with legacy interlocking systems, e.g.supplier based principles and solutions suited only to their products, and leading tosome of the extremely challenging cross-acceptance issues existing today.

5.2 Design Strategy

The case for the standardisation of internal principles is considered to lie inminimising differences in architecture, therefore lowering required stock holdings,improving flexibilities between systems etc. and other associated cost reductions thatwill obviously flow from such a standardised systems approach. The cost of aparticular system or sub-system can be substantially reduced when the purchasevolume is large, as in the retrofit of a railway, or a modernisation program. If allcountries were to order identical systems from many suppliers, rather like mobiletelephone handsets, major benefits would be experienced.

Furthermore, the mantra must be that it shall not be necessary or wise to createa culture whereby every engineer, project manager or supplier must re-invent the

wheel.The creative differences between the suppliers are becoming more obvious as

research continues in other UIC projects. Most importantly, the UIC GENERIS projectfound that the differences between railways interlocking functional requirements areappearing more and more to be the result of the historic acceptance of supplier-based solutions, rather than the railway administrations own development of uniquesignalling principles, or indeed in any effort to harmonise them with others. This withthe possible exception of weather based solutions.

Standardising the structure of the train control systems as a whole should greatly

improve the ability of networks to operate across borders national and international,and to develop the common operational core rule sets between member states asmentioned above. However, where differences arise in the operation and recoveryscenarios between the train control systems of adjoining administrations, thestructure of the system should provide for a degree of modularity, so that theaccommodating these differences does not require a system alteration, or the needto develop bespoke solutions outside the core system.

It should be noted, in addition that ERTMS does not, address the issue of cross-border traction supplies and the like which are beyond the scope of this paper andthe overall ETCS system. The potential need for more complex traction units to

accommodate variations in supply voltages will also remain unless this issue isaddressed.


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5.3 The Business Case

Funding for the train control system refurbishment associated with the changeto ERTMS operation is controlled by the EC and with the rationale that thereplacement of legacy systems like for like is no longer an option. In order to satisfythis situation and to also assist the Infrastructure managers in the renewalprogrammes of the future, it is becoming clear that the business needs as well as thetechnical needs of the railways of Europe must be supported by the TSIs. Furtherdevelopment of the TSIs into sub-sections that are closely aligned with individualrailway route operations should now be considered. The re-introduction of the issueof timescales for implementation that are driven by real benefits i.e. interoperabilityand cost efficient interoperable constituents is desirable also at this time.

Table 1 shows some relationships between typical line and operation typesfound in the UK, and the application of the High Speed TSI to them. It can be clearlyseen that many (and this is likely not just a UK situation) types of line and operationwould not fall within the scope of that TSI, and any attempt to implement itsprovisions to them inappropriately is likely to lead to vastly inflated costs whichwould make any renewal difficult to justify financially. It is therefore the challenge toboth railway administrations and suppliers to provide systems, based on ETCSconstituents (to achieve the economies of scale) that can readily be fitted to lines ofdifferent classes at cost effective rates. Provision should also be made to enableintroduction of alternative technologies in lieu of some of the ETCS sub-systemsprovided they interface with ETCS in the same way as the sub-system they replace.An example might be the use of satellite train location in lieu of balises on lightly-used lines. Such an approach will only work if the interfaces between the ETCSinfrastructure sub-systems are clearly delineated, and based on agreed open

specifications.The way forward to achieving these objectives requires a concerted effort by all

parties to produce flexible, modular, cross acceptable solutions based on ETCS atreasonable cost, with the ability to mix and match solutions from different suppliersdue to there being open, defined interfaces between infrastructure sub-systems..The sheer magnitude of such a task, requires a spirit of co-operation betweenrailways and suppliers alike that has rarely been seen before. The design anddelivery of harmonised infrastructure equipment by all parties to satisfy the needs ofthese ambitious programmes is central to the effort,. If successful, it will lead toreduced stockholdings and maximise standardisation between typical lines and,

where required, across national boundaries. Without it, the costs of the presentapproach to ERTMS deployment will remain a constant challenge to ERTMSimplementation, and over much longer timescales, and provoke much politicaldebate.

It is also believed that the migration process from todays trackside and train-borne legacy systems to ETCS would also be facilitated by the use of thisstandardised, modular approach based on open interfaces. The need for Europeanrailways and their suppliers to steer towards a standardisation and harmonisationprocess for infrastructure based equipment in an attempt to meet the business drivenrationale for equipping each designated line is clearly apparent.

Of course, the development of future systems must be performed in a bi-directional manner between the railways and their suppliers. Railway administrationsrealise that the supplier system is a profit centred organisation, and the rollout of


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ETCS should be nothing short of a profit driven realisation. The sources of fundsavailable for Railway Administrations to deploy ETCS are also coming underincreasing pressure, with extreme pressure to deliver the maximum value for eachinvestment. The need for systems to be cost effective and the result a Win Winfor all involved parties is paramount.

The current costly situation arises perhaps from the ERTMS focus oninteroperability and the lack of flexibility in the TSIs to address the differing needs ofparticular types of line. The processes of the past whereby many projects and subprojects have been begun, completed, and then scrapped or revised over the last fewyears should be reviewed as a part of the generation of a business case for each linetype to be converted. These discussions require a more international approach toERTMS than has perhaps been seen in the past, especially for those routesdesignated as International Train Access Routes (ITARs), and the development ofideas that form the backbone of the new interoperable European Network requires anapproach based upon needs and with a balanced view towards the costs.

Given that many national lines are not related in any way to cross border traffic,there is no obvious need to deal with them at this moment with regard toInteroperability. Whilst there may be a cost benefit in changing out the systemsemployed on such lines, this should only be considered within the long term and thenonly when traffic levels requires such updates. These fit into the so called RegionalRailways that at best can only be considered as feeder lines to the main orinternational lines, and may also require special derivations of the ETCS subsystemto suit their, less demanding, operational needs.

More importantly, these lines and their interfaces that do relate toInteroperability must be identified, and decisions made upon a harmonised wayforwards. This is true both at the system infrastructure level, and at the signalling andtrain control system level and with new train control equipment or modification oflegacy systems for the short term.

Seldom has the railway industry at large been presented with an opportunity tomodernise and rationalise on the scale envisaged under ERTMS and the TSIs. Theneed to develop plans and methods relating to the application of ETCS on corridorlines with very different characteristics e.g. International lines, mixed traffic main linesand regional lines is discussed below. Each of these has its challenges, and eachmay demand reviews of the safety strategies employed in relation to the cost ofapplication.


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Interoperable NO NO NO YES on NO Yes on YESLine ITAR ITAR

Speed KPH Max 70 Max 100 Max 100 Max 160 Max 160 130-250 250+

Capacity n/a Less Than 6tph 10 tph 10 tph 20 tph 15 tph

Tra in Pro tect ion L ine o f S ight NS / ETCS NS/ETCS ETCS On NS/ETCS ETCS OnITAR ITAR

Radio Nat. / GSM-R Nat. / GSM-R Nat. / GSM-R on NAT. / GSM-R on ITARGSM-R ITAR only GSM-R Nat./ETCS the

rest

Level Crossings Stop & Proceed Stop & Proceed Stand Integrated Integrated No but integrated& Barrier L.C Alone for capacity For Capacity if existing

Rol ling Stock 10 Tonnes 15 Tonnes 30 Tonnes 22 Tonnes 22 Tonnes 20 TonnesAxle Load

Brakes Track Brake Conv. Conv. Conv. Conv. Conv.

C ra sh W or th in ess T ra m & C oa ch H ea vy T ra m Co nv . C on v. Co nv . C on v.

T ra ck Ga ug e N at . Spe c. N at . Spec . N S / T SI N at. Spe c. Per T SI

Fencing Required NO No except No except Per TSI Yes YesUrban Areas Urban Areas

Track Character is ti cs Nat . Spec. Nat . Spec. Nat . Spec. Per TSI Nat . Spec Per TSI

HighSpeed TSI

Light RailRegional

LinesFreight

ConventionalMixed Traffic

ConventionalHigh Speed

High Speed

Table 1: Line Use and Relationships to the HS TSI


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5.4 Asset Utilisation Under ERTMS

The key considerations in an owners strategy for his assets are to obtain themaximum benefit from them over their operational lifetime. This may be achieved by

ensuring that they are maintained in such a way as to uphold their performance over theirdesign lifetime, and in having a reasonable view of when they should be replaced. Suchreplacement should ideally be before the renewal need is justified by deterioration in assetreliability. These statements are considered valid for both fixed infrastructure and trains.However, justification for the renewal of an asset before the end of its theoretical life canpose a number of political obstacles for infrastructure owners, and is one of the keychallenges presently at the heart of the deployment of ERTMS/ETCS in Europe.

The wholesale renewal of assets with useful lives left with the principal objective ofsecuring deployment of ERTMS/ETCS alone potentially presents a major politicalchallenge for some asset owners, due to the many conflicting pressures on the availability

of investment funds, and the means of demonstration in their political environment of thebenefit for expenditure committed. This demonstration is likely to be extremely sensitive tothe business practices of the railway administration concerned. The Administrations keycost-benefit indicator will often include e.g. a journey time between fixed points or may bebased upon the requirement for reliability that trains arrive at a given node in their journey,or a combination of both.

It could be argued then that it may be difficult to justify ERTMS/ETCS where reliabilityof arrival is a key performance indicator, as ERTMS/ETCS alone may not have asignificant impact on this parameter. If journey time is a key performance parameter for therailway administration, then the justification should be a little easier, although ameasurable improvement is only likely where the journey in question crosses a borderbetween administrations, rather than for journeys that remain within a singleadministration. It is clear that ERTMS/ETCS can contribute to increased capacity of lines,however this may not be a justification for asset renewal alone if there is no demand forany increase in capacity provided by the deployment.

Justification for a business case for ERTMS/ETCS application is then furthercompounded by the need for many lines, other than, perhaps, dedicated High Speed lines,needing to provide for a mix of interoperable trains and national trains, where thenational trains cannot justify the fitment of ERTMS/ETCS, as noted above. This raises

the spectre of many lines needing some form of ERTMS/ETCS deployment which allowsunfitted national trains to continue to operate among fitted interoperable trains. Thechallenge therefore is to provide a scalable deployment of ERTMS/ETCS in manyapplications, and which:

Provides the flexibility both to allow incremental deployment of ETCS on both infrastructureand trains and

Recognises that completion of the roll-out of ERTMS/ETCS will represent many years workfor those administrations with substantial networks, and

Is likely will require ERTMS/ETCS to co-exist and interface with each asset owners

heritage systems both during migration and in, many cases, during their operating life


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Allow each administration to develop a benefits case that is commensurate with their politicalsituation and decision environment

Provides for both evolution (co-existence with existing heritage systems) and revolution(complete and wholesale replacement of heritage systems)

Does not produce such a complex system that reliability declines, negating any benefits tobe achieved

5.5 Benefits of ETCS Fitment

From the days of colour light signalling and its variations between speed and routesignalling, it has been calculated that the headway inherent on such systems isrestricted to the distance between the unlimited speed point (green) and the actualstopping point after encountering the next signal at caution or preliminary caution.

It can be shown that with the fitment of ETCS or other continuous ATP systems thisheadway distance can be lowered to the distance between the first warning point andthe stopping point, which latter is determined from the agreed parameters forcertainty of braking performance. This, in some systems could amount to 2Km ofusable distance between trains if the signalling is correctly laid out, and thereforeshould reduce headway and increase capacity, and also improve the capability torecover from perturbation.

In the UK, ERTMS is perceived as a possible way of increasing the capability of thenetwork at key nodes where the present fixed block signalling system is considered

to be the constraint, usually as it is usually being optimised to the worst performingtrain. Unfortunately, the lack of agreed metrics for determining capacity andthroughput (see UIC 405R and UIC406) are making this a difficult case to make.


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5.6 Headway Concepts

Conventional Lineside Signalling

ETCS

Minimum Headway Distance

TrainLength Safety

Margin

Overlap

Minimum Distance for anUnrestricted Proceed Aspect

For Train B

DriverReactionDistance

Train A Train BBrakingDistance

1s t Cautionary Aspect onapproach to stop signal

Minimum Headway Distance

TrainLength

SafetyMargin

DriverReactionDistance

Train A Train BBrakingDistance

Target Stop Point (LOMA)

Figure 2: Headway Improvement from ETCS Based Signalling

6. Proposed Methodologies for Migration

This section is presented as a comment on the current situation within therailway community and to provoke discussion between all parties in the search fortechnical solutions to the migration issues as they apply to the different line andoperational issues. It has evolved from an understanding of the studies and papersproduced over the years to identify the major needs of the railways from anInterfacing and requirements standpoint. These were originally defined in relation tothe ERTMS elements of RBC, Interlocking and Object Controllers and theirassociated interfaces. The TCCS interfaces had been considered, but largelyignored from a technical standpoint, leaving a great need for future discussion. Itmust be recognised that both normal and fallback operations cannot be achievedwithout addressing them.

6.1 Past Efforts

The UIC ESIS Project attempted to bring the subject of standardisedcommunication interfaces at the trackside to the front and centre, realising that theseprovide a foundation to a more harmonised and open communications world. Theupcoming UIC ERTMS Platform Project (Euro-Interlocking Phase 2) promises tocontinue the work seen during Phase 1 (ESIS), and should include the conversion of,

and addition to, the functional requirements for interlocking systems with regard tothe ERTMS environment. It should also work towards a more standardisedarchitecture in line with harmonised operating rules and consistent failure modes. All


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of the foregoing will be required as the drive towards ERTMS, and the fulfilment ofthe TSI focus on Interoperability proceeds.

The operational scenarios to be supported by a system such as ERTMS alsorequire analysis to ensure consistent fault recognition, management, reaction andrectification across the railway networks of Europe. A review of the current and future

needs in this field will be required as an important element of the apportionment offunctional requirements and system architecture at the trackside. The ERTMSsubsystems GSM-R, Euro-Balise, Euro-Loop, Euro-Cab, Euro-radio and others havealready become standards in their own right and these will form the backbone of anyfuture system.

The ERTMS Memorandum of Understanding of March 2005 resulting from theimposition of the TSI presents an example whereby the issues of one group (Train-borne Systems) seemed paramount, and which left the trackside systems areacompletely unexplored. The issue of trackside system involvement in interoperabilityhas not been explored from either a migration, or new line standpoint by any TaskForce or interest group, and is therefore understood only by disparate groups, andespecially by the supply side.

The MOU, in line with the TSI referred also to national migration andimplementation plans for ERTMS Net: It was as well, only valid for 18 months, hardlyrepresenting sufficient time to present the proposals for trackside requirements in aninternational and meaningful way. It can be assumed that as this document isupdated that the MOU has expired or is about to expire.

6.2 The Suppliers

Related to ERTMS procurement, the railway companies have taken a path thatjoins suppliers into consortia to find a way forwards. Of course this approach seemsfine in that the Research & Development budget is reasonably evenly divided (part ofthe Win Win strategy): What is not so clear is the effect that this type ofprocurement strategy will have upon the future and the possibilities for a harmonisedapproach. It is good to see that elements of projects between supplier consortia arebeing tested between their sub-systems, and to some degree this process issuccessful. This is however only being carried out between members of aconsortium: It seems that there are few interoperable projects between consortia, orwithin which inter-consortia products are being subjected to the same test regimes

across national boundaries.

The focus then has been; firstly to adhere to the Interoperability directives96/48, and secondly to achieve maximum amount of funding from the EC. Mostimportantly the essential discussions on the need for a migration policy at all and theimportance of European ERTMS legislation forcing its implementation on certainTEN corridors has been largely ignored. Currently, there appears to be noconcerted effort within the EC to address both sides of the system level issuesarising from the Interoperability Directive; That is to say both train-borne and entiretrackside system. The results of discussion arising from this paper must go a longway towards addressing this problem.


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When one considers all the issues it must be considered that a concertedEuropean approach using pragmatic system engineering techniques is the only wayforwards to a manageable technical future

6.3 The Current Situation

Numerous rail links within the EU, and some without, have been planned as apart of the interoperability strategy. Some maps are included to demonstrate thelinking proposed by the EC and administered under the supervision of associationssuch as UNISIG/UNIFE/UIC/ERTMS Users Group/ERIG and latterly theAEIF/EIM/ERA/CER. This business structure is changing with the closing of theAEIF, and the introduction / strengthening of the EIM. The UIC / CER groups alsohave a role to play, but until now have been much involved with the train-bornesystems aspect of the ERTMS problem.

Table 1 above gave an example of how the TSI for High Speed has not really

considered the issues of real railway operation, especially over lines not dedicatedto neither international nor mixed traffic running at differing speeds. As can be seenthere may be as many as six differing line types operating different train types,weights lengths and performance criteria. The HS TSI is really only representative ofone of these. The table is as well, not wholly representative of all the railways ofEurope, with each one having similar but not exactly the same problems in thedecisions for ETCS fitment.

The structuring of technical and business groups and the combination of the twotogether must bring boundary definition for ERTMS trackside systems and othertasks at hand into sharp focus. Their mandate must be to reduce the duplication and

waste of effort that has been evidenced in the past whilst permitting a linear rolloutwith consideration for operations in the real world.

It is clear that the ideals and the arguments for harmonisation lie in the loweringof costs, efficiency of implementation, and reduction of project life-cycle times. Notone of these issues has yet been fulfilled by ERTMS projects.

7. Task Identification

7.1 System Type Identification.

As may be seen from Table 1 above, there must be differing solutions fordifferent categories of line. There are also considerations to be made as to the levelof safety integrity that is required for the type of line, traffic volumes etc. At a lowerlevel in the system choice, we must take into account the level of safety required fordata-communications between the elements of the control and communicationssystem.

Also, the types of system layout and functionality differ widely for lines of thesame type. Taken in context this makes the task of selecting trackside systemsarchitecture for ETCS a significant challenge. The differences already seen betweenthe ETCS Mainline project architectures and the regional lines development in


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Sweden are indicators of the way in which design solutions can drift away form thecommon ideal if not controlled by the customer railways.

7.2 Operational Scenarios

Historically it is either changes in operational requirements or the fallout fromcritical accidents that have driven developments in traditional signalling applicationsand principles, and usually within the boundaries of individual administrations. Theunavoidable design changes to equipment and its architecture to achieve thesechanges have evolved over the years along with the race to update to newtechnologies. Standardisation has, unfortunately, rarely been considered whenimplementing solutions to such changes.

Operational requirements in every case relate to many issues arising from therunning of trains. Some are listed below, and most or all drive the design andimplementation of the overarching signalling and control systems that protect them..

Headway Maintenance and improvement.

Train Separation (Junction Management and Node Handling).

The need for operational flexibility of the layout.

Maintaining operations during failures

Recovery scenarios from failure.

Splitting & Joining Trains.

Train Detection

The major changes in train control and operational strategies called for byERTMS on heavy rail non-transit applications require the same philosophicalapproach to development of future operational requirements. They also require aconsideration of just how much ETCS is really required, the lines over which it shouldbe applied and above all the timing of such applications when viewed against thecosts and benefits of its implementation.

The above issues and the technicalities associated with the changing andcommissioning of traditional signalling systems now need to be coalesced into ageneral system for the future. This development must not be on an ad hoc basis, butemploy the benefit of hindsight, and the availability of modern system engineeringstrategies to achieve the required goals. The same may be true for operationalscenario development, a subject seemingly neglected during the development of theSRS, and only written after its completion. There still appears to be a degree ofunhappiness with the scenarios developed by the ERTMS Users Group in any termsand these may not have been implemented nationally, or more especially,internationally.

In terms of normal operation and fall-back and recovery scenarios, it may wellbe that the SRS will require revision in order to address these issues, both in the

migrating railway and for the operation of new lines.A methodology has been explored in which system development for ERTMS

requirements are derived from a process of top-down extraction from Operational


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Requirements, and bottom-up construction from the translation of existing functionalprinciples and requirements i nto the ERTMS environment and architecture. Thisprocess applies in both the migrating, and the new railway cases.

Not the least of these concerns the need for an initial isolation of therequirements of the operators to permit them to dispatch trains. The ability to do this

safely and efficiently relies solely on the volume of information, both required by themand available, and whether the system is running normally or running in a fallbackstate. There arises then a necessity for the development of functional specificationsfor an interface between the TCCS and the RBC, and a further need to develop therequirements for operational fallback links between the TCCS and its associatedinterlocking equipment.

7.3 Migration Planning

In many meetings, seminars and gatherings the question has been asked: How

to protect the current investment in signalling, both trackside and train borne, thatmay have to last many years, and that currently may not be initially ERTMScompatible? This conundrum forms the backbone of the second issue to bediscussed herein. A subordinate to this concerns TEN routes equipped with olderstyle interlocking equipment and signalling, that need an implementation method forERTMS without replacing this in its entirety.

The first task then is to identify those lines that do apply, and take a look at theexisting signalling systems, their comparative age, and possible suitability for revisionover time, to ERTMS principles of operation. A group of railways has been formedfrom The Netherlands, Germany, Switzerland and Italy to research the first major

TEN corridor between Rotterdam and Milan, and the associated lines wouldobviously provide a good candidate for the research needed. The German railway,Die Bahn and its subsidiary DB Netz AG, Danish State Railways, BaneDanmark, andREFER Portugal have provided details of signalling and interlocking systems overtwo major TEN corridors, (one of which is a portion of the route mentioned above)and the others over one entire network. This data is included in Appendix A.

The problems faced for the future can be seen clearly, that interlocking systemsemployed over two of these routes are averaging 30 years of age, and due to pastcontracting strategies and other issues, do not necessarily reflect consistent design.In contrast, a large proportion of the Portuguese mainline network signalling has

been renewed within the last 10 years. Allowing for the fact that these mainlines wereequipped with ATP (EBICab 700) there is a reluctance to proceed to ERTMS with thescenario of a replacement program for all interlocking systems. The similaritybetween the railways is however that the systems are still not architecturallyconsistent, and represent a number of suppliers with different architectural solutions.The Portuguese network does, like many other railway administrations, howeverkeep to one set of generic signalling principles that underpin the application at eachspecific site.

The foregoing sets the scene for the choices with which the railways are faced o nTEN routes of differing characteristics. There is the issue of trains equipped with

current standard train borne ATP systems requiring to be modified to run on ERTMSLines, that of ERTMS equipped trains required to run on current ATP equipped lines,and finally the issue of how to migrate the signalling at the trackside to provide a


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simpler and inexpensive migration path for the trackside. There is also the businessdriven issue of whether and when the line should be fitted at all, based upon thecriteria of the business need, and the type of traffic envisaged.

The following figure1 indicates a process to achieve the migration ideal with allsystems addressed.

7.3.1 Fallback and Degraded Modes

In the case of fallback situations where the primary system is not performing,operating commands and information must continue to flow in such a way to maintaina given level of operation, and to assist in the recovery process, and keep trainsmoving safely. The development of a rationale by which these issues may beaddressed requires the same approach over all the railways of, initially the so-calledTEN routes, and later for other mainlines as they are added to the network. Thereis, no obvious reason why these scenarios and the systems developed for ERTMS

as a result, should be any different in Finland as in France in the long run, althoughthere are of course differences in the existing situation between countries. The roadto ERTMS then may require national strategies, but the focus and the outcome mustfollow the international strategies developed during the process.

By proper analysis of the operators needs, it is believed may be that thedesigner may be able to apportion functionality in such a way that SIL4communication links are not needed (e.g. by use of message coding to allow safetycritical messages to be transmitted over open networks (as is done in UK SSI),thereby saving money. -

As an example, the use of Vital Overrides between the dispatcher and theinterlocking can potentially be expensive due to them needing to have a defined levelof security, and which, depending on the architecture of the control system, can belocal to or remote from the control point. The abolition of, or at least re-considerationof the need for such functions as these has the ability to save considerably in new-era systems if railways can agree on commonality of practice in failure scenarios.The alternative may be by specifying the interfaces between the interlocking, thecontrol system and the vital override, and adopting a safety critical messageprotocol that allows messages to be transmitted over an open communicationchannel.

Some older signalling practices should also be addressed, especially perhaps beaddressed in terms of the aviation industry and its practices, when dealing withcommunication based systems in the ETCS world. The aircraft industry for exampletakes a notably different approach to vitality in its on-board communicationsstrategies.


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Definition ofRolling Stock Use

Migration via RollingStock

Migration viaInfrastructure

Roling Stock with newsystems

Two Systems:- Standard (ERTMS)- Modified to run on nationalnetwork

Homologated new / modifiedtrain systems

(New ) Sub-Fleet with newtrain systems:

- One system per train- National Standard (ERTMS)

Financing

New InfrastructureOne System The Standard

Homologated new / modifiedInfrastructure system

Partly Modified / ReplacedInfrastructure:

- National System- Modifications in thedirection of the standard

Result: Application ofstandards by migration(Interlocking and TrainProtection including:

- Interoperability- Increased Capacity- Increased Safety

Figure 3: Scenarios for Rolling Stock and Infrastructure Migration of Nation Specific Solutions to (European) Standards

Example: HSL Zuid Example: Asd - Ut

1 Courtesy of Prorail Netherlands

There is a need to provide an ultimate ERTMS solution for new rail lines, and whileimportant, the problems posed for rolling stock development and transfer are not sodifficult. What is difficult however is establishing norms for the equipping of such newlines to assure future standardization and true interoperability within the rules, and toensure that the strategies employed in migration are in fact reflected in the finalproduct for all lines. The great questions remain though, how best to adapt, eitherby existing equipment modification or by renewal, and how to create a truly Pan-European solution for those lines affected by the TSIs


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8. Interoperability & System Relationships

Over the last few years, the EC, together with its committees, have issueddirectives concerning railway interoperability between countries. If we take this to itslowest common denominator, this means neighbouring countries with common

routes, more commonly specified as TEN routes.As some nations are tackling this issue by building new lines for high speed, and

essentially passenger traffic, the issue of new technology commonality specificallyarises. It is essential that such lines have harmonised principles both of operation(both normal & under fault conditions) and of train control. How this is achieved iscurrently in the hands of the ERTMS Users Group and implicitly UNISIG / UNIFE.Their supporting documentation up until now gives no inclination towardsharmonised operations, and seems to have left the specification open enough topermit design diversity. This is arguably highly undesirable, given the foregoing inwhich a standardised product and specification is advocated. The wider issue arises

from the notion that major mixed traffic routes such as the DB Emmerich Basel(Part Rotterdam Milan), and the BaneDanmark route from Germany to Sweden viaCopenhagen will form a backbone of TEN routes. Where this is the case, the issueof replacement or modification of existing interlocking and trackside signallingequipment to suit the agreed ERTMS systems design comes to the front and centreof the grand design.

8.1 The Signaller and the TCCS

The role of the signaller and his interface with the signalling system via theTCCS is another area in which it seems that little public debate has been heard. The

manner in which these systems must be able to communicate with RBC, Vehicle orInterlocking in all types of operational situation is paramount to the development ofoperational rules, especially relating to system recovery after a fault affecting trafficmovement or safety.

It seems, although not perhaps publicly obvious that the interoperable interfacesrelate solely to the user i.e. the train driver & his train, and their relationship to thevisible parts of the control system. This exercise derives the interoperable interfacesas:

The train cab equipment: (Drivers HMI)

The line side signals (if any): (Drivers HMI)

The ERTMS line-side communication equipment (On-Board interface)

Given that the technology behind these is generally invisible to the user, onemay ask why there should be so much emphasis on commonality. One answer ofcourse lies in the nature of common failure states and how to recover from them in aunified fashion and using a harmonised operational rulebook. Others revolve aroundcost minimisation, provision of technical resources, staff training etc.

Missing from the above list is the TCCS and its interfaces coupled with theneeds of the signaller. The subject requires a completely separate review as it is bythe use of the interfaces provided that the signaller can use the rulebook as it is


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intended. Indeed the TCCS must be designed in support of that operational rule bookand the scenarios contained within. The search for a trackside principles startingpoint, must eventually elect to include TCCS functionality, insofar as it affects theuser interface requirements to the other trackside systems and centralisedinformation systems of the railway especially in the requirement to protect trafficduring incidents and to recover from failure.

This is a major issue, an it must be said that harmonisation here, and in thearea of operating rules, is likely to be a long hard road of national legal wrangling tohave maximum functionality transferred from interlocking to TCCS, and to rid thesystems of the operational override pitfalls that exist with us to this day under theguise of Operational Need rather than safety or business requirements.

9. Signalling Principles and Requirements

The railways of Europe are, given their history and the innate nationalism within,some of the most difficult entities with which to address the harmonisation issue andits associated problems. In the implementation of interlocking types, signal profiledifferences, speed versus route based signalling and so forth, there is no consensusas to harmonisation of signalling or operational principles for legacy systems. Theonset of ERTMS however presents us with a superb opportunity to achieve this.

Against this backdrop, and within interlocking and train safety systems alone,there are to name but a few:

Supplier specific types (especially design)

Electronic versus relay based systems

Free wired versus geographical systems

Mechanical interlocking

Internal / external line block

Track circuit block

Inumerable token / tablet / telephone based block systems for low traffic

and single lines

Level crossing equipment

There have been some very public examples of the pitfalls waiting for the unwaryengineer and the over optimistic operator that always wishes to maximise the use ofhis railway. The West Coast Main Line in the UK provided one of the best examplesin Europe in recent times, of the problems the signal & systems engineers face whencoming to grips with legacy systems and trying to build for the future. This line has inthe course of the last few years been the subject of huge debate, governmentinterference, national press revelations, inadequate strategies for renewal, poor

legacy track alignments, non standard loading gauge for Europe and poor systemengineering choices. In short, it has also been the victim of those operators that needto achieve maximum use of the network, with the ensuing inability to perform major


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re-signalling and other works in a convenient and timely fashion without causingmassive dislocation to the train service. The above should not generally apply whenbuilding new (hopefully dedicated) main line railways, whether high or mediumspeed, or just feeder lines but this reflection provides a good insight into the issuesfacing the migrating railway and signalling and track alignment upgrades.

From the European standpoint, the operational issues for ERTMS have beenfairly well defined in the various technical documents e.g. SRS. Unfortunately thesedo not provide the reader with a detailed insight as to the required principles(requirements) for the control and supervision of trackside systems in the ERTMSenvironment, either under full control or some type of fallback mode following a majorfailure.

The challenges therefore seem to revolve around the following issues anddecision paths.

Signal or re-signal from scratch only those high speed lines required for

European Interoperability as directed by the EU, and no more. Or, re signal as above, but include mixed traffic high speed lines

Or, re- use adapted existing signalling systems in a way that they conformto new principles and that lead directly to full ERTMS when obsolete.

Providing compatibility between existing heritage systems and ERTMS, toenable co-existence of the heritage system and ETCS, until the need forthe heritage system can be dispensed with.

10. Important Guidelines

As with all systems, the specifications as to use, functionality, and its operabilitystrategies under fault, remain the critical issues. The railway companies themselvesremain the best suited organisations to:

Design railway layouts, based upon their knowledge of train servicerequirements both present and future and with an innate knowledge of therequirements for safety.

Develop operational scenarios based upon the nature of the traffic and thedegree of departure from normal services

Design a fallback strategy based upon the rules of the railway as is. Negotiate revised fallback strategies based upon agreement between

neighbouring railways, or railways sharing a common line for the future.

Independent technical advisers or qualified signalling personnel within eachrailway or within a railway umbrella organisation are best suited to:

Prepare the functional requirements by which the proposed system will bedesigned.

Interpret the operation and fallback scenarios into a signalling and train

control system layout suitable for them, Determine the most suitable architectures for the signalling and train control

systems based upon a required commonality of use.


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situation. Whilst this minimizes the cost at trackside, the responsibility for providingthe Train Route now passes to the RBC.

When one comes to consider the architecture of these various subsystems, theaim must be to reduce costs to a slow as possible. Figure 5 shows architecture formain lines whereby certain functions are combined into systems of the same SIL

level thus avoiding the possibility that SIL 0 functions might actually be designed intoSIL 4 hardware and software. In this example, the virtual route setting and lockingtogether with the construction and issuance of movement authorities is performed bya SIL3 or 4 section of the RBC, whereas the routing development and scheduling ishandle by the TCCS / ARS, together called a TMS (Traffic Management System).This design is approaching that selected by the Swedish railways for their regionallines.

All these innovations, while desirable, cost money and effort both in terms ofdesign, installation and maintenance, and tend to be extremely complex. Thiscomplexity has in the past been solved by extremely reliable and proprietarysolutions, but in a modern, business oriented railway, this may not be ideal. Railwaysare now tending towards the installation of their own internal communicationsnetworks, with access facilities along the line for the interfaces that the modernrailway requires. Such innovations require exploration into the issues of opennetworks, and the data requirements to be transmitted over them.


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TCCSSignaller Functions &

DisplaysFallback Route SettingFallback Point MoveFallback Point Detect

ARSAutomatic Routing

FunctionsTimetable

Junction Management

RBC

RBCTrain Data Setting

M.A. SettingRailway TopographyVirtual Route Setting

ETCS Mode Train Position

Complex FieldInterlocking I/L I/LI/L

Physical Route Setting & LockingSignal Aspect Setting (Migration)

ATP ControlsPoint Machine Controls

Points HeatingSignal Lighting for Non ETCS Traffic

Points Position IndicatorsTVP Section ResetLockable Device Releases

Points DetectionPoints Heating Off / On

Signal Lamp Filament DetectionTVP Section Occupancy / Clearance /

Reset DataLockable Device Detection

A A

B

C C

D D

BB

Interfaces A: TCCS to RBC SIL 0Interfaces B: RBC to RBC SIL 4Interfaces C: RBC to Interlocking subsystems SIL 4Interfaces D: TCCS to Interlocking SIL 0-2Interfaces E: Interlocking to Interlocking SIL 4Interfaces F: RBC GSM-R Link to Vehicles SIL 4

E

FF

Figure 4: Mainline ERTMS Trackside Architecture 2006


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TCCSSignaller Functions &

DisplaysFallback Point MoveFallback Point Detect

ARSAutomatic Routing

FunctionsTimetable ManagementJunction ManagementRailway TopographyTrain Data Setting

RBC

RBC

M.A. SettingVirtual Route Setting

Signal Lighting Decision


Low LevelFunctions

FieldInterlocking

I/L I/LI/L

Point Machine DrivesSignal Lighting for Non ETCS Traffic

Points Position IndicatorsTVP Section Reset

Lockable Device ReleasesPoints Heating



Reset Data

A A

B

C C

D D

BB

Interfaces A: TCCS RBC SIL0Interfaces B: RBC RBC SIL 2Interfaces C: RBC - Interlocking subsystems SIL 0Interfaces D: TCCS Interlockings Direct Fallback SIL 0Interfaces F: RBC GSM-R SIL 4

FF

Figure 5: The Simplified Interlocking Approach to ETCS Trackside.

The UIC ESIS project feasibility study of 2004 set out originally to provoke

discussions concerning a standard for signalling system interfaces. The currentversion of the document, accepted by the Euro-Interlocking steering group ofNovember 2003, sets out two possible ERTMS L2 control system architectures. The


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acceptability of these options when set against the issues of open ended and limitedaccess lines, and migration will be discussed, along with proposals for a way forwardto a standard application for ERTMS at all levels based upon the use of OperationalScenarios to create a Top Down approach to development.

TCCS/ARSSignaller Functions &

DisplaysFallback Point MoveFallback Point Detect

RBCM.A. Setting

Virtual Route SettingSignal Lighting Decision


Low LevelFunctions

FieldInterlocking

I/L I/LI/L

Point Machine DrivesSignal Lighting for Non ETCS Traffic

Points Position IndicatorsTVP Section Reset

Lockable Device ReleasesPoints Heating



Reset Data

C

D D

B

Interfaces B: TCCSRBC TCCSRBC SIL 2Interfaces C: RBC - Interlocking subsystems SIL 0Interfaces D: TCCS Interlockings Direct Fallback SIL 0Interfaces F: RBC GSM-R SIL 4

F

C

Figure 6: Simplified ETCS for Regional or Light Traffic Lines


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TCCS

Kernel

I/L

O/C O/C O/C

RB C

Levelcrossing

Lineblock

DiagnosticSystem

Juridicalrecords

Track Elements

Category 1

Category 2

Category 3

I/ L

O/C O/C O/C

Miscellaneous

SafetySystems

Interlocking System Interlocking System

Kernel

TCCS

Kernel

I/L

O/C O/C O/C

RB C

Levelcrossing

Lineblock

DiagnosticSystem

Juridicalrecords

Track Elements

Category 1

Category 2

Category 3

I/ L

O/C O/C O/C

Miscellaneous

SafetySystems

Interlocking System Interlocking System

Kernel

Figure 7: UIC ESIS Feasibility Study - Signalling System Architecture A

TCCS

nI/L

O/C O/C O/C

nRBC

Levelcrossing

Lineblock

DiagnosticSystem

Juridicalrecords

Track Elements

Category 1

Category 2

Category 3

O/C O/C O/C

Miscellaneous

SafetySystems

Radio Interlocking System RIS

RIS

GSM-R

TCCS

nI/L

O/C O/C O/C

nRBC

Levelcrossing

Lineblock

DiagnosticSystem

Juridicalrecords

Track Elements

Category 1

Category 2

Category 3

O/C O/C O/C

Miscellaneous

SafetySystems

Radio Interlocking System RIS

RIS

GSM-R

Figure 8: UIC ESIS Feasibility Study - Signalling System Architecture B

It was noticeable from the UIC studies in Figures 7 & 8 that migration fromexisting interlocking systems was omitted from the discussion by an early decision.To include the subject was deemed to have made ESIS untenable. Add to this factthat migration is widely viewed by railways as a National issue, and one arrives atthe current situation. As mentioned earlier in this paper, the railway companies ofEurope are faced with somewhat more serious problems regarding the use of legacysystems, and these concerns we will consider herein.


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12. Architectural Strategy

As stated above, the architecture for the supplied ERTMS systems will fall outof, to name but a few, important issues:

The Business Case for the line to be re-signalled

The Type of line it is, and its relationships in Table 1

Available technological Know-How

Whether or not the existing systems exact a migration policy on the newsystem

Agreed International Standards

Given that the European railway world currently has many different mechanicaland relay-interlocking types, a selection of different electronic interlocking types,

and other legacy electro-mechanical signalling systems, it is not surprising thatdifficulties exist in the making of decisions for the future. It is only as a result of therequirement for adherence to European directives that are themselves notcomprehending the reality of the railways of today, that managers have been forcedto deal with the issues.

Whilst the interfaces between the elements that are supported internationally;namely trackside communications to and from rolling stock, are very advanced, andinternationally normalised, the proposed architecture of, and communicationbetween elements of the trackside systems are in general poorly understood for theentire ERTMS concept. There has been little evidence that the supply industry has

been willing to change from the protected market approach of the past and to worktogether to find a truly international solution to the train control system architectureproblem either. Numerous countries are involved with differing consortia fromindustry to develop solutions based on immediate, perhaps political or justpioneering goals, rather than the long-term goals of European train and tracksidecontrol systems harmonisation.

What is required within the ERTMS environment is a set of norms that will seeeach supplier providing elements of the subsystems that are truly interchangeable.For example, communications cards that can be used in any system to connectsimilar elements with similar power supply requirements, operate multiple or

identical protocols, and similar and multiple uses. This may only be achieved once aset of international system norms has been established, functional apportionmenthas been achieved, and interface specifications for all subsystems also agreedupon. The basis for this strategy revolves not just around interoperability, but alsofor reasons of cost and project risk reduction. These subsystems remain a majorcost driver for railways that must be addressed by the application of EuropeanStandards

The other necessity for future interlocking systems must be a modularapproach that enables certain parts of the logic to be retained for ERTMS use,whilst other parts are removed due to the functionality of the RBC and other sub-

systems. These functional splits are currently available in the architecture of mostinterlocking systems today, whether relay or software based.


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13. Interface Requirements

The interfaces between ERTMS /ETCS subsystems generally fit into four functionallinks. These are by no means standard, but represent the interconnections giventhe system architecture outlined above as a standard basic ETCS control system

architectureInterface Location Status General Application Level

RBC Interlocking Open or Proprietary SIL 2 or 4

Interlocking - TCCS Currently Flexibledependent upon theoperating requirements

SIL 0, 1 or 4 (dependentupon the operatingadministration

Interlocking interlocking Open SIL 4

TCCS RBC Open SIL 0 or 4

Interlocking Trackside(O/C Architecture

Generally Proprietary SIL 4

Table 2: Interface structures Analysis

The Safety Integrity Levels stated in the table indicate that should the architecturechange, or in fact the operating and legal requirements, then the degree of safety,

and therefore cost, may change. Some of the following diagrams will indicate theoptional differences that might be considered in this light.

There is a need to re-visit the interface issue for the migration situation. Thesame basic interfaces remain, as the system elements involved do not changegreatly. The evolving operational requirements to move trains in non-communicatingmode over an ERTMS equipped line, and to operate and monitor track elementswith failed system elements have led historically to an additional requirement toprovide an interface between the TCCS and each interlocking for fallback handlingand for special situations. It can be clearly seen that the functional apportionmentbetween elements of the ERTMS system will also affect the interface functional

requirements, and this issue is also addressed in the recommendations for theadoption of a fixed ERTMS system architecture for each level based on a balancebetween operational needs and safety, and cost effectiveness over the life cycle ofthe installation.

What is certain is that the design of the system, and an understanding of its realsubsystem tasks is a driver towards the reduction in the number and the requiredsafety level of the interfaces. The Regional Design for example has reduced thenumber of external interfaces to three from six, and quite possibly the degree ofcomplexity required in each has been reduced also. As in all things, risk analyseswill reveal whether such reductions are suitable, but what is fact is that this exercise

is ongoing, and that required SIL levels are falling.


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14. Migration Strategy

The subject of migration between existing signalling systems and ERTMS haslong been an issue between signalling engineers. What has not happened is thedevelopment of a concerted strategy by which this may be achieved.

This paper seeks to redress the balance, and to actively seek a suitablemethodology whereby existing signalling infrastructure investment may be retainedand utilised under the overall system requirements of ERTMS. Such a methodologymust be explored under one group, and currently that group is the ERTMS MigrationGroup.

Certain railways involved in current and past ERTMS Projects have determinedthat existing interlocking systems must be totally replaced with the same architecturewhen ERTMS is considered. A standpoint such as this has provoked investigationinto the protection of assets and investment. The Swedish railway (BV) may nowreconsider this, and there is a growing argument that complete replacement in somecases is technically needless when logical solutions can be found in the higher levelsof the system, namely the RBC, leaving the lower levels of the Interlocking to performas today.

It may well be that from the TEN route examples given in earlier sections andexpanded in the appendices, existing interlocking equipment may not lend itselfimmediately to modification, but with thought, most can be adapted, and with far lessexpenditure than that incurred during a complete interlocking replacement program.The risk element of working on old systems must be considered of course, but withsuitable mitigations in place serious investigation into the possibilities could now be

taking place.Figure 5 represents a possibility for reduced cost architecture for both new full

ERTMS lines and new or existing mixed traffic ERTMS lines. The concept is toprovide a reduced functionality trackside interlocking and an RBC with much greatercapability Movement Authority generation and virtual route locking areas. Theconcept provides an opportunity to investigate the current interlocking and signallingequipment on TEN routes, and to modify it, at reduced cost, to suit the aboveformat. The Interlocking equipment here only provides basic functionality such asDetector Locking, TVP supervision, simple time of operation locking, and supervisionof Point and signal aspects.

Realising that older systems suffer from wiring degradation, and limitedinterconnection availability a program such as this demands much thought, and thereis no effort herein to provide the detailed technical solutions. The obstacles mayperhaps be overcome with some cheaper alternatives, provided that the full routingand M.A functionality required for ERTMS is transferred to the RBC, and thatinterfacing strategies are developed to minimise the impact of ERTMS upon theremaining field equipment. The final model for ERTMS must also reflect the reducedfunctionality scenario at trackside as interlocking equipment is replaced by furtherattrition and old age.

A main driver for not removing the trackside equipment and for retention of thedirect locking parts of the interlocking relates to the necessity for signalling in mixedtraffic TEN routes during migration. It is considered that operators will not give up


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throughput during the migration period in favour of a non-dual mode operatingsystem. Such systems as the KCRC ATP in Hong Kong have largely overcome thisproblem, but with the use of interlocking systems providing the ATP and train-bornetransmission information instead of the RBC of ERTMS systems. Signals in this casewere equipped with an extra blue aspect, but this may not be necessary in theEuropean arena where consideration might be given to signal darkening instead.This is advocated purely on a cost basis as the addition of aspects to existing signalshas in the past proven to be an expensive option, especially in the requirement foradditional or modified logic to drive them.

A further operational issue during migration is that of throughput maintenance oreven an increase in track capacity. Whilst it may be feasible to increase the numberof trains in pure ERTMS systems by shortening block lengths etc. this task in amigration state would involve the movement of signals and any other track objectsconstraining headway. The costs associated with such activities must be carefullyconsidered in the light of previous experiences, especially the KCRC ATP project.

14.1 Existing Railway Signalling Architecture

As can be clearly seen from the data (kindly provided in the appendices byrailways for which migration poses a great problem) the existing interlocking systemson certain routes provide no simple path to an adequate and reasonably pricedmigration. The German example for the TEN routes between Emmerich and Baselreveals in great detail the problem that whatever the strategy to be employed, theexisting and aging signalling interlocking infrastructure cannot be ignored.

The strategies outlined herein have assumed that signalling systems on the

major routes have had some investment in the prior 40 years, so providing a solutionin one or more ways. What we are faced with in the German and Danish situationshowever is a complete re-signalling project in order to bring the systems up to dateand to be, at the same time, ERTMS compliant, if the existing interlocking systemscannot be modified.

Perhaps another data set of relevance here is that presented in the Euro-Interlocking Business Case for The European Railways. Although not completelyaccepted, this document contains invaluable further data from other railways thatgives further indications of the existent problems, and the percentages of existingequipment types. The information presented here attempts to fill the gaps in the

Euro-Interlocking document by providing data from DB for at least one main line, andwhilst this is not the whole picture, it is representative.

15. Node Handling

Many interlocking systems are placed for the control of major station areas ratherthan passing places or small stations along the line. A decision is required thereforeas to how these must operate in the ERTMS environment, or in fact whether nodesshould be included in the ERTMS equation.

An answer is related to the fact that if interoperability were to be applied in itstruest sense from the outset, the node issue would only apply to end stations forlong stretches of open line. The German high-speed lines provide a classic example


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of this where for example main stations like Cologne or Emmerich have not been re-signalled to meet the demands of ERTMS as there is no direct necessity to do so. Alltrains stop there, especially passenger trains, and therefore continuous ERTMS isnot required as trains may re-acquire communication with the control system uponentering the next l

vision and potential for future signalling stratergies

Documents