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Operating rules pose a major challenge to ETCS implementation

26 Feb 2008

Although common technical and functional specifications for the European Train Control System are laid down in the Technical Specifications for Interoperability, the lack of common operating rules could hinder the development of international corridors, suggests Chris Jackson

THE INTRODUCTION of the European Rail Traffic Management System has not had a smooth track record to date. More than one project has been delayed, and technical interoperability is far from being achieved.

Right across Europe, politicians and railway operators are putting their faith in ERTMS as the panacea for many of the rail industry's problems. More capacity, greater reliability, cross-border interoperability, ERTMS will solve them all. But time after time, the road to Utopia has been paved with problems - and not just technical teething troubles.

In many cases, there seems to be a basic lack of comprehension about what ERTMS is, and what it does. Or more specifically, about the technical elements of the signalling and train control aspects forming the European Train Control System.

ETCS is not a fully-specified signalling system that can be purchased and installed 'out of the box'. Rather it is a system architecture that defines how a wide range of separate elements - in many cases developed by more than one supplier - will function, and communicate with each other to meet a range of different train control applications.

Considerable effort has gone into fine-tuning the technical specifications, but many of the implementation issues relate to the establishment of new rules and regulations to integrate ERTMS with the existing railway infrastructure and operating procedures.

At the Railway Engineering conference in London last June1, the Director of ERTMS Customer Concepts in Siemens' Rail Automation business Dr Manfred Wernicke suggested that the process of defining the operating requirements and rules for each ETCS application had been significantly underestimated.

No operating standards

According to the Head of the European Railway Agency's ERTMS unit, Pio Guido, the omission of operating standards from the TSIs was intended to give railway operators and infrastructure managers the flexibility to apply ETCS to their networks in the most appropriate way.

Whereas the functional and system requirements specifications are clearly laid down2,3,4, the establishment of operating rules and development of safety cases for ETCS 'is a matter for individual railway undertakings or infrastructure managers', he said.

It is also clear that the migration processes and acceptance procedures are equally important for a successful ETCS implementation. And whilst it would seem logical to have another suite of standards for these aspects, operating procedures can differ substantially between railways - or in some cases even between divisions, lines or stations.

In most cases, Wernicke believed, the main constraints on ETCS implementation were the procedures and processes laid down for conventional signalling and train control systems used on the connecting routes.

Most ETCS projects to date have encountered problems which may have resulted from a lack of clear definition for the application rules. It has become clear that both the railway customer and the suppliers need to prepare a clearly-defined set of requirements for each ETCS application, given the wide range of equipment combinations now available. If a railway authority or infrastructure manager simply uses the FRS as a catalogue to specify the required functionality, it seems unlikely that this will give a satisfactory result.

Defining operating rules

Wernicke argued in his paper that for any set of tasks, the detailed operating requirements would be influenced by three factors:

  • mandatory rules;
  • infrastructure and equipment;
  • operating practices.

Mandatory rules are the essential requirements for safe operation, such as those laid down in Germany's EBO (Railway Building & Operation Regulations). Not all railways have everything in their written rule book, but the key rules differ between railways more by their comprehensiveness than their content, he felt.

Infrastructure and equipment covers everything used for day-to-day operation - lineside and on-board equipment, and even staff. Operational practice is the use of this infrastructure and equipment to move freight and passenger traffic in line with the mandatory rules. In many countries extra 'train working regulations' are needed to achieve a practical compromise between operations, capacity and safety.

Different system architectures, arising from historical development or the use of equipment from different suppliers, will be reflected in differing rules for degraded operation when components malfunction or fail. Depending on the existing technical standards, the pressure to maintain operational capacity and the degree of redundancy, each railway will have its own specific regulations to deal with degraded operation.

Both Wernicke and Guido accepted that full harmonisation of railway operating rules could not be achieved without greater standardisation of railway infrastructure and equipment - and not just the ERTMS elements.

For this reason, we are unlikely to see any meaningful standardisation of ETCS operating rules in the near future, with the possible exception of some rules and symbols for the Driver-Machine Interface.

Normal and degraded operation

Nevertheless, as ETCS is rolled out more widely, Wernicke suggested that it may become possible to establish some common implementation processes. Recognising the need to focus on operating requirements at an early stage of any project, he said Siemens had adopted 'a systematic approach to the customisation of ERTMS and ETCS to meet prevailing local conditions'.

The first step should be to prepare a clear definition of the tasks for a proposed ETCS application, and any interactions with existing operations. But Wernicke explained that this could not be based on the technical functions, because the application rules had not yet been determined.

His systematic approach started with the primary transport requirements, and interpreted each operational task using the SRS. As the solutions for each task were rarely independent, establishing the final ETCS package would be an iterative process, he continued.

Another important input was the Tolerable Hazard Rates for equipment failures, where safety requirements were expressed in terms of the prevention of a hazard. This in turn would link the ETCS operational tasks into a wider risk analysis for the railway as a whole.

But using the completed set of operational tasks and THRs would only result, in most cases, in an ETCS specification for normal operation. Wernicke emphasised that a systematic approach to the detection of failures and the recovery from degraded operation was also critical. For the malfunctioning or failure of any individual element, he identified four key questions:

  • what urgent measures are needed to deal with the failure?
  • how do we recover the vehicle(s) or train(s) involved in the failure?
  • what level of degraded operation should be permitted to deal with other train(s), and how should this be performed?
  • how is normal operation to be resumed?

The assessment of degraded situations could then be fed back into the specifications for normal operation. To minimise the number of iterations, Wernicke suggested that it might be better to start by drawing up a draft 'operational concept' which combined the key factors influencing both normal and degraded modes.

Similar assessments would also be needed for maintenance procedures, both planned and unplanned. Only when all the normal, maintenance and degraded operations had been defined would it be possible to identify the requirements and responsibilities for each of the so-called ETCS Domain Entities, and to establish the final operating, application and engineering rules.

This final system definition could then be used as a reference document for the development process. It would also be used to help prove the integrity of the ETCS installation during final approval by the relevant safety authority.

International conundrum

It has become clear that there is still no common agreement on how railways should operate using ETCS . Every application is primarily defined by the local requirements for degraded operation, which in turn are set by the nature and condition of the existing national railway infrastructure.

'The emergence of international standards for the application and operation of ETCS will depend on the convergence of infrastructure and equipment standards', warned Wernicke. And that was likely to require a great deal of investment over many years.

With each railway currently defining its own rules for domestic ETCS operation, it is difficult to foresee how the European Commission's strategy of developing international ERTMS corridors (RG 5.07 p275) will work out in practice. Partial application and mixed operation in each country will require the development of local operating rules, and it will be very difficult - if not impossible - to harmonise these rules to optimise the use of ETCS along the whole corridor.

This is ironic, of course, because one of the drivers for the development of ERTMS in the first place was to encourage interoperability and enable rail to compete more effectively for cross-border traffic. But we have already seen different railways adopting local changes to the system requirements specifications in order to get their initial ETCS applications operational, which results in a lack of technical compatibility along the corridors.

ERA is currently working to achieve a 'bug-free' SRS Version 2.3.0 for interoperable ETCS Level 2 operation, but for the next few years, at least, it seems likely that the practical constraints on setting operating rules will keep the railways and their suppliers firmly focused on getting their domestic applications right first.

Les règlements d'exploitation se posent comme un défi à l'établissement ?de l' ETCS

Bien que les spécifications communes techniques et fonctionnelles destinées à l'European Train Control System soient écrites dans les Spécifications techniques pour l'interopérabilité, les experts de l'industrie laissent entendre que le manque de règlements communs d'exploitation pourraient gêner le développement de corridors internationaux. Les règles locales d'exploitation sont largement basées sur les normes nationales et sont lourdement influencés par les règlements de circulation en situation dégradée, qui déterminent la manière dont les dirigeants de l'infrastructure peuvent conserver les capacités d'exploitation en cas de panne ou de dysfonctionnement de leur système traditionnel de régulation du traffic

Betriebsvorschriften sind eine Herausforderung zur Implementierung von ETCS

Obwohl die allgemeinen technischen und funktionellen Spezifikationen für das Europäische Zugsicherungssystem ETCS in den Technischen Spezifikationen zur Interoperabilität festgeschrieben sind, stellen Experten fest, dass der Mangel von gemeinsamen Betriebsvorschriften die Entwicklung von internationalen Korridoren behindern können. Lokale Betriebsvorschriften basieren weitgehend auf nationalen Normen und sind stark beeinflusst von den Regeln für reduzierten Betrieb, welchen es den Infrastruktur-Organisationen ermöglichen soll, den Betrieb bei Ausfall oder Fehlfunktion der alten, nationalen Zugsicherungssysteme aufrecht zu erhalte

Las reglas operativas suponen todo un reto para la implementación ?del ETCS

A pesar de que las especificaciones funcionales y técnicas comunes para el ETCS (sistema europeo de control de trenes) se determinan en las Especificaciones técnicas de interoperabilidad, los expertos de la industria sugieren que la falta de reglas operativas comunes podría dificultar el desarrollo de los correderos internacionales. Las regulaciones operativas locales se basan en buena parte en los estándares nacionales y están muy influenciadas por las reglas para el funcionamiento degradado; determinan cómo pueden los gestores de infraestructura conservar la capacidad operativa en caso de errores o fallos en sus sistemas heredados de control ferroviario

  • CAPTION: ETCS Level 2 is now in use on the Roma - Napoli and Torino - Novara high speed lines, using Version 2.2.2. RFI expects to complete the installation of Level 2 on its Alta Capacità network by 2009, but other Italian sections of the European corridors will only be provided with Level 1 Photo: David Campione
  • CAPTION: The European Commission's ERTMS corridors strategy is intended to encourage competition in the international rail freight market, but open access operators still face the challenges of equipping their locos for multiple signalling and train control systems?
  • CAPTION: Photo: Ernst-Joachim Gerlach
  • CAPTION: Swiss Federal Railways' Mattstetten - Rothrist line is closely integrated with existing tracks in the Bern - Olten corridor, so the ETCS operating rules have been strongly influenced by the requirements of the conventional signalling
  • CAPTION: Following the fitting of ETCS to a batch of its Class 189 electric locos, Railion is now operating revenue freight trains over the Betuwe Route in the Netherlands. But the line's Level 2 specification is not currently compatible with that adopted on other parts of the Rotterdam - Genoa Corridor A


1. Wernicke M. Customising ERTMS/ ETCS . Railway Engineering, London, June 2007.

2. ETCS and GSM-R Rules and Principles: HS OPE-TSI. Annex A. European Association for Railway Interoperability, December 2005.

3. TSI CCS Conventional Rail System, content of all mandatory specifications of Annex A. European Railway Agency, March 2006.

4. TSI CCS High-speed Rail System, content of all mandatory specifications of Annex A. European Railway Agency, November 2006.