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ERTMS / Eurointerlocking

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Background & Policy context

Signalling with outdoors and indoors equipment is a specific asset of the guided railway system. It has traditionally been a national domain embedded in national rules and regulations with high safety requirements. This is currently still the case, despite of the big technological changes which have especially affected the interlockings.

As interlockings are not directly located at the interface between track and trains, these very sophisticated and highly safety-relevant devices have not yet been in the central focus for European harmonisation. However there is an increasing awareness that today’s interlockings could become a serious obstacle to the roll-out of ETCS, especially in the radio based configuration.

UIC launched the Euro-Interlocking project in 1999, when the new ETCS with its three levels of application began to become reality and when it was foreseeable that similar efforts for harmonisation and joint development would also become necessary in the adjacent signalling environment. From the beginning on the reduction of life-cycle costs, improved performance and optimal compliance with ETCS have been the main targets.

Euro-Interlocking has now become, within the UIC, one of the projects of common interest supported by all member Railways of the Infrastructure Forum.


The functional requirements are developed on a common platform, with the use of a standardised glossary, standardised commands and statuses as well as standardised requirement structures. The requirements are captured in English and are apportioned to individual railways through the process of tagging.


Parent Programmes
Institution Type
Non-profit organisation
Institution Name
UIC - Union Internationale des Chemins de fer
Type of funding


The Euro-lnterlocking Data Preparation work was established to promote the standardisation of data exchange file formats for interlocking applications. The EuroInterlocking Project has contributed to the development of standardised file formats for interlocking data exchange.

These standardised means of exchanging information between different phases of the data preparation process are needed to fulfil the CENELEC process for safety and reliability. Euro-Interlocking file format standards describe a common European structure and framework for project and configuration data transfer between data preparation tools and for data exchange between railways and suppliers.

The environment for this work is the requirements management tool DOORS, which enables precise tracking and change management and good traceability by linking the requirements from their source data to corresponding domain knowledge to test cases and hazards. The DOORS tool permits the identification and extraction of a common core of requirements, which consists shared requirements of all participating railways.

A complete data base of requirements is set and regularly updated once new requirements are tagged. It is resident at UIC Headquarters in Paris with controlled access from outside. The related “Use & Maintenance” leaflet is in its draft form and gives the railway members more insight into the data base and the process set to manage the data base.

Innovation aspects

Based on the findings of the Euro-Interlocking Business Case, the European railway infrastructure management organisations are spending over 4,000 million Euros per year on investments and maintenance of interlocking systems for their network. Organisations are also investing a lot of resources for data preparation work, which could be at least partly automated.

Other results

The last step in the generation of the common core is harmonisation. An analysis of the differences in functionality between the individual railways is made, and proposals generated for changing or adapting particular functions were suggested. These changes have to be examined by all involved parties in the individual railways. The simulator produced by the project should ease this process.


The Generic Hazard List work was started early in 2005 with a contract between the Technical University of Braunschweig and the UIC Euro-Interlocking Project in Zurich.

Phase 1 involved the generation of a document outlining the processes is used in identifying hazards related to railways in general and especially in relation to signalling and interlocking systems. This opening document provided the foundation for generation of the Generic Hazard List in 2005-06 and the completed article was circulated to the railways for evaluation late in 2005. The Generic Hazard List complete with cross reference tables to the Euro-Interlocking functional requirements in existence at the time was published in March 2006 and again circulated to the participating railways.

An offshoot of this was the generation of a process of inversion of each hazard to generate a High Level Safety Requirement. This was completed on a one-to-one basis, and shortly afterwards the University of Braunschweig completed the cross referencing work between the hazards, a more complete set of functional requirements and the completed high level safety requirements. This not only gave an updated picture of the Hazard List itself but ensured that no “holes” were found between the functions and the generic safety requirements for the systems.

Finally in May 2006 all the documents produced were placed under DOORS control, and the cross references provided in DOORS by means of the “Linking” facility. With close agreement between the teams this work was completed in June 2006 and the final documents issued to the railways for their comments. To date one set of comments has been received; those from REFER Portuguese Railways, and more would be appreciated in order to have the widest possible acceptance for the processes.

There is one other task remaining that involves the previous set of EI High Level Requirements. When the Generic Process and its data have been accepted, the original high level data require to be revised to avoid duplication. These requirements furthermore require changes to bring them into line with the revised project processes. The recommended changes have been discussed and agreed at the Euro-Interlocking Steering Groups and it remains for the DOORS data to be revised and re-issued for agreement and acceptance.


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