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Mobility and Transport

What are the legal basis and the key documents?

ERTMS legislation mainly covers two aspects of the system: the technical description and the process for putting it into service. In addition to these core legislations, there is also additional legislation, which is related to the use of ERTMS.

The following figure gives an overview of the scope of the main legislation directly related to ERTMS enforced at a European level.


On a hierarchy scale, the highest documents related to Interoperability in the Railway frame are the EC Directives. Below there are EC Decisions that develop essential and technical requirements in more depth.

The Interoperability Directive (EU) 2016/797 sets out a number of essential requirements to be met for interoperability, which include safety, reliability and availability, health, environmental protection and technical compatibility along with others specific to certain subsystems. Member States had a transitional period to transpose this directive by 16 June 2020. The transposition deadline was extended until 31 October 2020. The Directive also requires the adoption of binding Technical Specifications for Interoperability (TSIs).

The Technical Specifications of Interoperability for Control Command and Signalling (TSI CCS) Commission Regulation (EU) 2016/919 is the legal basis of ERTMS specification, amended by the Commission Implementing Regulation (EU) 2019/776, 2020/387 and 2020/420. It includes the definition of the essential requirements, the subsystem and interface functional and technical specifications, and establishes the necessary list of constituents, interfaces and procedures for their assessment. In legal terms, it is a Commission Regulation, thus directly applicable to all actors without transposition to national law. This also means that any actor can use national courts to enforce this regulation.

Annex A of the CCS TSI includes the list of “subsets,” which contain the ERTMS system requirement specifications and a functional description of its different constituents. This Annex A contains three sets of technical specifications for ERTMS that can be applied to the projects. Contained in each of the sets of technical specifications, are two types of documents:

  • Mandatory specifications, which must be fulfilled by any ERTMS system, subsystem or component to achieve interoperability. Any deviation from the specifications must be transparently identified, and its potential impact on interoperability should be assessed.
  • Optional specifications that provide additional recommendations for the definition of the ERTMS subsystems.

The System Required Specifications (SRS) are among the specific technical requirements stated in Annex A and are called “SUBSET-026”. This is the main document containing all the detailed technical specifications of the ERTMS system.

The European Railway Agency (ERA) as the ERTMS system authority, is in charge of the management, modification and production of the specifications related to the ERTMS.