UNISIG

The European Train Control System (ETCS) is a signalling, control and train protection system designed to replace the many incompatible safety systems currently used by European railways, especially on high-speed lines.

ETCS requires standard trackside equipment and a standard controller within the train cab. In its final form, all lineside information is passed to the driver electronically, removing the need for lineside signals that, at high speed, could be almost impossible to see or assimilate.

The need for ETCS stems from European Union (EU) Directive 96/48 about the interoperability of high-speed trains, followed by Directive 2001/16 extending the concept of interoperability to the conventional rail system. ETCS specifications have become part of, or are referred to, the technical specification for interoperability for (railway) control-command systems, which is a piece of European legislation managed by the European Railway Agency. It is a legal requirement that all new, upgraded or renewed tracks and rolling stock in the European railway system should adopt ETCS, possibly keeping legacy systems for backward compatibility. Many networks outside the EU have also adopted ETCS, generally for high-speed rail projects.

ETCS is specified at four different levels:

Because ETCS is in many parts implemented in software, some wording from software technology is occupied. Versions are called System Requirement Specification (SRS). This is a bundle of documents, which may have different versioning for each document. A main version is called Baseline (BL).

The European railway network grew from separate national networks with little more in common than standard gauge. Notable differences include voltages, loading gauge, couplings, signalling and control systems. By the end of the 1980s there were 14 national standard train control systems in use across the EU, and the advent of high-speed trains showed that signalling based on lineside signals is insufficient.

Both factors led to efforts to reduce the time and cost of cross-border traffic. On 4 and 5 December 1989, a working group including Transport Ministers resolved a master plan for a trans-European high-speed rail network, the first time that ETCS was suggested. The Commission communicated the decision to the European Council, which approved the plan in its resolution of 17 December 1990. This led to a resolution on 91/440/EEC as of 29 July 1991, which mandated the creation of a requirements list for interoperability in high-speed rail transport. The rail manufacturing industry and rail network operators had agreed on creation of interoperability standards in June 1991. Until 1993 the organizational framework was created to start technical specifications that would be published as Technical Specifications for Interoperability (TSI). The mandate for TSI was resolved by 93/38/EEC. In 1995 a development plan first mentioned the creation of the European Rail Traffic Management System (ERTMS).

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