Technical Specifications for Interoperability (TSI)
The European Union has created a legal basis for the TSI with Council Directive 2008/57/EC of 17.6.2008 as a replacement for Council Directive 96/48/EC (interoperability of the trans-European high-speed rail system) and Directive 2001/16/EC (interoperability of the conventional rail system). Various TSI have come into force since 2006. In the EU member states, the TSI are superordinate to national regulations. In Switzerland the TSI are considered to be accepted standards and rules of diligence (Implementation provisions to the Railways Ordinance).
The objective is to define uniform rules for the railways as a system, ensuring international, interoperable and safe transport within the EU. In addition to the stretches previously considered on the Trans-European Transport Network (TEN-T), the rules will be extended to the whole normal-gauge network of the EU, and the "high-speed" and "conventional rail system" fields will be merged.
The EU Commission mandates the European Railway Agency (ERA), which has its seat in Valenciennes, with concrete and timed development of TSI projects.
However, the TSI cover only part of the whole regulatory field. National testing continues to form a substantial part of the required safety certification. The approach of cross acceptance will therefore remain important, until the approval process has been more completely harmonised via European specifications. Because of the durability of the railway systems, this process will probably take several decades.