The Technical Specifications for Interoperability (TSIs) define the technical and operational standards which must be met by each subsystem or part of subsystem in order to meet the essential requirements and ensure the interoperability of the railway system of the European Union.
Directive (EU) 2016/797 defines the subsystems, either structural or functional, forming part of the railway system of the European Union.
For each of those subsystems, the essential requirements need to be specified and the technical specifications determined, particularly in respect of constituents and interfaces, in order to meet those essential requirements. The essential requirements can be summarised as safety, reliability and availability, health, environmental protection, technical compatibility and accessibility.
