TSIs translate the essential requirements of the Interoperability Directive into concrete technical rules for each subsystem of the rail system, and they drive the conformity-assessment work of the Notified Bodies. For a fleet investor they are the yardstick of what a vehicle may legally do over its life, and their revisions are the most common source of retrofit cost.
Legal basis
Directive (EU) 2016/797 sets the essential requirements every subsystem must meet: safety, reliability and availability, health, environmental protection, technical compatibility and accessibility. TSIs are adopted by the Commission as implementing acts on the basis of ERA recommendations and concretise those requirements subsystem by subsystem.
The subsystems and their TSIs
Structural subsystems: infrastructure (INF), energy (ENE), trackside and on-board control-command and signalling (CCS), and rolling stock — locomotives and passenger rolling stock (LOC&PAS) and freight wagons (WAG). Functional subsystems: operation and traffic management (OPE) and telematics applications for passengers (TAP) and freight (TAF). Cross-cutting TSIs: persons with reduced mobility (PRM), safety in railway tunnels (SRT) and noise (NOI).
The 2023 revision
The 2023 TSI package (notably Implementing Regulation (EU) 2023/1694 amending the rolling-stock, infrastructure, energy, PRM, noise, tunnel and operation TSIs, and Implementing Regulation (EU) 2023/1695 on CCS) consolidated a large set of changes: ETCS Baseline 4 and the path to ATO, provisions for new traction technologies, the European Rail Traffic Management System migration framework and further harmonisation of freight-wagon rules. ERA is preparing the next revision cycle, including the merger of TAP and TAF into a single telematics TSI. The financing consequences of the 2023 package are discussed in the note on TSI 2023 and residual value.
Conformity assessment and Notified Bodies
Conformity with a TSI is demonstrated through the assessment modules of Decision 2010/713/EU and the TSI itself. A Notified Body (NoBo), designated by a Member State, carries out the EC verification and issues the certificate underpinning the EC declaration of verification for the subsystem; interoperability constituents carry an EC declaration of conformity or suitability for use. Where national rules apply, a Designated Body (DeBo) assesses against them.
Transitional regimes
TSIs carry transitional provisions for projects at an advanced stage, for vehicles already authorised and for open points where notified national rules continue to apply. Reading a TSI therefore means reading its scope, its transitional article and the corresponding ERA application guide together. For a lessor the decisive questions are whether a TSI change triggers a new authorisation, whether retrofit is mandatory or only required on upgrade or renewal, and who bears the cost under the lease and the transport contract.
Selected references
Directive (EU) 2016/797 · Decision 2010/713/EU (modules) · Implementing Regulations (EU) 1302/2014 (LOC&PAS), 321/2013 (WAG), 1299/2014 (INF), 2023/1695 (CCS), each as amended, notably by Implementing Regulation (EU) 2023/1694 · ERA application guides.
Related topic notes
- Track access & capacity allocation · Track-access charges
- Fourth Railway Package · TSI · Safety certification & vehicle authorisation · ECM
- Freight corridors & combined transport · Passenger rights · State aid for rail · Altmark
Last reviewed: 19 October 2026.