Following the UK’s exit from the EU and the ending of the transition period on 31 December 2020, EU Technical Specifications for Interoperability (TSIs) have ceased to apply in the UK. The technical content of TSIs at the end of the transition period have been replicated as National Technical Specification Notices (NTSNs), which came into effect on 1 January 2021. These are published by the Secretary of State on the Department for Transport (DfT) website. Track-changed versions of the NTSNs are published below for guidance purposes only. The track-changed versions of the NTSNs show how the NTSNs differ from the corresponding TSIs. The NTSNs published by the Secretary of State are the relevant legal standards to be complied with under the Railways (Interoperability) Regulations 2011 (as amended).

NTSNs define the technical and operational standards which must be met to satisfy the ‘essential requirements’, and to ensure the interoperability of the railway system. This allows all parts of our network to run as a whole system, providing benefits for our customers and our society.

The essential requirements are safety, reliability and availability, health, environmental protection, technical compatibility and accessibility. ‘Interoperability’ is defined in the Railways (Interoperability) Regulations 2011 (as amended) as ‘the ability of the rail system to allow the safe and uninterrupted movement of trains which accomplish the required levels of performance for those lines’.

Who must comply with NTSNs?

The Railways (Interoperability) Regulations 2011 (as amended) mandates compliance with NTSNs on the rail system The scope of the rail system where the NTSNs apply can be found on the DfT website. For further information, see our Complying with Legislation page.

You must comply with an NTSN if you are building new railway sub-systems or carrying out a major upgrade or renewal of an existing railway sub-system. Replacement of parts of a sub-system on a like-for-like basis, for example replacing track with track of a similar specification, does not trigger a legal obligation to comply with NTSNs. The NTSNs also contain requirements for interoperability constituents (ICs).

For further information on ICs see the page on interoperability constituents and the ICs NTSN below.

Advice about whether a specific project must comply with NTSNs can be obtained from the DfT.

How do NTSNs relate to national technical rules?

National technical rules (NTRs) are used for the following purposes:

  • To fill identified 'open points' in NTSNs. Open points are identified in an annex to an NTSN if certain technical aspects corresponding to the essential requirements cannot be explicitly covered in the NTSN.
  • To support ‘UK specific cases’ in NTSNs. A UK specific case is a special provision relating to the technical specifications for a subsystem or an interoperability constituent to allow for its compatibility with the rail system, which is set out in an NTSN or an NTR.
  • To set out requirements to maintain technical compatibility between existing assets (or processes) that do not conform to the requirements of NTSNs and new, upgraded or renewed assets that do conform to NTSNs.

From 1 January 2021, the Railways (Interoperability) Regulations 2011 requires the Secretary of State to publish a list of all NTRs applying in the UK. RSSB recommends to the DfT the list of NTRs contained in Railway Group Standards.