Rail interoperability: current national technical rules 14.4.2026 | Her Majesty's Revenue and Customs National technical rules (NTRs) supplement National Technical Specification Notices (NTSN) with network or country-specific requirements. NTRs can perform several functions, such as: making a provision for country or network-specific cases filling in open points identified in the national technical specification notices (NTSNs) setting requirements to maintain technical compatibility with existing assets that do not conform to the requirements of NTSNs Background Under Regulation 3C of the Railways Interoperability Regulations 2011, the Secretary of State for Transport must publish a list of all national technical rules (NTRs) applying in the United Kingdom and the list must, where appropriate, specify the notified national technical rule (NNTR) that an NTR replaces. These are the lists of NTRs for infrastructure and vehicles that replace the lists of NNTRs previously notified to the Commission by the Secretary of State. Related documents Exclusions from the Railways (Interoperability) Regulations 2011 Railway interoperability: National Technical Specification Notices (NTSNs) https://www.gov.uk/government/publications/rail-interoperability-current-national-technical-rules