National Technical Specification Notices

There are 13 NTSNs:

• 11, each with a corresponding TSI, cover requirements for subsystems
• 2 cover assessment procedures.

They’re broken down into four main categories, as below.

Structural 

Control Command and Signalling (CCS): This relates to all trackside and on-board equipment required to command and control movements of trains. It includes interfaces and compatibility between different systems.

Energy (ENE): This relates to the electrification system. It includes overhead lines and the trackside of the electricity consumption measuring system.

Infrastructure (INF): This relates to the infrastructure subsystem. It includes stations, platforms, tracks, bridges, and tunnels.

Rolling Stock - Locomotive and Passenger (LOC&PAS): This relates to locomotives and passenger rolling stock requirements. It includes the interaction with track, aerodynamic effects, coupling, braking, doors, and visible/audible warning devices.

Rolling Stock - Freight Wagons (WAG): This relates to freight wagon requirements. It includes compatibility with trackside equipment, running gear, coupling, and braking.

Rolling Stock - Noise (NOI): This relates to requirements for all rolling stock (locomotives, passenger vehicles, and freight wagons) to limit noise emissions.

Functional

Operation and Traffic Management (OPE): This relates to the procedures for the operation of trains. It includes train composition and professional qualifications.

Telematics Applications for Passenger Services (TAP): This relates to applications for passenger services. It includes systems that give passengers information before and during the journey, as well as reservation and payment systems.

Telematics Applications for Freight (TAF): This relates to applications for freight services. It includes allocation systems, payment and invoicing systems, and management of connections with other modes of transport.

Transverse (more than one subsystem)

Accessibility (ACC): This relates to requirements for persons with reduced mobility for both rolling stock (such as provision for wheelchairs) and stations (such as route identification and facilities).

Safety in Railway Tunnels (SRT): This relates to requirements to ensure safety in railway tunnels, spanning the infrastructure, energy, and rolling stock subsystems.

Assessments

Modules for the procedures for assessment of conformity or suitability for use and UK verification: This replaces Commission Decision 2010/713/EU on ‘modules for the procedures for assessment of conformity, suitability for use and EC verification to be used in the technical specifications for interoperability’.

Assessment and further assessment of ICs: These are procedures for the assessment of interoperability constituents (ICs) against UK-specific cases. It includes the further assessment of ICs that hold an ‘EC’ declaration of conformity or suitability for use.

You must comply with all applicable NTSNs if:

• You’re building new railway subsystem.
• You’re carrying out a major upgrade or renewal of an existing railway subsystem.

and either:

• The subsystem isn't in the approved list of exclusions from RIR.
• You don't have an exemption granted by the DfT.

Like-for-like replacements, such as replacing track with track of a similar specification, don’t trigger a legal obligation to comply with NTSNs.

The DfT has more advice about whether a project must comply with NTSNs.

Please note that NTSNs are only applicable in GB. TSIs continue to have effect in Northern Ireland.

For further information, see: 

• Complying with legislation
• Guidance on the application of railway standards

If you can’t comply with an applicable NTSN, you’ll need an exemption from the DfT. Regulations 14 and 14A of RIR set out the conditions and the process for this.

The first step is to check the NTSN issues log on this page to see if this has already been raised and if the solution resolves your issue.

If not, please submit a Request for Help outlining:

• the problem
• the outcome you are seeking
• the reasons for this.

Your request will be considered by the relevant mirror group(s), our professional heads or technical experts, the relevant standards committee, and the DfT to determine the next steps.

The NTSN change process is similar to the process for changes to our standards but with an extra period of DfT decision making. 

This process is the same whether the change is related to a TSI change or a request from the GB rail industry. The process is detailed in the Railway Standards Code and Manual and the Working Agreement for the 2023/24 revisions.

1. Firstly, there’s an initial assessment with the relevant mirror group(s), which consists of technical experts from across industry, our professional heads, and the DfT. This is to determine whether and how this should be progressed.
   
   
2. Secondly, there’s a period of assessment led by us and the relevant mirror group(s) to develop a business case for change (BCfC). This sets out initial proposals for development and it is approved by the relevant standards committee(s).
   
   
3. Following standards committee approvals, we and the mirror group further develop the BCfC to include the proposed NTSN text and required analysis to support the change. This is provided to the relevant standards committee(s) for approval before wider industry consultation.
   
   
4. Then, there’s a period of industry consultation to capture any wider challenges or concerns. The responses to consultation and any changes to the NTSN proposals are approved by standards committees as the formal industry recommendation to the DfT.
   
   
5. Once the industry recommendation has been provided to DfT, the process and timing for a decision to publish a revised NTSN depend on the significance of the changes being proposed and the scrutiny required. Once the Secretary of State for Transport publishes a revised NTSN, this takes effect.

The NTSN issues log is a list of issues we’re aware of and proposed solutions. The proposed solution may be a clarification given directly through the issues log or a change to the NTSN.

Although we manage this log, anyone can raise an issue through a Request for Help.

Maintaining and publishing this log helps answer questions that may arise across the sector and track progress against resolving issues. It’s regularly reviewed by the relevant mirror group(s) and DfT.

Following the publication of revised TSIs in the European Union in September 2023, we issued a formal industry recommendation for revisions to the CCS, INF, LOC&PAS, WAG, NOI, OPE, and PRM NTSNs to the DfT on 29 February 2024.

For the revision to the ENE NTSN, industry consensus wasn’t reached, so an RSSB recommendation was made based on the evidence provided through the review and consultation. This was submitted to the DfT on 15 March 2024.

The documents we provided to the DfT are published on our consultation portal. They include:

• the cover letters accompanying these recommendations
• the proposed NTSN text
• the BCfC with an assessment and justification of proposals
• the consultation comments and responses.

This revision to the NTSNs was limited to addressing previously known issues and principally to consider changes in the TSIs. However, other important issues have been raised, and it is clear that there are many ways these NTSNs can continue to be improved. These revisions are the first step of progressive improvement. We’ve recorded matters that weren’t addressed in this revision, and work has already commenced on some.

We’ve prepared resources to understand and identify the differences between NTSN versions. These are:

• a track-checked version showing the differences between the NTSNs published on 2 May 2025 and the previous NTSNs published on 1 January 2021
• a briefing note for each NTSN providing a high-level overview of the NTSN, including its background, what it’s about, what’s changed from the previous version, the benefits, and who the document is for
• a BCfC for each NTSN, setting out the industry-recommended revisions to the NTSN and an assessment of the impacts of those revisions.