TSI certification is one of the most misunderstood processes in the railway industry. Manufacturers entering the EU market for the first time — and even experienced operators planning significant vehicle modifications — frequently underestimate the time, documentation and coordination it requires. This guide explains what TSI certification is, when it applies, how the process works, and what it costs in time and resources to get right.
What Does TSI Stand For?
TSI stands for Technical Specifications for Interoperability. These are binding EU regulations, issued under Directive (EU) 2016/797 on the interoperability of the railway system within the European Union, that define the technical and operational requirements for railway subsystems operating on the Trans-European Rail Network (TEN-T).
The TSIs are the regulatory texts that lay the technical foundation for the single European rail network. To create a single railway area, the TSIs ensure that signalling is the same from country to country, so trains can be driven the same way anywhere in Europe. TSIs set the technical requirements for safe interoperability between rail system components. Railwayspare-parts
TSIs are not guidelines or voluntary standards — they are mandatory law in all EU member states, applying directly without the need for national transposition. A vehicle that does not comply with the applicable TSIs cannot receive authorisation to operate on the TEN-T network.
Which TSIs Apply to Rolling Stock?
The European Union Agency for Railways (ERA) maintains several TSIs relevant to rolling stock:
LOC&PAS TSI — covers locomotives and passenger rolling stock, including electric multiple units, diesel multiple units and passenger coaches.
WAG TSI — covers freight wagons. The current version is Commission Regulation (EU) No 321/2013, most recently updated by Commission Implementing Regulation (EU) 2025/458 of March 2025. The WAG TSI has been applicable from 01 January 2025 in its current form, covering technical design and production requirements for freight wagons operating on the Trans-European Rail Network. Railway Technology
NOI TSI — covers rolling stock noise, setting maximum permitted noise emission levels for both stationary and moving vehicles.
CR TSI (Control-Command and Signalling) — covers on-board ETCS and radio equipment, relevant to any rolling stock operating on lines equipped with ERTMS.
The Role of the Notified Body (NoBo)
TSI certification is carried out by Notified Bodies (NoBos). NNTR (National Notified Technical Rules) certification is handled by Designated Bodies (DeBos), following the same basic assessment and certification rules. TSI certification ensures that both European-wide standards and local requirements are met. Rail-wagons
A NoBo is an independent assessment body formally notified to the European Commission as competent to assess conformity with specific TSIs. Major European NoBos include TÜV SÜD, TÜV Rheinland, Bureau Veritas, Lloyd’s Register Rail and the Rail Safety and Standards Board (RSSB) in the UK.
The NoBo’s role is to review your technical file, witness tests, assess your quality management system and ultimately issue an EC certificate of conformity — the document that allows you to submit a vehicle authorisation application to the ERA (or ORR in the UK).
The TSI Certification Process Step by Step
Step 1: Gap Analysis
Before engaging a NoBo, a thorough gap analysis identifies which TSI requirements apply to your vehicle, which are already met by your design and which require additional design work, testing or documentation. This is the most valuable early investment in the certification process — it prevents expensive surprises during NoBo assessment.
Step 2: Technical File Preparation
The technical file is the core documentation package submitted to the NoBo. It includes design drawings, material specifications, calculation reports, simulation results and test plans. For a complete new vehicle type, preparing a compliant technical file typically requires 6–12 months of dedicated engineering work.
Step 3: Type Testing
The TSI specifies which tests must be performed and witnessed by the NoBo. For rolling stock this typically includes structural load tests, dynamic behaviour tests (track friendliness, ride quality), braking performance tests, noise measurements and electromagnetic compatibility (EMC) tests. Testing must be conducted at accredited test facilities.
Step 4: NoBo Assessment
The NoBo reviews the technical file, assesses test results against TSI requirements, conducts factory audits and raises any technical queries that must be resolved before certification can proceed. This phase typically takes 3–6 months for a straightforward vehicle type.
Step 5: EC Certificate of Conformity and Vehicle Authorisation
Once the NoBo is satisfied, they issue an EC certificate of conformity. This certificate, together with the technical file, forms the basis of the vehicle authorisation application submitted to the ERA’s One-Stop-Shop (OSS) for vehicles operating across multiple EU member states.
How Long Does TSI Certification Take?
For a completely new vehicle type with no prior certification history, the process from gap analysis to vehicle authorisation typically takes 18–36 months. For a variant of an existing certified type — for example, a new wagon variant based on a certified platform — the process can be significantly shorter, sometimes 6–12 months.
The most common causes of delay are incomplete technical files at NoBo submission, test failures requiring design modifications and unresolved technical queries during the NoBo assessment phase. All three are preventable with thorough upfront preparation.
When Does a Modification Require New TSI Certification?
Not every change to a rolling stock vehicle triggers a new certification process. The key question is whether the modification changes the vehicle’s authorised technical parameters. Replacing a component like-for-like with the same certified part requires only maintenance documentation. Fitting a component from a different supplier to the same specification may require a Designated Body assessment. Changing the vehicle’s axle load, speed capability, gauge compatibility or braking system almost always requires a new or amended vehicle authorisation.
TSI Certification Consultancy from Rolling Stock Connect+
Our TSI certification consultancy service supports rolling stock manufacturers and operators through every stage of the homologation process — from initial gap analysis through technical file preparation, NoBo coordination, type testing support and authorisation submission. We work across EU and UK markets and maintain working relationships with the major European Notified Bodies.
Contact us at sertcakar@milburg.co.uk to discuss your certification programme, or visit our TSI certification service page for more information.
Slug: what-is-tsi-certification-guide-rolling-stock-manufacturers Category: Industry Intelligence Target keywords: TSI certification, railway homologation, TSI consultancy, EU railway certification, Notified Body