Rail transit electronic components EU testing and certification requirements

Understand the EN 50155, EN 50121 and EN 45545 standard families at a glance, and avoid the risks of outdated versions, wrong part selection and incomplete documentation

Who This Guide Is For

This document is written for enterprises with EU rail market access and testing needs:

How to use: Readers with limited time should prioritise Chapter 07 (cross-reference lookup) and Chapter 11 (pitfalls to avoid).

Table of Contents

• 01　Compliance Architecture
• 02　Legal Layer: Directives and TSIs
• 03　EN 45545 Fire Protection Standard Family
  • 3.1　Family Structure and the Seven Parts
  • 3.2　Hazard Level HL1–HL3 Classification
  • 3.3　EN 45545-2: Fire Behaviour of Materials and Components
  • 3.4　EN 45545-5: Fire Safety of Electrical Equipment
  • 3.5　CLC/TR 50750:2025: Implementation Guide for Electronic Equipment
• 04　EN 50121 Electromagnetic Compatibility Family
  • 4.1　Family Structure and Part Selection
  • 4.2　Part-by-Part Detail
  • 4.3　EMC Test Items for On-Board Equipment
  • 4.4　EN 50121-3-2 Revision Status
• 05　EN 50155:2026 Core Standard for On-Board Electronics
• 06　Functional Safety, Software and Mechanical Standards
• 07　Standard Family Cross-Reference Table
• 08　Performance Criteria: A / B / C
• 09　Presumption of Conformity and ERA Technical Opinions
• 10　Technical File Checklist
• 11　Common Pitfalls and Failure Modes
• 12　Implementation Path and Cost Control

01　Compliance Architecture

EU rail equipment compliance rests on a two-layer structure of mandatory legislation plus harmonised standards. Understanding this hierarchy is the prerequisite for avoiding rework of any technical file.

Four Standard Families for Component Products

Railway electronic components face four independent, concurrently applicable standard families. They address different layers of the problem, cannot substitute for one another, and none of them can be skipped.

### ⚠️ Key clarification: rail products do not bear CE marking

Rail vehicles and their subsystems are expressly excluded from the CE directive system. Conformity is demonstrated through EC Verification under the TSIs, carried out by a Notified Body (NoBo), which issues an EC verification declaration. Final authorisation is issued centrally by the European Union Agency for Railways (ERA) — since the Fourth Package, Member States no longer authorise individually. Note however that at equipment level, ordinary CE directives may still apply in parallel, and the corresponding conformity assessment must be completed separately.

02　Legal Layer: Directives and TSIs

Framework Legislation

TSIs Directly Relevant to Electronic Components

On TSI Telematics The former TAP TSI and TAF TSI are being merged into a single TSI Telematics. The draft (ED10) met strong objections from CER, EIM and UIP at RISC level, being considered insufficiently mature and likely to impose additional economic burden; it has not yet been put to the vote. Projects involving electronic systems for ticketing or freight consignment notes should design against the current TSIs and reserve interfaces for change.

03　EN 45545 Fire Protection Standard Family

EN 45545 is developed by CEN/TC 256 and was issued progressively from 2013. It is cited in the EU interoperability technical specifications and progressively replaces former national standards (such as DIN 5510-2, BS 6853, NF F 16-101). Since 2016 the family has been the mandatory fire safety baseline for rail vehicle materials across the EU. For electronic components, fire safety is not a whole-vehicle concern — EN 45545-2 directly addresses printed board assemblies (PBAs), enclosures, cabinets and racks, while EN 45545-5 sets out dedicated requirements for the electrical equipment itself.

3.1　Family Structure and the Seven Parts

Background on standard evolution The family has undergone prolonged revision since publication. Following the 2013 issue, TC 256 working groups pursued a range of work: verifying Parts 1 to 7, developing a new fire test standard for passenger seats, developing new smoke and toxicity test standards, and developing a Fire Containment and Control Systems (FCCS) standard. The seat and toxicity test items in particular proved far more labour-intensive than anticipated, and the COVID-19 pandemic compounded the delays. At present most parts have completed their 2024 revision (-3, -4, -6), while -1, -2, -5 and -7 remain on the 2013 baseline plus amendments. Mind the version gap when selecting.

3.2　Hazard Level HL1–HL3 Classification

Hazard levels are determined by EN 45545-1 from the combination of operational category (OC) and design category. They reflect evacuation difficulty rather than the intrinsic severity of a fire. Operational Categories

Design Categories

Hazard Level Matrix

Engineering implications

• HL1 — lowest requirements, for trams and surface-running light rail with good evacuation conditions
• HL2 — intermediate requirements, for most regional and intercity trains; includes tunnels with constrained evacuation
• HL3 — highest requirements, for underground metro vehicles, long-tunnel vehicles and sleeper trains where evacuation is severely restricted

Key classification principle The hazard level is determined by the characteristics of the complete vehicle — a component supplier’s own risk assessment cannot change it. Component manufacturers must select the R-requirements and test matrix against the HL level notified by the vehicle builder; they cannot self-reduce the requirement. Typical distribution: urban trams generally fall under HL1; sleeper trains running through long tunnels typically require HL3; metro vehicles are predominantly HL3.

3.3　EN 45545-2: Fire Behaviour of Materials and Components

EN 45545-2 is the core part of the fire safety system. It specifies fire performance requirements for materials and components used in the construction and fit-out of rail vehicles, assigning requirement sets according to hazard level.

The R-Requirement System

The standard manages materials and components through R-requirements, with 26 items numbered R1 to R26. Each R item corresponds to a product category and defines its applicable tests and limits.

Execution logic:

1. Confirm which R item the product falls under
2. Establish the target hazard level (HL1 / HL2 / HL3) notified by the vehicle builder
3. Look up the applicable tests and limits for that combination
4. Prepare specimens, test and assess against the criteria

Four Fire Performance Dimensions

For cables, hoses and seals, additional tests may apply, such as single-wire or bundle burning, smoke density and halogen acid gas release.

Important positioning of the standard EN 45545 does not certify products; it qualifies the performance of materials and components. This determines how documentation responsibility is distributed across the supply chain:

• Component manufacturers: test each material grade used in rail applications, issue test reports at the relevant R item and hazard level, record the wall thickness range and production-representative geometry tested, and provide these documents to vehicle builders and system integrators
• Vehicle builders / system integrators: aggregate supplier test reports to demonstrate that the complete vehicle meets the fire requirements for its category, and submit this to the competent authority
• Notified Bodies: assess conformity with the TSI fire provisions for locomotives and passenger rolling stock during vehicle type authorisation, relying on these documented evidence items

A gap in your documentation is a gap in the vehicle’s compliance evidence.

Material Modification and General Plastics

Two common judgement errors in engineering practice:

• General-purpose thermoplastics generally fail EN 45545-2 at HL2/HL3 without flame-retardant modification; dedicated flame-retardant grades are required
• Halogen-free flame-retardant grades have become the default choice for compliant rail components
• Solutions based on POM, PPS, PA66 and fluororubber (FKM) are well established. POM, with its high rigidity, wear resistance and dimensional stability, is widely used for seat armrests and door system components; PPS, with its high temperature and chemical resistance, dominates battery pack assemblies and connector housings

Regarding Material Colour

Once a material grade has been tested and classified within a defined wall thickness range, all colour variants within that range qualify without re-testing. This gives designers real freedom — specify the flame-retardant grade first, then manage colour through qualified pigment systems without triggering a new test cycle.

### ⚠️ Version status

The currently valid version of EN 45545-2 is 2020+A1:2023 (Official Journal citation status must be verified per version). Some national adoptions set transition periods — for example, the Slovak STN EN 45545-2 (corresponding to the 2020 edition) carries a withdrawal date of 2026-10-31, replaced by STN EN 45545-2+A1:2024-01. Secondary sources also reference a revision introducing new requirements for carbon-fibre-reinforced polymer (CFRP) skin-type structural parts (dual limits on PHRR and Dsmax), mandatory from 2026-10-01 for aviation-derived high-speed trains and cross-border EMU projects. If your project involves CFRP structural components, verify the official text and scope of this revision with the competent authority or test laboratory — this information comes from a secondary source and has not been directly confirmed against the Official Journal.

3.4　EN 45545-5: Fire Safety of Electrical Equipment

EN 45545-5 sets mandatory fire safety requirements for the selection and installation of electrical equipment. Its primary objectives are to minimise the probability of a fire starting from an electrical source and to limit the effects of any fire that may occur. Scope covers all electrical equipment and its installation on rail vehicles, including high- and low-voltage switchgear cabinets, power converters, transformers, batteries, wiring, cables and electronic control units. Applicable vehicle types: high-speed trains, regional and suburban trains, metros, trams, trolleybuses, track-guided buses and magnetic levitation vehicles.

Two Technical Pillars

Design Measures for Fire Prevention

Fire Containment and Control Measures

E-Requirement Sets

The central mechanism of EN 45545-5 is a set of requirement sets designated with an “E” prefix (e.g. E1, E4, E5). Each set defines a specific combination of preventive and protective measures tailored to the risk associated with that equipment type.

3.5　CLC/TR 50750:2025: Implementation Guide for Electronic Equipment

### 🆕 Published June 2025 — a key document for component suppliers

CLC/TR 50750:2025, Report on the use of EN 45545-2 and EN 45545-5 for electronic equipment on board rolling stock, was published by CENELEC/TC 9X on 5 June 2025 (date of availability 2025-06-06). It was produced by working group TC 9X/WG 29 and runs to 32 pages. This report is the most directly applicable official document currently available for fire safety compliance of electronic equipment.

Position and boundaries

Technical topics covered

Why this report matters most to component suppliers

Recommendation Component suppliers should use CLC/TR 50750:2025 together with EN 45545-2 and EN 45545-5. Although not mandatory, it reflects the current mainstream interpretation adopted by competent authorities and NoBos, and carries practical value in preparing technical files and handling clarification requests. A companion document, TR 50718:2025 Guidelines for the use of EN 45545-2 for Ni-Cd batteries on board rolling stock, should also be consulted if the product contains batteries.

04　EN 50121 Electromagnetic Compatibility Family

The EN 50121 family is the product-family EMC standard set for rail transport, maintained by CENELEC/TC 9X and covering everything from complete vehicles to individual apparatus, and from infrastructure to rolling stock. Its objectives are bidirectional: on one hand limiting electromagnetic leakage from the rail system to the outside world, and on the other ensuring equipment is not disturbed in the strong electromagnetic environment of railways — interference from traction equipment affecting signalling systems, for instance, can have serious consequences.

4.1　Family Structure and Part Selection

The family comprises 6 parts, divided into product-family standards and product standards:

Key selection rule — deciding whether “apparatus” falls under -3-2 or -4 / -5:

• Signalling and telecommunication equipment mounted on vehicles → EN 50121-3-2
• Signalling and telecommunication equipment installed inside the substation and connected to substation equipment → EN 50121-5
• Signalling and telecommunication equipment installed in wayside cabinets, interlocking areas or on platforms → EN 50121-4

This boundary is the most common source of error in EMC test plan preparation. Equipment installation location and interface topology must be clarified with the customer at project kick-off. Some parts have recently been subdivided into sub-parts such as -4-4 and -4-5 (covering rolling stock interference and cross-domain interference mitigation); check the latest part list before selecting.

Product family standards (-1, -2) take precedence over generic EMC standards (such as the EN 61000-6-x series). Where a product falls within the harmonic current or voltage fluctuation limits of EN 61000-3-2 / -3-3 / -3-11 / -3-12, those standards apply in parallel and must be satisfied alongside.

4.2　Part-by-Part Detail

EN 50121-1:2017 — General

The structural and content master of the family. Specifies the performance criteria applicable across the family; Clause 5 provides EMC management guidance.

Important limitation: this part alone is insufficient to presume conformity with the essential requirements of the EMC Directive. It must be used in conjunction with other parts. A technical file cannot cite -1 alone as evidence of conformity.

Excluded from scope: nuclear electromagnetic pulse, abnormal operating conditions (e.g. fault conditions), and induction effects of direct lightning strikes.

EN 50121-2:2017 — Emission of the Entire Railway System to the Outside World

Describes the electromagnetic environment of the entire railway system, including urban public transport and light rail; specifies emission limits at system boundaries; and provides measurement methods for verifying emissions together with cartography values for typical areas. Its significance lies in defining the boundary conditions between the rail system and the outside world — during equipment design, consideration must be given to whether the cumulative level of its own emissions, conducted or radiated along the line, exceeds limits at the system boundary.

EN 50121-3-1:2017 — Rolling Stock: Train and Complete Vehicle

Applies to all types of rail vehicle, covering traction stock and trainsets, including vehicles running on city streets. This is a whole-vehicle level verification standard, applicable once the complete vehicle has been integrated. While equipment is still in development, performing immunity testing on every complete vehicle is impractical — use EN 50121-3-2 instead.

EN 50121-3-2 — Rolling Stock: Apparatus ★

The core EMC standard for on-board electronic components. Applies to the emission and immunity requirements of electrical and electronic equipment intended for use on rail vehicles, at the stage of integrating the apparatus into the vehicle.

This part also solves a practical engineering problem: whole-vehicle immunity testing is often impractical, so an apparatus-level standard serves as the alternative means. This is why it is the most widely applied standard in the component supplier community.

EN 50121-4 — Signalling and Telecommunication Apparatus

Applies to signalling and telecommunication apparatus installed in interlocking areas, wayside cabinets and other wayside locations including platforms — vital equipment such as interlocking, signals, point machines and level crossings — together with power supply systems belonging to such apparatus.

For apparatus with numerous similar ports, the standard recommends testing a representative sample — 20% of ports, or at least four ports — covering the different termination types.

EN 50121-5 — Fixed Power Supply Installations and Apparatus

Applies to the EMC emission and immunity characteristics of electrical and electronic equipment and systems intended for use in railway fixed installations associated with power supply.

4.3　EMC Test Items for On-Board Equipment

Against EN 50121-3-2, tests for on-board electronic components are organised as emission and immunity, applied port by port. Emission (EMI)

Immunity (EMS)

Principle of test selection: not every port and every item requires full testing. Test items must be determined by the port types, configuration and actual operating conditions of the apparatus, and the basis for selection must be stated in the technical file — this is a key focus of NoBo review.

4.4　EN 50121-3-2 Revision Status

### ⚠️ Verify version status project by project

EN 50121-3-2:2016+A1:2019 remains the currently valid version. The revision prEN 50121-3-2:2025 is currently at the CENELEC enquiry stage, is not yet a European Standard, and must not be cited as a basis for compliance — this is a common error in practice. The revision will bring significant technical changes; continued monitoring is required before formal publication:

The new power frequency magnetic field test and the added surge requirements for specific supply system ports may affect existing designs; assess them early in the design stage.

05　EN 50155:2026 Core Standard for On-Board Electronics

### 🆕 Version update

EN 50155 was published as EN 50155:2026 on 1 May 2026 and entered into force on that date; the previous version EN 50155:2021 was withdrawn simultaneously. If technical specifications, test plans or customer specifications still reference the 2021 edition, they are out of date and must be updated immediately.

Scope

Covers control, regulation, protection, diagnostic and power supply electronic equipment installed on rail vehicles, together with related subsystem components such as external doors, on-board ETCS functionality and wheel slide protection. It comprises electronic components (resistors, capacitors, transistors, diodes, integrated circuits, hybrid integrated circuits, application-specific integrated circuits, wound components and relays) and recognised associated components (connectors, mechanical parts), mainly mounted on printed circuit boards. Sensors (e.g. current, voltage, speed) and semiconductor drive units for power electronic devices are within scope. Complete semiconductor drive units and power converters are covered by EN 61287-1.

Content framework

Covers operating conditions, design, documentation, testing and integration requirements, together with the hardware and software requirements necessary for compliant and reliable equipment. Note that the specific practices required to achieve a defined safety integrity level or functional safety are not covered by this standard, but the standard applies to the hardware of all rolling stock electronic equipment or systems performing safety-related functions.

Principal changes from the 2021 edition

Informative annexes cover system-level test methodology, severity of service conditions by vehicle location, example compliance summaries, the lifecycle of programmable devices, design suggestions and the relationship to EU directives.

06　Functional Safety, Software and Mechanical Standards

Functional Safety and RAMS

Software

Mechanical and Electrical

Parallel CE Directives

07　Standard Family Cross-Reference Table

Quick lookup for component suppliers — locate the governing standard by verification dimension.

08　Performance Criteria: A / B / C

The central mechanism of both the EN 50155 and EN 50121 systems is the performance criterion — every test must have its pass criterion declared in advance and verified item by item. Incorrect criterion selection is a frequent cause of technical files being rejected by the NoBo.

Power interruption test mapping example Select the criterion by interruption duration: ≤ 10 ms requires criterion A; 10 – 20 ms supports criterion B; > 20 ms may accept criterion C. Such mappings must be established in advance in the test plan and confirmed with the customer.

Criteria in EMC testing Immunity tests under the EN 50121 family likewise apply the performance criteria system specified in EN 50121-1. The applicable criterion level for each test item must be stated in the EMC management plan.

No performance criteria in fire testing The EN 45545 system uses limit-based assessment rather than performance criteria: results must directly satisfy the specific numerical limits of the relevant R item or E item, with no A/B/C grading. The corresponding check in the technical file is “measured value versus limit”.

09　Presumption of Conformity and ERA Technical Opinions

Citing a harmonised standard grants presumption of conformity, but only for the specific edition cited in the Official Journal (OJ). This is the decisive test of whether compliance is valid.

### ⚠️ Current status

The EN 50155 editions currently cited in the OJ are EN 50155:2007 and EN 50155:2021. Whether EN 50155:2026 achieves citation depends on OJ updates and adoption of an ERA technical opinion. New projects should adopt a dual-track approach: complete design against the 2026 edition while substantiating equivalence to the cited edition in the technical file. The same logic applies to the EN 50121 and EN 45545 families — the OJ-cited edition of each part must be verified individually; it cannot be assumed that the latest edition of every part is cited simply because the family as a whole is harmonised. For EN 45545, the cited editions include EN 45545-1:2013, EN 45545-2:2013+A1, EN 45545-3:2013, EN 45545-3:2024, EN 45545-4:2013, EN 45545-4:2024, EN 45545-5:2013+A1, EN 45545-6:2013 and EN 45545-7:2013 — note that the cited edition of -2 remains 2013+A1 while the 2024 revision is still in progress.

Role and current status of ERA Technical Opinions

A Technical Opinion issued by ERA under Regulation (EU) 2016/796 can declare a new version of a standard an AMOC (acceptable means of compliance), opening a route to compliance for the new version before the TSI revision completes, and usually allowing old and new versions to be used in parallel.

### ⚠️ Counter-example: a standard removed from the recognised list

EN 15227:2020+A1:2024 was removed from the list of voluntary applicable standards by ERA/OPI/2025-7, and may not be used pending a dedicated technical opinion. The revision had extended the relaxed crashworthiness requirements of the heavy-duty coupler scenario to any locomotive fitted with a central coupling system, including the Digital Automatic Coupler (DAC) — while the purpose of the retrofit is precisely to add DAC to existing locomotives, which carries a clear risk of degrading the current safety level.

10　Technical File Checklist

The technical file is the substantive vehicle of conformity assessment. The following is the minimum complete set for submission to NoBo review.

10.1　Design and Technical Description

• Data sheets, system block diagrams, circuit schematics
• Installation instructions (including mounting location, fixing method, clearance requirements)
• Interface definitions and port schedules, including EMC port classification (the basis of the EMC test plan)
• Bill of materials (BOM) and identification of critical items
• Wiring definitions and cable specifications
• EMC management plan (prepared per Clause 5 of EN 50121-1)
• Fire protection class declaration (target HL level and its basis, including the OC / design category combination)

10.2　Environmental Classes and Derating Declaration

• Selection basis for temperature classes (OT / ST)
• Humidity conditions, ingress protection level
• Vibration and shock levels, with the corresponding mounting locations
• Supply parameters (nominal voltage, variation range, interruption tolerance)
• Fire hazard level (EN 45545-1) together with material and component evidence
• Dielectric and insulation coordination information (EN 50124-1)

10.3　EMC Test Report

• Emission and immunity results listed port by port
• Achievement judgement for the performance criterion applicable to each test
• Justification for the selection of test items
• Explanation of representative port sampling (where many ports of the same type exist)
• Type test report, with evidence of laboratory accreditation (ISO/IEC 17025, ILAC MRA)

10.4　Fire Safety Documentation

10.5　Other Test Reports

• Itemised results of environmental, mechanical and electrical tests
• Definitions of type test and routine test procedures
• Deviation statements and technical justification

10.6　Software and Configuration Management

• Software integrity level (SPL) allocation basis and its correspondence to the system-level allocation analysis
• Software development lifecycle records per EN 50716:2023
• Static analysis, dynamic testing and code coverage reports
• Supporting tool qualification evidence (particularly compilers; T3 requires an in-service feedback dossier)
• Application data configuration items, release notes and change control records

10.7　Quality Management

• Production consistency control plan
• Supply chain and critical item traceability
• Product life commitment and service life basis (EN 50155 default L4)
• Maintainability and serviceability design description, including test equipment interfaces

11　Common Pitfalls and Failure Modes

The following 21 items are the issues most frequently causing technical file rejection or certification rework in practice, grouped by cause. They may be used as a pre-submission self-check list.

11.1　Version and Applicability Errors

11.2　Wrong EMC Part Selection

11.3　Design and Safety Deficiencies

11.4　Process and Documentation Gaps

12　Implementation Path and Cost Control

Twelve-Step Implementation Path

The three decisions that must be locked earliest Cost is driven principally by environmental class, EMC test item selection and fire hazard level. Completing the confirmation of these three before design freeze avoids rework and repeated testing caused by class escalation, wrong part selection or non-compliant material.

Cost Control Points

Notes

This document is based on publicly available information as of October 2026. EU rail technical legislation and harmonised standards update frequently, and the following versions are in progress. Verify against official texts before use:

• EN 50155:2026 (in force 2026-05-01) and EN 50129:2026 are progressing through Official Journal citation and ERA technical opinion adoption
• prEN 50121-3-2:2025 is at the CENELEC enquiry stage and is not yet a European Standard
• In the EN 45545 family, Parts -3, -4 and -6 have 2024 editions, while -1, -2, -5 and -7 remain on the 2013 baseline plus amendments
• A secondary source references new CFRP requirements in EN 45545-2 (PHRR and Dsmax limits, mandatory from 2026-10-01), which have not been directly verified against the Official Journal text. Projects involving CFRP structural components should confirm the scope with the competent authority or test laboratory

Before executing an actual project, rely on the official text on EUR-Lex, the CENELEC standards database, ERA technical opinion originals and version confirmation from the selected test laboratory. Clause numbers cited here are for quick reference; formal technical file references must be checked against the standard originals.