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Guide · Rail & Metro · Built in India
EN 50126 is the CENELEC standard series for railway RAMS: the specification and demonstration of reliability, availability, maintainability and safety. Part 1, EN 50126-1:2017, sets out a generic RAMS process built on a 12-phase system lifecycle. Part 2, EN 50126-2:2017, gives a systems approach to safety, including how safety requirements and safety integrity levels are derived and apportioned. The series applies to signalling, rolling stock and fixed installations, and both parts were amended in 2024.
The short answer
EN 50126 (Railway applications, The specification and demonstration of Reliability, Availability, Maintainability and Safety (RAMS)) has two parts: Part 1, Generic RAMS process, which replaced EN 50126-1:1999, and Part 2, Systems approach to safety, which replaced the technical report CLC/TR 50126-2:2007. Both were prepared by CENELEC technical committee CLC/TC 9X. The series forms part of the railway-sector application of IEC 61508 and is independent of technology: it gives railway duty holders and suppliers a tailorable process for specifying RAMS requirements and showing they are met. It applies to new systems and, as far as reasonably practicable, to the modified parts of existing systems; unmodified systems do not have to be brought under it. Amendments EN 50126-1:2017/A1:2024 and EN 50126-2:2017/A1:2024 update both parts, and the international counterpart of Part 1, IEC 62278-1:2025, was published in July 2025.
Why it matters
Passenger announcement and information systems, IP CCTV and remote diagnostics units are subsystems of a train or station, so their reliability, availability and maintainability feed into the performance of the whole railway system, and some of their functions may form part of the safety argument, depending on the system safety analysis. EN 50126 is the process a railway duty holder and its suppliers use to turn system-level RAMS and safety targets into requirements for each subsystem, and to show that those requirements are met. It is also where integrity levels come from: the software standards EN 50657 and EN 50716 rely on the EN 50126 process to allocate them.
Key requirements
A summary of what railway specifications usually draw from EN 50126-1 and EN 50126-2. Always check the exact edition and amendments named in your tender.
EN 50126-1 organises RAMS work around a system lifecycle drawn as a V: concept; system definition and operational context; risk analysis and evaluation; specification of system requirements; architecture and apportionment of system requirements; design and implementation; manufacture; integration; system validation; system acceptance; operation, maintenance and performance monitoring; and decommissioning. Each phase has defined RAMS tasks, and the process can be tailored to the type and size of the system where this is justified.
Hazards are identified, and the risk they pose is analysed and evaluated. Risk can be shown to be acceptable by applying codes of practice, by comparison with a similar reference system, or by explicit risk estimation, the same three principles used in the EU common safety method for risk assessment, Regulation (EU) No 402/2013. EN 50126-1 gives guidance on calibrating a risk matrix, and EN 50126-2 covers the ALARP principle and deriving tolerable hazard rates.
EN 50126-2 gives methods to derive the safety requirements and safety integrity requirements for a system and to apportion them to its subsystems. For safety-related electronic functions it sets out a SIL table and how SIL 1 to SIL 4 are allocated, plus requirements for basic integrity. It does not allow safety integrity levels to be allocated to non-electronic functions.
Each lifecycle phase is verified, and the system is validated against its requirements before acceptance. EN 50126-1 also covers organisation and independence of roles, independent safety assessment and the safety case: the structured argument and evidence that a system is adequately safe. Its annexes give guidance on the RAMS plan and on RAM parameters such as reliability and maintainability measures.
Related standards
EN 50126 sits at the top of the railway safety standards and defines the system-level RAMS and safety process; together with other suitable standards it means separate compliance with IEC 61508 does not need to be shown. EN 50129 covers safety-related electronic systems for signalling, and the software standards EN 50128 and EN 50657, now superseded by EN 50716:2023, cover software; each takes its integrity level from the EN 50126 process. EN 50155 covers onboard electronic equipment itself, and cybersecurity is covered separately by CLC/TS 50701 and IEC 62443. Agree at tender stage which standard, edition and amendments apply.
Checklist
Use these points when writing a specification or comparing suppliers. Ask for documented, project-specific evidence for the exact product and configuration rather than relying on a datasheet statement.
Standard and edition: does the specification name EN 50126-1:2017 and EN 50126-2:2017, with or without the 2024 A1 amendments, or IEC 62278-1:2025?
RAM targets: which reliability, availability and maintainability targets, such as failure rates and repair times, apply to the subsystem, and how will they be demonstrated in service?
RAMS plan: will the supplier provide a RAMS plan covering the lifecycle phases, activities, roles and deliverables for its scope of supply?
Safety requirements: which hazards and safety requirements has the system safety process apportioned to the subsystem, and are any of its functions safety-related?
Integrity level: if a safety-related electronic function is involved, which SIL or basic integrity has been allocated to it, and by whom?
Evidence and assessment: what verification, validation and safety case evidence is expected, and is independent safety assessment required?
Maintenance and sourcing: how will maintainability, spares, obsolescence and performance monitoring be handled over the life of the fleet, and does your programme favour Built in India / Make in India manufacturing?
Envision TechWorks
Envision TechWorks products are designed, manufactured and tested in an ISO 9001:2015 facility in India: production-ready and Built in India for Make in India programmes. PAPIS onboard passenger announcement and information hardware is built to EN 50155, and production includes in-circuit and functional test, AOI and X-ray inspection, and thermal cycling. Share the RAMS requirements named in your tender, such as the standard edition, targets and any integrity levels, and the team can discuss your requirements.
Related
Rolling-stock software explained: basic integrity and SIL 1 to SIL 4, lifecycle, tools and its successor EN 50716.
Read the EN 50657 guide →Passenger announcement and information system for metro trainsets, with hardware built to EN 50155.
See PAPIS product details →Onboard and station IP surveillance with centralised video management and vandal-resistant cameras for rolling stock and stations.
See IP CCTV product details →Railway cybersecurity with IEC 62443: zones and conduits, security levels SL 1 to SL 4 and secure development for onboard and station systems.
Read the TS 50701 guide →Platform and concourse displays that show route maps, arrivals, service status and emergency messages on sunlight-readable screens, managed centrally from the control room.
See Station PIS product details →IoT remote diagnostics for locomotive and rolling stock fleets — edge data acquisition, cloud analytics and predictive maintenance alerts, Built in India.
See RDPMS product details →FAQ
EN 50126 is the CENELEC standard series Railway applications, The specification and demonstration of Reliability, Availability, Maintainability and Safety (RAMS). Part 1 sets out a generic RAMS process based on the system lifecycle, and Part 2 gives a systems approach to safety. The current editions are EN 50126-1:2017 and EN 50126-2:2017, each amended in 2024.
RAMS stands for reliability, availability, maintainability and safety. In railway terms it describes how dependably a system performs over its life: how often it fails, how much of the time it is ready for use, how quickly it can be restored, and how well risk to people is controlled. EN 50126 treats the four together so that conflicts between them can be managed.
EN 50126-1 defines the generic RAMS process: the 12-phase lifecycle, RAMS management and the safety case. EN 50126-2 supports its safety management process with methods for risk assessment, deriving and apportioning safety requirements, allocating SILs to safety-related electronic functions, and safety demonstration and acceptance.
No. EN 50126-2 states that it does not define rules or processes for certifying railway products against the standard, RAMS targets for specific railway applications, or an approval process by the safety authority. Those come from the project contract, the system safety process and the applicable regulations, so ask for project-specific evidence rather than a general claim.
Envision TechWorks designs, manufactures and tests products in an ISO 9001:2015 facility in India. Share the RAMS requirements named in your tender, such as the standard edition, reliability and maintainability targets and any integrity levels, and the team can discuss your requirements, Built in India.
Share the RAMS standard, edition and targets named in your tender, and the team will discuss your requirements, Built in India.