scope:

Is primarily intended to apply to "fail-safe" and "high-integrity" systems (e.g.: main-line signalling and ATP systems), rather than medium or low-integrity systems (e.g.: running "on-sight", or in marshalling yards where points are moved as vehicles approach). However, in all cases the hazard analysis and risk assessment processes defined in EN 50126 are necessary, in order to identify the safety requirements for each particular situation. This includes those cases where the analysis and assessment reveal that no safety requirements exist; however, once this conclusion has been reached (i.e.: that the situation is non-safety-related), and provided the conclusion is not revised as a consequence of later changes, this safety standard ceases to be applicable. Applies to the acceptance of the specification, design, construction, installation, acceptance, operation, maintenance and modification/extension of complete systems, and also to individual subsystems and equipment within the complete system. Applies to generic subsystems and equipment (both application-independent and those intended for a particular class of application), and also to systems/subsystems/equipment for specific applications.