scope:

This European Prestandard is applicable to safety-related electronic systems (including sub-systems and equipment) for railway signalling applications. This standard is primarily intended to apply "fail-safe" and "high-integrity" systems (e.g.: main-line signalling and ATP systems), rather than medium or low-integrity systems. 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. It 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. It also 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. It is not applicable to existing systems/subsystems/equipment (i.e. those which had already been accepted prior to the creation of this standard). However, as far as reasonable practicable, this standard should be applied to modifications and extensions to existing systems, subsystems and equipment. It applies to the functional safety of railway signalling systems.