IEC 62425:2025 is applicable to safety-related electronic systems (including subsystems and equipment) for railway signalling applications. This document applies to generic systems (i.e. generic products or systems defining a class of applications), as well as to systems for specific applications. The scope of this document, and its relationship with other IEC and CENELEC standards, are shown in Figure 1. This document is applicable only to the functional safety of systems. It does not deal with other aspects of safety such as the occupational health and safety of personnel. While functional safety of systems clearly can have an impact on the safety of personnel, there are other aspects of system design which can also affect occupational health and safety and which are not covered by this document. Cybersecurity aspects of functional safety are addressed only to a limited extent. This document applies to all the phases of the life cycle of a safety-related electronic system, focusing in particular on phases 5 (architecture and apportionment of system requirements) to 10 (system acceptance) as defined in IEC 62278-1: -
Requirements for systems which are not related to safety are outside the scope of this document. This document is not applicable to existing systems, subsystems or equipment which had already been accepted prior to the development of this document. However, so far as reasonably practicable, it is applicable to modifications and extensions to existing systems, subsystems and equipment. This document is primarily applicable to systems, subsystems or equipment which have been specifically designed and manufactured for railway signalling applications. It is also applicable, so far as reasonably practicable, to general-purpose or industrial equipment (e.g. power supplies, display screens or other commercial off the shelf items), which is procured for use as part of a safety-related electronic system. This document is aimed at railway duty holders, railway suppliers, and assessors as well as at safety authorities, although it does not define an approval process to be applied by the safety authorities. This second edition cancels and replaces the first edition published in 2007. This edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous edition:
a) a better alignment with the life cycle phases defined in IEC 62278-1 has been made;
b) Clause 5 describes the requirements that apply to the development of safety-related electronic systems (until phase 9 of the life cycle);
c) Clause 8 focuses on the requirements for safety acceptance and approval of safety-related electronic systems and subsequent phases;
d) requirements and guidance have been added in Clause 6 on the following topics:
- reuse of pre-existing systems,
- safety-related tools,
- impact of cybersecurity threats on functional safety,
- specific application safety cases;
e) requirements for the structure and content of the safety case are now defined in a dedicated Clause 7;
f) Annex A has been updated for the specification and allocation of safety integrity requirements;
g) the content of former Annex D has been merged with Annex B, and the content has been changed from informative to normative;
h) the status of Annex E has been changed from informative to normative;
i) an Annex F has been added as an informative annex on User Programmable Integrated Circuits.
A more detailed comparison of changes between IEC 62425:2007 and this document can be found in Annex G.