IEC 62425:2025
(Main)Railway applications - Communication, signalling and processing systems - Safety related electronic systems for signalling
Railway applications - Communication, signalling and processing systems - Safety related electronic systems for signalling
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.
Applications ferroviaires - Systèmes de signalisation, de télécommunications et de traitement - Systèmes électroniques de sécurité pour la signalisation
La CEI 62425:2024 s'applique aux systèmes électroniques liés à la sécurité (y compris les sous-systèmes et équipements) pour les applications de signalisation ferroviaire.
Le présent document s'applique aux systèmes génériques (c'est-à-dire aux produits ou systèmes génériques définissant une classe d'applications), ainsi qu'aux systèmes destinés à des applications spécifiques.
Ce document s'applique uniquement à la sécurité fonctionnelle des systèmes. Il ne traite pas d'autres aspects de la sécurité tels que la santé et la sécurité au travail du personnel. Bien que la sécurité fonctionnelle des systèmes puisse clairement avoir un impact sur la sécurité du personnel, il existe d'autres aspects de la conception du système qui peuvent également affecter la santé et la sécurité au travail et qui ne sont pas couverts par ce document. Les aspects de cybersécurité de la sécurité fonctionnelle ne sont abordés que dans une mesure limitée.
Le présent document s'applique à toutes les phases du cycle de vie d'un système électronique relatif à la sécurité, en se concentrant en particulier sur les phases 5 (architecture et répartition des exigences du système) à 10 (acceptation du système) telles que définies dans la CEI 62278-1 : -.
Les exigences relatives aux systèmes qui ne sont pas liées à la sécurité sortent du domaine d'application du présent document.
Ce document ne s'applique pas aux systèmes, sous-systèmes ou équipements existants qui avaient déjà été acceptés avant l'élaboration de ce document. Toutefois, dans la mesure du possible, elle s'applique aux modifications et extensions des systèmes, sous-systèmes et équipements existants.
Le présent document s'applique principalement aux systèmes, sous-systèmes ou équipements spécialement conçus et fabriqués pour les applications de signalisation ferroviaire. Elle s'applique également, dans la mesure du possible, aux équipements industriels ou à usage général (par exemple, alimentations électriques, écrans d'affichage ou autres articles commerciaux disponibles dans le commerce), qui sont achetés pour être utilisés dans le cadre d'un système électronique lié à la sécurité.
Ce document s'adresse aux titulaires d'obligations ferroviaires, aux fournisseurs ferroviaires et aux évaluateurs ainsi qu'aux autorités de sécurité, bien qu'il ne définisse pas de processus d'approbation à appliquer par les autorités de sécurité.
Cette deuxième édition annule et remplace la première édition publiée en 2007. Cette édition constitue une révision technique.
Cette édition inclut les modifications techniques importantes suivantes par rapport à l'édition précédente :
a) un meilleur alignement avec les phases du cycle de vie définies dans la CEI 62278-1 a été réalisé ;
b) L'article 5 décrit les exigences qui s'appliquent au développement de systèmes électroniques liés à la sécurité (jusqu'à la phase 9 du cycle de vie) ;
c) L'article 8 se concentre sur les exigences relatives à l'acceptation et à l'approbation de sécurité des systèmes électroniques liés à la sécurité et aux phases ultérieures ;
d) des exigences et des orientations ont été ajoutées à l'article 6 sur les sujets suivants :
1) réutilisation de systèmes préexistants,
2) outils liés à la sécurité,
3) impact des menaces de cybersécurité sur la sécurité fonctionnelle,
4) cas spécifiques de sécurité des applications ;
e) les exigences relatives à la structure et au contenu du dossier de sécurité sont désormais définies dans un article 7 dédié ;
f) L'annexe A a été mise à jour pour la spécification et l'attribution des exigences en matière d'intégrité de sécurité ;
g) le contenu de l'ancienne annexe D a été fusionné avec l'annexe B, et le contenu est passé d'informatif à normatif ;
h) le statut de l'Annexe E est passé d'informatif à normatif ;
i) une annexe F a été ajoutée à titre d'annexe informative sur les circuits intégrés programmables par l'utilisateur.
Une comparaison plus détaillée des changements entre la CEI 62
General Information
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Standards Content (Sample)
IEC 62425 ®
Edition 2.0 2025-05
COMMENTED VERSION
INTERNATIONAL
STANDARD
Railway applications – Communication, signalling and processing systems –
Safety related electronic systems for signalling
ICS 45.060.01 ISBN 978-2-8327-0420-2
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– 2 – IEC 62425:2025 CMV © IEC 2025
CONTENTS
FOREWORD . 6
INTRODUCTION . 9
1 Scope . 10
2 Normative references . 11
3 Terms, definitions and abbreviated terms . 12
3.1 Terms and definitions . 12
3.2 Abbreviated terms . 22
4 Overall framework of this document . 23
5 Requirements for developing safety-related electronic systems . 25
5.1 General . 25
5.2 The quality management process . 25
5.3 The safety management process. 27
5.3.1 General . 27
5.3.2 Guideline for structuring documentation . 27
5.3.3 Safety life cycle . 28
5.3.4 Safety organization . 28
5.3.5 Safety plan . 30
5.3.6 Hazard log . 31
5.3.7 Safety requirements specification . 31
5.3.8 System design for safety . 31
5.3.9 Safety operation and maintenance plan . 32
5.3.10 Safety verification . 32
5.3.11 Safety validation . 33
5.3.12 Safety qualification tests . 34
5.3.13 Management of safety-related application conditions . 35
5.3.14 Safety justification . 36
5.3.15 Independent safety assessment . 37
6 Requirements for elements following different life cycles . 37
6.1 General . 37
6.2 Use of pre-existing items . 38
6.2.1 General . 38
6.2.2 Requirements for use of complete pre-existing systems . 39
6.2.3 Requirements for use of pre-existing equipment . 39
6.3 Safety-related tools for electronic systems . 40
6.4 Physical security and cybersecurity. 41
7 The safety case: structure and content . 42
7.1 The safety case structure . 42
7.2 The technical safety report . 44
7.3 Generic and specific safety cases . 53
7.4 Provisions for the specific application safety case . 53
7.5 Dependencies between safety cases . 54
8 System safety acceptance and subsequent phases . 55
8.1 System safety acceptance process . 55
8.2 Operation, maintenance and performance monitoring . 59
8.3 Modification and retrofit . 59
8.4 Decommissioning and disposal . 59
Annex A (normative) Safety integrity levels . 60
A.1 General . 60
A.2 Safety requirements . 60
A.3 Safety integrity . 61
A.4 Determination of safety integrity requirements . 61
A.4.1 General . 61
A.4.2 Risk assessment . 63
A.4.3 Hazard control . 65
A.4.4 Identification and treatment of new hazards arising from design . 71
A.5 Allocation of SILs . 72
A.5.1 General aspects . 72
A.5.2 Relationship between SIL and associated TFFR . 73
Annex B (normative) Management of faults for safety-related functions . 75
B.1 General . 75
B.2 General concepts . 75
B.2.1 Detection and negation times . 75
B.2.2 Composition of two independent items . 76
B.3 Effects of faults . 77
B.3.1 Effects of single faults . 77
B.3.2 Independence of items. 79
B.3.3 Detection of single faults . 84
B.3.4 Action following detection (retention of safe state) . 87
B.3.5 Effects of multiple faults . 88
B.3.6 Defence against systematic faults . 91
Annex C (normative) Identification of hardware component failure modes . 92
C.1 General . 92
C.2 General procedure . 92
C.3 Procedure for integrated circuits . 92
C.4 Procedure for components with inherent physical properties . 93
C.5 General provisions concerning component failure modes . 93
Annex D (informative) Example of THR/TFFR/FR apportionment and SIL allocation. 111
Annex E (normative) Techniques and measures for the avoidance of systematic faults
and the control of random and systematic faults . 113
E.1 General . 113
E.2 Tables of techniques and measures . 115
Annex F (informative) Guidance on User Programmable Integrated Circuits. 123
F.1 General . 123
F.1.1 Purpose . 123
F.1.2 Terminology and context . 123
F.2 UPIC life cycle . 124
F.2.1 General . 124
F.2.2 Organization, roles, responsibilities and personnel competencies . 126
F.2.3 UPIC Requirements . 126
F.2.4 UPIC Architecture and Design . 127
F.2.5 Logic Component Design . 128
F.2.6 Logic Component Coding . 128
F.2.7 Logic Component Verification . 128
F.2.8 UPIC Physical Implementation . 128
– 4 – IEC 62425:2025 CMV © IEC 2025
F.2.9 UPIC Integration . 128
F.2.10 UPIC Validation . 128
F.2.11 Requirements for use of pre-existing logic components . 128
F.3 Detailed technical requirements for UPIC . 128
F.3.1 Guidance on safety architecture . 128
F.3.2 Protection against random faults – architectural principles . 129
F.3.3 Protection against systematic faults – techniques and measures . 129
Annex G (informative) Changes in this document compared to IEC 62425:2007. 138
Bibliography .
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