CEN/TR 17696:2021

SLOVENSKI STANDARD
01-december-2021
Železniške naprave - Vzdrževanje vozil - Vodilo za prepoznavanje in ravnanje z
varnostno kritičnimi sestavnimi deli železniških vozil
Railway applications - Vehicle Maintenance - Guide for identification and management of
Safety Critical Components for railway vehicles
Bahnanwendungen - Fahrzeuginstandhaltung - Leitfaden zur Identifizierung und dem
Management von Sicherheitskritischen Komponenten für Schienenfahrzeuge
Applications Ferroviaires - Maintenance des véhicules - Guide pour l’identification et le
management des Composants Critiques de Sécurité pour les véhicules ferroviaires
Ta slovenski standard je istoveten z: CEN/TR 17696:2021
ICS:
45.060.01 Železniška vozila na splošno Railway rolling stock in
general
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

CEN/TR 17696
TECHNICAL REPORT
RAPPORT TECHNIQUE
October 2021
TECHNISCHER BERICHT
ICS 45.060.01
English Version
Railway applications - Vehicle Maintenance - Guide for
identification and management of Safety Critical
Components for railway vehicles
Applications Ferroviaires - Maintenance des véhicules - Bahnanwendungen - Fahrzeuginstandhaltung -
Guide pour l'identification et le management des Leitfaden zur Identifizierung und dem Management
Composants Critiques de Sécurité pour les véhicules von Sicherheitskritischen Komponenten für
ferroviaires Schienenfahrzeuge

This Technical Report was approved by CEN on 20 September 2021. It has been drawn up by the Technical Committee CEN/TC
256.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2021 CEN All rights of exploitation in any form and by any means reserved Ref. No. CEN/TR 17696:2021 E
worldwide for CEN national Members.

Contents           Page
Foreword . 3
Introduction . 4
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 5
4 Symbols and abbreviations . 6
5 SCCs definition . 6
5.1 General . 6
5.2 Identification of accidents and consequences related to SCCs definition . 7
6 SCCs requirements: actors and vehicles involved . 8
6.1 General . 8
6.2 SCCs requirements and actors involved . 8
6.3 SCCs requirements and their applicability to railway vehicles . 9
6.4 Tables of SCCs requirements with actors and vehicles involved . 10
7 SCCs management process and identification . 13
7.1 SCCs management process . 13
7.2 SCCs deliverables. 18
7.3 Methods for the identification of SCCs . 19
7.3.1 General . 19
7.3.2 Identification of SCCs through a bottom-up method . 20
7.3.3 Identification of SCCs through a top-down method . 24
Annex A (informative) SCCs references capture . 27
Annex B (informative) Comprehension of SCCs definition . 34
Annex C (informative) Considerations on specific wording of the SCCs definition . 39
Annex D (informative) Using statistics of “serious accidents” . 40
Bibliography . 42

Foreword
This document (CEN/TR 17696:2021) has been prepared by Technical Committee CEN/TC 256 “Railway
applications”, the secretariat of which is held by DIN.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
Any feedback and questions on this document should be directed to the users’ national standards body.
A complete listing of these bodies can be found on the CEN website.
Introduction
The following document is focused on the new concept of Safety Critical Component (SCC) introduced in
the recent framework of the European legislation.
1 Scope
The objective of this document is to provide an overview of the SCCs requirements captured from the
current legislation and the actors involved in their fulfilment.
In addition, this document aims to promote a common understanding of those requirements together
with practical arrangements to fulfil them in a proper way and giving guidance for the SCCs identification
and management.
The objective of the document is neither to produce an applicable list of SCCs nor to provide for examples
of SCCs.
This document is applicable to vehicles only. The definition of “vehicle” is as in Art. 3(21) of the Safety
Directive [3].
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
renewal
any major substitution work on a subsystem or part subsystem which does not change the overall
performance of the subsystem
3.2
upgrade
upgrading
any major modification work on a subsystem or part subsystem which improves the overall performance
of the subsystem
3.3
refurbishment
programme of interior/exterior work, other than routine maintenance or repair, undertaken on a railway
vehicle to restore or enhance the level of design and performance
3.4
engineering change
change to a railway vehicle, including control software, in the area of design, construction or maintenance
which affects, or potentially affects, conformity to applicable requirements
4 Symbols and abbreviations
For the purposes of this document, the following abbreviations apply with reference to Article 15 of
Regulation (EU) 2018/545 (Practical arrangements for vehicle authorisation).
Table 1 — Abbreviations
Symbol Designation
SCC/SCCs Safety Critical Component/s
REX Return on Experience
TSI Technical Specification for Interoperability
REF Reference
CSI Common Safety Indicator
CSM Common Safety Method
ECM Entity in Charge of Maintenance
RU Railway Undertaking
5 SCCs definition
5.1 General
The definition of SCCs is the combination of REF13 or REF14 (see Annex A for REFs captured) and the
definition of “serious accident” as in Article 3(12) of the Safety Directive [3].
The definition of “safety critical components” in REF13 and REF14 is the same. Here below REF14 is
shown in detail:
REF14
The Annex to Regulation (EU) No 1302/2014 (TSI Loc & Pas) is amended as follows:
……
(39) point (4) of section 4.2.12.1 is replaced by the following:
‘(4) The documentation also includes a list of safety critical components. Safety critical components are
components for which a single failure has a credible potential to lead directly to a serious accident as defined
in Article 3(12) of Directive (EU) 2016/798.
The “serious accident” captured from Article 3(12) of the Safety Directive [3] is defined as:
Article 3 Definitions
(12) ‘serious accident’ means any train collision or derailment of trains resulting in the death of at least
one person or serious injuries to five or more persons or extensive damage to rolling stock, the infrastructure
or the environment, and any other accident with the same consequences which has an obvious impact on
railway safety regulation or the management of safety; ‘extensive damage’ means damage that can be
immediately assessed by the investigating body to cost at least EUR 2 million in total;
Based on the above-mentioned references, the following is the complete definition of Safety Critical
Components:
Safety critical components are components for which a single failure has a credible potential to lead
directly to:
— any train collision or derailment of trains resulting in the death of at least one person or serious
injuries to five or more persons or extensive damage to rolling stock, the infrastructure or the
environment; and
— any other accident with the same consequences which has an obvious impact on railway safety
regulation or the management of safety;
‘extensive damage’ means damage that can be immediately assessed by the investigating body to cost at
least EUR 2 million in total.
5.2 Identification of accidents and consequences related to SCCs definition
As shown in 5.1, the SCCs definition is fundamentally based on the occurrence of a “serious accident”.
The “serious accident” definition identifies typical railway accidents and their specific consequences,
which aids the comprehension of the SCCs definition.
Based on the definitions reported in Annex B, a list of typical railway accidents and a list of consequences
related to the definition of SCCs can be compiled. These lists can be used for subsequent analyses in order
to identify the safety critical components.
The following is a non-exhaustive list of accidents, related to the definition of SCCs, caused by the single
failure of a vehicle’s component:
Table 2 — SCCs - List of accidents
derailment
collision collision of train with obstacle collision of train with rail
vehicle
level crossing accident
accident to persons involving persons falling from trains passengers in station hurt by
rolling stock in motion train
persons hit by a railway vehicle
or by an object attached to, or
that has become detached from,
the vehicle
fire/explosion fires in an area inside or outside
the railway premises
dangerous goods release during pollution of an area by liquid,
transport solid or gas release of goods
objects detached from trains
electrocution
other accidents causing damage material damage to an area (e.g. damage to rolling stocks
trees pulled down by rolling stock
in motion, infrastructure
damage, railway premises, …)
A more complete list of accidents to be considered can be obtained through experience, historical data
and statistics.
The consequences to be considered as the effect of the accident are the following (single effect or
combination of effects):
Table 3 — SCCs – List of consequences
death of at least one person
serious injuries to five or more persons
damage to rolling stock, the infrastructure or the environment assessed to cost at least 2 million EUR in
total
6 SCCs requirements: actors and vehicles involved
6.1 General
The recent framework of the European legislation contains many new inputs related specifically to SCCs.
These inputs state the SCCs requirements to be accomplished and the actors involved in their
accomplishment.
Annex A contains the list of SCCs references and requirements captured from the legislation.
6.2 SCCs requirements and actors involved
The following table collects the outcome of the capture process in Annex A splitting the SCCs
requirements among the different actors involved.
Table 4 — SCCs Requirements capture
Doc. Short Title REF N. Actors involved
Ref.
N°
[1] Agency REF1 Agency
regulation
[2] Interoperability REF2 Commission
Directive
REF3 All
[3] Safety Directive REF4 Commission
REF5 ECM, ECM functions
[4] ECM Regulation REF6 Manufacture
...