ISO 26262-9:2018
(Main)Road vehicles — Functional safety — Part 9: Automotive safety integrity level (ASIL)-oriented and safety-oriented analyses
Road vehicles — Functional safety — Part 9: Automotive safety integrity level (ASIL)-oriented and safety-oriented analyses
This document is intended to be applied to safety-related systems that include one or more electrical and/or electronic (E/E) systems and that are installed in series production road vehicles, excluding mopeds. This document does not address unique E/E systems in special vehicles such as E/E systems designed for drivers with disabilities. NOTE Other dedicated application-specific safety standards exist and can complement the ISO 26262 series of standards or vice versa. Systems and their components released for production, or systems and their components already under development prior to the publication date of this document, are exempted from the scope of this edition. This document addresses alterations to existing systems and their components released for production prior to the publication of this document by tailoring the safety lifecycle depending on the alteration. This document addresses integration of existing systems not developed according to this document and systems developed according to this document by tailoring the safety lifecycle. This document addresses possible hazards caused by malfunctioning behaviour of safety-related E/E systems, including interaction of these systems. It does not address hazards related to electric shock, fire, smoke, heat, radiation, toxicity, flammability, reactivity, corrosion, release of energy and similar hazards, unless directly caused by malfunctioning behaviour of safety-related E/E systems. This document describes a framework for functional safety to assist the development of safety-related E/E systems. This framework is intended to be used to integrate functional safety activities into a company-specific development framework. Some requirements have a clear technical focus to implement functional safety into a product; others address the development process and can therefore be seen as process requirements in order to demonstrate the capability of an organization with respect to functional safety. This document does not address the nominal performance of E/E systems. This document specifies the requirements for Automotive Safety Integrity Level (ASIL)-oriented and safety-oriented analyses, including the following: — requirements decomposition with respect to ASIL tailoring; — criteria for coexistence of elements; — analysis of dependent failures; and — safety analyses. Annex A provides an overview on objectives, prerequisites and work products of this document.
Véhicules routiers — Sécurité fonctionnelle — Partie 9: Analyses liées aux niveaux d'intégrité de sécurité automobile (ASIL) et à la sécurité
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INTERNATIONAL ISO
STANDARD 26262-9
Second edition
2018-12
Road vehicles — Functional safety —
Part 9:
Automotive safety integrity level
(ASIL)-oriented and safety-oriented
analyses
Véhicules routiers — Sécurité fonctionnelle —
Partie 9: Analyses liées aux niveaux d'intégrité de sécurité automobile
(ASIL) et à la sécurité
Reference number
ISO 26262-9:2018(E)
©
ISO 2018
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ISO 26262-9:2018(E)
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© ISO 2018
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ISO 26262-9:2018(E)
Contents Page
Foreword .v
Introduction .vii
1 Scope . 1
2 Normative references . 2
3 Terms and definitions . 2
4 Requirements for compliance . 2
4.1 Purpose . 2
4.2 General requirements . 2
4.3 Interpretations of tables . 3
4.4 ASIL-dependent requirements and recommendations . 3
4.5 Adaptation for motorcycles . 3
4.6 Adaptation for trucks, buses, trailers and semi-trailers. 4
5 Requirements decomposition with respect to ASIL tailoring . 4
5.1 Objectives. 4
5.2 General . 4
5.3 Inputs to this clause . 5
5.3.1 Prerequisites . 5
5.3.2 Further supporting information . 5
5.4 Requirements and recommendations . 5
5.5 Work products . 9
6 Criteria for coexistence of elements . 9
6.1 Objectives. 9
6.2 General . 9
6.3 Inputs to this clause . 9
6.3.1 Prerequisites . 9
6.3.2 Further supporting information .10
6.4 Requirements and recommendations .10
6.5 Work products .10
7 Analysis of dependent failures .11
7.1 Objectives.11
7.2 General .11
7.3 Inputs to this clause .12
7.3.1 Prerequisites .12
7.3.2 Further supporting information .12
7.4 Requirements and recommendations .12
7.5 Work products .14
8 Safety analyses .14
8.1 Objectives.14
8.2 General .15
8.3 Inputs to this clause .16
8.3.1 Prerequisites .16
8.3.2 Further supporting information .16
8.4 Requirements and recommendations .16
8.5 Work products .18
Annex A (informative) Overview of and document flow of Automotive Safety Integrity Level
(ASIL)-oriented and safety-oriented analyses .19
Annex B (informative) Example architectures for Coexistence of elements and
Decomposition of requirements .23
Annex C (informative) Framework for Identifying Dependent Failures .25
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ISO 26262-9:2018(E)
Bibliography .29
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ISO 26262-9:2018(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/directives ).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/patents ).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following
URL: www .iso .org/iso/foreword .html .
This document was prepared by Technical Committee ISO/TC 22, Road vehicles, Subcommittee SC 32,
Electrical and electronic components and general system aspects.
This edition of ISO 26262 series of standards cancels and replaces the edition ISO 26262:2011 series of
standards, which has been technically revised and includes the following main changes:
— requirements for trucks, buses, trailers and semi-trailers;
— extension of the vocabulary;
— more detailed objectives;
— objective oriented confirmation measures;
— management of safety anomalies;
— references to cyber security;
— updated target values for hardware architecture metrics;
— guidance on model based development and software safety analysis;
— evaluation of hardware elements;
— additional guidance on dependent failure analysis;
— guidance on fault tolerance, safety related special characteristics and software tools;
— guidance for semiconductors;
— requirements for motorcycles; and
— general restructuring of all parts for improved clarity.
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ISO 26262-9:2018(E)
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www .iso .org/members .html.
A list of all parts in the ISO 26262 series can be found on the ISO website.
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ISO 26262-9:2018(E)
Introduction
The ISO 26262 series of standards is the adaptation of IEC 61508 series of standards to address the
sector specific needs of electrical and/or electronic (E/E) systems within road vehicles.
This adaptation applies to all activities during the safety lifecycle of safety-related systems comprised
of electrical, electronic and software components.
Safety is one of the key issues in the development of road vehicles. Development and integration of
automotive functionalities strengthen the need for functional safety and the need to provide evidence
that functional safety objectives are satisfied.
With the trend of increasing technological complexity, software content and mechatronic
implementation, there are increasing risks from systematic failures and random hardware failures,
these being considered within the scope of functional safety. ISO 26262 series of standards includes
guidance to mitigate these risks by providing appropriate requirements and processes.
To achieve functional safety, the ISO 26262 series of standards:
a) provides a reference for the automotive safety lifecycle and supports the tailoring of the activities
to be performed during the lifecycle phases, i.e., development, production, operation, service and
decommissioning;
b) provides an automotive-specific risk-based approach to determine integrity levels [Automotive
Safety Integrity Levels (ASILs)];
c) uses ASILs to specify which of the requirements of ISO 26262 are applicable to avoid unreasonable
residual risk;
d) provides requirements for functional safety management, design, implementation, verification,
validation and confirmation measures; and
e) provides requirements for relations between customers and suppliers.
The ISO 26262 series of standards is concerned with functional safety of E/E systems that is achieved
through safety measures including safety mechanisms. It also provides a framework within which
safety-related systems based on other technologies (e.g. mechanical, hydraulic and pneumatic) can be
considered.
The achievement of functional safety is influenced by the development process (including such
activities as requirements specification, design, implementation, integration, verification, validation
and configuration), the production and service processes and the management processes.
Safety is intertwined with common function-oriented and quality-oriented activities and work
products. The ISO 26262 series of standards addresses the safety-related aspects of these activities and
work products.
Figure 1 shows the overall structure of the ISO 26262 series of standards. The ISO 26262 series of
standards is based upon a V-model as a reference process model for the different phases of product
development. Within the figure:
— the shaded “V”s represent the interconnection among ISO 26262-3, ISO 26262-4, ISO 26262-5,
ISO 26262-6 and ISO 26262-7;
— for motorcycles:
— ISO 26262-12:2018, Clause 8 supports ISO 26262-3;
— ISO 26262-12:2018, Clauses 9 and 10 support ISO 26262-4;
— the specific clauses are indicated in the following manner: “m-n”, where “m” represents the number
of the particular part and “n” indicates the number of the clause within that part.
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ISO 26262-9:2018(E)
EXAMPLE “2-6” represents ISO 26262-2:2018, Clause 6.
Figure 1 — Overview of the ISO 26262 series of standards
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INTERNATIONAL STANDARD ISO 26262-9:2018(E)
Road vehicles — Functional safety —
Part 9:
Automotive safety integrity level (ASIL)-oriented and
safety-oriented analyses
1 Scope
This document is intended to be applied to safety-related systems that include one or more electrical
and/or electronic (E/E) systems and that are installed in series production road vehicles, excluding
mopeds. This document does not address unique E/E systems in special vehicles such as E/E systems
designed for drivers with disabilities.
NOTE Other dedicated application-specific safety standards exist and can complement the ISO 26262 series
of standards or vice versa.
Systems and their components released for production, or systems and their components already under
development prior to the publication date of this document, are exempted from the scope of this edition.
This document addresses alterations to existing systems and their components released for production
prior to the publication of this document by tailoring the safety lifecycle depending on the alteration.
This document addresses integration of existing systems not developed according to this document and
systems developed according to this document by tailoring the safety lifecycle.
This document addresses possible hazards caused by malfunctioning behaviour of safety-related E/E
systems, including interaction of these systems. It does not address hazards related to electric shock,
fire, smoke, heat, radiation, toxicity, flammability, reactivity, corrosion, release of energy and similar
hazards, unless directly caused by malfunctioning behaviour of safety-related E/E systems.
This document describes a framework for functional safety to assist the development of safety-
related E/E systems. This framework is intended to be used to integrate functional safety activities
into a company-specific development framework. Some requirements have a clear technical focus to
implement functional safety into a product; others address the development process and can therefore
be seen as process requirements in order to demonstrate the capability of an organization with respect
to functional safety.
This document does not address the nominal performance of E/E systems.
This document specifies the requirements for Automotive Safety Integrity Level (ASIL)-oriented and
safety-oriented analyses, including the following:
— requirements decomposition with respect to ASIL tailoring;
— criteria for coexistence of elements;
— analysis of dependent failures; and
— safety analyses.
Annex A provides an overview on objectives, prerequisites and work products of this document.
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ISO 26262-9:2018(E)
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 26262-1:2018, Road vehicles — Functional safety — Part 1: Vocabulary
ISO 26262-2:2018, Road vehicles — Functional safety — Part 2: Management of Functional Safety
ISO 26262-3:2018, Road vehicles — Functional safety — Part 3: Concept phase
ISO 26262-4:2018, Road vehicles — Functional safety — Part 4: Product development at the system level
ISO 26262-5:2018, Road vehicles — Functional safety — Part 5: Product development at the hardware level
ISO 26262-6:2018, Road vehicles — Functional safety — Part 6: Product development at the software level
ISO 26262-7:2018, Road vehicles — Functional safety — Part 7: Production, operation, service and
decommissioning
ISO 26262-8:2018, Road vehicles — Functional safety — Part 8: Supporting processes
3 Terms and definitions
For the purposes of this document, the terms, definitions and abbreviated terms given in
ISO 26262-1:2018 apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at http: //www .electropedia .org/
— ISO Online browsing platform: available at https: //www .iso .org/obp
4 Requirements for compliance
4.1 Purpose
This clause describes how:
a) to achieve compliance with the ISO 26262 series of standards;
b) to interpret the tables used in the ISO 26262 series of standards; and
c) to interpret the applicability of each clause, depending on the relevant ASIL(s).
4.2 General requirements
When claiming compliance with the ISO 26262 series of standards, each requirement shall be met,
unless one of the following applies:
a) tailoring of the safety activities in accordance with ISO 26262-2 has been performed that shows
that the requirement does not apply; or
b) a rationale is available that the non-compliance is acceptable and the rationale has been evaluated
in accordance with ISO 26262-2.
Informative content, including notes and examples, is only for guidance in understanding, or for
clarification of the associated requirement, and shall not be interpreted as a requirement itself or as
complete or exhaustive.
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ISO 26262-9:2018(E)
The results of safety activities are given as work products. “Prerequisites” are information which shall
be available as work products of a previous phase. Given that certain requirements of a clause are
ASIL-dependent or may be tailored, certain work products may not be needed as prerequisites.
“Further supporting information” is information that can be considered, but which in some cases is not
required by the ISO 26262 series of standards as a work product of a previous phase and which may be
made available by external sources that are different from the persons or organizations responsible for
the functional safety activities.
4.3 Interpretations of tables
Tables are normative or informative depending on their context. The different methods listed in a table
contribute to the level of confidence in achieving compliance with the corresponding requirement. Each
method in a table is either:
a) a consecutive entry (marked by a sequence number in the leftmost column, e.g. 1, 2, 3), or
b) an alternative entry (marked by a number followed by a letter in the leftmost column, e.g. 2a, 2b, 2c).
For consecutive entries, all listed highly recommended and recommended methods in accordance with
the ASIL apply. It is allowed to substitute a highly recommended or recommended method by others
not listed in the table, in this case, a rationale shall be given describing why these comply with the
corresponding requirement. If a rationale can be given to comply with the corresponding requirement
without choosing all entries, a further rationale for omitted methods is not necessary.
For alternative entries, an appropriate combination of methods shall be applied in accordance with the
ASIL indicated, independent of whether they are listed in the table or not. If methods are listed with
different degrees of recommendation for an ASIL, the methods with the higher recommendation should
be preferred. A rationale shall be given that the selected combination of methods or even a selected
single method complies with the corresponding requirement.
NOTE A rationale based on the methods listed in the table is sufficient. However, this does not imply a bias
for or against methods not listed in the table.
For each method, the degree of recommendation to use the corresponding method depends on the ASIL
and is categorized as follows:
— “++” indicates that the method is highly recommended for the identified ASIL;
— “+” indicates that the method is recommended for the identified ASIL; and
— “o” indicates that the method has no recommendation for or against its usage for the identified ASIL.
4.4 ASIL-dependent requirements and recommendations
The requirements or recommendations of each sub-clause shall be met for ASIL A, B, C and D, if not
stated otherwise. These requirements and recommendations refer to the ASIL of the safety goal. If ASIL
decomposition has been performed at an earlier stage of development, in accordance with Clause 5, the
ASIL resulting from the decomposition shall be met.
If an ASIL is given in parentheses in the ISO 26262 series of standards, the corresponding sub-clause
shall be considered as a recommendation rather than a requirement for this ASIL. This has no link with
the parenthesis notation related to ASIL decomposition.
4.5 Adaptation for motorcycles
For items or elements of motorcycles for which requirements of ISO 26262-12 are applicable,
the requirements of ISO 26262-12 supersede the corresponding requirements in this document.
Requirements of ISO 26262-2 that are superseded by ISO 26262-12 are defined in Part 12.
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ISO 26262-9:2018(E)
4.6 Adaptation for trucks, buses, trailers and semi-trailers
Content that is intended to be unique for trucks, buses, trailers and semi-trailers (T&B) is indicated
as such.
5 Requirements decomposition with respect to ASIL tailoring
5.1 Objectives
If ASIL decomposition is applied, the objectives of this clause are:
a) to ensure that a safety requirement is decomposed into redundant safety requirements at the next
level of detail, and that these are allocated to sufficiently independent design elements; and
b) to apply ASIL decomposition according to permitted ASIL decomposition schemas.
NOTE The independence mentioned in this clause is technical independence and not organizational
independence (see ISO 26262-1:2018, 3.78)
5.2 General
The ASIL of the safety goals of an item under development is propagated throughout the item's
development. Starting from safety goals, the safety requirements are derived and refined during the
development phases. The ASIL, as an attribute of the safety goal, is inherited by each subsequent safety
requirement. The safety requirements are allocated to architectural elements, starting with functional
safety requirements allocated to elements of system architectural design and finally resulting in safety
requirements allocated to the hardware and/or software elements.
ASIL decomposition is a method of ASIL tailoring during the concept and development phases. During
the safety requirements allocation process, benefit can be obtained from architectural decisions
including the existence of sufficiently independent architectural elements. This offers the opportunity
— to implement safety requirements redundantly by these independent architectural elements, and
— to assign a potentially lower ASIL to (some of) these decomposed safety requirements.
If the architectural elements are not sufficiently independent, then the redundant requirements and
the architectural elements inherit the initial ASIL.
ASIL decomposition is an ASIL tailoring measure that can be applied to the functional, technical,
hardware or software safety requirements of the item or element.
In general, ASIL decomposition allows the apportioning of the ASIL of a safety requirement between
several elements that ensure compliance with the same safety requirement addressing the same safety
goal. ASIL decomposition between an intended functionality and its corresponding safety mechanism
is allowed under certain conditions (see 5.4.7).
The requirements specific to the random hardware failures, including the evaluation of the hardware
architectural metrics and the evaluation of safety goal violations due to random hardware failures (see
ISO 26262-5:2018, Clause 8 and Clause 9) remain unchanged by ASIL decomposition.
An example architecture decomposition is given in Annex B.
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ISO 26262-9:2018(E)
5.3 Inputs to this clause
5.3.1 Prerequisites
The following information shall be available:
— the safety requirements at the level at which the ASIL decomposition
...
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