ISO 26262-3:2011

INTERNATIONAL ISO
STANDARD 26262-3
First edition
2011-11-15
Road vehicles — Functional safety —
Part 3:
Concept phase
Véhicules routiers — Sécurité fonctionnelle —
Partie 3: Phase de projet
Reference number
©
ISO 2011
©  ISO 2011
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Published in Switzerland
ii © ISO 2011 – All rights reserved

Contents Page
Foreword . iv
Introduction . v
1  Scope . 1
2  Normative references . 1
3  Terms, definitions and abbreviated terms . 2
4  Requirements for compliance . 2
4.1  General requirements . 2
4.2  Interpretations of tables . 2
4.3  ASIL-dependent requirements and recommendations . 3
5  Item definition . 3
5.1  Objectives . 3
5.2  General . 3
5.3  Inputs to this clause . 3
5.4  Requirements and recommendations . 4
5.5  Work products . 4
6  Initiation of the safety lifecycle . 5
6.1  Objectives . 5
6.2  General . 5
6.3  Inputs to this clause . 5
6.4  Requirements and recommendations . 5
6.5  Work products . 6
7  Hazard analysis and risk assessment . 6
7.1  Objectives . 6
7.2  General . 7
7.3  Inputs to this clause . 7
7.4  Requirements and recommendations . 7
7.5  Work products . 12
8  Functional safety concept . 12
8.1  Objectives . 12
8.2  General . 12
8.3  Inputs to this clause . 13
8.4  Requirements and recommendations . 14
8.5  Work products . 16
Annex A (informative) Overview and document flow of concept phase . 17
Annex B (informative) Hazard analysis and risk assessment . 18
Bibliography . 25

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.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
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.
ISO 26262-3 was prepared by Technical Committee ISO/TC 22, Road vehicles, Subcommittee SC 3,
Electrical and electronic equipment.
ISO 26262 consists of the following parts, under the general title Road vehicles — Functional safety:
 Part 1: Vocabulary
 Part 2: Management of functional safety
 Part 3: Concept phase
 Part 4: Product development at the system level
 Part 5: Product development at the hardware level
 Part 6: Product development at the software level
 Part 7: Production and operation
 Part 8: Supporting processes
 Part 9: Automotive Safety Integrity Level (ASIL)-oriented and safety-oriented analyses
 Part 10: Guideline on ISO 26262
iv © ISO 2011 – All rights reserved

Introduction
ISO 26262 is the adaptation of IEC 61508 to comply with needs specific to the application sector 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 of future automobile development. New functionalities not only in areas such
as driver assistance, propulsion, in vehicle dynamics control and active and passive safety systems
increasingly touch the domain of system safety engineering. Development and integration of these
functionalities will strengthen the need for safe system development processes and the need to provide
evidence that all reasonable system 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. ISO 26262 includes guidance to
avoid these risks by providing appropriate requirements and processes.
System safety is achieved through a number of safety measures, which are implemented in a variety of
technologies (e.g. mechanical, hydraulic, pneumatic, electrical, electronic, programmable electronic) and
applied at the various levels of the development process. Although ISO 26262 is concerned with functional
safety of E/E systems, it provides a framework within which safety-related systems based on other
technologies can be considered. ISO 26262:
a) provides an automotive safety lifecycle (management, development, production, operation, service,
decommissioning) and supports tailoring the necessary activities during these lifecycle phases;
b) provides an automotive-specific risk-based approach to determine integrity levels [Automotive Safety
Integrity Levels (ASIL)];
c) uses ASILs to specify applicable requirements of ISO 26262 so as to avoid unreasonable residual risk;
d) provides requirements for validation and confirmation measures to ensure a sufficient and acceptable
level of safety being achieved;
e) provides requirements for relations with suppliers.
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 by the management processes.
Safety issues are intertwined with common function-oriented and quality-oriented development activities and
work products. ISO 26262 addresses the safety-related aspects of development activities and work products.
Figure 1 shows the overall structure of this edition of ISO 26262. ISO 26262 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 between ISO 26262-3, ISO 26262-4, ISO 26262-5,
ISO 26262-6 and ISO 26262-7;
 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.
EXAMPLE “2-6” represents Clause 6 of ISO 26262-2.
Figure 1 — Overview of ISO 26262

vi © ISO 2011 – All rights reserved

1. Vocabulary
2. Management of functional safety
2-6 Safety management during the concept phase 2-7 Safety management after the item´s release
2-5 Overall safety management
and the product development for production
3. Concept phase 4. Product development at the system level 7. Production and operation
4-5 Initiation of product
4-11 Release for production
3-5 Item definition 7-5 Production
development at the system level
4-10 Functional safety assessment
7-6 Operation, service
3-6 Initiation of the safety lifecycle
4-6 Specification of the technical
(maintenance and repair), and
safety requirements
decommissioning
4-9 Safety validation
3-7 Hazard analysis and risk
assessment
4-7 System design 4-8 Item integration and testing
3-8 Functional safety
concept
5. Product development at the 6. Product development at the
hardware level software level
5-5 Initiation of product 6-5 Initiation of product
development at the hardware level development at the software level
5-6 Specification of hardware
safety requirements
5-7 Hardware design 6-7 Software architectural design
5-8 Evaluation of the hardware 6-8 Software unit design and
architectural metrics implementation
5-9 Evaluation of the safety goal
6-9 Software unit testing
violations due to random hardware
failures
6-10 Software integration and
5-10 Hardware integration and
testing
testing
6-11 Verification of software safety
requirements
8. Supporting processes
8-5 Interfaces within distributed developments 8-10 Documentation
8-6 Specification and management of safety requirements 8-11 Confidence in the use of software tools
8-7 Configuration management 8-12 Qualification of software components
8-8 Change management 8-13 Qualification of hardware components
8-9 Verification 8-14 Proven in use argument
9. ASIL-oriented and safety-oriented analyses
9-5 Requirements decomposition with respect to ASIL tailoring 9-7 Analysis of dependent failures
9-6 Criteria for coexistence of elements 9-8 Safety analyses
10. Guideline on ISO 26262
INTERNATIONAL STANDARD ISO 26262-3:2011(E)

Road vehicles — Functional safety —
Part 3:
Concept phase
1 Scope
ISO 26262 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 passenger cars with a maximum gross
vehicle mass up to 3 500 kg. ISO 26262 does not address unique E/E systems in special purpose vehicles
such as vehicles designed for drivers with disabilities.
Systems and their components released for production, or systems and their components already under
development prior to the publication date of ISO 26262, are exempted from the scope. For further
development or alterations based on systems and their components released for production prior to the
publication of ISO 26262, only the modifications will be developed in accordance with ISO 26262.
ISO 26262 addresses possible hazards caused by malfunctioning behaviour of E/E safety-related 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 E/E safety-related systems.
ISO 26262 does not address the nominal performance of E/E systems, even if dedicated functional
performance standards exist for these systems (e.g. active and passive safety systems, brake systems,
Adaptive Cruise Control).
This part of ISO 26262 specifies the requirements for the concept phase for automotive applications, including
the following:
 item definition,
 initiation of the safety lifecycle,
 hazard analysis and risk assessment, and
 functional safety concept.
2 Normative references
The following referenced documents are indispensable for the application 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 26262-1:2011, Road vehicles — Functional safety — Part 1: Vocabulary
ISO 26262-2:2011, Road vehicles — Functional safety — Part 2: Management of functional safety
ISO 26262-4:2011, Road vehicles — Functional safety — Part 4: Product development at the system level
ISO 26262-8:2011, Road vehicles — Functional safety — Part 8: Supporting processes
ISO 26262-9:2011, Road vehicles — Functional safety — Part 9: Automotive Safety Integrity Level (ASIL)-
oriented and safety-oriented analyses
3 Terms, definitions and abbreviated terms
For the purposes of this document, the terms, definitions and abbreviated terms given in ISO 26262-1:2011
apply.
4 Requirements for compliance
4.1 General requirements
When claiming compliance with ISO 26262, each requirement shall be complied with, unless one of the
following applies:
a) tailoring of the safety activities in accordance with ISO 26262-2 has been planned and shows that the
requirement does not apply, or
b) a rationale is available that the non-compliance is acceptable and the rationale has been assessed in
accordance with ISO 26262-2.
Information marked as a “NOTE” or “EXAMPLE” 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.
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 ISO 26262 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.
4.2 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 methods shall be applied as recommended in accordance with the ASIL. If
methods other than those listed are to be applied, a rationale shall be given that these fulfil the corresponding
requirement.
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 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.
2 © ISO 2011 – All rights reserved

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;
 “o” indicates that the method has no recommendation for or against its usage for the identified ASIL.
4.3 ASIL-dependent requirements and recommendations
The requirements or recommendations of each subclause shall be complied with 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 ISO 26262-9:2011,
Clause 5, the ASIL resulting from the decomposition shall be complied with.
If an ASIL is given in parentheses in ISO 26262, the corresponding subclause 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.
5 Item definition
5.1 Objectives
The first objective is to define and describe the item, its dependencies on, and interaction with, the
environment and other items.
The second objective is to support an adequate understanding of the item so that the activities in subsequent
phases can be performed.
5.2 General
This clause lists the requirements and recommendations for establishing the definition of the item with regard
to its functionality, interfaces, environmental conditions, legal requirements, hazards, etc. This definition
serves to provide sufficient information about the item to the persons who conduct the subsequent subphases:
“Initiation of safety lifecycle” (see Clause 6), “Hazard analysis and risk assessment” (see Clause 7) and
“Functional safety concept” (see Clause 8).
NOTE Table A.1 provides an overview of objectives, prerequisites and work products of the concept phase.
5.3 Inputs to this clause
5.3.1 Prerequisites
None.
5.3.2 Further supporting information
The following information can be considered:
 any information that already exists concerning the item, e.g. a product idea, a project sketch, relevant
patents, the results of pre-trials, the documentation from predecessor items, relevant information on other
independent items.
5.4 Requirements and recommendations
5.4.1 The functional and non-functional requirements of the item as well as the dependencies between the
item and its environment shall be made available.
NOTE 1 Requirements can be classified as safety-related after safety goals and their respective ASIL have been
defined.
NOTE 2 The required information is a necessary input for the item definition although it is not safety-related. If not
already available, its generation can be triggered by the requirements of this clause.
This information includes:
a) the functional concept, describing the purpose and functionality, including the operating modes and states
of the item;
b) the operational and environmental constraints;
c) legal requirements (especially laws and regulations), national and international standards;
d) behaviour achieved by similar functions, items or elements, if any;
e) assumptions on behaviour expected from the item; and
f) potential consequences of behaviour shortfalls including known failure modes and hazards.
NOTE This can include known safety-related incidents on similar items.
5.4.2 The boundary of the item, its interfaces, and the assumptions concerning its interaction with other
items and elements, shall be defined considering:
a) the elements of the item;
NOTE The elements could also be based on other technology
b) the assumptions concerning the effects of the item's behaviour on other items or elements, that is the
environment of the item;
c) interactions of the item with other items or elements;
d) functionality required by other items, elements and the environment;
e) functionality required from other items, elements and the environment;
f) the allocation and distribution of functions among the involved systems and elements; and
g) the operating scenarios which impact the functionality of the item.
5.5 Work products
Item definition resulting from the requirements of 5.4.
4 © ISO 2011 – All rights reserved

6 Initiation of the safety lifecycle
6.1 Objectives
The first objective of the initiation of the safety lifecycle is to make the distinction between a new item
development and a modification to an existing item (see ISO 26262-2:2011, Figure 2).
The second objective is to define the safety lifecycle activities (see ISO 26262-2:2011, Figure 2) that will be
carried out in the case of a modification.
6.2 General
Based on the item definition, the safety lifecycle is initiated by distinguishing between either a new
development, or a modification of an existing item. In the case of a modification, the tailoring of the
safety-related activities takes place.
6.3 Inputs to this clause
6.3.1 Prerequisites
The following information shall be available:
 item definition in accordance with 5.5.
6.3.2 Further supporting information
The following information can be considered:
 any existing information, not already covered by the item definition, being useful for conducting the impact
analysis.
EXAMPLE Product concept, requests for change, implementation planning, proven in use argument.
6.4 Requirements and recommendations
6.4.1 Determination of the development category
6.4.1.1 It shall be determined whether the item is either a new development, or if it is a modification of an
existing item or its environment:
a) in the case of a new development, the development shall be continued with the hazard analysis and risk
assessment in accordance with Clause 7;
b) in the case of a modification of the item or its environment the applicable lifecycle subphases and
activities shall be determined in accordance with 6.4.2.
NOTE A proven in use argument can be applied to modification (see ISO 26262-8:2011, Clause 14).
6.4.2 Impact analysis and possible tailored safety lifecycle, in the case of modification
6.4.2.1 An impact analysis shall be carried out in order to identify and describe the intended modification
applied to the item or its environment and to assess the impact of these modifications.
NOTE 1 Modifications to the item include design modifications and implementation modifications. Design modification
can result from requirements modifications (e.g. functional or performance enhancement or cost optimisation).
Implementation modifications do not affect the specification or performance of the item, but only the implementation
features.
EXAMPLE Implementation modifications can result from corrections of software, or the use of new development or
production tools.
NOTE 2 Modifications to configuration data or calibration data are considered as modifications to the item if they
impact the functional behaviour of the item.
NOTE 3 Modifications to the environment of the item can result from the installation of the item in a new target
environment (e.g. another vehicle variant) or by the upgrading of other items or elements interacting with (or in the vicinity
of) the item.
6.4.2.2 The impact analysis shall identify and address areas affected by the modifications to the item and
modifications between previous and future conditions of use of the item, including:
a) operational situations and operating modes;
b) interfaces with the environment;
c) installation characteristics such as location within the vehicle, vehicle configurations and variants; and
d) a range of environmental conditions e.g. temperature, altitude, humidity, vibrations, Electromagnetic
Interference (EMI) and fuel types.
6.4.2.3 The implication of the modification with regard to functional safety shall be identified and
described.
6.4.2.4 The affected work products that need to be updated shall be identified and described.
6.4.2.5 The safety activities shall be tailored in accordance with the applicable lifecycle phases.
6.4.2.6 Tailoring shall be based on the results of the impact analysis.
6.4.2.7 The results of tailoring shall be included in the safety plan in accordance with ISO 26262-2:2011,
6.4.3.
6.4.2.8 The affected work products shall be reworked.
NOTE The affected work products include the validation plan (see ISO 26262-4).
6.4.2.9 In the case of missing work products or work products that do not comply with ISO 26262, the
necessary activities to reach ISO 26262 compliance shall be determined.
6.5 Work products
6.5.1 Impact analysis resulting from the requirements of 6.4.2.1 to 6.4.2.4.
6.5.2 Safety plan (refined) resulting from the requirements 6.4.2.5 to 6.4.2.9.
7 Hazard analysis and risk assessment
7.1 Objectives
The objective of the hazard analysis and risk assessment is to identify and to categorise the hazards that
malfunctions in the item can trigger and to formulate the safety goals related to the prevention or mitigation of
the hazardous events, in order to avoid unreasonable risk.
6 © ISO 2011 – All rights reserved

7.2 General
Hazard analysis, risk assessment and ASIL determination are used to determine the safety goals for the item
such that an unreasonable risk is avoided. For this, the item is evaluated with regard to its potential hazardous
events. Safety goals and their assigned ASIL are determined by a systematic evaluation of hazardous events.
The ASIL is determined by considering the estimate of the impact factors, i.e. severity, probability of exposure
and controllability. It is based on the item’s functional behaviour; therefore, the detailed design of the item
does not necessarily need to be known.
7.3 Inputs to this clause
7.3.1 Prerequisites
The following information shall be available:
 item definition in accordance with 5.5.
7.3.2 Further supporting information
The following information can be considered:
 impact analysis, if applicable (see 6.5.1); and
 relevant information on other independent items (from external source).
7.4 Requirements and recommendations
7.4.1 Initiation of the hazard analysis and risk assessment
7.4.1.1 The hazard analysis and risk assessment shall be based on the item definition.
7.4.1.2 The item without internal safety mechanisms shall be evaluated during the hazard analysis and
risk assessment, i.e. safety mechanisms intended to be implemented or that have already been implemented
in predecessor items shall not be considered in the hazard analysis and risk assessment.
NOTE 1 In the evaluation of an item, available and sufficiently independent external measures can be beneficial.
EXAMPLE Electronic stability control can mitigate the effect of failures in chassis systems by providing increased
control if it is shown to be available and sufficiently independent.
NOTE 2 Safety mechanisms of the item that are intended to be implemented or that have already been implemented
are incorporated as part of the functional safety concept.
7.4.2 Situation analysis and hazard identification
7.4.2.1 Situation analysis
7.4.2.1.1 The operational situations and operating modes in which an item's malfunctioning behaviour will
result in a hazardous event shall be described, both for cases when the vehicle is correctly used and when it
is incorrectly used in a foreseeable way.
NOTE The operational situation addresses the limits within which the item is expected to behave in a safe manner.
For example, a normal passenger road vehicle is not expected to travel cross-country at high speed.
7.4.2.2 Hazard identification
7.4.2.2.1 The hazards shall be determined systematically by using adequate techniques.
NOTE Techniques such as brainstorming, checklists, quality history, FMEA and field studies can be used for the
extraction of hazards at the item level.
7.4.2.2.2 Hazards shall be defined in terms of the conditions or behaviour that can be observed at the
vehicle level.
NOTE 1 In general, each hazard will have a variety of potential causes related to the item's implementation but they do
not need to be considered in the hazard analysis and risk assessment for the definition of the conditions or behaviour,
which result from a functional behaviour of the item.
NOTE 2 Only hazards associated with the item itself can be considered, every other system (external measure) is
presumed to be functioning correctly provided it is sufficiently independent.
7.4.2.2.3 The hazardous events shall be determined for relevant combinations of operational situations and
hazards.
7.4.2.2.4 The consequences of hazardous events shall be identified.
NOTE If failures at an item level induce the loss of several functions of the item, then the situation analysis and
hazard identification considers the resulting hazardous events from the combined malfunctional behaviour of the item or
vehicle.
EXAMPLE Failure of the vehicle electrical power supply system can cause the simultaneous loss of a number of
functions including “engine torque”, “power assisted steering” and “forward illumination”.
7.4.2.2.5 If there are hazards identified in 7.4.2.2 that are outside of the scope of ISO 26262 (see Clause 1),
then the need for appropriate measures to mitigate or control these hazards shall be highlighted and reported
to the responsible persons.
NOTE As these hazards are outside the scope of ISO 26262, hazard classification is not necessary.
7.4.3 Classification of hazardous events
7.4.3.1 All hazardous events identified in 7.4.2.3 shall be classified, except those that are outside the
scope of ISO 26262.
NOTE If classification of a given hazard with respect to severity, probability of exposure or controllability is difficult to
make, it is classified conservatively, i.e. whenever there is any doubt, a higher ASIL classification is given rather than a
lower.
7.4.3.2 The severity of potential harm shall be estimated based on a defined rationale for each hazardous
event. The severity shall be assigned to one of the severity classes S0, S1, S2 or S3 in accordance with
Table 1.
NOTE 1 The risk assessment of hazardous events focuses on the harm to each person potentially at risk – including
the driver or the passengers of the vehicle causing the hazardous event, and other persons potentially at risk such as
cyclists, pedestrians or occupants of other vehicles. The description of the Abbreviated Injury Scale (AIS) can be used for
characterising the severity and can be found in Annex B. For informative examples of different types of severity and
accidents see Annex B.
NOTE 2 The severity class can be based on a combination of injuries, and this can lead to a higher evaluation of the
severity than would result from just looking at single injuries.
NOTE 3 The estimate considers reasonable sequences of events for the situation being evaluated.
NOTE 4 The severity determination is based on a representative sample of individuals for the target markets.
8 © ISO 2011 – All rights reserved

Table 1 — Classes of severity
Class
S0 S1 S2 S3
Light and moderate Severe and life-threatening Life-threatening injuries (survival
Description No injuries
injuries injuries (survival probable) uncertain), fatal injuries

7.4.3.3 The severity class S0 may be assigned if the hazard analysis determines that the consequences
of a malfunctioning behaviour of the item are clearly limited to material damage and do not involve harm to
persons. If a hazard is assigned to severity class S0, no ASIL assignment is required.
7.4.3.4 The probability of exposure of each operational situation shall be estimated based on a defined
rationale for each hazardous event. The probability of exposure shall be assigned to one of the probability
classes, E0, E1, E2, E3 and E4, in accordance with Table 2.
NOTE 1 For classes E1 to E4, the difference in probability from one E class to the next is an order of magnitude.
NOTE 2 The exposure determination is based on a representative sample of operational situations for the target
markets.
NOTE 3 For details and examples related to the probability of exposure see Annex B.
Table 2 — Classes of probability of exposure regarding operational situations
Class
E0 E1 E2 E3 E4
Description Incredible Very low probability Low probability Medium probability High probability

7.4.3.5 The number of vehicles equipped with the item shall not be considered when estimating the
probability of exposure.
NOTE The evaluation of the probability of exposure is performed assuming each vehicle is equipped with the item.
This means that the argument “the probability of exposure can be reduced, because the item is not present in every
vehicle (as only some vehicles are equipped with the item)” is not valid.
7.4.3.6 Class E0 may be used for those situations that are suggested during hazard analysis and risk
assessment, but which are considered to be extremely unusual, or incredible, and therefore not followed up. A
rationale shall be recorded for the exclusion of these situations. If a hazard is assigned to exposure class E0,
no ASIL assignment is required.
EXAMPLE E0 can be used in the case of “force majeure” risk (see Clause B.3).
7.4.3.7 The controllability of each hazardous event, by the driver or other persons potentially at risk, shall
be estimated based on a defined rationale for each hazardous event. The controllability shall be assigned to
one of the controllability classes C0, C1, C2 and C3 in accordance with Table 3.
NOTE 1 For classes C1 to C3, the difference in probability from one C class to the next is an order of magnitude.
NOTE 2 The evaluation of the controllability is an estimate of the probability that the driver or other persons potentially
at risk are able to gain sufficient control of the hazardous event, such that they are able to avoid the specific harm. For this
purpose, the parameter C is used, with the classes C1, C2 and C3, to classify the potential of avoiding harm. It is assumed
that the driver is in an appropriate condition to drive (e.g. he/she is not tired), has the appropriate driver training (he/she
has a driver's licence) and is complying with all applicable legal regulations, including due care requirements to avoid risks
to other traffic participants. Some examples, which serve as an interpretation of these classes, are listed in Table B.4.
Reasonably foreseeable misuse is considered.
NOTE 3 Where the hazardous event is not related to the control of the vehicle direction and speed, e.g. potential limb
entrapment in moving parts, the controllability can be an estimate of the probability that the person at risk is able to
remove themselves, or to be removed by others from the hazardous situation. When considering controllability, note that
the person at risk might not be familiar with the operation of the item.
NOTE 4 When controllability involves the actions of multiple traffic participants, the controllability assessment can be
based on the controllability of the vehicle with the malfunctioning item, and the likely action of other participants.
Table 3 — Classes of controllability
Class
C0 C1 C2 C3
Description Controllable in general Simply controllable Normally controllable Difficult to control or uncontrollable

7.4.3.8 Class C0 may be used for hazards addressing the unavailability of the item if they do not affect
the safe operation of the vehicle (e.g. some driver assistance systems). Class C0 may also be assigned if
dedicated regulations exist that specify the functional performance with respect to a defined hazard, and C0 is
argued using the corresponding existing experience concerning sufficient controllability. If a hazard is
assigned to the controllability class C0, no ASIL assignment is required.
EXAMPLE A dedicated regulation is the certification of a vehicle system with a precise definition of forces or
acceleration values in the case of a failure.
7.4.4 Determination of ASIL and safety goals
7.4.4.1 An ASIL shall be determined for each hazardous event using the parameters "severity",
"probability of exposure" and "controllability" in accordance with Table 4.
NOTE 1 Four ASILs are defined: ASIL A, ASIL B, ASIL C and ASIL D, where ASIL A is the lowest safety integrity level
and ASIL D the highest one.
NOTE 2 In addition to these four ASILs, the class QM (quality management) denotes no requirement to comply with
ISO 26262.
Table 4 — ASIL determination
Controllability class
Severity class Probability class
C1 C2 C3
E1 QM QM QM
E2 QM QM QM
S1
E3 QM QM A
E4 QM A B
E1 QM QM QM
E2 QM QM A
S2
E3 QM A B
E4 A B C
E1 QM QM A
E2 QM A B
S3
E3 A B C
E4 B C D
10 © ISO 2011 – All rights reserved

7.4.4.2 It shall be ensured that the chosen level of detail of the list of operational situations does not lead
to an inappropriate lowering of the ASIL of the corresponding safety goals.
NOTE A very detailed list of operational situations (see 7.4.2.1.1) for one hazard, with regard to the vehicle state,
road conditions and environmental conditions, can lead to a very granular classification of hazardous events. This can
make it easier to rate controllability and severity. However, a larger number of different operational situations can lead to a
consequential reduction of the respective classes of exposure, and thus to an inappropriate lowering of the ASIL of the
corresponding safety goals.
7.4.4.3 A safety goal shall be determined for each hazardous event with an ASIL evaluated in the hazard
analysis. If similar safety goals are determined, these may be combined into one safety goal.
NOTE Safety goals are top-level safety requirements for the item. They lead to the functional safety requirements
needed to avoid an unreasonable risk for each hazardous event. Safety goals are not expressed in terms of technological
solutions, but in terms of functional objectives.
7.4.4.4 The ASIL determined for the hazardous event shall be assigned to the corresponding safety goal.
If similar safety goals are combined into a single one, in accordance with 7.4.4.3, the highest ASIL shall be
assigned to the combined safety goal.
NOTE If combined safety goals refer to the same hazard in different situations, then the resulting ASIL of the safety
goal is the highest one of the considered safety goals of every situation.
7.4.4.5 If a safety goal can be achieved by transitioning to, or by maintaining, one or more safe states,
then the corresponding safe state(s) shall be specified.
NOTE Safe states are further elaborated in Clause 8.
EXAMPLE A safe state could be switched off, locked, vehicle stationary, and maintained functionality in the case of
a failure over a defined time.
7.4.4.6 The safety goals together with their attributes (ASIL) shall be specified in accordance with
ISO 26262-8:2011, Clause 6.
NOTE The safety goal can include features such as the fault tolerant time interval, or physical characteristics (e.g. a
maximum level of unwanted steering-wheel torque, maximum level of unwanted acceleration) if they were relevant to the
ASIL determination.
7.4.5 Verification
7.4.5.1 The hazard analysis, risk assessment and the safety goals shall be verified in accordance with
ISO 26262-8:2011, Clause 9, to show their:
a) completeness with regard to situations (7.4.2.1) and hazards (7.4.2.2);
b) compliance with the item definition;
c) consistency with related hazard analyses and risk assessments;
d) completeness of the coverage of the hazardous events; and
e) consistency of the assigned ASILs with the corresponding hazardous events.
NOTE This verification review checks the hazard analysis and risk assessment of the item for correctness and
completeness, i.e. considered situations, hazards and parameter estimations (severity, probability of exposure and
controllability). In contrast, the confirmation review of the hazard analysis and risk assessment in accordance with
ISO 26262-2, checks formally that the hazard analysis and risk assessment procedure complies with the requirements of
Clause 7. The confirmation review is performed by a person or persons from a different department or organisation, than
the developers of the item.
ISO 26262-
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