ISO/SAE PAS 22736:2021
(Main)Taxonomy and definitions for terms related to driving automation systems for on-road motor vehicles
Taxonomy and definitions for terms related to driving automation systems for on-road motor vehicles
This document describes [motor] vehicle driving automation systems that perform part or all of the dynamic driving task (DDT) on a sustained basis. It provides a taxonomy with detailed definitions for six levels of driving automation, ranging from no driving automation (Level 0) to full driving automation (Level 5), in the context of [motor] vehicles (hereafter also referred to as “vehicle” or “vehicles”) and their operation on roadways: Level 0: No Driving Automation Level 1: Driver Assistance Level 2: Partial Driving Automation Level 3: Conditional Driving Automation Level 4: High Driving Automation Level 5: Full Driving Automation These level definitions, along with additional supporting terms and definitions provided herein, can be used to describe the full range of driving automation features equipped on [motor] vehicles in a functionally consistent and coherent manner. “On‑road” refers to publicly accessible roadways (including parking areas and private campuses that permit public access) that collectively serve all road users, including cyclists, pedestrians, and users of vehicles with and without driving automation features. The levels apply to the driving automation feature(s) that are engaged in any given instance of on-road operation of an equipped vehicle. As such, although a given vehicle may be equipped with a driving automation system that is capable of delivering multiple driving automation features that perform at different levels, the level of driving automation exhibited in any given instance is determined by the feature(s) that are engaged. This document also refers to three primary actors in driving: the (human) user, the driving automation system, and other vehicle systems and components. These other vehicle systems and components (or the vehicle in general terms) do not include the driving automation system in this model, even though as a practical matter a driving automation system may actually share hardware and software components with other vehicle systems, such as a processing module(s) or operating code. The levels of driving automation are defined by reference to the specific role played by each of the three primary actors in performance of the DDT and/or DDT fallback. “Role” in this context refers to the expected role of a given primary actor, based on the design of the driving automation system in question and not necessarily to the actual performance of a given primary actor. For example, a driver who fails to monitor the roadway during engagement of a Level 1 adaptive cruise control (ACC) system still has the role of driver, even while s/he is neglecting it. Active safety systems, such as electronic stability control (ESC) and automatic emergency braking (AEB), and certain types of driver assistance systems, such as lane keeping assistance (LKA), are excluded from the scope of this driving automation taxonomy because they do not perform part or all of the DDT on a sustained basis, but rather provide momentary intervention during potentially hazardous situations. Due to the momentary nature of the actions of active safety systems, their intervention does not change or eliminate the role of the driver in performing part or all of the DDT, and thus are not considered to be driving automation, even though they perform automated functions. In addition, systems that inform, alert, or warn the driver about hazards in the driving environment are also outside the scope of this driving automation taxonomy, as they neither automate part or all of the DDT, nor change the driver’s role in performance of the DDT (see 8.13). It should be noted, however, that crash avoidance features, including intervention-type active safety systems, may be included in vehicles equipped with driving automation systems at any level. For automated driving system (ADS) features (i.e., Levels 3 to 5) that perform the complete DDT, crash mitigation and avoidance capability is part of ADS functionality (see also 8.13).
Taxonomie et définitions des termes relatifs aux systèmes de conduite automatisée des véhicules routiers à moteur
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PUBLICLY ISO/SAE
AVAILABLE PAS
SPECIFICATION 22736
First edition
2021-08
Taxonomy and definitions for terms
related to driving automation systems
for on-road motor vehicles
Taxonomie et définitions des termes relatifs aux systèmes de conduite
automatisée des véhicules routiers à moteur
Reference number
ISO/SAE PAS 22736:2021(E)
©
ISO/SAE International 2021
---------------------- Page: 1 ----------------------
ISO/SAE PAS 22736:2021(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO/SAE International 2021
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication
may be reproduced, or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or
posting on the internet or an intranet, without prior written permission. Permission can be requested from either ISO or SAE
International at the respective address below or ISO’s member body in the country of the requester.
ISO copyright office SAE International
CP 401 • Ch. de Blandonnet 8 400 Commonwealth Dr.
CH-1214 Vernier, Geneva Warrendale, PA, USA 15096
Phone: +41 22 749 01 11 Phone: 877-606-7323 (inside USA and Canada)
Phone: +1 724-776-4970 (outside USA)
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Published in Switzerland by ISO, published in the USA by SAE International
ii © ISO/SAE International 2021 – All rights reserved
---------------------- Page: 2 ----------------------
ISO/SAE PAS 22736:2021(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.
SAE International is a global association of more than 128,000 engineers and related technical experts in
the aerospace, automotive and commercial-vehicle industries. Standards from SAE International are used
to advance mobility engineering throughout the world. The SAE Technical Standards Development
Program is among the organization's primary provisions to those mobility industries it serves aerospace,
automotive, and commercial vehicle. These works are authorized, revised, and maintained by the
volunteer efforts of more than 9,000 engineers, and other qualified professionals from around the world.
SAE subject matter experts act as individuals in the standards process, not as representatives of their
organizations. Thus, SAE standards represent optimal technical content developed in a transparent, open,
and collaborative process.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1 and the SAE Executive Standards Committee Policy. 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 and SAE International 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).
SAE Executive Standards Committee Rules provide that: “This document is published to advance the state
of technical and engineering sciences. The use of this document is entirely voluntary, and its applicability
and suitability for any particular use, including any patent infringement arising therefrom, is the sole
responsibility of the user.”
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of 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
www.iso.org/iso/foreword.html.
This document was jointly prepared by Technical Committee ISO/TC 204, Intelligent transport systems,
and SAE On-Road Automated Driving Committee, Definitions Task Force.
This document and its counterpart document published by SAE (SAE J3016 APR2021) are technically
equivalent. The only difference between the documents is the standard number and name and minor
editorial elements.
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. Alternatively, to provide
feedback on this document, please visit https://www.sae.org/standards/content/j3016_202104/.
© ISO/SAE International 2021 – All rights reserved iii
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ISO/SAE PAS 22736:2021(E)
TABLE OF CONTENTS
1. SCOPE . 1
2. REFERENCES . 2
2.1 Applicable Documents . 2
2.1.1 SAE Publications . 2
2.1.2 ANSI Accredited Publications . 2
2.1.3 Other Publications . 2
2.2 List of Abbreviations . 2
3. DEFINITIONS . 3
4. TAXONOMY OF DRIVING AUTOMATION . 22
5. LEVELS OR CATEGORIES OF DRIVING AUTOMATION . 28
5.1 Level or Category 0 - No Driving Automation . 28
5.2 Level or Category 1 - Driver Assistance . 28
5.3 Level or Category 2 - Partial Driving Automation . 29
5.4 Level or Category 3 - Conditional Driving Automation. 29
5.5 Level or Category 4 - High Driving Automation . 29
5.6 Level or Category 5 - Full Driving Automation . 30
6. SIGNIFICANCE OF OPERATIONAL DESIGN DOMAIN (ODD) . 30
7. DEPRECATED TERMS . 32
7.1 Autonomous, Driving Modes(s), Self-Driving, Unmanned, Robotic . 33
7.1.1 Autonomous . 33
7.1.2 Driving Mode(s). 33
7.1.3 Self-Driving . 33
7.1.4 Unmanned . 33
7.1.5 Robotic . 33
7.2 Automated or Autonomous Vehicle . 34
7.3 Control . 34
8. ADDITIONAL DISCUSSION . 34
9. NOTES . 40
Figure 1 Examples of driving automation system features/types that could be available during a given
trip . 6
Figure 2 Schematic (not a control diagram) view of driving task showing DDT portion . 7
Figure 3 . 9
Figure 4 . 9
Figure 5 . 10
Figure 6 . 10
Figure 7 . 10
Figure 8 . 11
Figure 9 Diagram showing vehicle axes of motion (SAE J670) . 12
Figure 10 Simplified logic flow diagram for assigning driving automation level to a feature . 25
Figure 11 ODD relative to driving automation levels . 32
Figure 12 ODD relative to driving automation levels . 32
Figure 13 Use case sequence for a Level 3 feature showing ADS engaged, occurrence of a failure or
out-of-ODD condition, and the fallback-ready user performing the fallback, or, if the fallback-
ready user fails to do so, a failure mitigation strategy, such as stop-in-lane . 37
Figure 14 Use case sequence at Level 4 showing ADS engaged, a catastrophic event (e.g., complete
power failure) and the system achieving a minimal risk condition . 37
Table 1 Summary of levels of driving automation . 23
Table 2 Roles of human user and driving automation system by level of driving automation . 26
Table 3 User roles while a driving automation system is engaged . 28
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PUBLICLY AVAILABLE SPECIFICATION ISO/SAE PAS 22736:2021(E)
Taxonomy and definitions for terms related to driving
automation systems for on-road motor vehicles
1. SCOPE
This document describes [motor] vehicle driving automation systems that perform part or all of the dynamic
driving task (DDT) on a sustained basis. It provides a taxonomy with detailed definitions for six levels of driving
automation, ranging from no driving automation (Level 0) to full driving automation (Level 5), in the context of
[motor] vehicles (hereafter also referred to as “vehicle” or “vehicles”) and their operation on roadways:
Level 0: No Driving Automation
Level 1: Driver Assistance
Level 2: Partial Driving Automation
Level 3: Conditional Driving Automation
Level 4: High Driving Automation
Level 5: Full Driving Automation
These level definitions, along with additional supporting terms and definitions provided herein, can be used to
describe the full range of driving automation features equipped on [motor] vehicles in a functionally consistent
and coherent manner. “On-road” refers to publicly accessible roadways (including parking areas and private
campuses that permit public access) that collectively serve all road users, including cyclists, pedestrians, and
users of vehicles with and without driving automation features.
The levels apply to the driving automation feature(s) that are engaged in any given instance of on-road operation
of an equipped vehicle. As such, although a given vehicle may be equipped with a driving automation system
that is capable of delivering multiple driving automation features that perform at different levels, the level of
driving automation exhibited in any given instance is determined by the feature(s) that are engaged.
This document also refers to three primary actors in driving: the (human) user, the driving automation system,
and other vehicle systems and components. These other vehicle systems and components (or the vehicle in
general terms) do not include the driving automation system in this model, even though as a practical matter a
driving automation system may actually share hardware and software components with other vehicle systems,
such as a processing module(s) or operating code.
The levels of driving automation are defined by reference to the specific role played by each of the three primary
actors in performance of the DDT and/or DDT fallback. “Role” in this context refers to the expected role of a
given primary actor, based on the design of the driving automation system in question and not necessarily to
the actual performance of a given primary actor. For example, a driver who fails to monitor the roadway during
engagement of a Level 1 adaptive cruise control (ACC) system still has the role of driver, even while s/he is
neglecting it.
Active safety systems, such as electronic stability control (ESC) and automatic emergency braking (AEB), and
certain types of driver assistance systems, such as lane keeping assistance (LKA), are excluded from the scope
of this driving automation taxonomy because they do not perform part or all of the DDT on a sustained basis,
but rather provide momentary intervention during potentially hazardous situations. Due to the momentary nature
of the actions of active safety systems, their intervention does not change or eliminate the role of the driver in
performing part or all of the DDT, and thus are not considered to be driving automation, even though they
perform automated functions. In addition, systems that inform, alert, or warn the driver about hazards in the
driving environment are also outside the scope of this driving automation taxonomy, as they neither automate
part or all of the DDT, nor change the driver’s role in performance of the DDT (see 8.13).
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ISO/SAE PAS 22736:2021(E)
It should be noted, however, that crash avoidance features, including intervention-type active safety systems,
may be included in vehicles equipped with driving automation systems at any level. For automated driving
system (ADS) features (i.e., Levels 3 to 5) that perform the complete DDT, crash mitigation and avoidance
capability is part of ADS functionality (see also 8.13).
2. REFERENCES
2.1 Applicable Documents
The following publications form a part of this specification to the extent specified herein. Unless otherwise
indicated, the latest issue of SAE publications shall apply.
2.1.1 SAE Publications
Available from SAE International, 400 Commonwealth Drive, Warrendale, PA 15096-0001, Tel: 877-606-7323
(inside USA and Canada) or +1 724-776-4970 (outside USA), www.sae.org.
SAE J670 Vehicle Dynamics Terminology
SAE J3063 Active Safety Systems Terms and Definitions
Shi, E., Gasser, T., Seeck, A., and Auerswald, R., “The Principles of Operation Framework: A Comprehensive
Classification Concept for Automated Driving Functions,” SAE Intl. J CAV 3(1):27-37, 2020,
https://doi.org/10.4271/12-03-01-0003.
2.1.2 ANSI Accredited Publications
Copies of these documents are available online at http://webstore.ansi.org/.
ANSI D16.1-2007 Manual on Classification of Motor Vehicle Traffic Accidents
2.1.3 Other Publications
49 U.S.C. § 30102(a)(6) (definition of [motor] vehicle)
Crash Avoidance Metrics Partnership - Automated Vehicle Research Consortium, “Automated Vehicle
Research for Enhanced Safety - Final Report,” available at https://www.regulations.gov/document?D=NHTSA-
2014-0070-0003.
Gasser, T. et al., “Legal Consequences of an Increase in Vehicle Automation,” July 23, 2013, available at
http://bast.opus.hbz-
nrw.de/volltexte/2013/723/pdf/Legal_consequences_of_an_increase_in_vehicle_automation.pdf.
Michon, J.A., 1985, “A Critical View of Driver Behavior Models: What Do We Know, What Should We Do?” In
Evans, L. and Schwing, R.C. (Eds.). Human behavior and traffic safety (pp. 485-520). New York: Plenum Press,
1985.
Smith, B.W., “Engineers and Lawyers Should Speak the Same Robot Language,” in ROBOT LAW (2015),
available at https://newlypossible.org.
2.2 List of Abbreviations
ACC Adaptive cruise control
ADAS Advanced driver assistance system
ADS Automated driving system
ADS-DV Automated driving system-dedicated vehicle
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ISO/SAE PAS 22736:2021(E)
AEB Automatic emergency braking
DDT Dynamic driving task
DSRC Dedicated short range communications
ESC Electronic stability control
LKA Lane keeping assistance
ODD Operational design domain
OEDR Object and event detection and response
3. DEFINITIONS
3.1 ACTIVE SAFETY SYSTEM (SAE J3063)
Active safety systems are vehicle systems that sense and monitor conditions inside and outside the vehicle for
the purpose of identifying perceived present and potential dangers to the vehicle, occupants, and/or other road
users, and automatically intervene to help avoid or mitigate potential collisions via various methods, including
alerts to the driver, vehicle system adjustments, and/or active control of the vehicle subsystems (brakes, throttle,
suspension, etc.).
NOTE: For purposes of this report, systems that meet the definition of active safety systems are considered to
have a design purpose that is primarily focused on improving safety rather than comfort, convenience,
or general driver assistance. Active safety systems warn or intervene during a high-risk event or
maneuver.
3.2 AUTOMATED DRIVING SYSTEM (ADS)
The hardware and software that are collectively capable of performing the entire DDT on a sustained basis,
regardless of whether it is limited to a specific operational design domain (ODD); this term is used specifically
to describe a Level 3, 4, or 5 driving automation system.
NOTE: In contrast to ADS, the generic term “driving automation system” (see 3.6) refers to any Level 1 to 5
system or feature that performs part or all of the DDT on a sustained basis. Given the similarity between
the generic term, “driving automation system,” and the Level 3 to 5 specific term, “automated driving
system,” the latter term should be capitalized when spelled out and reduced to its abbreviation, ADS,
as much as possible, while the former term should not be.
3.3 [DRIVERLESS OPERATION] DISPATCHING ENTITY
An entity that dispatches an ADS-equipped vehicle(s) in driverless operation.
NOTE: The functions carried out by a dispatching entity may be divided among one or several agents,
depending on the usage specification for the ADS-equipped vehicle(s) in question.
EXAMPLE: A fleet of Level 4 closed campus ADS-dedicated vehicles is placed into service by a driverless
operation dispatching entity, which engages the ADS for each vehicle after verifying its operational
readiness and disengages the ADS when each vehicle is taken out of service.
3.4 DISPATCH [IN DRIVERLESS OPERATION]
To place an ADS-equipped vehicle into service in driverless operation by engaging the ADS.
NOTE 1: The term “dispatch,” as used outside of the context of ADS-equipped vehicles, is generally understood
to mean sending a particular vehicle to a particular pick-up or drop-off location for purposes of
providing a transportation service. In the context of ADS-equipped vehicles, and as used herein, this
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ISO/SAE PAS 22736:2021(E)
term includes software-enabled dispatch of multiple ADS-equipped vehicles in driverless operation
that may complete multiple trips involving pick-up and drop-off of passengers or goods throughout a
day or other pre-defined period of service, and which may involve multiple agents performing various
tasks related to the dispatch function. In order to highlight this specialized use of the term dispatch,
the term is modified and conditioned by the stipulation that it refers exclusively to dispatching vehicles
in driverless operation.
NOTE 2: Only ADS-equipped vehicles capable of driverless operation (namely, an ADS-DV or a dual-mode
vehicle) are potentially subject to being dispatched.
3.5 DRIVING AUTOMATION
The performance by hardware/software systems of part or all of the DDT on a sustained basis.
3.6 DRIVING AUTOMATION SYSTEM OR TECHNOLOGY
The hardware and software that are collectively capable of performing part or all of the DDT on a sustained
basis; this term is used generically to describe any system capable of Level 1 to 5 driving automation.
NOTE: In contrast to this generic term for any Level 1 to 5 system, the specific term for a Level 3 to 5 system
is “automated driving system (ADS).” Given the similarity between the generic term, “driving automation
system,” and the Level 3 to 5 specific term, “Automated Driving System,” the latter term should be
capitalized when spelled out and reduced to its abbreviation, ADS, as much as possible, while the
former term should not be (see 3.2).
3.7 [DRIVING AUTOMATION SYSTEM] FEATURE
A Level 1-5 driving automation system’s design-specific functionality at a given level of driving automation within
a particular ODD, if applicable.
NOTE 1: Because the term “driving automation system” subsumes both driver support features and ADS
features, it is also acceptable to refer to them as such.
NOTE 2: A given driving automation system may have multiple features, each associated with a particular level
of driving automation and ODD.
NOTE 3: Each feature satisfies a usage specification.
NOTE 4: Features may be referred to by generic names (e.g., automated parking) or by proprietary names.
EXAMPLE 1: A Level 3 ADS feature that performs the DDT, excluding DDT fallback, in high-volume traffic on
fully access-controlled freeways.
EXAMPLE 2: A Level 4 ADS feature that performs the DDT, including DDT fallback, in a specified geo-fenced
urban center.
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ISO/SAE PAS 22736:2021(E)
3.7.1 MANEUVER-BASED FEATURE
A driving automation system feature equipped on a conventional vehicle that either:
1. Supports the driver by executing a limited set of lateral and/or longitudinal vehicle motion control actions
sufficient to fulfil a specific, narrowly defined use case (e.g., parking maneuver), while the driver performs
the rest of the DDT and supervises the Level 1 or Level 2 feature’s performance (i.e., Level 1 or Level 2
driver support features);
or
2. Executes a limited set of lateral and longitudinal vehicle motion control actions, as well as associated object
and event detection and response (OEDR) and all other elements of the complete DDT in order to fulfil a
specific, narrowly defined use case without human supervision (Level 3 or 4 ADS features).
EXAMPLE 1: A Level 1 parking assistance feature automatically performs the lateral vehicle motion control
actions necessary to parallel park a vehicle, while the driver performs the longitudinal vehicle
motion control actions and supervises the feature.
EXAMPLE 2: A Level 2 parking assistance feature automatically performs the lateral and longitudinal vehicle
motion control actions necessary to parallel park a vehicle under the supervision of the driver.
EXAMPLE 3: A Level 3 highway overtaking assistance feature automatically performs the lateral and
longitudinal vehicle motion control actions, as well as associated OEDR, necessary to pass a
slower-moving vehicle on a multi-lane highway when activated by the driver or fallback-ready
user.
3.7.2 SUB-TRIP FEATURE
A driving automation system feature equipped on a conventional vehicle that requires a human driver to perform
the complete DDT for at least part of every trip.
NOTE: Sub-trip features require a human driver to operate the vehicle between the point-of-origin and the
boundary of the feature’s ODD and/or after leaving the feature’s ODD until the destination is reached
(i.e., trip completion).
EXAMPLE 1: A Level 1 adaptive cruise control (ACC) feature performs longitudinal vehicle motion control
functions to support the driver in maintaining consistent headway to a lead vehicle in its lane when
travelling at higher speeds.
EXAMPLE 2: A Level 2 highway feature performs lateral and longitudinal vehicle motion control functions to
support the driver in maintaining position within its lane of travel, as well as consistent headway
to a lead vehicle in its lane when travelling at higher speeds.
EXAMPLE 3: A Level 3 traffic jam feature performs the complete DDT on a fully access-controlled freeway in
dense traffic, but requires a human driver to operate the vehicle upon ODD exit (e.g., when traffic
clears, as well as before entering the congested freeway, and again upon exiting it).
EXAMPLE 4: During a given vehicle trip, a user with a Level 4 automated parking feature dispatches the vehicle
in driverless operation for the purpose of finding a parking space in a nearby designated parking
facility. Following a period of shopping, the user retrieves the vehicle via dispatch in order to begin
his/her trip home.
3.7.3 FULL-TRIP FEATURE
ADS features that operate a vehicle throughout complete trips.
EXAMPLE 1: A Level 4 ADS-DV is dispatched in driverless operation for purposes of providing ride-hailing
services to customers located within its geo-fenced area of operation.
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ISO/SAE PAS 22736:2021(E)
EXAMPLE 2: A Level 5 dual-mode vehicle is dispatched in driverless operation by its owner to go to a
designated airport, pick up several family members, and bring them home. All vehicle occupants
remain passengers throughout the return trip.
Figure 1 illustrates how a trip could be completed by use of various combinations of driving automation features
engaged at different levels of driving automation.
Figure 1 — Examples of driving automation system features/types that could be available during a
given trip
3.8 DRIVER SUPPORT [DRIVING AUTOMATION SYSTEM] FEATURE
A general term for Level 1 and Level 2 driving automation system features.
NOTE: Level 1 (driver assistance) and Level 2 (partial automation) features are capable of performing only part
of the DDT, and thus require a driver to perform the remainder of the DDT, as well as to supervise the
feature’s performance while engaged. As such, these features, when engaged, support—but do not
replace—a driver in performing the DDT.
3.9 DRIVERLESS OPERATION [OF AN ADS-EQUIPPED VEHICLE]
On-road operation of an ADS-equipped vehicle that is unoccupied, or in which on-board users are not drivers
or in-vehicle fallback-ready users.
NOTE 1: ADS-DVs are always dispatched in driverless operation (subject to NOTE 3 in 3.33.3).
NOTE 2: ADS-equipped dual-mode vehicles may be dispatched in driverless operation.
NOTE 3: On-board passengers are neither drivers nor fallback-ready users.
EXAMPLE: A Level 4 ADS-DV is dispatched in driverless operation for purposes of providing transportation
service.
3.10 DYNAMIC DRIVING TASK (DDT)
All of the real-time operational and tactical functions required to operate a vehicle in on-road traffic, excluding
the strategic functions such as trip scheduling and selection of destinations and waypoints, and including,
without limitation, the following subtasks:
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ISO/SAE PAS 22736:2021(E)
1. Lateral vehicle motion control via steering (operational).
2. Longitudinal vehicle motion control via acceleration and deceleration
...
INTERNATIONAL ISO/SAE
STANDARD 22736
First edition
Taxonomy and definitions for terms
related to driving automation systems
for on-road motor vehicles
Taxonomie et définitions des termes relatifs aux systèmes de conduite
automatisée des véhicules routiers à moteur
PROOF/ÉPREUVE
Reference number
ISO/SAE 22736:2021(E)
©
ISO/SAE International 2021
---------------------- Page: 1 ----------------------
ISO/SAE 22736:2021(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO/SAE International 2021
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication
may be reproduced, or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or
posting on the internet or an intranet, without prior written permission. Permission can be requested from either ISO or SAE
International at the respective address below or ISO’s member body in the country of the requester.
ISO copyright office SAE International
CP 401 • Ch. de Blandonnet 8 400 Commonwealth Dr.
CH-1214 Vernier, Geneva Warrendale, PA, USA 15096
Phone: +41 22 749 01 11 Phone: 877-606-7323 (inside USA and Canada)
Phone: +1 724-776-4970 (outside USA)
Fax: 724-776-0790
Email: copyright@iso.org Email: CustomerService@sae.org
Website: www.iso.org Website: www.sae.org
Published in Switzerland by ISO, published in the USA by SAE International
ii PROOF/ÉPREUVE © ISO/SAE International 2021 – All rights reserved
---------------------- Page: 2 ----------------------
ISO/SAE 22736:2021(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.
SAE International is a global association of more than 128,000 engineers and related technical experts in
the aerospace, automotive and commercial-vehicle industries. Standards from SAE International are used
to advance mobility engineering throughout the world. The SAE Technical Standards Development
Program is among the organization's primary provisions to those mobility industries it serves aerospace,
automotive, and commercial vehicle. These works are authorized, revised, and maintained by the
volunteer efforts of more than 9,000 engineers, and other qualified professionals from around the world.
SAE subject matter experts act as individuals in the standards process, not as representatives of their
organizations. Thus, SAE standards represent optimal technical content developed in a transparent, open,
and collaborative process.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1 and the SAE Executive Standards Committee Policy. 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 and SAE International 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).
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ISO/SAE 22736:2021(E)
TABLE OF CONTENTS
1. SCOPE . 1
2. REFERENCES . 2
2.1 Applicable Documents . 2
2.1.1 SAE Publications . 2
2.1.2 ANSI Accredited Publications . 2
2.1.3 Other Publications . 2
2.2 List of Abbreviations . 2
3. DEFINITIONS . 3
4. TAXONOMY OF DRIVING AUTOMATION . 22
5. LEVELS OR CATEGORIES OF DRIVING AUTOMATION . 28
5.1 Level or Category 0 - No Driving Automation . 28
5.2 Level or Category 1 - Driver Assistance . 28
5.3 Level or Category 2 - Partial Driving Automation . 29
5.4 Level or Category 3 - Conditional Driving Automation. 29
5.5 Level or Category 4 - High Driving Automation . 29
5.6 Level or Category 5 - Full Driving Automation . 30
6. SIGNIFICANCE OF OPERATIONAL DESIGN DOMAIN (ODD) . 31
7. DEPRECATED TERMS . 32
7.1 Autonomous, Driving Modes(s), Self-Driving, Unmanned, Robotic . 33
7.1.1 Autonomous . 33
7.1.2 Driving Mode(s). 33
7.1.3 Self-Driving . 33
7.1.4 Unmanned . 33
7.1.5 Robotic . 33
7.2 Automated or Autonomous Vehicle . 34
7.3 Control . 34
8. ADDITIONAL DISCUSSION . 34
9. NOTES . 40
Figure 1 Examples of driving automation system features/types that could be available during a given
trip . 6
Figure 2 Schematic (not a control diagram) view of driving task showing DDT portion . 7
Figure 3 . 9
Figure 4 . 9
Figure 5 . 10
Figure 6 . 10
Figure 7 . 10
Figure 8 . 11
Figure 9 Diagram showing vehicle axes of motion (SAE J670) . 12
Figure 10 Simplified logic flow diagram for assigning driving automation level to a feature . 25
Figure 11 ODD relative to driving automation levels . 32
Figure 12 ODD relative to driving automation levels . 32
Figure 13 Use case sequence for a Level 3 feature showing ADS engaged, occurrence of a failure or
out-of-ODD condition, and the fallback-ready user performing the fallback, or, if the fallback-
ready user fails to do so, a failure mitigation strategy, such as stop-in-lane . 37
Figure 14 Use case sequence at Level 4 showing ADS engaged, a catastrophic event (e.g., complete
power failure) and the system achieving a minimal risk condition . 37
Table 1 Summary of levels of driving automation . 23
Table 2 Roles of human user and driving automation system by level of driving automation . 26
Table 3 User roles while a driving automation system is engaged . 28
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INTERNATIONAL STANDARD ISO/SAE 22736:2021(E)
Taxonomy and Definitions for Terms Related to Driving
Automation Systems for On-Road Motor Vehicles
1. SCOPE
This document describes [motor] vehicle driving automation systems that perform part or all of the dynamic
driving task (DDT) on a sustained basis. It provides a taxonomy with detailed definitions for six levels of driving
automation, ranging from no driving automation (Level 0) to full driving automation (Level 5), in the context of
[motor] vehicles (hereafter also referred to as “vehicle” or “vehicles”) and their operation on roadways:
Level 0: No Driving Automation
Level 1: Driver Assistance
Level 2: Partial Driving Automation
Level 3: Conditional Driving Automation
Level 4: High Driving Automation
Level 5: Full Driving Automation
These level definitions, along with additional supporting terms and definitions provided herein, can be used to
describe the full range of driving automation features equipped on [motor] vehicles in a functionally consistent
and coherent manner. “On-road” refers to publicly accessible roadways (including parking areas and private
campuses that permit public access) that collectively serve all road users, including cyclists, pedestrians, and
users of vehicles with and without driving automation features.
The levels apply to the driving automation feature(s) that are engaged in any given instance of on-road operation
of an equipped vehicle. As such, although a given vehicle may be equipped with a driving automation system
that is capable of delivering multiple driving automation features that perform at different levels, the level of
driving automation exhibited in any given instance is determined by the feature(s) that are engaged.
This document also refers to three primary actors in driving: the (human) user, the driving automation system,
and other vehicle systems and components. These other vehicle systems and components (or the vehicle in
general terms) do not include the driving automation system in this model, even though as a practical matter a
driving automation system may actually share hardware and software components with other vehicle systems,
such as a processing module(s) or operating code.
The levels of driving automation are defined by reference to the specific role played by each of the three primary
actors in performance of the DDT and/or DDT fallback. “Role” in this context refers to the expected role of a
given primary actor, based on the design of the driving automation system in question and not necessarily to
the actual performance of a given primary actor. For example, a driver who fails to monitor the roadway during
engagement of a Level 1 adaptive cruise control (ACC) system still has the role of driver, even while s/he is
neglecting it.
Active safety systems, such as electronic stability control (ESC) and automatic emergency braking (AEB), and
certain types of driver assistance systems, such as lane keeping assistance (LKA), are excluded from the scope
of this driving automation taxonomy because they do not perform part or all of the DDT on a sustained basis,
but rather provide momentary intervention during potentially hazardous situations. Due to the momentary nature
of the actions of active safety systems, their intervention does not change or eliminate the role of the driver in
performing part or all of the DDT, and thus are not considered to be driving automation, even though they
perform automated functions. In addition, systems that inform, alert, or warn the driver about hazards in the
driving environment are also outside the scope of this driving automation taxonomy, as they neither automate
part or all of the DDT, nor change the driver’s role in performance of the DDT (see 8.13).
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ISO/SAE 22736:2021(E)
It should be noted, however, that crash avoidance features, including intervention-type active safety systems,
may be included in vehicles equipped with driving automation systems at any level. For automated driving
system (ADS) features (i.e., Levels 3 to 5) that perform the complete DDT, crash mitigation and avoidance
capability is part of ADS functionality (see also 8.13).
2. REFERENCES
2.1 Applicable Documents
The following publications form a part of this specification to the extent specified herein. Unless otherwise
indicated, the latest issue of SAE publications shall apply.
2.1.1 SAE Publications
Available from SAE International, 400 Commonwealth Drive, Warrendale, PA 15096-0001, Tel: 877-606-7323
(inside USA and Canada) or +1 724-776-4970 (outside USA), www.sae.org.
SAE J670 Vehicle Dynamics Terminology
SAE J3063 Active Safety Systems Terms and Definitions
Shi, E., Gasser, T., Seeck, A., and Auerswald, R., “The Principles of Operation Framework: A Comprehensive
Classification Concept for Automated Driving Functions,” SAE Intl. J CAV 3(1):27-37, 2020,
https://doi.org/10.4271/12-03-01-0003.
2.1.2 ANSI Accredited Publications
Copies of these documents are available online at http://webstore.ansi.org/.
ANSI D16.1-2007 Manual on Classification of Motor Vehicle Traffic Accidents
2.1.3 Other Publications
49 U.S.C. § 30102(a)(6) (definition of [motor] vehicle)
Crash Avoidance Metrics Partnership - Automated Vehicle Research Consortium, “Automated Vehicle
Research for Enhanced Safety - Final Report,” available at https://www.regulations.gov/document?D=NHTSA-
2014-0070-0003.
Gasser, T. et al., “Legal Consequences of an Increase in Vehicle Automation,” July 23, 2013, available at
http://bast.opus.hbz-
nrw.de/volltexte/2013/723/pdf/Legal_consequences_of_an_increase_in_vehicle_automation.pdf.
Michon, J.A., 1985, “A Critical View of Driver Behavior Models: What Do We Know, What Should We Do?” In
Evans, L. and Schwing, R.C. (Eds.). Human behavior and traffic safety (pp. 485-520). New York: Plenum Press,
1985.
Smith, B.W., “Engineers and Lawyers Should Speak the Same Robot Language,” in ROBOT LAW (2015),
available at https://newlypossible.org.
2.2 List of Abbreviations
ACC Adaptive cruise control
ADAS Advanced driver assistance system
ADS Automated driving system
ADS-DV Automated driving system-dedicated vehicle
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AEB Automatic emergency braking
DDT Dynamic driving task
DSRC Dedicated short range communications
ESC Electronic stability control
LKA Lane keeping assistance
ODD Operational design domain
OEDR Object and event detection and response
3. DEFINITIONS
3.1 ACTIVE SAFETY SYSTEM (SAE J3063)
Active safety systems are vehicle systems that sense and monitor conditions inside and outside the vehicle for
the purpose of identifying perceived present and potential dangers to the vehicle, occupants, and/or other road
users, and automatically intervene to help avoid or mitigate potential collisions via various methods, including
alerts to the driver, vehicle system adjustments, and/or active control of the vehicle subsystems (brakes, throttle,
suspension, etc.).
NOTE: For purposes of this report, systems that meet the definition of active safety systems are considered to
have a design purpose that is primarily focused on improving safety rather than comfort, convenience,
or general driver assistance. Active safety systems warn or intervene during a high-risk event or
maneuver.
3.2 AUTOMATED DRIVING SYSTEM (ADS)
The hardware and software that are collectively capable of performing the entire DDT on a sustained basis,
regardless of whether it is limited to a specific operational design domain (ODD); this term is used specifically
to describe a Level 3, 4, or 5 driving automation system.
NOTE: In contrast to ADS, the generic term “driving automation system” (see 3.6) refers to any Level 1 to 5
system or feature that performs part or all of the DDT on a sustained basis. Given the similarity between
the generic term, “driving automation system,” and the Level 3 to 5 specific term, “automated driving
system,” the latter term should be capitalized when spelled out and reduced to its abbreviation, ADS,
as much as possible, while the former term should not be.
3.3 [DRIVERLESS OPERATION] DISPATCHING ENTITY
An entity that dispatches an ADS-equipped vehicle(s) in driverless operation.
NOTE: The functions carried out by a dispatching entity may be divided among one or several agents,
depending on the usage specification for the ADS-equipped vehicle(s) in question.
EXAMPLE: A fleet of Level 4 closed campus ADS-dedicated vehicles is placed into service by a driverless
operation dispatching entity, which engages the ADS for each vehicle after verifying its operational
readiness and disengages the ADS when each vehicle is taken out of service.
3.4 DISPATCH [IN DRIVERLESS OPERATION]
To place an ADS-equipped vehicle into service in driverless operation by engaging the ADS.
NOTE 1: The term “dispatch,” as used outside of the context of ADS-equipped vehicles, is generally understood
to mean sending a particular vehicle to a particular pick-up or drop-off location for purposes of
providing a transportation service. In the context of ADS-equipped vehicles, and as used herein, this
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term includes software-enabled dispatch of multiple ADS-equipped vehicles in driverless operation
that may complete multiple trips involving pick-up and drop-off of passengers or goods throughout a
day or other pre-defined period of service, and which may involve multiple agents performing various
tasks related to the dispatch function. In order to highlight this specialized use of the term dispatch,
the term is modified and conditioned by the stipulation that it refers exclusively to dispatching vehicles
in driverless operation.
NOTE 2: Only ADS-equipped vehicles capable of driverless operation (namely, an ADS-DV or a dual-mode
vehicle) are potentially subject to being dispatched.
3.5 DRIVING AUTOMATION
The performance by hardware/software systems of part or all of the DDT on a sustained basis.
3.6 DRIVING AUTOMATION SYSTEM OR TECHNOLOGY
The hardware and software that are collectively capable of performing part or all of the DDT on a sustained
basis; this term is used generically to describe any system capable of Level 1 to 5 driving automation.
NOTE: In contrast to this generic term for any Level 1 to 5 system, the specific term for a Level 3 to 5 system
is “automated driving system (ADS).” Given the similarity between the generic term, “driving automation
system,” and the Level 3 to 5 specific term, “Automated Driving System,” the latter term should be
capitalized when spelled out and reduced to its abbreviation, ADS, as much as possible, while the
former term should not be (see 3.2).
3.7 [DRIVING AUTOMATION SYSTEM] FEATURE
A Level 1-5 driving automation system’s design-specific functionality at a given level of driving automation within
a particular ODD, if applicable.
NOTE 1: Because the term “driving automation system” subsumes both driver support features and ADS
features, it is also acceptable to refer to them as such.
NOTE 2: A given driving automation system may have multiple features, each associated with a particular level
of driving automation and ODD.
NOTE 3: Each feature satisfies a usage specification.
NOTE 4: Features may be referred to by generic names (e.g., automated parking) or by proprietary names.
EXAMPLE 1: A Level 3 ADS feature that performs the DDT, excluding DDT fallback, in high-volume traffic on
fully access-controlled freeways.
EXAMPLE 2: A Level 4 ADS feature that performs the DDT, including DDT fallback, in a specified geo-fenced
urban center.
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3.7.1 MANEUVER-BASED FEATURE
A driving automation system feature equipped on a conventional vehicle that either:
1. Supports the driver by executing a limited set of lateral and/or longitudinal vehicle motion control actions
sufficient to fulfil a specific, narrowly defined use case (e.g., parking maneuver), while the driver performs
the rest of the DDT and supervises the Level 1 or Level 2 feature’s performance (i.e., Level 1 or Level 2
driver support features);
or
2. Executes a limited set of lateral and longitudinal vehicle motion control actions, as well as associated object
and event detection and response (OEDR) and all other elements of the complete DDT in order to fulfil a
specific, narrowly defined use case without human supervision (Level 3 or 4 ADS features).
EXAMPLE 1: A Level 1 parking assistance feature automatically performs the lateral vehicle motion control
actions necessary to parallel park a vehicle, while the driver performs the longitudinal vehicle
motion control actions and supervises the feature.
EXAMPLE 2: A Level 2 parking assistance feature automatically performs the lateral and longitudinal vehicle
motion control actions necessary to parallel park a vehicle under the supervision of the driver.
EXAMPLE 3: A Level 3 highway overtaking assistance feature automatically performs the lateral and
longitudinal vehicle motion control actions, as well as associated OEDR, necessary to pass a
slower-moving vehicle on a multi-lane highway when activated by the driver or fallback-ready
user.
3.7.2 SUB-TRIP FEATURE
A driving automation system feature equipped on a conventional vehicle that requires a human driver to perform
the complete DDT for at least part of every trip.
NOTE: Sub-trip features require a human driver to operate the vehicle between the point-of-origin and the
boundary of the feature’s ODD and/or after leaving the feature’s ODD until the destination is reached
(i.e., trip completion).
EXAMPLE 1: A Level 1 adaptive cruise control (ACC) feature performs longitudinal vehicle motion control
functions to support the driver in maintaining consistent headway to a lead vehicle in its lane when
travelling at higher speeds.
EXAMPLE 2: A Level 2 highway feature performs lateral and longitudinal vehicle motion control functions to
support the driver in maintaining position within its lane of travel, as well as consistent headway
to a lead vehicle in its lane when travelling at higher speeds.
EXAMPLE 3: A Level 3 traffic jam feature performs the complete DDT on a fully access-controlled freeway in
dense traffic, but requires a human driver to operate the vehicle upon ODD exit (e.g., when traffic
clears, as well as before entering the congested freeway, and again upon exiting it).
EXAMPLE 4: During a given vehicle trip, a user with a Level 4 automated parking feature dispatches the vehicle
in driverless operation for the purpose of finding a parking space in a nearby designated parking
facility. Following a period of shopping, the user retrieves the vehicle via dispatch in order to begin
his/her trip home.
3.7.3 FULL-TRIP FEATURE
ADS features that operate a vehicle throughout complete trips.
EXAMPLE 1: A Level 4 ADS-DV is dispatched in driverless operation for purposes of providing ride-hailing
services to customers located within its geo-fenced area of operation.
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EXAMPLE 2: A Level 5 dual-mode vehicle is dispatched in driverless operation by its owner to go to a
designated airport, pick up several family members, and bring them home. All vehicle occupants
remain passengers throughout the return trip.
Figure 1 illustrates how a trip could be completed by use of various combinations of driving automation features
engaged at different levels of driving automation.
Figure 1 — Examples of driving automation system features/types that could be available during a
given trip
3.8 DRIVER SUPPORT [DRIVING AUTOMATION SYSTEM] FEATURE
A general term for Level 1 and Level 2 driving automation system features.
NOTE: Level 1 (driver assistance) and Level 2 (partial automation) features are capable of performing only part
of the DDT, and thus require a driver to perform the remainder of the DDT, as well as to supervise the
feature’s performance while engaged. As such, these features, when engaged, support—but do not
replace—a driver in performing the DDT.
3.9 DRIVERLESS OPERATION [OF AN ADS-EQUIPPED VEHICLE]
On-road operation of an ADS-equipped vehicle that is unoccupied, or in which on-board users are not drivers
or in-vehicle fallback-ready users.
NOTE 1: ADS-DVs are always dispatched in driverless operation (subject to NOTE 3 in 3.33.3).
NOTE 2: ADS-equipped dual-mode vehicles may be dispatched in driverless operation.
NOTE 3: On-board passengers are neither drivers nor fallback-ready users.
EXAMPLE: A Level 4 ADS-DV is dispatched in driverless operation for purposes of providing transportation
service.
3.10 DYNAMIC DRIVING TASK (DDT)
All of the real-time operational and tactical functions required to operate a vehicle in on-road traffic, excluding
the strategic functions such as trip scheduling and selection of destinations and waypoints, and including,
without limitation, the following subtasks:
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1. Lateral vehicle motion control via steering (operational).
2. Longitudinal vehicle motion control via acceleration and deceleration (operational).
3. Monitoring the driving environment
...
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