Road vehicles -- Test method to evaluate the performance of autonomous emergency braking systems

This document specifies a method to evaluate the behaviour of a vehicle equipped with an autonomous emergency braking system (AEBS), or dynamic brake support (DBS) during several accident scenarios. Those accidents occur during a straight-line driving when the vehicle under test (VUT) approaches another vehicle in the same lane. Both vehicles are aligned in longitudinal axis to each other. The most important part of the vehicle behaviour during these accidents scenarios is the capacity to avoid or mitigate the collision. Systems requiring driver intervention are not in the scope of this document. NOTEÂ Â Â Â Â Depending on accidentology, only a part of the scenarios can be used for an evaluation of performance. AEB system evaluation based upon this document is limited to longitudinal accident scenarios.

Véhicules routiers -- Méthode d'essai pour évaluer la performance des systèmes automatiques de freinage d'urgence

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Status
Published
Publication Date
22-Jul-2021
Current Stage
9092 - International Standard to be revised
Start Date
24-Nov-2021
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INTERNATIONAL ISO
STANDARD 22733-1
First edition
2021-07
Road vehicles — Test method
to evaluate the performance of
autonomous emergency braking
systems —
Part 1:
Car-to-car
Véhicules routiers — Méthode d'essai pour évaluer la performance
des systèmes automatiques de freinage d'urgence —
Partie 1: Voiture à voiture
Reference number
ISO 22733-1:2021(E)
ISO 2021
---------------------- Page: 1 ----------------------
ISO 22733-1:2021(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 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 at the address

below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2021 – All rights reserved
---------------------- Page: 2 ----------------------
ISO 22733-1:2021(E)
Contents Page

Foreword ..........................................................................................................................................................................................................................................v

Introduction ................................................................................................................................................................................................................................vi

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Variables ....................................................................................................................................................................................................................... 3

4.1 Reference system .................................................................................................................................................................................. 3

4.2 Lateral offset ............................................................................................................................................................................................. 3

4.3 Variables to be measured ............................................................................................................................................................... 4

5 Equivalent vehicle target ............................................................................................................................................................................. 4

6 Measuring equipment and data processing ............................................................................................................................. 4

6.1 General ........................................................................................................................................................................................................... 4

6.2 Description ................................................................................................................................................................................................. 4

6.3 Transducer installation.................................................................................................................................................................... 5

6.4 Calibration .................................................................................................................................................................................................. 5

6.5 Data processing ...................................................................................................................................................................................... 5

7 Test conditions ....................................................................................................................................................................................................... 5

7.1 General ........................................................................................................................................................................................................... 5

7.2 General data ............................................................................................................................................................................................... 5

7.3 Test track ...................................................................................................................................................................................................... 5

7.4 Weather conditions ............................................................................................................................................................................. 5

7.5 Surroundings ............................................................................................................................................................................................ 6

7.6 VUT .................................................................................................................................................................................................................... 6

7.6.1 General vehicle condition ......................................................................................................................................... 6

7.6.2 AEB system settings ...................................................................................................................................................... 6

7.6.3 Deployable pedestrian protection systems............................................................................................... 7

7.6.4 Tyres ........................................................................................................................................................................................... 7

7.6.5 Braking system .................................................................................................................................................................. 7

7.6.6 Other influencing system .......................................................................................................................................... 7

7.6.7 Loading conditions of the vehicle ...................................................................................................................... 8

8 Test procedure ........................................................................................................................................................................................................ 8

8.1 Test preparation ..................................................................................................................................................................................... 8

8.1.1 Brake conditioning ......................................................................................................................................................... 8

8.1.2 Tyre conditioning ............................................................................................................................................................ 8

8.2 Test scenarios ........................................................................................................................................................................................... 9

8.3 Test conduct ...........................................................................................................................................................................................10

8.4 Test execution .......................................................................................................................................................................................10

8.4.1 Speed .......................................................................................................................................................................................10

8.4.2 Validity criteria ...............................................................................................................................................................10

8.4.3 End of test conditions ...............................................................................................................................................11

8.4.4 Determination of speed incremental steps ............................................................................................11

9 DBS tests (optional) ........................................................................................................................................................................................11

10 Performance metrics ....................................................................................................................................................................................11

10.1 Maximum speed of VUT at which collision is avoided: V ..........................................................................

VUT 11

10.2 Mean longitudinal acceleration of the VUT: (A ) .....................................................................................

VUT mean 11

10.3 Maximum longitudinal acceleration of the VUT with DBS: (A ) ...................................................

VUT max 12

10.4 Average increase rate of longitudinal acceleration of VUT with DBS: (A ) .........

VUT increase rate 12

10.5 Impact speed of VUT at which collision first occurs: V ..........................................................................

impact 12

10.6 Activation time of AEBS: T ...................................................................................................................................................

AEB 12

10.7 Activation time of FCW: T ....................................................................................................................................................

FCW 12
© ISO 2021 – All rights reserved iii
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ISO 22733-1:2021(E)

10.8 Maximum yaw rate of the VUT: ψψ .............................................................................................................................12

VUT

10.9 Lateral offset of the VUT: Y ..................................................................................................................................................

VUT 12

10.10 Maximum steering wheel velocity of VUT: Ω ......................................................................................................

VUT 12

Annex A (informative) Brake application procedure .......................................................................................................................13

Annex B (informative) Test report .......................................................................................................................................................................15

Bibliography .............................................................................................................................................................................................................................18

iv © ISO 2021 – All rights reserved
---------------------- Page: 4 ----------------------
ISO 22733-1:2021(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.

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 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 prepared by Technical Committee ISO/TC 22, Road Vehicles, Subcommittee SC 33,

Vehicle dynamics and chassis components.
A list of all parts in the ISO 22733 series can be found on the ISO website.

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.
© ISO 2021 – All rights reserved v
---------------------- Page: 5 ----------------------
ISO 22733-1:2021(E)
Introduction

The capacity to avoid or mitigate a collision during potential accident is an important part of the

performance of an autonomous emergency braking system. This document is intended to assess

performance of an autonomous emergency braking system under defined test scenario only.

NOTE Moreover, insufficient knowledge is available concerning the relationship between overall vehicle

dynamic properties and accident avoidance. (A substantial amount of work is necessary to acquire enough and

reliable data on the correlation between accident avoidance and vehicle dynamic properties in general and the

results of these tests in particular.)
vi © ISO 2021 – All rights reserved
---------------------- Page: 6 ----------------------
INTERNATIONAL STANDARD ISO 22733-1:2021(E)
Road vehicles — Test method to evaluate the performance
of autonomous emergency braking systems —
Part 1:
Car-to-car
1 Scope

This document specifies a method to evaluate the behaviour of a vehicle equipped with an autonomous

emergency braking system (AEBS), or dynamic brake support (DBS) during several accident scenarios.

Those accidents occur during a straight-line driving when the vehicle under test (VUT) approaches

another vehicle in the same lane. Both vehicles are aligned in longitudinal axis to each other.

The most important part of the vehicle behaviour during these accidents scenarios is the capacity to

avoid or mitigate the collision.
Systems requiring driver intervention are not in the scope of this document.

NOTE Depending on accidentology, only a part of the scenarios can be used for an evaluation of performance.

AEB system evaluation based upon this document is limited to longitudinal accident scenarios.

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 8855:2011, Road vehicles — Vehicle dynamics and road-holding ability — Vocabulary

ISO 15037-1:2019, Road vehicles — Vehicle dynamics test methods — Part 1: General conditions for

passenger cars

ISO 19206-1, Road vehicles — Test devices for target vehicles, vulnerable road users and other objects, for

assessment of active safety functions — Part 1: Requirements for passenger vehicle rear-end targets

3 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO 8855, ISO 15037-1 and the

following apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
AEB
autonomous emergency braking

braking applied automatically by the vehicle in response to the detection of a likely collision to reduce

the vehicle speed and potentially avoid the collision
© ISO 2021 – All rights reserved 1
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ISO 22733-1:2021(E)
3.2
CCRs
car-to-car rear stationary

collision in which a vehicle travels forward towards another stationary vehicle and the frontal structure

of the vehicle strikes the rear structure of the stationary vehicle
3.3
CCRm
car-to-car rear moving

collision in which a vehicle travels forward towards another vehicle travelling at constant speed and

the frontal structure of the vehicle strikes the rear structure of the leading vehicle

3.4
CCRb
car-to-car rear braking

collision in which a vehicle travels forward towards another vehicle travelling at constant speed and

then decelerates, and the frontal structure of the vehicle strikes the rear structure of the leading vehicle

3.5
DBS
dynamic brake support

system that further amplifies the driver braking demand in response to the detection of a likely collision

to achieve a greater deceleration
3.6
EVT
equivalent vehicle target
vehicle target as defined in ISO 19206-1
3.7
FCW
forward collision warning

audiovisual warning provided automatically by the vehicle in response to the detection of a likely

collision to alert the driver
3.8
peak braking coefficient
PBC

measure of tyre-to-road surface friction based on the maximum deceleration of a rolling tyre

Note 1 to entry: Measured using ASTM E1136-10, at a speed of 64,4 km/h, without water delivery.

3.9
TTC
time-to-collision

remaining time before the VUT strikes the EVT (3.6), assuming that the VUT and EVT travel at constant

speed
3.10
VUT
vehicle under test

vehicle tested with a pre-crash collision mitigation or avoidance system on board

3.11
AEB
time when the AEB (3.1) system activates

Note 1 to entry: Activation time is determined by identifying the last data point where the filtered acceleration

2 2

signal is below -1 m/s , and then going back to the point in time where the acceleration first crossed -0,3 m/s .

2 © ISO 2021 – All rights reserved
---------------------- Page: 8 ----------------------
ISO 22733-1:2021(E)
3.12
FCW
time when the audible warning of the FCW (3.7) starts

Note 1 to entry: The starting point is determined by audible analysis or video analysis.

3.13
impact
vehicle velocity at which the VUT hits the EVT (3.6)
3.14
rel_impact

relative speed at which the VUT hits the EVT (3.6) by subtracting the velocity of the EVT from Vimpact

(3.13) at the time of collision
4 Variables
4.1 Reference system
The reference earth frame according to ISO 8855:2011, 2.8 is defined as:
— X axis: intended straight line path projected on the ground to front;
— Y axis: perpendicular to X axis on the ground to left;
— Z axis: perpendicular to the ground to the top.
4.2 Lateral offset

The lateral offset is determined as the lateral distance between the centre of the front of the VUT and

the centre of the rear of the EVT when measured in parallel to the intended straight-lined path as shown

in Figure 1.
Key
1 intended straight-lined path
2 VUT
3 VUT path
4 EVT
5 EVT path
Figure 1 — Coordinate system and notation
The lateral offset is defined as YY+ .
VUTe__rrorEVT error

The origin is an arbitrary point on X axis. The Y and Y are measured in the reference

VUT target_error
frame and the Y is identical to Y .
target_error EVTe_ rror
© ISO 2021 – All rights reserved 3
---------------------- Page: 9 ----------------------
ISO 22733-1:2021(E)
4.3 Variables to be measured

Table 1 lists all relevant variables to be measured. All dynamic data shall be sampled and recorded at

a frequency of at least 100 Hz. EVT and VUT data shall be synchronized by using the differential GPS

(DGPS) time stamp of the EVT.
Table 1 — Variables to be measured
Variable Symbol
CCRs and CCRm: T equals TTC = 4 s T
0 0
CCRb: T when EVT starts decelerating
T , time when AEB activates T
Time
AEB AEB
T , time when FCW activates T
FCW FCW
T , time when VUT impacts EVT T
impact impact
Position of the VUT during the entire test
X , Y
VUT VUT
Position
Position of the EVT during the entire test
X , Y
EVT EVT
Speed of the VUT during the entire test:
VUT
— V , speed when VUT impacts EVT V
impact impact
Speed
— V , relative speed when VUT impacts EVT V
reli_ mpact reli_ mpact
Speed of the EVT during the entire test
EVT
Yaw velocity of the VUT during the entire test 
VUT
Yaw velocity
Yaw velocity of the EVT during the entire test 
EVT
Acceleration of the VUT during the entire test
EVT
Acceleration
Acceleration of the EVT during the entire test
EVT
An example of a test report is given in Annex B.
5 Equivalent vehicle target

The equivalent vehicle target (EVT) shall meet the requirements as defined in ISO 19206-1.

6 Measuring equipment and data processing
6.1 General

The test conditions on measurement equipment and data processing shall be in accordance with

ISO 15037-1:2019, Clause 6, unless otherwise specified below.
6.2 Description

VUT and EVT shall be equipped with data measurement and acquisition equipment to sample and

record data with an accuracy of at least:
— VUT and EVT speed to 0,1 km/h;
— VUT and EVT lateral and longitudinal position to 0,03 m;
— VUT and EVT yaw rate to 0,1°/s;
— VUT and EVT longitudinal acceleration to 0,1 m/s ;
— steering wheel velocity to 1,0°/s.
4 © ISO 2021 – All rights reserved
---------------------- Page: 10 ----------------------
ISO 22733-1:2021(E)
6.3 Transducer installation

The transient vehicle pitch changes shall not adversely affect the measurement of the velocity and

distance variables for the chosen transducer system.
6.4 Calibration

All transducers shall be calibrated according to the manufacturer’s instructions. The transducer

manufacturer’s recommended application software and firmware version shall be used. If parts of

the measuring system can be adjusted, such calibration shall be performed immediately before the

beginning of the tests.
6.5 Data processing
Filter the measured data as follows:
— position and speed are not filtered and are used in their raw state;

— acceleration with a 12-pole phaseless Butterworth filter with a cut-off frequency of 10 Hz;

— yaw rate with a 12-pole phaseless Butterworth filter with a cut-off frequency of 10 Hz;

— force with a 12-pole phaseless Butterworth filter with a cut-off frequency of 10 Hz.

7 Test conditions
7.1 General

The test conditions shall be in accordance with ISO 15037-1:2019, Clause 6, unless otherwise specified

below.
7.2 General data

General data on the test vehicle and test conditions shall be recorded as specified in ISO 15037-1:2019,

6.4.1.
7.3 Test track

Conduct tests on a dry (no visible moisture on the surface), uniform, solid-paved surface with a

consistent slope between level and 1 %. The test surface shall have a minimal peak braking coefficient

(PBC) of 0,9.

The surface shall be paved and shall not contain any irregularities (e.g. large dips or cracks, manhole

covers or reflective studs) that may give rise to abnormal sensor measurements within a lateral

distance of 3,0 m to either side of the theoretical path line and with a longitudinal distance of 30 m

beyond the position of VUT/EVT at the end of the test.

Lane markings are allowed. However, testing may only be conducted in an area where typical road

markings depicting a driving lane may not be parallel to the test path within 3,0 m either side. Lines

or markings may cross the test path but may not be present in the area where AEB activation and/or

braking after FCW is expected.
7.4 Weather conditions

Conduct tests in dry conditions with ambient temperature above 0 °C and below 45 °C.

The surface temperature of the test track shall be between +10 °C and +50 °C.
© ISO 2021 – All rights reserved 5
---------------------- Page: 11 ----------------------
ISO 22733-1:2021(E)

No precipitation shall be falling and the horizontal visibility at ground level shall be greater than 1 km.

Wind speeds shall be below 5 m/s to minimise EVT and VUT disturbance.

Natural ambient illumination shall be homogenous in the test area and more than 1 000 lx for daylight

testing with no strong shadows cast across the test area other than those caused by the VUT or EVT.

Ensure testing is not performed while driving towards or away from the sun when there is direct

sunlight.

Measure and record the following parameters preferably at the commencement of every single test or

at least every 30 min:
1) ambient temperature in °C;
2) track temperature in °C;
3) wind speed and direction m/s;
4) ambient illumination in lx.

Weather conditions are based on ISO 21994. For some proving grounds where the lower limit of ambient

temperature of 0 °C is difficult to achieve, a lower value can be adopted. However, in that case, the lower

limit values shall be reported.
7.5 Surroundings

Conduct testing such that there are no other vehicles, obstructions, other objects or persons protruding

above the test surface that may give rise to abnormal sensor measurements within a lateral distance

of 3,0 m to either side of the test path and within a longitudinal distance of 30 m beyond the position at

which the test finishes. Test areas where the VUT needs to pass under overhead signs, bridges, gantries

or other significant structures are not permitted.

The general view ahead and to either side of the test area shall comprise of a wholly plain man made or

natural environment (e.g. further test surface, plain coloured fencing or hoardings, natural vegetation

or sky) and shall not comprise any highly reflective surfaces or contain any vehicle-like silhouettes that

may give rise to abnormal sensor measurements.
7.6 VUT
7.6.1 General vehicle condition

The VUT condition shall be in accordance with the vehicle manufacturer’s specifications, particularly

with respect to the suspension geometries, power train (e.g. differentials and locks) configuration, and

tyre fitment.
7.6.2 AEB system settings

If different settings are available, a setting shall be selected and finally reported. This setting shall

not be changed until the entire test procedure is completed. The test procedure can be repeated for

different settings if needed.

The AEB test protocol defined by EuroNCAP provides the following instruction for the AEB setting

selection.

Set any driver configurable elements of the AEB and/or FCW system (e.g. the timing of the collision

warning or the braking application if present) to the middle setting or midpoint and then next latest

setting similar to the examples shown in Table 2.
6 © ISO 2021 – All rights reserved
---------------------- Page: 12 ----------------------
ISO 22733-1:2021(E)
Table 2 — AEB and/or FCW system setting for testing
Available settings Selected setting
a b
Setting 1 , Setting 2 Setting 2
a b
Setting 1 , Setting 2, Setting 3 Setting 2
a b
Setting 1 , Setting 2, Setting 3, Setting 4 Setting 3
Early brake triggering.
Late brake triggering.

The aim of EuroNCAP is to compare the performance of different vehicles with the same way of setting

selection.

The purpose of this document is to measure the performance of AEB on one given vehicle. Then if

several settings are available, the performance can be evaluated in any given setting.

7.6.3 Deployable pedestrian protection systems

When the vehicle is equipped with a deployable pedestrian protection system, this system shall be

deactivated before the AEB tests commence.
7.6.4 Tyres

Generally, all measurements shall be conducted with original fitment tyres. If several types of tyres are

available, the type of tyres shall be reported.

For a general tyre condition, new tyres shall be fitted on the test vehicle according to the manufacturer’s

specifications. If not specified otherwise by the tyre manufacturer, they shall be run-in according to the

tyre conditioning procedure specified in 8.1.2. After running-in, maintain the run-in tyres in the same

position on the vehicle for the duration of the testing.

Tyres shall have a tread depth of at least 90 % of the original value across the whole breadth of the

tread and around the whole circumference of the tyre.

Tyres shall be manufactured not more than one year before the test. The date of manufacturing shall be

noted in the presentation of test conditions (see Annex B).
Tyre
...

FINAL
INTERNATIONAL ISO/FDIS
DRAFT
STANDARD 22733-1
ISO/TC 22/SC 33
Road vehicles — Test method
Secretariat: DIN
to evaluate the performance of
Voting begins on:
2021-04-26 autonomous emergency braking
systems —
Voting terminates on:
2021-06-21
Part 1:
Car-to-car
Véhicules routiers — Méthode d'essai pour évaluer la performance
des systèmes automatiques de freinage d'urgence —
Partie 1: Voiture à voiture
RECIPIENTS OF THIS DRAFT ARE INVITED TO
SUBMIT, WITH THEIR COMMENTS, NOTIFICATION
OF ANY RELEVANT PATENT RIGHTS OF WHICH
THEY ARE AWARE AND TO PROVIDE SUPPOR TING
DOCUMENTATION.
IN ADDITION TO THEIR EVALUATION AS
Reference number
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO-
ISO/FDIS 22733-1:2021(E)
LOGICAL, COMMERCIAL AND USER PURPOSES,
DRAFT INTERNATIONAL STANDARDS MAY ON
OCCASION HAVE TO BE CONSIDERED IN THE
LIGHT OF THEIR POTENTIAL TO BECOME STAN-
DARDS TO WHICH REFERENCE MAY BE MADE IN
NATIONAL REGULATIONS. ISO 2021
---------------------- Page: 1 ----------------------
ISO/FDIS 22733-1:2021(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 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 at the address

below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2021 – All rights reserved
---------------------- Page: 2 ----------------------
ISO/FDIS 22733-1:2021(E)
Contents Page

Foreword ..........................................................................................................................................................................................................................................v

Introduction ................................................................................................................................................................................................................................vi

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Variables ....................................................................................................................................................................................................................... 3

4.1 Reference system .................................................................................................................................................................................. 3

4.2 Lateral offset ............................................................................................................................................................................................. 3

4.3 Variables to be measured ............................................................................................................................................................... 4

5 Equivalent vehicle target ............................................................................................................................................................................. 4

6 Measuring equipment and data processing ............................................................................................................................. 4

6.1 General ........................................................................................................................................................................................................... 4

6.2 Description ................................................................................................................................................................................................. 4

6.3 Transducer installation.................................................................................................................................................................... 5

6.4 Calibration .................................................................................................................................................................................................. 5

6.5 Data processing ...................................................................................................................................................................................... 5

7 Test conditions ....................................................................................................................................................................................................... 5

7.1 General ........................................................................................................................................................................................................... 5

7.2 General data ............................................................................................................................................................................................... 5

7.3 Test track ...................................................................................................................................................................................................... 5

7.4 Weather conditions ............................................................................................................................................................................. 5

7.5 Surroundings ............................................................................................................................................................................................ 6

7.6 VUT .................................................................................................................................................................................................................... 6

7.6.1 General vehicle condition ......................................................................................................................................... 6

7.6.2 AEB system settings ...................................................................................................................................................... 6

7.6.3 Deployable pedestrian protection systems............................................................................................... 7

7.6.4 Tyres ........................................................................................................................................................................................... 7

7.6.5 Braking system .................................................................................................................................................................. 7

7.6.6 Other influencing system .......................................................................................................................................... 7

7.6.7 Loading conditions of the vehicle ...................................................................................................................... 8

8 Test procedure ........................................................................................................................................................................................................ 8

8.1 Test preparation ..................................................................................................................................................................................... 8

8.1.1 Brake conditioning ......................................................................................................................................................... 8

8.1.2 Tyre conditioning ............................................................................................................................................................ 8

8.2 Test scenarios ........................................................................................................................................................................................... 9

8.3 Test conduct ...........................................................................................................................................................................................10

8.4 Test execution .......................................................................................................................................................................................10

8.4.1 Speed .......................................................................................................................................................................................10

8.4.2 Validity criteria ...............................................................................................................................................................10

8.4.3 End of test conditions ...............................................................................................................................................11

8.4.4 Determination of speed incremental steps ............................................................................................11

9 DBS tests (optional) ........................................................................................................................................................................................11

10 Performance metrics ....................................................................................................................................................................................11

10.1 Maximum speed of VUT at which collision is avoided: V ..........................................................................

VUT 11

10.2 Mean longitudinal acceleration of the VUT: (A ) .....................................................................................

VUT mean 11

10.3 Maximum longitudinal acceleration of the VUT with DBS: (A ) ...................................................

VUT max 12

10.4 Average increase rate of longitudinal acceleration of VUT with DBS: (A ) .........

VUT increase rate 12

10.5 Impact speed of VUT at which collision first occurs: V ..........................................................................

impact 12

10.6 Activation time of AEBS: T ...................................................................................................................................................

AEB 12

10.7 Activation time of FCW: T ....................................................................................................................................................

FCW 12
© ISO 2021 – All rights reserved iii
---------------------- Page: 3 ----------------------
ISO/FDIS 22733-1:2021(E)

10.8 Maximum yaw rate of the VUT: ψψ .............................................................................................................................12

VUT

10.9 Lateral offset of the VUT: Y ..................................................................................................................................................

VUT 12

10.10 Maximum steering wheel velocity of VUT: Ω ......................................................................................................

VUT 12

Annex A (informative) Brake application procedure .......................................................................................................................13

Annex B (informative) Test report .......................................................................................................................................................................15

Bibliography .............................................................................................................................................................................................................................18

iv © ISO 2021 – All rights reserved
---------------------- Page: 4 ----------------------
ISO/FDIS 22733-1:2021(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.

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).

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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 prepared by Technical Committee ISO/TC 22, Road Vehicles, Subcommittee SC 33,

Vehicle dynamics and chassis components.
A list of all parts in the ISO 22733 series can be found on the ISO website.

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.
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ISO/FDIS 22733-1:2021(E)
Introduction

The capacity to avoid or mitigate a collision during potential accident is an important part of the

performance of an autonomous emergency braking system. This document is intended to assess

performance of an autonomous emergency braking system under defined test scenario only.

NOTE Moreover, insufficient knowledge is available concerning the relationship between overall vehicle

dynamic properties and accident avoidance. (A substantial amount of work is necessary to acquire enough and

reliable data on the correlation between accident avoidance and vehicle dynamic properties in general and the

results of these tests in particular.)
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FINAL DRAFT INTERNATIONAL STANDARD ISO/FDIS 22733-1:2021(E)
Road vehicles — Test method to evaluate the performance
of autonomous emergency braking systems —
Part 1:
Car-to-car
1 Scope

This document specifies a method to evaluate the behaviour of a vehicle equipped with an autonomous

emergency braking system (AEBS), or dynamic brake support (DBS) during several accident scenarios.

Those accidents occur during a straight-line driving when the vehicle under test (VUT) approaches

another vehicle in the same lane. Both vehicles are aligned in longitudinal axis to each other.

The most important part of the vehicle behaviour during these accidents scenarios is the capacity to

avoid or mitigate the collision.
Systems requiring driver intervention are not in the scope of this document.

NOTE Depending on accidentology, only a part of the scenarios can be used for an evaluation of performance.

AEB system evaluation based upon this document is limited to longitudinal accident scenarios.

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 8855:2011, Road vehicles — Vehicle dynamics and road-holding ability — Vocabulary

ISO 15037-1:2019, Road vehicles — Vehicle dynamics test methods — Part 1: General conditions for

passenger cars

ISO 19206-1, Road vehicles — Test devices for target vehicles, vulnerable road users and other objects, for

assessment of active safety functions — Part 1: Requirements for passenger vehicle rear-end targets

3 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO 8855, ISO 15037-1 and the

following apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
AEB
autonomous emergency braking

braking applied automatically by the vehicle in response to the detection of a likely collision to reduce

the vehicle speed and potentially avoid the collision
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ISO/FDIS 22733-1:2021(E)
3.2
CCRs
car-to-car rear stationary

collision in which a vehicle travels forward towards another stationary vehicle and the frontal structure

of the vehicle strikes the rear structure of the stationary vehicle
3.3
CCRm
car-to-car rear moving

collision in which a vehicle travels forward towards another vehicle travelling at constant speed and

the frontal structure of the vehicle strikes the rear structure of the leading vehicle

3.4
CCRb
car-to-car rear braking

collision in which a vehicle travels forward towards another vehicle travelling at constant speed and

then decelerates, and the frontal structure of the vehicle strikes the rear structure of the leading vehicle

3.5
DBS
dynamic brake support

system that further amplifies the driver braking demand in response to the detection of a likely collision

to achieve a greater deceleration
3.6
EVT
equivalent vehicle target
vehicle target as defined in ISO 19206-1
3.7
FCW
forward collision warning

audiovisual warning provided automatically by the vehicle in response to the detection of a likely

collision to alert the driver
3.8
peak braking coefficient
PBC

measure of tyre-to-road surface friction based on the maximum deceleration of a rolling tyre

Note 1 to entry: Measured using ASTM E1136-10, at a speed of 64,4 km/h, without water delivery.

3.9
TTC
time-to-collision

remaining time before the VUT strikes the EVT (3.6), assuming that the VUT and EVT travel at

constant speed
3.10
VUT
vehicle under test

vehicle tested with a pre-crash collision mitigation or avoidance system on board

3.11
AEB
time when the AEB (3.1) system activates

Note 1 to entry: Activation time is determined by identifying the last data point where the filtered acceleration

2 2

signal is below -1 m/s , and then going back to the point in time where the acceleration first crossed -0,3 m/s .

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ISO/FDIS 22733-1:2021(E)
3.12
FCW
time when the audible warning of the FCW (3.7) starts

Note 1 to entry: The starting point is determined by audible analysis or video analysis.

3.13
impact
vehicle velocity at which the VUT hits the EVT (3.6)
3.14
rel_impact

relative speed at which the VUT hits the EVT (3.6) by subtracting the velocity of the EVT from Vimpact

(3.13) at the time of collision
4 Variables
4.1 Reference system
The reference earth frame according to ISO 8855:2011, 2.8 is defined as:
— X axis: intended straight line path projected on the ground to front;
— Y axis: perpendicular to X axis on the ground to left;
— Z axis: perpendicular to the ground to the top.
4.2 Lateral offset

The lateral offset is determined as the lateral distance between the centre of the front of the VUT and

the centre of the rear of the EVT when measured in parallel to the intended straight-lined path as shown

in Figure 1.
Key
1 intended straight-lined path
2 VUT
3 VUT path
4 EVT
5 EVT path
Figure 1 — Coordinate system and notation
The lateral offset is defined as YY+ .
VUTe__rrorEVT error

The origin is an arbitrary point on X axis. The Y and Y are measured in the reference

VUT target_error
frame and the Y is identical to Y .
target_error EVTe_ rror
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ISO/FDIS 22733-1:2021(E)
4.3 Variables to be measured

Table 1 lists all relevant variables to be measured. All dynamic data shall be sampled and recorded at

a frequency of at least 100 Hz. EVT and VUT data shall be synchronized by using the differential GPS

(DGPS) time stamp of the EVT.
Table 1 — Variables to be measured
Variable Symbol
CCRs and CCRm: T equals TTC = 4 s T
0 0
CCRb: T when EVT starts decelerating
T , time when AEB activates T
Time
AEB AEB
T , time when FCW activates T
FCW FCW
T , time when VUT impacts EVT T
impact impact
Position of the VUT during the entire test
X , Y
VUT VUT
Position
Position of the EVT during the entire test
X , Y
EVT EVT
Speed of the VUT during the entire test:
VUT
— V , speed when VUT impacts EVT V
impact impact
Speed
— V , relative speed when VUT impacts EVT V
reli_ mpact reli_ mpact
Speed of the EVT during the entire test
EVT
Yaw velocity of the VUT during the entire test 
VUT
Yaw velocity
Yaw velocity of the EVT during the entire test 
EVT
Acceleration of the VUT during the entire test
EVT
Acceleration
Acceleration of the EVT during the entire test
EVT
An example of a test report is given in Annex B.
5 Equivalent vehicle target

The equivalent vehicle target (EVT) shall meet the requirements as defined in ISO 19206-1.

6 Measuring equipment and data processing
6.1 General

The test conditions on measurement equipment and data processing shall be in accordance with

ISO 15037-1:2019, Clause 6, unless otherwise specified below.
6.2 Description

VUT and EVT shall be equipped with data measurement and acquisition equipment to sample and

record data with an accuracy of at least:
— VUT and EVT speed to 0,1 km/h;
— VUT and EVT lateral and longitudinal position to 0,03 m;
— VUT and EVT yaw rate to 0,1°/s;
— VUT and EVT longitudinal acceleration to 0,1 m/s ;
— steering wheel velocity to 1,0°/s.
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ISO/FDIS 22733-1:2021(E)
6.3 Transducer installation

The transient vehicle pitch changes shall not adversely affect the measurement of the velocity and

distance variables for the chosen transducer system.
6.4 Calibration

All transducers shall be calibrated according to the manufacturer’s instructions. The transducer

manufacturer’s recommended application software and firmware version shall be used. If parts of

the measuring system can be adjusted, such calibration shall be performed immediately before the

beginning of the tests.
6.5 Data processing
Filter the measured data as follows:
— position and speed are not filtered and are used in their raw state;

— acceleration with a 12-pole phaseless Butterworth filter with a cut-off frequency of 10 Hz;

— yaw rate with a 12-pole phaseless Butterworth filter with a cut-off frequency of 10 Hz;

— force with a 12-pole phaseless Butterworth filter with a cut-off frequency of 10 Hz.

7 Test conditions
7.1 General

The test conditions shall be in accordance with ISO 15037-1:2019, Clause 6, unless otherwise

specified below.
7.2 General data

General data on the test vehicle and test conditions shall be recorded as specified in

ISO 15037-1:2019, 6.4.1.
7.3 Test track

Conduct tests on a dry (no visible moisture on the surface), uniform, solid-paved surface with a

consistent slope between level and 1 %. The test surface shall have a minimal peak braking coefficient

(PBC) of 0,9.

The surface shall be paved and shall not contain any irregularities (e.g. large dips or cracks, manhole

covers or reflective studs) that may give rise to abnormal sensor measurements within a lateral

distance of 3,0 m to either side of the theoretical path line and with a longitudinal distance of 30 m

beyond the position of VUT/EVT at the end of the test.

Lane markings are allowed. However, testing may only be conducted in an area where typical road

markings depicting a driving lane may not be parallel to the test path within 3,0 m either side. Lines

or markings may cross the test path but may not be present in the area where AEB activation and/or

braking after FCW is expected.
7.4 Weather conditions

Conduct tests in dry conditions with ambient temperature above 0 °C and below 45 °C.

The surface temperature of the test track shall be between +10 °C and +50 °C.
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ISO/FDIS 22733-1:2021(E)

No precipitation shall be falling and the horizontal visibility at ground level shall be greater than 1 km.

Wind speeds shall be below 5 m/s to minimise EVT and VUT disturbance.

Natural ambient illumination shall be homogenous in the test area and more than 1 000 lx for daylight

testing with no strong shadows cast across the test area other than those caused by the VUT or EVT.

Ensure testing is not performed while driving towards or away from the sun when there is direct

sunlight.

Measure and record the following parameters preferably at the commencement of every single test or

at least every 30 min:
1) ambient temperature in °C;
2) track temperature in °C;
3) wind speed and direction m/s;
4) ambient illumination in lx.

Weather conditions are based on ISO 21994. For some proving grounds where the lower limit of ambient

temperature of 0 °C is difficult to achieve, a lower value can be adopted. However, in that case, the lower

limit values shall be reported.
7.5 Surroundings

Conduct testing such that there are no other vehicles, obstructions, other objects or persons protruding

above the test surface that may give rise to abnormal sensor measurements within a lateral distance

of 3,0 m to either side of the test path and within a longitudinal distance of 30 m beyond the position at

which the test finishes. Test areas where the VUT needs to pass under overhead signs, bridges, gantries

or other significant structures are not permitted.

The general view ahead and to either side of the test area shall comprise of a wholly plain man made or

natural environment (e.g. further test surface, plain coloured fencing or hoardings, natural vegetation

or sky) and shall not comprise any highly reflective surfaces or contain any vehicle-like silhouettes that

may give rise to abnormal sensor measurements.
7.6 VUT
7.6.1 General vehicle condition

The VUT condition shall be in accordance with the vehicle manufacturer’s specifications, particularly

with respect to the suspension geometries, power train (e.g. differentials and locks) configuration, and

tyre fitment.
7.6.2 AEB system settings

If different settings are available, a setting shall be selected and finally reported. This setting shall

not be changed until the entire test procedure is completed. The test procedure can be repeated for

different settings if needed.

The AEB test protocol defined by EuroNCAP provides the following instruction for the AEB setting

selection.

Set any driver configurable elements of the AEB and/or FCW system (e.g. the timing of the collision

warning or the braking application if present) to the middle setting or midpoint and then next latest

setting similar to the examples shown in Table 2.
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ISO/FDIS 22733-1:2021(E)
Table 2 — AEB and/or FCW system setting for testing
Available settings Selected setting
a b
Setting 1 , Setting 2 Setting 2
a b
Setting 1 , Setting 2, Setting 3 Setting 2
a b
Setting 1 , Setting 2, Setting 3, Setting 4 Setting 3
Early brake triggering.
Late brake triggering.

The aim of EuroNCAP is to compare the performance of different vehicles with the same way of setting

selection.

The purpose of this document is to measure the performance of AEB on one given vehicle. Then if

several settings are available, the performance can be evaluated in any given setting.

7.6.3 Deployable pedestrian protection systems

When the vehicle is equipped with a deployable pedestrian protection system, this system shall be

deactivated before the AEB tests commence.
7.6.4 Tyres

Generally, all measurements shall be conducted with original fitment tyres. If several types of tyres are

available, the type of tyres shall be reported.
For a general tyre condition, new tyres shall be fitted
...

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