ISO 21994:2022

INTERNATIONAL ISO
STANDARD 21994
Second edition
2022-11
Passenger cars — Stopping distance
at straight-line braking with ABS —
Open-loop test method
Voitures particulières — Distance d'arrêt de freinage en ligne droite
avec ABS — Méthode d'essai en boucle ouverte
Reference number
© ISO 2022
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ii
Contents Page
Foreword .v
Introduction . vi
1 S c op e . 1
2 Nor m at i ve r ef er enc e s . 1
3 Terms and definitions . 1
4 P r i nc iple . 1
5 Va r i able s . 2
5.1 R eference system . 2
5.2 V ariables to be measured . 2
6 Mea su r i n g e qu ipment . 2
6 .1 D e s c r ip t ion . 2
6.2 T ransducer installation . 3
6.3 Calibration . 3
6.4 D ata processing. 3
7 Te s t c ond it ion s .3
7.1 G eneral test conditions . 3
7.2 G eneral data . 3
7.3 T est track . 4
7.4 Environmental conditions . 4
7.5 T est vehicle . 4
7.5.1 G eneral vehicle condition . 4
7.5.2 Tyres . 4
7.5.3 Braking system . 5
7.5.4 L oading conditions of the vehicle . 5
8 Te s t pr o c e du r e .5
8.1 T est preparation . 5
8.1.1 Defining the measurement distance . 5
8.1.2 Conditioning tyres and brake system . 5
8.2 Measurements . . 6
8.2.1 Brake disc temperature . 6
8.2.2 I nitial driving condition . 6
8.2.3 Brake pedal actuation . 6
8.2.4 C onditions during braking . 7
8.2.5 N umber of measurements . 7
9 D ata evaluation and presentation of results . 7
9.1 G eneral . 7
9.2 N omenclature of distances and decelerations . 8
9.3 Determination of normalized stopping distance s . 8
A100,norm
9.3.1 Determination of mean deceleration of a single test run . 8
9.3.2 D etermination of the normalized stopping distance of a single test run . 9
9.3.3 Determination of mean deceleration and mean normalized stopping
distance . 9
9.4 D etermining of ABS-braking distance s (100) (optional) . 9
L90,norm
9.5 D etermination of normalized build-up distance s (optional) . 10
F10,norm
Annex A (informative) Test report − General data .11
Annex B (informative) Test report − Test conditions and results .13
Annex C (informative) Test sequence, specific terms and background information .15
Annex D (normative) Method for determination of F .20
ABS
iii
Annex E (normative) Requirements for measurements and measuring equipment .24
Annex F (normative) Structure of the stopping distance calculation .26
Bibliography .27
iv
Foreword
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This document was prepared by Technical Committee ISO/TC 22, Road vehicles, Subcommittee SC 33,
Vehicle dynamics and chassis components.
This second edition cancels and replaces the first edition (ISO 21994:2007), which has been technically
revised.
The main changes are as follows:
— variables in formulae have been corrected.
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.
v
Introduction
The stopping distance of a road vehicle is an important part of vehicle performance and active vehicle
safety. Any given vehicle, together with its driver and the prevailing environment, constitutes a unique
closed-loop system. The task of determining the stopping distance is therefore, very difficult, since
there is a significant interaction between these driver-vehicle-environment elements, each of which is
complex in itself.
Test conditions and tyres have a strong influence on test results. Therefore, only vehicle stopping
distances obtained under comparable test and tyre conditions are comparable to one another.
vi
INTERNATIONAL STANDARD ISO 21994:2022(E)
Passenger cars — Stopping distance at straight-line
braking with ABS — Open-loop test method
1 S cope
This document specifies an open-loop test method to determine the stopping distance of a vehicle
during a straight-line braking manoeuvre, with the anti-lock braking system (ABS) fully engaged. This
document applies to passenger cars as defined in ISO 3833 and light trucks.
This document specifies a reference method and is especially designed to ensure high repeatability.
2 Normat ive 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, Road vehicles — Vehicle dynamics and road-holding ability — Vocabulary
ISO 15037
...