ISO 16234:2006

Heavy commercial vehicles and buses - Straight-ahead braking on surfaces with split coefficient of friction - Open-loop test method

ISO 16234:2006 describes an open-loop test method for determining vehicle reactions during a straight-line braking manoeuvre on a surface having a split coefficient of friction. It applies to heavy vehicles, i.e. commercial vehicles, commercial vehicle combinations, buses and articulated buses as defined in ISO 3833 (trucks and trailers with maximum weight above 3,5 tonnes and buses and articulated buses with maximum weight above 5 tonnes, according to ECE and EC vehicle classification, categories M3, N2, N3, O3 and O4). The method is limited to vehicles in which at least the first unit is equipped with an anti-lock braking system. It is valid for braking with service-brake systems only or in combination with retarders and/or engine brakes.

Véhicules utilitaires lourds — Freinage en ligne droite sur surfaces à adhérence mixte — Méthode d'essai en boucle ouverte

General Information

• Status: Published
• Publication Date: 05-Dec-2006
• ICS: 43.080.01 - Commercial vehicles in general
• Technical Committee: ISO/TC 22/SC 33 - Vehicle dynamics and chassis components
• Drafting Committee: ISO/TC 22/SC 33/WG 6 - Vehicle dynamics of heavy commercial vehicles and buses
• Current Stage: 9093 - International Standard confirmed
• Start Date: 24-Feb-2021
• Completion Date: 13-Dec-2025

Overview

ISO 16234:2006 - "Heavy commercial vehicles and buses - Straight‑ahead braking on surfaces with split coefficient of friction - Open‑loop test method" defines an open‑loop test procedure to quantify vehicle reactions during straight‑line braking when the road surface has a split coefficient of friction (high on one side, low on the other). It applies to heavy vehicles as defined in ISO 3833 (categories M3, N2, N3, O3, O4) and requires that at least the first unit is fitted with an anti‑lock braking system (ABS). The method covers service‑brake operation alone or combined with retarders/engine brakes.

Key Topics and Requirements

• Test principle: Measure vehicle yaw reaction and longitudinal acceleration during full braking across a split‑friction track (open‑loop, steering held fixed).
• Vehicle scope: Heavy trucks, combinations, buses and articulated buses (see ISO 3833 weight/classification limits).
• ABS requirement: At least the first unit must have an ABS fitted.
• Test track: One side high friction, the other low friction (difference between coefficients ≥ 0.4). Low side may use natural ice or artificial surfaces; friction must be measured and recorded before and after runs.
• Initial conditions & control: Steering wheel held within ±3°; braking applied rapidly to 100% (pedal stroke or pedal force ≥ 500 N for hydraulic systems). First runs recommended at 30 km/h, then increased by 10 km/h increments.
• Measured variables (minimum): longitudinal velocity, yaw velocity per unit, brake pedal position/force, steering‑wheel angle, yaw articulation angles, longitudinal acceleration, initial brake temperature. Recommended additional data: brake pressures, wheel speeds, sideslip angle and lateral acceleration.
• Brake condition: Brakes must be burnished and free of contamination; initial brake temperatures reported (typical disc: 50–200 °C; drum: 50–150 °C).
• Safety: Tests can produce large yaw/articulation angles and loss of control - use sufficient run‑off area, anti‑jack‑knife devices and outriggers where appropriate.
• Measurement & reporting: Instrumentation and transducers per ISO 15037‑2:2002; test reports follow templates in Annex A/B of ISO 16234.

Applications and Users

• Vehicle dynamics test engineers validating braking behavior on mixed‑adhesion surfaces.
• OEMs and suppliers evaluating ABS, brake system performance and vehicle stability under split‑friction scenarios.
• Test labs developing reference data for comparative handling studies and safety development. Note: ISO 16234 results quantify a limited aspect of dynamic behavior and - per the standard - are not intended as a regulatory test or sole basis for safety certification.

Related Standards

• ISO 3833 - vehicle types, terms and definitions
• ISO 15037‑2:2002 - general conditions for heavy vehicle dynamic tests (instrumentation)
• ISO 611, ISO 8855 - terminology and vehicle dynamics vocabulary
• ISO 8349 - referenced friction measurement method

Keywords: ISO 16234:2006, split coefficient of friction, heavy commercial vehicles, straight‑ahead braking, open‑loop test method, ABS, vehicle dynamics, split‑friction track.

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 16234
First edition
2006-12-01
Heavy commercial vehicles and buses —
Straight-ahead braking on surfaces with
split coefficient of friction — Open-loop
test method
Véhicules utilitaires lourds — Freinage en ligne droite sur surfaces à
adhérence mixte — Méthode d'essai en boucle ouverte

Reference number
©
ISO 2006
PDF disclaimer
This PDF file may contain embedded typefaces. In accordance with Adobe's licensing policy, this file may be printed or viewed but
shall not be edited unless the typefaces which are embedded are licensed to and installed on the computer performing the editing. In
downloading this file, parties accept therein the responsibility of not infringing Adobe's licensing policy. The ISO Central Secretariat
accepts no liability in this area.
Adobe is a trademark of Adobe Systems Incorporated.
Details of the software products used to create this PDF file can be found in the General Info relative to the file; the PDF-creation
parameters were optimized for printing. Every care has been taken to ensure that the file is suitable for use by ISO member bodies. In
the unlikely event that a problem relating to it is found, please inform the Central Secretariat at the address given below.

©  ISO 2006
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means,
electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or
ISO's member body in the country of the requester.
ISO copyright office
Case postale 56 • CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail [e-mail]
Web www.iso.org
Published in Switzerland
ii © ISO 2006 – All rights reserved

Contents Page
Foreword. iv
Introduction . v
1 Scope . 1
2 Normative references . 1
3 Terms, definitions and symbols. 1
3.1 Terms and definitions. 1
3.2 Symbols . 1
4 Principle. 2
5 Measuring equipment. 2
6 Variables . 2
7 Test conditions . 3
7.1 General. 3
7.2 Test track . 3
7.3 Test vehicle . 4
8 Test method. 4
8.1 Condition and temperature of the brakes . 4
8.2 Initial driving conditions . 4
8.3 Performance of the braking procedure . 4
8.4 Time references . 5
9 Data evaluation . 6
9.1 General. 6
9.2 Validity criteria . 7
9.3 Time history. 7
9.4 Characteristic values. 7
9.5 Further additional evaluation . 8
Annex A (normative) Test report — General data and test conditions . 9
Annex B (normative) Test report — Presentation of results . 10
Bibliography . 15

Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 16234 was prepared by Technical Committee ISO/TC 22, Road vehicles, Subcommittee SC 9, Vehicle
dynamics and road-holding ability.
iv © ISO 2006 – All rights reserved

Introduction
The dynamic behaviour of a road vehicle is a most important aspect of active vehicle safety. Any given
vehicle, together with its driver and the prevailing environment, constitutes a unique closed-loop system. The
task of evaluating the dynamic behaviour is therefore very difficult, since significant interactions of these
driver-vehicle-road elements are each complex in themselves. A description of the behaviour of the road
vehicle must inevitably involve information obtained from a number of tests of different types.
Since this test method quantifies only a small part of the complete handling characteristics, the results of this
test can only be considered significant for a correspondingly small part of the overall dynamic behaviour.
Moreover, sufficient knowledge is not available to correlate overall vehicle dynamic properties with accident
prevention. A large amount of work is necessary to acquire sufficient and reliable data on the correlation
between accident prevention and vehicle dynamic properties in general, and the results of this test in
particular. Therefore, it is not possible to use this method and test results for regulation purposes.

INTERNATIONAL STANDARD ISO 16234:2006(E)

Heavy commercial vehicles and buses — Straight-ahead
braking on surfaces with split coefficient of friction —
Open-loop test method
1 Scope
This international Standard describes an open-loop test method for determining vehicle reactions during a
straight-line braking manoeuvre on a surface having a split coefficient of friction.
It applies to heavy vehicles, i.e. commercial vehicles, commercial vehicle combinations, buses and articulated
buses as defined in ISO 3833 (trucks and trailers with maximum weight above 3,5 tonnes and buses and
articulated buses with maximum weight above 5 tonnes, according to ECE and EC vehicle classification,
categories M3, N2, N3, O3 and O4).
The method is limited to vehicles in which at least the first unit is equipped with an anti-lock braking system. It
is valid for braking with service-brake systems only or in combination with retarders and/or engine brakes.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
ISO 611, Road vehicles — Braking of automotive vehicles and their trailers — Vocabulary
ISO 3833, Road vehicles — Types — Terms and definitions
ISO 8855, Road vehicles — Vehicle dynamics and road-holding ability — Vocabulary
ISO 15037-2:2002, Road vehicles — Vehicle dynamics test methods — Part 2: General conditions for heavy
vehicles and buses
3 Terms, definitions and symbols
3.1 Terms and definitions
For the purposes of this International Standard, the terms and definitions in ISO 611, ISO 15037-2:2002 and
ISO 8855 apply.
3.2 Symbols
For the purposes of this International Standard, the symbols in ISO 15037-2:2002 and ISO 8855 apply.
4 Principle
The objective of this test method is to determine the effects on the yaw reaction and the longitudinal
acceleration of a vehicle produced by a braking manoeuvre on a straight roadway having a low coefficient of
friction on one side and a high coefficient of friction on the other side.
Test results are strongly influenced by friction coefficients as well as the difference in friction between the left
and right side of the course. A large difference between the left- and right-side friction conditions is desirable.
Surface properties other than friction coefficient (e.g. roughness, ice or synthetic materials, etc.) that are not
quantified by the friction coefficient alone exert an important influence on the test results. For this reason, it is
difficult to establish the surface conditions in a reproducible way. Therefore, comparison of results should only
be made for tests done on a given track within a short time period. It may also be useful to include tests of a
reference vehicle.
The initial condition for the test is driving in a straight line at constant velocity. The steering wheel is held fixed
after the braking manoeuvre is initiated. During the test, the operating functions and vehicle responses are
measured and recorded. Characteristic values are determined from the measured signals.
5 Measuring equipment
The measuring equipment, transducer installation and data processing shall be in accordance with
ISO 15037-2:2002.
6 Variables
The variables of motion used to describe the behaviour of the vehicle shall be related to the intermediate axis
system (X, Y, Z) of the individual vehicle units (See ISO 8855 and ISO 15037-2:2002).
The variables that shall be determined for compliance with this International Standard are:
⎯ longitudinal velocity, v ,
x

⎯ yaw velocity of each unit of the test vehicle, ψ ,
i,i==1,nn number of units
⎯ brake pedal position (for vehicles with air brake systems),
⎯ brake pedal force (for vehicles with hydraulic brake systems),
⎯ steering-wheel angle, δ ,
H
J
⎯ yaw articulation angles, Γ ,
i
⎯ longitudinal acceleration, a ,
x
⎯ initial brake temperatures, T .
B,0
It is also recommended that the following variables be determined:
⎯ supply pressure and brake pressures of interest, p ,
B
⎯ rotational velocity of wheels, ω or equivalent wheel speeds from electronic systems,
i, i=1,. n
⎯ sideslip angle of the first unit, β ,
a .
⎯ lateral acceleration,
y
2 © ISO 2006 – All rights reserved

Typical operating ranges of the variables to be determined for this International Standard are shown in Table 1
and in ISO 15037-2:2002.
Table 1 — Variables, typical operating ranges and recommended maximum errors of variables not
listed in ISO 15037-2:2002
Reco
...