ISO 18868:2013

INTERNATIONAL ISO
STANDARD 18868
First edition
2013-07-01
Commercial road vehicles — Coupling
equipment between vehicles in
multiple vehicle combinations —
Strength requirements
Véhicules routiers utilitaires — Équipement de couplage entre
véhicules dans des combinaisons de véhicules multiples — Exigences
de résistance
Reference number
©
ISO 2013
© ISO 2013
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ii © ISO 2013 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Terms and definitions . 1
3 Symbols . 2
4 ISO vehicle combinations definition . 4
4.1 ISO vehicle combination 1 . 4
4.2 ISO vehicle combination 2 . 4
4.3 ISO vehicle combination 3 . 4
4.4 ISO vehicle combination 4 . 4
4.5 ISO vehicle combination 5 . 4
5 General requirements . 5
5.1 Vehicle combination handling . 5
5.2 Determination of minimum coupling equipment performance capability required for a
specific vehicle combination . 5
6 Worked numerical examples . 8
6.1 ISO combination 1: truck + dolly + A-semi (numerical example) . 8
6.2 ISO combination 2: tractor + A-semi + centre-axle trailer (numerical example) . 9
6.3 ISO combination 3: tractor + A-semi + dolly + A-semi (numerical example) . 9
6.4 ISO combination 4: truck + centre-axle trailer + centre-axle trailer (numerical example) 10
6.5 ISO combination 5: tractor + link-trailer + A-semi (B-train) (numerical example).10
Bibliography .11
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. 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. 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.
The committee responsible for this document is ISO/TC 22, Road vehicles, Subcommittee SC 15,
Interchangeability of components of commercial vehicles and buses.
iv © ISO 2013 – All rights reserved

Introduction
This International Standard specifies general requirements and definitions to secure the safe operation
of mechanical couplings between individual vehicles in a multiple-vehicle combination.
The expanded application of multiple-vehicle combinations brings new perspectives and needs into
the area of trailer couplings. This has made evident the need for a consolidated method to handle the
dimensioning of mechanical couplings applied in multiple-vehicle combinations. This International
Standard is meant to facilitate the interaction between International Standards and relevant regulations.
The drivers for the introduction of this International Standard are
— the development of the European modular system making multiple-vehicle combinations (road
trains) more of a global application, and
— the lack of rules for the dimensions of couplings used together with converter dolly. Those
applications are already very common on the roads today.
The limited number of types of multiple-vehicle combinations addressed in this International Standard
is the result of a voting process among the nations. Other types may be added in later editions as
experience is gained.
INTERNATIONAL STANDARD ISO 18868:2013(E)
Commercial road vehicles — Coupling equipment
between vehicles in multiple vehicle combinations —
Strength requirements
1 Scope
This International Standard defines different multiple-vehicle combinations (vehicle combinations with
more than one coupling point) and the formulae to calculate the requirement of performance for the coupling
equipment used in those vehicle combinations. Vehicle categories concerned are N2, N3, O3, and O4.
NOTE For these vehicle combinations, the formulae in this International Standard override the formulae in
References [6], [7], [8], and [9] that apply to vehicle combinations with one coupling point only. However, the
capability of the coupling equipment is still determined through tests as defined in References [6], [7], [8], and [9].
2 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
2.1
centre-axle trailer (CAT)
trailer where the axle(s) is(are) positioned close to the centre of gravity of the trailer such that (when uniformly
loaded) only a small static vertical load, not exceeding 10 % of the load corresponding to the maximum
design total mass of the trailer or 1 000 daN (whichever is less), is transmitted to the towing vehicle
2.2
converter dolly
towed vehicle with one axle group or single axle and a fifth wheel coupling, designed to be combined
with a semi-trailer
Note 1 to entry: In cases where the drawbar of the converter dolly is hinged, the combination of a converter dolly
and a semi-trailer is equivalent to a full trailer.
Note 2 to entry: The drawbar of a converter dolly may be rigid or hinged. A hinged drawbar is free to pivot around
an axle that is perpendicular to the vertical plane.
Figure 1 — Converter dolly
2.3
drawbar trailer
trailer having at least two axles, of which at least one is a steered axle, equipped with a towing device
(drawbar) which can move vertically (in relation to the trailer) and that transmits less than 100 daN as
a static vertical load to the towing vehicle
2.4
semi-trailer
trailer which is designed and constructed to be by means of a kingpin coupled to a tractor unit or to a
converter dolly and that impose a substantial vertical load on the towing vehicle
2.5
A-trailer
semi-trailer in a multiple-vehicle combination that is towed on a converter dolly
2.6
link–trailer (or B-trailer)
semi-trailer with a fifth wheel mounted at the rear such that a semi-trailer could be towed by the link-trailer
2.7
tractor
motor vehicle built to tow a semi-trailer
2.8
truck
motor vehicle built to tow a full trailer or a centre-axle trailer
1)
3 Symbols
3.1
S
mass imposed vertically on the coupling under static conditions by the CAT loaded to its maximum
design total mass
3.2
T
technically permissible maximum total mass, in tonnes, of the towing vehicle including, as applicable,
the vertical static load, S, of a CAT or the vertical static load, U, imposed by a semi-trailer
3.3
R
technically permissible maximum total mass, in tonnes, of the full trailer (with drawbar free to move in
the vertical plane) or of the semi-trailer
3.4
C
mass, in tonnes, transmitted to the ground by the axle(s) of the CAT loaded to its maximum total design mass
3.5
U (U , U , U )
T d b
mass, in tonnes, imposed vertically on the fifth wheel of a tractor (U ), a converter dolly (U ), or a
T d
B-trailer (U ) by the semi-trailer loaded to its maximum total design mass
b
Note 1 to entry: The total mass of a semi-trailer (R) is divided into two parts for the calculation: the front part (U )
x
and the rear part (R ) giving the bogey mass.
b
3.6
W
d
tare mass, in tonnes, of a converter dolly
3.7
g
acceleration due to gravity (assumed as 9,81 m/s )
1) The symbols defined below are in line with those used in UNECE R55.
2 © ISO 2013 – All rights reserved

3.8
a
equivalent vertical acceleration in the coupling point, dependent on the kind of suspension on the rear
axle(s) of the towing vehicle including a constant factor
3.8.1
a
1,8 m/s for vehicles with air suspension or equivalent
3.8.2
a
2,4 m/s for vehicles with other suspension
3.9
X (X )
i
length, in metres, of the loading area of the centre-axle trailer
3.10
L (L )
i
theoretical drawbar length, in metres, i.e. the distance between the centre of the drawbar eye and the
centre of the axle assembly of the centre-axle trailer
3.11
t
i
distance, in meter, from the centre of axles of a centre-axle trailer to its rear coupling point
3.12
R
b
mass, in tonnes, transmitted to the ground by the axle(s) of the semi-trailer loaded to its maximum
total design mass
3.13
C
d
mass, in tonnes, transmitted to the ground by the axle(s) of the converter dolly including U
d
3.14
D (D )
c
D-value is a comparative value determined by calculating for the longitudinal forces occurring between
a towing vehicle and a trailer
Note 1 to entry: D, expressed in kilonewtons.
Note 2 to entry: For applications where a drawbar coupling is subject to vertical forces, the related D-value is
designated D . Defined by the formulae given in the tables of 5.2.2.
c
3.15
V
V-value is a comparative value determined by calculating for the vertical forces occurring between a
towing vehicle and a centre-axle trailer
Note 1 to entry: Defined by the formulae given in the tables of 5.2.2.
3.16
A and B
parameters used in the calculations.
Note 1 to entry: “A” is the total mass forward of the coupling point.
Note 2 to entry: “B” is the total mass behind the coupling point.
Note 3 to entry: Their detailed definitions as sum of masses are given in the tables of 5.2.2.
4 ISO vehicle combinations definition
4.1 ISO vehicle combination 1
Figure 2 — truck + dolly + A-semi
4.2 ISO vehicle combination 2
Figure 3 — tractor + A-semi + centre-axle trailer
4.3 ISO vehicle combination 3
Figure 4 — tractor + A-semi + dolly + A-semi
4.4 ISO vehicle combination 4
Figure 5 — truck + centre-axle trailer + centre-axle trailer
4.5 ISO vehicle combination 5
Figure 6 — tractor + link-trailer + A-semi (B-train)
4 © ISO 2013 – All rights reserved

5 General requirements
5.1 Vehicle combination handling
A prerequisite for the coupling performance requirements of this International Standard is that the
overall design of the ve
...