Regulation No. 79-01

Name:Regulation No. 79-01
Description:Steering Equipment.
Official Title:Uniform Provisions Concerning the Approval of: Vehicles with Regard to Steering Equipment.
Country:ECE - United Nations
Date of Issue:1988-11-30
Amendment Level:01 Series, Supplement 5
Number of Pages:37
Vehicle Types:Bus, Car, Heavy Truck, Light Truck, Trailer
Subject Categories:Steering, Wheels and Tyres
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Keywords:

steering, vehicle, system, control, approval, equipment, regulation, energy, paragraph, means, transmission, systems, trailer, annex, failure, type, requirements, driver, provisions, wheels, supply, electrical, vehicles, function, maximum, case, manufacturer, performance, towing, steered, speed, amendments, warning, test, defined, series, technical, forces, service, operation, conditions, trailers, part, hydraulic, mechanical, effort, angle, braking, safety, force

Text Extract:

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E/ECE/324
) Rev.1/Add.78/Rev.2/Amend.2
E/ECE/TRANS/505 )
February 22, 2017
STATUS OF UNITED NATIONS REGULATION
ECE 79-01
UNIFORM PROVISIONS CONCERNING THE APPROVAL OF:
VEHICLES WITH REGARD TO STEERING EQUIPMENT
Incorporating:
Supplement 1 to the 00 series of amendments
Date of Entry into Force: 11.02.90
Corr. 1 to the 00 series of amendments
Dated: 09.11.90
Supplement 2 to the 00 series of amendments
Date of Entry into Force: 05.12.94
01 series of amendments
Date of Entry into Force: 14.08.95
Corr. 2 to the 00 series of amendments
Dated: 30.06.95
Supplement 1 to the 01 series of amendments
Date of Entry into Force: 07.02.99
Supplement 2 to the 01 series of amendments
Date of Entry into Force: 31.01.03
Supplement 3 to the 01 series of amendments
Date of Entry into Force: 04.04.05
Supplement 4 to the 01 series of amendments
Date of Entry into Force: 13.02.14
Supplement 5 to the 01 series of amendments
Date of Entry into Force: 09.02.17

REGULATION
REGULATION NO. 79
UNIFORM PROVISIONS CONCERNING THE APPROVAL OF VEHICLES
WITH REGARD TO STEERING EQUIPMENT
Introduction
1. Scope
2. Definitions
3. Application for Approval
4. Approval
5. Construction Provisions
6. Test Provisions
7. Conformity of Production
CONTENTS
8. Penalties for Non-conformity of Production
9. Modification and Extension of Approval of the Vehicle Type
10. Production Definitely Discontinued
11. Names and Addresses of Technical Services Responsible for Conducting Approval Tests
and of Administrative Departments
ANNEXES
Annex 1
Annex 2
Annex 3
Annex 4
Annex 5
Annex 6
Annex 7
Communication Concerning the Approval or Refusal or Extension or Withdrawal of Approval
or Production Definitely Discontinued of a Vehicle Type with Regard to Steering Equipment
Pursuant to Regulation No. 79
Arrangements of Approval Marks
Braking Performance for Vehicles Using the Same Energy Source to Supply Steering
Equipment and Braking Device
Additional Provisions for Vehicles Equipped with ASE
Provisions for Trailers Having Purely Hydraulic Steering Transmission
Special Requirements to be Applied to the Safety Aspects of Complex Electronic Vehicle
Control Systems
Special provisions for the powering of trailer steering systems from the towing vehicle.

1. SCOPE
1.1. This Regulation applies to the steering equipment of vehicles of Categories M, N and O ;
1.2. This Regulation does not apply to:
1.2.1. Steering equipment with a purely pneumatic transmission;
1.2.2. Autonomous Steering Systems as defined in Paragraph 2.3.3;
2. DEFINITIONS
For the purposes of this Regulation:
2.1. "Approval of a vehicle" means the approval of a vehicle type with regard to its steering
equipment.
2.2. "Vehicle type" means a vehicle which does not differ with respect to the manufacturer's
designation of the vehicle type and in essential characteristics such as:
2.2.1. Type of steering equipment, steering control, steering transmission, steered wheels, and
energy source.
2.3. "Steering equipment" means all the equipment the purpose of which is to determine the
direction of movement of the vehicle.
The steering equipment consists of:
The steering control,
The steering transmission,
The steered wheels,
The energy supply, if any.
2.3.1. "Steering control" means the part of the steering equipment which controls its operation, it
may be operated with or without direct intervention of the driver. For steering equipment in
which the steering forces are provided solely or partly by the muscular effort of the driver the
steering control includes all parts up to the point where the steering effort is transformed by
mechanical, hydraulic or electrical means.

2.3.6. "Energy supply" includes those parts of the steering equipment which provide it with
energy, regulate that energy and where appropriate, process and store it. It also includes
any storage reservoirs for the operating medium and the return lines, but not the vehicle's
engine (except for the purpose of Paragraph 5.3.2.1.) or its drive to the energy source.
2.3.6.1. "Energy source" means the part of the energy supply, which provides the energy in the
required form.
2.3.6.2. "Energy reservoir" means that part of the energy supply in which the energy provided by
the energy source is stored, for example, a pressurised fluid reservoir or vehicle battery.
2.3.6.3. "Storage reservoir" means that part of the energy supply in which the operating medium is
stored at or near to the atmospheric pressure, for example a fluid reservoir.
2.4. Steering parameters
2.4.1. "Steering control effort" means the force applied to the steering control in order to steer
the vehicle.
2.4.2. "Steering time" means the period of time from the beginning of the movement of the
steering control to the moment at which the steered wheels have reached a specific steering
angle.
2.4.3. "Steering angle" means the angle between the projection of a longitudinal axis of the
vehicle and the line of intersection of the wheel plane (being the central plane of the wheel,
normal to the axis around which it rotates) and the road surface.
2.4.4. "Steering forces" mean all the forces operating in the steering transmission.
2.4.5. "Mean steering ratio" means the ratio of the angular displacement of the steering control
to the mean of the swept steering angle of the steered wheels for a full lock-to-lock turn;
2.4.6. "Turning circle" means the circle within which are located the projections onto the ground
plane of all the points of the vehicle, excluding the external-devices for indirect vision and
the front direction indicators, when the vehicle is driven in a circle;
2.4.7. "Nominal radius of steering control" means in the case of a steering wheel the shortest
dimension from its centre of rotation to the outer edge of the rim. In the case of any other
form of control it means the distance between its centre of rotation and the point at which
the steering effort is applied. If more than one such point is provided, the one requiring the
greatest effort shall be used.

2.5.3. Depending on the arrangement of the steered wheels, the following types of steering
equipment are distinguished:
2.5.3.1. "Front-wheel steering equipment" in which only the wheels of the front axle(s) are
steered. This includes all wheels which are steered in the same direction;
2.5.3.2. "Rear-wheel steering equipment" in which only the wheels of the rear axle(s) are steered.
This includes all wheels which are steered in the same direction;
2.5.3.3. "Multi-wheel steering equipment" in which the wheels of one or more of each of the front
and the rear axle(s) are steered;
2.5.3.3.1. "All-wheel steering equipment" in which all the wheels are steered.
2.5.3.3.2. "Buckle steering equipment" in which the movement of chassis parts relative to each
other is directly produced by the steering forces.
2.6. Types of Steering Transmission
Depending on the way the steering forces are transmitted, the following types of steering
transmission are distinguished:
2.6.1. "Purely mechanical steering transmission" means a steering transmission in which the
steering forces are transmitted entirely by mechanical means.
2.6.2. "Purely hydraulic steering transmission" means a steering transmission in which the
steering forces, somewhere in the transmission, are transmitted only by hydraulic means.
2.6.3. "Purely electric steering transmission" means a steering transmission in which the
steering forces, somewhere in the transmission, are transmitted only through electric
means.
2.6.4. "Hybrid steering transmission" means a steering transmission in which part of the
steering forces are transmitted through one and the other part through another of the
above-mentioned means. However, in the case where any mechanical part of the
transmission is designed only to give position feedback and is too weak to transmit the total
sum of the steering forces, this system shall be considered to be purely hydraulic or purely
electric steering transmission.
2.7. "Electric control line" means the electrical connection which provides the steering control
function to the trailer. It comprises the electrical wiring and connector and includes the parts
for data communication and the electrical energy supply for the trailer control transmission.

4.4.1. a circle surrounding the Letter "E" followed by the distinguishing number of the country
which has granted approval;
4.4.2. the number of this Regulation, followed by the Letter R, a dash and the approval number to
the right of the circle prescribed in Paragraph 4.4.1.
4.5. If the vehicle conforms to a vehicle type approved, under one or more other Regulations
annexed to the Agreement, in the country which has granted approval under this
Regulation, the symbol prescribed in Paragraph 4.4.1. need not be repeated; in such a case
the Regulation and approval numbers and the additional symbols of all the Regulations
under which approval has been granted in the country which has granted approval under
this Regulation shall be placed in vertical columns to the right of the symbol prescribed in
Paragraph 4.4.1.
4.6. The approval mark shall be clearly legible and shall be indelible.
4.7. The approval mark shall be placed close to or on the vehicle data plate affixed by the
manufacturer.
4.8. Annex 2 to this Regulation gives examples of arrangements of approval marks.
5. CONSTRUCTION PROVISIONS
5.1. General Provisions
5.1.1. The steering equipment shall ensure easy and safe handling of the vehicle up to its
maximum design speed or in case of a trailer up to its technically permitted maximum
speed. There must be a tendency to self-centre when tested in accordance with Paragraph 6.2.
with the intact steering equipment. The vehicle shall meet the requirements of Paragraph 6.2.
in the case of motor vehicles and of Paragraph 6.3. in the case of trailers. If a vehicle is
fitted with an auxiliary steering system, it shall also meet the requirements of Annex 4.
Trailers equipped with hydraulic steering transmissions shall comply also with Annex 5.
5.1.2. It must be possible to travel along a straight section of road without unusual steering
correction by the driver and without unusual vibration in the steering system at the maximum
design speed of the vehicle.

5.1.8. Steering Transmission
5.1.8.1. Adjustment devices for steering geometry must be such that after adjustment a positive
connection can be established between the adjustable components by appropriate locking
devices.
5.1.8.2. Steering transmission which can be disconnected to cover different configurations of a
vehicle (e.g. on extendable semi-trailers), must have locking devices which ensure positive
relocation of components; where locking is automatic, there must be an additional safety
lock which is operated manually.
5.1.9. Steered Wheels
The steered wheels shall not be solely the rear wheels. This requirement does not apply to
semi-trailers.
5.1.10. Energy Supply
The same energy supply may be used for the steering equipment and other systems.
However in the case of a failure in any system which shares the same energy supply
steering shall be ensured in accordance with the relevant failure conditions of
Paragraph 5.3.
5.1.11. Control Systems
The requirements of Annex 6 shall be applied to the safety aspects of electronic vehicle
control systems that provide or form part of the control transmission of the steering function
including advanced driver assistance steering systems. However, systems or functions, that
use the steering system as the means of achieving a higher level objective, are subject to
Annex 6 only insofar as they have a direct effect on the steering system. If such systems are
provided, they shall not be deactivated during type approval testing of the steering system.
5.2. Special Provisions for Trailers
5.2.1. Trailers (with the exception of semi-trailers and centre-axle trailers) which have more than
one axle with steered wheels and semi-trailers and centre-axle trailers which have at least
one axle with steered wheels must fulfil the conditions given in Paragraph 6.3. However, for
trailers with self-tracking steering equipment a test under Paragraph 6.3. is not necessary if
the axle load ratio between the unsteered and the self-tracking axles equals or exceeds 1.6.
under all loading conditions.
However for trailers with self-tracking steering equipment, the axle load ratio between
unsteered or articulated steered axles and friction-steered axles shall be at least 1 under all
loading conditions.
5.2.2. If the towing vehicle of a vehicle combination is driving straight ahead, the trailer and towing
vehicle must remain aligned. If alignment is not retained automatically, the trailer must be
equipped with a suitable adjustment facility for maintenance.

5.3.2. Power Assisted Steering Systems
5.3.2.1. Should the engine stop or a part of the transmission fail, with the exception of those parts
listed in Paragraph 5.3.1.1., there shall be no immediate changes in steering angle. As long
as the vehicle is capable of being driven at a speed greater than 10km/h the requirements
given in Paragraph 6., relating to a system with a failure, shall be met.
5.3.3. Full Power Steering Systems
5.3.3.1. The system shall be designed such that the vehicle cannot be driven indefinitely at speeds
above 10km/h where there is any fault which requires operation of the warning signal
referred to in Paragraph 5.4.2.1.1.
5.3.3.2. In case of a failure within the control transmission, with the exception of those parts listed in
Paragraph 5.1.4., it shall still be possible to steer with the performance laid down in
Paragraph 6. for the intact steering system.
5.3.3.3. In the event of a failure of the energy source of the control transmission, it shall be possible
to carry out at least 24 "figure of eight" manoeuvres, where each loop of the figure is 40m
diameter at 10km/h speed and at the performance level given for an intact system in
Paragraph 6. The test manoeuvres shall begin at an energy storage level given in
Paragraph 5.3.3.5.
5.3.3.4. In the event of a failure within the energy transmission, with the exception of those parts
listed in Paragraph 5.3.1.1., there shall not be any immediate changes in steering angle. As
long as the vehicle is capable of being driven at a speed greater than 10km/h the
requirements of Paragraph 6. for the system with a failure shall be met after the completion
of at least 25 "figure of eight" manoeuvres at 10km/h minimum speed, where each loop of
the figure is 40m diameter.
The test manoeuvres shall begin at an energy storage level given in Paragraph 5.3.3.5.
5.3.3.5. The energy level to be used for the tests referred to in Paragraphs 5.3.3.3. and 5.3.3.4. shall
be the energy storage level at which a failure is indicated to the driver.
In the case of electrically powered systems subject to Annex 6, this level shall be the worst
case situation outlined by the manufacturer in the documentation submitted in connection
with Annex 6 and shall take into account the effects of e.g. temperature and ageing on
battery performance.

5.5. Provisions for the Periodic Technical Inspection of Steering Equipment
5.5.1. As far as practicable and subject to agreement between the vehicle manufacturer and the
type approval authority, the steering equipment and its installation shall be so designed that,
without disassembly, its operation can be checked with, if necessary, commonly used
measuring instruments, methods or test equipment.
5.5.2. It must be possible to verify in a simple way the correct operational status of those
Electronic Systems, which have control over steering. If special information is needed, this
shall be made freely available.
5.5.2.1. At the time of Type Approval the means implemented to protect against simple unauthorized
modification to the operation of the verification means chosen by the manufacturer
(e.g. warning signal) shall be confidentially outlined.
Alternatively this protection requirement is fulfilled when a secondary means of checking the
correct operational status is available.
6. TEST PROVISIONS
6.1. General Provisions
6.1.1. The test shall be conducted on a level surface affording good adhesion.
6.1.2. During the test(s) the vehicle shall be loaded to its technically permissible maximum mass
and its technically permissible maximum load on the steered axle(s).
In the case of axles fitted with ASE, this test shall be repeated with the vehicle loaded to its
technically permissible maximum mass and the axle equipped with ASE loaded to its
maximum permissible load.
6.1.3. Before the test begins, the tyre pressures shall be as prescribed by the manufacturer for the
mass specified in Paragraph 6.1.2. when the vehicle is stationary.
6.1.4. In the case of any systems that use electrical energy for part or all of the energy supply, all
performance tests shall be carried out under conditions of actual or simulated electrical load
of all essential systems or systems components which share the same energy supply.
Essential systems shall comprise at least lighting systems, windscreen wipers, engine
management and braking systems.
6.2. Provisions for Motor Vehicles
6.2.1. It must be possible to leave a curve with a radius of 50m at a tangent without unusual
vibration in the steering equipment at the following speed:
Category M vehicles: 50km/h
Category M , M , N , N and N vehicles: 40km/h
or the maximum design speed if this is below the speeds given above.

6.3. Provisions for Trailers
6.3.1. The trailer must travel without excessive deviation or unusual vibration in its steering
equipment when the towing vehicle is travelling in a straight line on a flat and horizontal road
at a speed of 80km/h or the technically permissible maximum speed indicated by the trailer
manufacturer if this is less than 80km/h.
6.3.2. With the towing vehicle and trailer having adopted a steady state turn corresponding to a
turning circle radius of 25m (see Paragraph 2.4.6.) at a constant speed of 5km/h, the circle
described by the rearmost outer edge of the trailer shall be measured. This manoeuvre shall
be repeated under the same conditions but at a speed of 25km/h ± 1km/h. During these
manoeuvres, the rearmost outer edge of the trailer travelling at a speed of 25km/h ± 1km/h
shall not move outside the circle described at a constant speed of 5km/h by more than
0.7m.
6.3.3. No part of the trailer must move more than 0.5m beyond the tangent to a circle with a radius
of 25m when towed by a vehicle leaving the circular path described in Paragraph 6.3.2.
along the tangent and travelling at a speed of 25km/h. This requirement must be met from
the point the tangent meets the circle to a point 40m along the tangent. After that point the
trailer must fulfill the condition specified in Paragraph 6.3.1.
6.3.4. The annular ground area swept by the towing vehicle/trailer combination with an intact
steering system, driving at no more than 5km/h in a constant radius circle with the front
outer corner of the towing vehicle describing a radius of 0.67 × vehicle combination length
but not less than 12.5m is to be measured.
6.3.4.1. If, with a fault in the steering system, the measured swept annular width is > 8.3m, then this
must not be an increase of more than 15% compared with the corresponding value
measured with the intact steering system.
There shall not be any increase in the outer radius of the swept annular width.
6.3.5. The tests described in Paragraphs 6.3.2., 6.3.3. and 6.3.4. shall be conducted in both
clockwise and anti-clockwise directions.
7. CONFORMITY OF PRODUCTION
The Conformity of Production Procedures shall comply with those set out in the
1958 Agreement, Appendix 2 (E/ECE/324–E/ECE/TRANS/505/Rev.2), with the following
requirements:
7.1. The holder of the approval must ensure that results of the conformity of production tests are
recorded and that the annexed documents remain available for a period determined in
agreement with the approval authority or technical service. This period must not exceed
10 years counted from the time when production is definitely discontinued.
7.2. The type approval authority or technical service which has granted type approval may at any
time verify the conformity control methods applied in each production facility. The normal
frequency of these verifications shall be once every two years.

ANNEX 1
COMMUNICATION
(Maximum format: A4 (210 x 297mm))
issued by:
Name of administration
.......................................................
.......................................................
.......................................................
Concerning
APPROVAL GRANTED
APPROVAL EXTENDED
APPROVAL REFUSED
APPROVAL WITHDRAWN
PRODUCTION DEFINITELY DISCONTINUED
of a vehicle type with regard to steering equipment pursuant to Regulation No. 79
Approval No. .................................................. Extension No. ................................
1. Trade name or mark of vehicle ..................................................................................................
2. Vehicle type ................................................................................................................................
3. Manufacturer's name and address ............................................................................................
4. If applicable, name and address of manufacturer's representative
...................................................................................................................................................
5. Brief description of the steering equipment:
5.1. Type of steering equipment .......................................................................................................
5.2. Steering control ..........................................................................................................................
5.3. Steering transmission.................................................................................................................
5.4. Steered wheels ..........................................................................................................................
5.5. Energy source ............................................................................................................................
6. Results of tests, vehicle characteristics .....................................................................................
6.1. Steering effort required to achieve a turning circle of 12m radius with an intact system and
20m radius with a system in the failed condition .......................................................................

ANNEX 2
ARRANGEMENTS OF APPROVAL MARKS
Model A
(See Paragraph 4.4. of this Regulation)
a = 8mm min.
The above approval mark affixed to a vehicle shows that the vehicle type concerned has, with regard to
steering equipment, been approved in the Netherlands (E4) pursuant to Regulation No. 79 under
approval No. 012439. The approval number indicates that the approval was granted in accordance with
the requirements of Regulation No. 79 incorporating the 01 series of amendments.
Model B
(See Paragraph 4.5. of this Regulation)
a = 8mm min.
The above approval mark affixed to a vehicle shows that the vehicle type concerned has been approved
in the Netherlands (E4) pursuant to Regulation Nos. 79 and 31. The approval numbers indicate that, at
the dates when the respective approvals were given, Regulation No. 79 incorporating the 01 series of
amendments and Regulation No. 31 included the 01 series of amendments.

3. After any failure in the steering equipment, or the energy supply, it shall be possible after eight
full stroke actuations of the service brake control, to achieve at the ninth application, at least the
performance prescribed for the secondary (emergency) braking system (See table below).
In the case where secondary performance requiring the use of stored energy is achieved by a
separate control, it shall still be possible after eight full stroke actuations of the service brake
control to achieve at the ninth application, the residual performance (See table below).
SECONDARY AND RESIDUAL EFFICIENCY
Category
V (km/h)
Secondary braking
(m/s )
Residual braking
(m/s )
M 100 2.44 –
M and M 60 2.5 1.5
N
(i) 70 2.2 1.3
(ii) 100 2.44 –
N 50 2.2 1.3
N 40 2.2 1.3

2.2.1.1. Circular test
The vehicle shall be driven into a test circle with a radius "R" (m) and a speed "V" (km/h)
corresponding to its category and the values given in the table below:
Vehicle category R V
M and N 100 80
M and N 50 50
M and N 50 45
The failure shall be introduced when the specified test speed has been reached. The test
shall include driving in a clockwise direction and in a counter-clockwise direction.
2.2.1.2. Transient test
2.2.1.2. Until uniform test procedures have been agreed, the vehicle manufacturer shall provide the
technical services with their test procedures and results for transient behaviour of the
vehicle in the case of failure.
2.3. Warning Signals in Case of Failure
2.3.1. Except for parts of ASE not considered susceptible to breakdown as specified in
Paragraph 5.3.1.1. of this Regulation, the following failure of ASE shall be clearly brought to
the attention of the driver.
2.3.1.1. A general cut-off of the ASE electrical or hydraulic control.
2.3.1.2. Failure of the ASE energy supply.
2.3.1.3. A break in the external wiring of the electrical control if fitted.

1. GENERAL
ANNEX 6
SPECIAL REQUIREMENTS TO BE APPLIED TO THE SAFETY ASPECTS
OF COMPLEX ELECTRONIC VEHICLE CONTROL SYSTEMS
This Annex defines the special requirements for documentation, fault strategy and verification
with respect to the safety aspects of Complex Electronic Vehicle Control Systems
(Paragraph 2.3. below) as far as this Regulation is concerned.
This Annex may also be called, by special paragraphs in this Regulation, for safety related
functions which are controlled by electronic system(s).
This Annex does not specify the performance criteria for "The System" but covers the
methodology applied to the design process and the information which must be disclosed to
the technical service, for type approval purposes.
This information shall show that "The System" respects, under normal and fault conditions, all
the appropriate performance requirements specified elsewhere in this Regulation.
2. DEFINITIONS
For the purposes of this Annex,
2.1. "Safety concept" is a description of the measures designed into the system, for example
within the electronic units, so as to address system integrity and thereby ensure safe
operation even in the event of an electrical failure.
The possibility of a fall-back to partial operation or even to a back-up system for vital vehicle
functions may be a part of the safety concept.
2.2. "Electronic control system" means a combination of units, designed to co-operate in the
production of the stated vehicle control function by electronic data processing.
Such systems, often controlled by software, are built from discrete functional components
such as sensors, electronic control units and actuators and connected by transmission links.
They may include mechanical, electro-pneumatic or electro-hydraulic elements. "The
System", referred to herein, is the one for which type approval is being sought.
2.3. "Complex electronic vehicle control systems" are those electronic control systems which
are subject to a hierarchy of control in which a controlled function may be over-ridden by a
higher level electronic control system/function.
A function which is over-ridden becomes part of the complex system.
2.4. "Higher-Level control" systems/functions are those which employ additional processing
and/or sensing provisions to modify vehicle behaviour by commanding variations in the
normal function(s) of the vehicle control system.
This allows complex systems to automatically change their objectives with a priority which
depends on the sensed circumstances.

3.2.3. Limits defining the boundaries of functional operation (Paragraph 2.8.) shall be stated where
appropriate to system performance.
3.3. System Layout and Schematics
3.3.1. Inventory of Components
A list shall be provided, collating all the units of "The System" and mentioning the other
vehicle systems which are needed to achieve the control function in question.
An outline schematic showing these units in combination, shall be provided with both the
equipment distribution and the interconnections made clear.
3.3.2. Functions of the Units
The function of each unit of "The System" shall be outlined and the signals linking it with other
units or with other vehicle systems shall be shown. This may be provided by a labelled block
diagram or other schematic, or by a description aided by such a diagram.
3.3.3. Interconnections
Interconnections within "The System" shall be shown by a circuit diagram for the electric
transmission links, by a piping diagram for pneumatic or hydraulic transmission equipment
and by a simplified diagrammatic layout for mechanical linkages.
3.3.4. Signal Flow and Priorities
There shall be a clear correspondence between these transmission links and the signals
carried between Units. Priorities of signals on multiplexed data paths shall be stated wherever
priority may be an issue affecting performance or safety as far as this Regulation is
concerned.
3.3.5. Identification of Units
Each unit shall be clearly and unambiguously identifiable (e.g. by marking for hardware and
marking or software output for software content) to provide corresponding hardware and
documentation association.
Where functions are combined within a single unit or indeed within a single computer, but
shown in multiple blocks in the block diagram for clarity and ease of explanation, only a single
hardware identification marking shall be used. The manufacturer shall, by the use of this
identification, affirm that the equipment supplied conforms to the corresponding document.
3.3.5.1. The identification defines the hardware and software version and, where the latter changes
such as to alter the function of the Unit as far as this Regulation is concerned, this
identification shall also be changed.
3.4. Safety Concept of the Manufacturer
3.4.1. The manufacturer shall provide a statement which affirms that the strategy chosen to achieve
"The System" objectives will not, under non-fault conditions, prejudice the safe operation of
systems which are subject to the prescriptions of this Regulation.

4. VERIFICATION AND TEST
4.1. The functional operation of "The System", as laid out in the documents required in
Paragraph 3., shall be tested as follows:
4.1.1. Verification of the Function of "The System"
As the means of establishing the normal operational levels, verification of the performance of
the vehicle system under non-fault conditions shall be conducted against the manufacturer's
basic benchmark specification unless this is subject to a specified performance test as part of
the approval procedure of this or another Regulation.
4.1.2. Verification of the Safety Concept of Paragraph 3.4
The reaction of "The System" shall, at the discretion of the type approval authority, be
checked under the influence of a failure in any individual unit by applying corresponding
output signals to electrical units or mechanical elements in order to simulate the effects of
internal faults within the unit.
4.1.2.1. The verification results shall correspond with the documented summary of the failure analysis,
to a level of overall effect such that the safety concept and execution are confirmed as being
adequate.

2.5. Wiring and Connectors
2.5.1. The cables used to supply the trailer electrical energy shall have a conductor cross-sectional
area compatible with the continuous current defined in Paragraph 2.3. above.
2.5.2. Until a uniform standard has been defined the connector used to connect to the trailer shall
fulfil the following:
(a)
(b)
(c)
The pins shall have a current carrying capacity compatible with the maximum
continuous current defined in Paragraph 2.3. above;
Until uniform standards have been agreed the environmental protection of the
connector shall be appropriate to the application and included in the Annex 6
assessment; and
The connector shall not be interchangeable with an existing electrical connector
currently used on the towing vehicle i.e. ISO 7638, ISO 12098, etc.
2.6. Marking
2.6.1. The towing vehicle shall be marked to indicate the maximum current available for the trailer
as defined in Paragraph 2.3. above.
The marking shall be indelible and positioned so that it is visible when connecting the
electrical interface referenced in Paragraph 2.5.2. above.
3. REQUIREMENTS FOR TRAILERS
3.1. The maximum current requirement of the trailer steering system shall be defined by the
vehicle manufacturer.
3.2. The nominal operating voltage is 24V.
3.3. The electrical energy available from the towing vehicle shall only be used as follows:
(a)
Exclusively for use by the trailer steering system;
or
(b)
For the trailer steering system and to power auxiliary systems on the trailer provided
the steering system has priority and is protected from an overload external to the
steering system. This protection shall be a function of the trailer steering system.

3.7. Marking
3.8.1. Trailers equipped with a connector for the supply of electrical energy to the trailer steering
system shall be marked to include the following information:
(a)
(b)
The maximum current requirement for the trailer steering system as defined in
Paragraph 3.1. above.
The functionality of the trailer steering system including the impact on manoeuvrability
when the connector is connected and disconnected.
The marking shall be in indelible form and positioned so that it is visible when connecting to
the electrical interface referenced in Paragraph 3.3.2. above.
Steering Equipment.