This is Schedule 4 of the Heavy-vehicle Brakes Rule.

 

Schedule 4     Heavy Vehicle Brake Code, Second edition

First edition published 1991
Second edition published June 1997

ISBN 0-478-20615-1

Land Transport Safety Authority, PO Box 2840, Wellington, New Zealand
Telephone 04-494 8600, Fax 04-494 8601

 

Acknowledgement

The Land Transport Safety Authority (LTSA) gratefully acknowledges the substantial contributions made by the Chairman and members of the original Heavy Vehicle Brake Code Committee, individually and collectively, in the preparation of this Code and for the support given to committee members by their respective employers.

The LTSA would also like to thank the various organisations that have made vehicles, equipment and services available, for without their support the production of this Code would not have been possible.

The LTSA is grateful to the present members of the Heavy Vehicle Brake Code Technical Advisory Group for their continuing support and guidance for the on-going implementation of the Code.

 

Contents

Preface to the first edition

Preface to the second edition

Aims of the Code

1.0     Scope and interpretation

2.0     Definitions

3.0     Compliance

4.0     Specifications

5.0     Exemptions for power-driven vehicles which are equipped to tow trailers

 

Appendices

A.     Distribution of braking among the axles of vehicles and requirements for compatibility between towing vehicle and trailer.

B.     The standard procedure for measuring the response time on vehicles equipped with compressed air brakes (based on ECE 13 Annex 6).

C.     Statement of compliance with the New Zealand Heavy Vehicle Braking Code.

D.     Pressure test connections for air-braking systems

E.     Provisions for air compressors and their receivers (based on ECE13, Annex 7)

 

Preface to the first edition

Background to the New Zealand situation

In New Zealand, power-driven vehicles are imported from overseas suppliers, the majority coming from Europe, North America, Japan and Australia. The result is that the local powered-vehicle population has variations of the braking systems common to the country of origin. Locally manufactured trailers generally use imported brake components and are only required to meet emergency stop and parking performances.

By legislation, New Zealand has lower individual axle loadings than are common in the countries from which the power-driven vehicles and trailer components are sourced. The road tax on heavy vehicles is collected through a system known as Road User Charges and applies to vehicles over 3500 kg gross weight. It is allocated according to gross vehicle mass, axle configuration and distance travelled. This form of road tax has given rise to a situation where operators are encouraged to fit additional axles to reduce possible road damage. Braking problems therefore can arise because the axles used on these vehicles are designed for substantially higher loadings and are fitted with brakes sized accordingly.

 

The Code

This Code has been developed to improve the braking performance of heavy vehicles in New Zealand by an industry-based committee consisting of representatives from the MVMA, NZRTA, IRTENZ, IRL, NZTTMF and LTSA. The code is based on European brake performance requirements, namely the United Nation Economic Commission of Europe Regulation 13, (ECE 13). To facilitate its adoption into the Brake Code, some simplifications to the regulation have been made and special New Zealand requirements have been included. Every effort has been made to minimise the extent of modifications necessary for existing vehicles to meet the Code requirements.

This Code has been gazetted as the recommended alternative braking standard (under Regulation 16A(2) of the Heavy Motor Vehicle Regulations 1974) to the current Interim Performance Heavy Vehicle Braking Specification, for vehicle combinations operating with a gross combined mass (GCM) of between 39,000 kg and 44,000 kg.

 

Preface to the second edition

The present Heavy Vehicle Brake Code Technical Advisory Group (TAG) was established in 1993 to replace the original Heavy Brake Code Committee. The Technical Advisory Group is made up of representatives from the transport industry and advises the Land Transport Safety Authority on the continuing implementation of the Code.

It is intended that in due course:

• • the Code will be the principal guide to compliance with the statutory braking requirements for heavy vehicles;
• • the range of vehicles the Code currently applies to may be extended. The present lower limit of 39,000 kg GCM may be reduced further to cover all significant heavy vehicles operating in combination.

Any extension to the range of heavy vehicles covered by this Code would only be made after consultation with the TAG and transport industry.

Vehicle combinations operating in excess of 44,000 kg and with a valid overweight permit are exempted from having to comply with this Code by notice in the New Zealand Gazette.

 

Aims of the code

The aim of this Code is to improve heavy vehicle safety by standardising braking performance by:

• • ensuring certified individual vehicles in a fully laden state meet the required braking performance at all levels of braking and axle loads permitted under the Heavy Motor Vehicle Regulations 1974;
• • ensuring the continuing compliance of vehicles certified to this Code;
• • improving the compatibility between powered vehicles and trailers to ensure that vehicles in a combination function in harmony, provide optimum brake performance and improve directional stability; and
• • introducing a brake control system with common characteristics on all heavy motor vehicles operating between 39,000 kg and 44,000 kg GCM. This ensures protection of individual vehicles, efficient emergency braking and safe parking of individual vehicles and vehicle combination.

 

Auxiliary brake equipment

The requirements for supplementary brake equipment (which are permitted by the Code) are specified. This equipment includes such items as trailer hand control, anti-lock braking systems (ABS), load sensing devices and engine retarders. If any of this equipment is fitted to a certified vehicle then the vehicle must be re-certified.

 

1.0     Scope and interpretation

This Code is the preferred alternative braking standard to the Interim Performance Specification for Heavy Vehicle Braking, published by the previous Ministry of Transport. All vehicles operating in combination, with a GCM between 39,000 kg and 44,000 kg, must comply with either braking standard. Any changes to the application of the Code will be published in the New Zealand Gazette.

This Code applies to power-driven and towed vehicles equally with each vehicle assessed individually.

In this Code the words must or shall indicate a mandatory requirement to be met in order to comply with the Code. The word should indicates a recommendation.

 

2.0     Definitions

2.1     General

2.1.1     After market: the general market place in which vehicle parts, in particular friction material, are supplied by producers and importers other than the original vehicle manufacturers (OE).

2.1.2     Brake code mass (BCM): the maximum laden mass of a vehicle as calculated using statutory maximum axle load criteria. (This measure of vehicle mass must be used in all code calculations (refer Appendix "A".), but not entered on the vehicle’s Certificate of Compliance.)

2.1.3     Certifier: a person who is a manufacturer or their agent and any other person who is recognised by the Director as being experienced in the braking of heavy motor vehicles for the purposes of the Code. Certified has a corresponding meaning.

2.1.4     Code: the New Zealand Heavy Vehicle Brake Code, Second Edition.

2.1.5     Drawing vehicle: a vehicle equipped to tow a trailer and includes a truck, a tractor unit or trailer, e.g. the centre trailer of a B-train.

2.1.6     Examiner: a person who has passed a suitable training course recognised by the New Zealand Qualifications Authority and is recognised by the Director as being experienced in the braking of heavy motor vehicles and who can act on a Certifier’s behalf to certify that a vehicle meets the Code.

2.1.7     Gross vehicle mass (GVM) the gross laden mass of a vehicle as specified by the manufacturer or the Director, whichever is the greater.

2.1.8     Gross combination mass (GCM) is equal to the sum of the manufacturer’s recommended GVMs of the towing and towed vehicles operating in a combination. It is the greater of that specified by the manufacturer of the drawing vehicle(s) or the Director.

2.1.9     Manufacturer: for the purposes of this Code, means a person acceptable to the Director, who engages in the manufacture, assembly, or importation of vehicles with a GVM of more than 3500 kg.

2.1.10     Mass and weight: have the same meaning in the Code.

2.1.11     Operator: means a person who drives or causes or permits a vehicle to be on any road.

2.1.12     The Director: means the Director of Land Transport Safety or persons with authority duly delegated by the Director for the purposes of this Code.

2.1.13     The Statutory Authority: means the Crown agency responsible for enforcing transport legislation.

2.1.14     Tractor: means a vehicle designed to tow articulated trailers.

2.1.15     Vehicle type: a category of vehicle which does not differ in such essential respects as:

• • vehicle category (e.g., passenger vehicle or goods vehicle, power-driven vehicle or trailer);
• • gross vehicle mass (as defined above);
• • distribution of mass among the axles;
• • type of brake system;
• • number, relative position and arrangement of the axles and suspension types.

2.1.16     Unladen mass: means the mass of the vehicle complete with fuel and equipment necessary for it to undertake its designed purpose.

2.1.17     A wheel: in the Code means a disc assembly on which a vehicle runs and includes the wheel disc, rim and tyre. A twin wheel is taken to mean two wheels.

2.1.18     Modify: means to change a vehicle from its original state by altering or substituting any part or component; but does not include repair. Modified and modification have corresponding meanings.

 

2.2     Trailer Definitions

2.2.1     Centre axle trailer: also known as a simple trailer means a trailer (not being a full trailer or semi-trailer) fitted with a drawbar rigidly attached to the chassis or body of the trailer.

2.2     Full trailer: a trailer fitted with at least two axle sets equipped with a drawbar which controls the direction of the front axle set and which does not transmit any significant vertical load to the towing vehicle.

2.2.3     Semi-trailer: also known as an articulated trailer means a trailer having one axle set positioned behind the centre of gravity of the vehicle (when fully laden) so that a substantial portion of the towed vehicle’s laden mass (GVM) is carried by the towing vehicle.

2.2.4     Simple trailer: also known as a centre axle trailer means a trailer (not being a full trailer or semi-trailer) fitted with a drawbar rigidly attached to the chassis or body of the trailer.

2.2.5     Trailer: a vehicle without motive power that is constructed for the purpose of being towed or propelled by a motor vehicle from which it is readily detachable.

 

2.3     Brake Definitions

2.3.1     Auxiliary line: also known as auxiliary, means an air supply line run from the towing vehicle to the trailer(s) to operate equipment other than brakes.

2.3.2     Auxiliary braking equipment: brake equipment supplementary to the fundamental brake system which gives the driver greater control and improved brake performance, such equipment includes:

• • anti-lock braking system (ABS) - a central brake control system which limits the locking up of wheels during a brake application;
• • load sensing device - a device which controls the brake air pressure to a particular axle, depending on the load carried by that axle;
• • trailer hand control - a manual control that can be used by the driver to apply a gradated braking action to the trailer alone;
• • retarder - fitted to either the vehicle’s engine or transmission to augment its braking capability during a prolonged brake application, e.g. a long descent.

2.3.3     Air brake system: a system in which braking requires the use of compressed air.

2.3.4     An axle set: in terms of brake relining refers to when the brake lining is replaced at one end of an axle, the brake lining at the other end of the same axle must also be replaced using the same material.

2.3.5     Brake: means the assembly in which frictional forces opposing the movement of the vehicle are developed.

2.3.6     A brake application occurs when the service brakes of a vehicle have been applied and released.

2.3.7     Brake coupling: also known as a coupling head or coupling block, the device for connecting the control and supply lines of the drawing vehicle to the control and supply lines of the trailer.

2.3.8     Braking force: the retarding force generated by a brake assembly.

2.3.9     Brake system: means the combination of parts whose function is to progressively reduce the speed of a moving vehicle or bring it to a halt, or keep it stationary if it is already halted. The system includes the control, the circuit and the foundation brake.

2.3.10     Circuit: the combination of components between the control and the foundation brake that links them functionally. The circuit may be mechanical, hydraulic, pneumatic, electrical or mixed. Where the braking power is derived from or assisted by a source of energy independent of the driver but controlled by the driver, the reservoir of energy in the device is likewise part of the circuit.

2.3.11     Control: part of a brake system which is actuated directly by the driver to regulate the energy required for braking a vehicle. This energy may be the muscular energy of the driver, or energy from another source controlled by the driver.

2.3.12     Control (Service) line: the part of the circuit which transmits the service brake signal.

2.3.13     Coupling head: also known as a brake coupling means the device for connecting the control and supply lines of the drawing vehicle to the control and supply lines of the trailer.

2.3.14     Effective tyre radius: is the rolling radius of the tyre under the maximum permitted load. For the purposes of the Code, it is equal to the height of the axle centre line above the road’s surface. Where the rolling radius is within 5% of the nominal tyre radius, the nominal tyre radius must be used.

2.3.15     Emergency brake: a system that makes it possible to undertake a controlled stop of a vehicle or combination in the event of a failure of the service brake.

2.3.16     Foundation brake: the basic brake assembly fitted to each axle or road wheel which produces the braking force necessary to bring a vehicle to a stop. Includes the complete drum or disc brake.

2.3.17     Gradated braking: braking which can be easily and progressively varied in a controlled manner. The resultant brake force must vary in direct proportion to the action of the control.

2.3.18     Load sensing device: a device fitted to an axle to regulate the braking effort of that axle in proportion to the load carried by it. (See Appendix A.7.)

2.3.19     Park brake or parking brake: a brake readily applied and capable of remaining applied for an indefinite period without further adjustment after the initial application.

2.3.20     Pressure: refers to the pressure of compressed air in a brake system, using a pressure gauge.

2.3.21     Retarder: a device permanently fitted to a powered vehicle to provide a continuous braking effort not generated by a brake. (See 2.3.2).

2.3.22     Service brake: a brake normally used intermittently to slow down and stop a vehicle.

2.3.23     Supply (Emergency) line: the part of the circuit through which air required to actuate the brakes is supplied.

2.3.24     Spring brake: a brake in which the energy required for braking is supplied by one or more springs acting as an energy storage device.

2.3.25     Threshold pressure: the lowest air pressure at which braking is deemed to have commenced, as measured in the control line at the coupling head. (See A.8, Appendix A.)

2.3.26     Trailer hand control: means a hand operated control capable of applying a gradated braking action on the towed vehicle(s) only.

 

3.0     Compliance

3.1     Initial compliance of a vehicle with this Code is the responsibility of the Certifier.

3.1.1     The Certifier must provide the Director with one copy of the Statement of Compliance for each vehicle as requested, in the format prescribed in Appendix C or as generated by the latest authorised Brake Code computer programme.

3.1.2     The Certifier must supply one copy of the Statement of Compliance (in the format prescribed in Appendix C or as generated by the latest authorised Brake Code computer programme) to the vehicle’s operator. The operator of the vehicle is responsible for ensuring that the Statement of Compliance remains with the vehicle’s documentation, but not necessarily on the vehicle.

3.1.3     The Certifier is responsible for the safe keeping of all the calculations, test reports and other documentation for each vehicle issued with a Statement of Compliance and also for making copies of such material available to the Director on request. This material must include:

• a) A set of calculations which must demonstrate compliance as follows:
  • • service brake performance (refer to Appendix A);
  • • emergency brake performance (refer to 4.1.2);
  • • parking brake performance, only on vehicles with spring brakes fitted to more than half of the wheels in contact with the road surface;
  • • where auxiliary braking equipment has been fitted, details of its performance and possible effects on the primary, secondary and parking brake systems of the vehicle.
• b) A demonstration of compliance with the following requirements:
  • • service brake performance (refer to 4.1.1);
  • • parking brake performance (refer to 4.1.3) unless determined by calculation as above;
  • • compressors and air reservoirs (refer to 2.0 Appendix E);
  • • current New Zealand pressure vessel requirements;
  • • brake torque reaction test (refer to A.3.3.b);
  • • load sensing valve operation (refer to A.7).
• c) A schematic diagram of the brake circuit including a list of the components in the braking system.
• d) A label of permanent material must be fixed to the vehicle, as close as practicable to the vehicle’s manufacturers’ identification plate. The label must include the words “..NZHVBC Edition No. .......”.
• Certifiers should include the details of following items of the brake system on this label:
  • • size of brake chambers;
  • • effective length of slack adjusters;
  • • the size of tyres at time of certification to the Code; and
  • • grade of lining material used.
• e) Where significant changes have been made to the brake system, it is the responsibility of the operator to ensure the vehicle’s brake system:
  • • remains in compliance with the Code (refer 3.2.2); and
  • • that a new data label is issued by the Certifier reflecting any system changes.

3.1.4     When a Certifier ceases to be involved with the design certification to this Code, the above mentioned records must be forwarded to another practising Certifier and the Director notified of this change.

 

3.2     Continued Compliance

Continued compliance of a vehicle with the Code is the responsibility of the vehicle operator.

3.2.1     Maintaining the brake system:

• a) The maintenance of a certified vehicle’s brakes and brake system must follow good trade practice so that the vehicle’s continued compliance with the Code is not compromised. Full and detailed records must be kept of the work undertaken and of the parts supplied and installed. A copy of this information must be made available to the vehicle operator.
• b) Only components which do not alter the performance and quality as originally specified by the Certifier can be used when maintaining a certified brake system. Replacement brake linings must be supplied with a compliance certificate in accordance with the details on the Statement of Compliance and fitted in axle sets (refer 4.1.5 and Appendix C).

3.2.2     Modifications to the vehicle or the brake system:

• a) For every significant modification of the vehicle or of its braking system, the brake systems must be re-certified to ensure continued compliance with this Code. A new Statement of Compliance must be issued.
• b) The Certifier must provide the Director with the full details of the modification and complete the modification portion of the Statement of Compliance with the amended information (in the format prescribed in Appendix C or current Brake Code computer programme). The vehicle operator must ensure a copy of this modification certificate remains with the vehicle records.
• c) Where the modification is appropriate to all vehicles of a particular vehicle type, the Certifier may issue a certificate to this effect which clearly defines the modification and the vehicles for which it is appropriate.

 

4.0     Specifications

4.1     Requirements of the brake system

Before a vehicle can be set up to comply with the Brake Code, it must meet the current serviceability requirements laid down by the statutory authority and the specifications of the braking equipment manufacturer.

The brake system as defined in 2.3.9, must also comply with the following provisions.

4.1.1     Service brakes must be capable of:

• - stopping the fully laden vehicle within 7 metres from 30 km/h (equivalent to an average deceleration of 5 m/s²); and
• - controlling the movement and retardation of the vehicle or vehicles in combination by means of a gradated braking action. The driver must be able to achieve this gradated braking action from the driving seat without removing their hands from the steering control.

Note: Where the vehicle was first registered in New Zealand on or after 1 November 1990, the service brake must operate on all wheels in contact with the road (wheel definition refer to 2.1.17).

4.1.2     The emergency brakes must be:

• - capable of stopping the fully laden vehicle or vehicle combination within 18 metres from 30 km/h (equivalent to an average deceleration of 2m/s²) in the event of failure of the service brake system; and
• - operable from the driving seat while keeping at least one hand on the steering control.

Note: Where the vehicle was first registered in New Zealand on or after 1 November 1990 the emergency brake must operate on at least half of the road wheels. (wheel definition refer to 2.1.17).

For the purposes of this provision, it is assumed that not more than one failure of the service brake system will occur at any one time.

4.1.3     The park brake(s) must be able to:

• · hold the fully laden vehicle on both a rising and falling gradient of 1 in 5 on a surface sealed to highway standard; or
• · bring the fully laden vehicle to a stop in 18 m from 30 km/h; and
• · remain in the applied position by a purely mechanical device, which after the initial application, remains applied indefinitely; or
• · be operated from the normal driving position, and cause the vehicle, and any vehicle that it is designed to tow, to be brought to a standstill, subject in the case of a trailer to the provisions of 4.4.1.

Note: Where the vehicle was registered in New Zealand on or after 1 November 1990 the emergency brake must operate on at least half of the wheels in contact with the road (wheel definition refer to 2.1.17).

4.1.4     Brakes must be capable of ready manual or automatic adjustment to accommodate wear. The components of the control circuit and foundation brakes must possess a reserve of travel so that, when the brakes become heated or the brake linings have reached a certain degree of wear, effective braking is maintained without the need for immediate adjustment.

4.1.5     All components and devices in the brake system (including hoses and air connections) must comply with at least one appropriate and recognised international, national or association standard where such standards exist. Recognised standards include:

• • Australian Design Rule (ADR)
• • Standards Association of Australia Standard (AS)
• • Society of Automotive Engineers Standard (SAE)
• • British Standard (BS)
• • Japanese Industrial Standard (JIS)
• • Economic Commission of Europe Regulation (ECE)
• • European Economic Community Directive (EEC)
• • International Standard Organisation Standard (ISO)
• • German Industrial Standard (DIN)

In addition to other standards recognised by the Director.

• Note: In all cases the supplier and importer is responsible for providing proof of compliance.
• a) For newly registered vehicles:
  • • the friction materials are fitted as original equipment (OE) by the manufacturer and meet an appropriate and recognised standard;
  • • a design coefficient of friction is supplied by the vehicle manufacturer.
• b) Supplying the after market, the friction material must:
  • • be approved by either the vehicle’s original manufacturer or by the supplier for a specific application;
  • • comply with an internationally recognised and appropriate standard;
  • • be supplied with a design coefficient of friction.
• Note: Claims of compliance and nominated coefficients of friction must be supported by:
  • • documented proof from the manufacturer of the friction material;
  • • evidence of the friction material being used in similar vehicles and conditions.
• c) Recognised friction material standards are included in the following:
  • • JIS D4411: Brake Linings for Automobiles
  • • ECE R 13.05 Uniform Provisions Concerning the Approval of Vehicles with Regard to Braking
  • • 71/320/EEC: Braking Systems
  • • FMVSS 121: Air Brake Systems. Truck, Buses and Trailers (modified to New Zealand conditions).

Note: The Federal Motor Vehicle Safety Standard (FMVSS) No 121 test results must be modified to take into account the lighter axle loads used in New Zealand. The modification applies to the test results obtained under this standards’ dynamometer test procedure, where:

Friction material manufacturers’ test wheel load = M	New Zealand wheel load = 4000 kg
Friction material manufacturers’ test AL Factor* = AL	New Zealand AL Factor* = 120

Then

From the plotted results of the dynamometer test, the Brake Retardation Graph, determine the brake retardation "Y" for the given chamber air pressure of 80 psi, using the relationship :

Modified brake retardation R = X x Y > 0.41

4.1.6     Vehicles which have had anti-lock braking systems (ABS) fitted must comply with all the requirements of this Code.

4.1.7     Traction control systems may utilise the brake system components provided the system is fail-safe and does not interfere with normal braking processes.

4.1.8     A trailer hand control valve must not modify the effect of the normal service braking action on the trailer, and must be self cancelling (i.e., must automatically return to the off position when released.)

[* the AL Factor is equal to the product of the length (inches) of the slack adjuster, multiplied by the chamber area (inches squared) and expressed in inches cubed.]

 

4.2     Air Brake System

4.2.1     A pressure test connection complying with the dimensional requirements of Appendix D must be fitted to the air inlet of the least favourably placed brake chamber (or pneumatic device in the case of partly pneumatic brake systems) on each independent circuit of the braking system. (See also Appendix B.)

4.2.2     Spring brakes are the preferred type of park brake for coded vehicles.

4.2.3     Compressed air braking systems incorporating load sensing devices or any valve which can be adjusted to modify the system pressure, must be fitted with pressure test connections in the pressure line upstream and downstream of the device. The pressure test connections must be in accordance with Appendix D.

4.2.4     Air connections between all towing vehicles and trailers must be of the two line system using a one piece coupling, e.g. a Duomatic coupling, or when an auxiliary air supply (separate from the braking system) is required for a trailer, a Trimatic coupling.

4.2.5     All power-driven vehicles must be valved and piped by the manufacturer or authorised agent, to an appropriate coupling location, unless the manufacturer forbids the attachment of a trailer with a GVM of more than 3500 kg to a particular vehicle type.

4.2.6     The control (service) and supply (emergency) air lines on a coded vehicle must be installed so that when facing the cover of the female section of the coupling housing:

• • the control (service) line must be on the left side of the housing and coloured blue or black and the supply (emergency) line must be on the right side of the housing and be coloured red or yellow; and
• • the required colour coding must be situated within 150 mm of the coupling or junction.

    Typical duomatic coupling        Typical triomatic coupling

4.2.7     The coupling block must be situated close to the centre line, preferably to the right hand side (ie driver’s side) of centre.

4.2.8     For vehicles towing semi-trailers, the hoses connecting the towing and towed vehicles are to be considered as part of the towing vehicle or be detachable at both ends. On other vehicle types, the hoses are to be treated as part of the trailer and must be securely attached to the drawbar.

Caution: The female coupling mounted on the front of a semi-trailer MUST NEVER be fitted with check valves.

4.2.9     Each air reservoir in an air brake system must be fitted with a condensate drain valve at the lowest point. Where an automatic condensate valve is fitted, it must have a provision for manual operation.

 

4.3     Power-driven Vehicles

4.3.1     The systems providing service, emergency and parking brake vehicles first registered on or after 1 November 1990 may have common components so long as they fulfil the following conditions:

• a) There must be only two controls (however, see Section 5), in addition to any trailer hand control (refer to 2.3.26) which may be fitted, independent of each other and readily accessible to the driver from the driving seat.
• b) The controls and associated systems of the service brake and the park brake must be independent of each other.
• c) The emergency brake system control may be combined with either the service brake control or the park brake control and the resulting emergency braking action must be gradatable. If the service and the emergency braking systems have the same control, the park brake must be so designed that it can be applied when the vehicle is in motion without endangering the directional stability of the fully laden vehicle.
• d) Where a vehicle’s service brakes depend exclusively on compressed air, there must be at least two completely independent brake actuating circuits, each with its own air reservoir. Each circuit must supply the foundation brakes at both ends of one or more axles so that when applied either by itself or in conjunction with the emergency brakes, the required level of braking can be achieved without compromising the directional stability of the fully laden vehicle. Refer to 4.4.3 regarding compounding of braking efforts.

4.3.2     Gauges must be fitted to indicate to the driver the pressure in each independent service brake air reservoir (as defined in 4.3.1.d)) and must be visible to the driver in the normal driving position.

4.3.3     Where there are separate controls for the service brake system and the emergency brake system, simultaneous actuation of the two controls must not render both the service brake system and the emergency brake system inoperative, either when both brake systems are in good working order or when one of them is faulty.

4.3.4     Every vehicle equipped with compressed air operated service brakes and where the prescribed emergency braking performance cannot be achieved without the use of the compressed air, the air reservoirs must be equipped with a low pressure alarm device in addition to any pressure gauges. This alarm must sound loudly when the brake reservoir pressures fall below the minimum safe operating pressure recommended by the manufacturer. The reservoir of compressed air with the compressor stopped must be sufficient to provide:

• • a minimum of five full brake applications with full release;
• • achieve the prescribed emergency braking before the low pressure alarm sounds; and
• • two full brake applications thereafter.

The alarm devices must be directly and permanently connected to the circuit. (See 4.3.7.f)).

The low pressure alarm may be rendered inoperative while:

• • the park-brake is applied; and
• • the selector is in the Park position in vehicles fitted with an automatic transmission.

In verifying compliance with this clause, the vehicle’s brakes must be correctly adjusted.

4.3.5     Where auxiliary equipment uses compressed air, the braking circuits shall be protected to ensure they will have first call upon the air supply from the compressor, should the system air pressure fall below the level indicated in 4.3.4.

4.3.6     All retarders, in particular the exhaust and engine compression type of brake, must not be able to stall the vehicle’s engine under any circumstances. The retarder’s control system must be capable of disengaging the retarder at the engine speed recommended by the vehicle manufacturer, when slowing down from its normal operating speed range.

4.3.7     The braking systems of power-driven vehicles capable of towing a trailer of more than 3500 kg GVM must meet the following requirements:

• a) Be capable of supplying the necessary air supply and brake control for the combination at the vehicle’s GCM so as to comply with Appendices A and E.
• b) The service brake system of the towing vehicle must include automatic protection (tractor protection) to preserve the integrity of the towing vehicle’s brake circuits should the trailer’s brake system fail, so that the towing vehicle meets the mandatory braking requirements for emergency braking.
• c) When the towing vehicle’s emergency braking system comes into action, there must be a braking action on the trailer.
  
  If the requirements of the specification section of this Code (section 4) are achieved by compliance with ECE 13, then when the towing vehicle’s emergency braking system operates, there must be a gradated application of the service brake on the trailer.
• d) Where the towing vehicle’s service brake system consists of at least two independent sub systems and a fault occurs in one them, those sub-systems not affected by the fault must be capable of actuating the brakes on the trailer. It must be possible to gradate this braking action.
• e) In the event of a breakage of or a leak between the connecting “supply line” between the towing vehicle and trailer, the driver must be able to actuate the brakes of the trailer from his normal driving position using either the service or park brake control.
• f) If the requirements of this specifications section of the Code are achieved by compliance with ECE 13, then on air braked vehicles there should be an acoustic alarm device which is activated when the pressure at the coupling head of the supply line drops below 450 kPa. This alarm device may be combined with that described in 4.3.4 of this Code.

 

4.4     Trailers and semi-trailers

4.4.1     The trailer park brake system must be capable of:

• • Stopping a fully laden full trailer automatically in a progressive manner, when the supply line either:
  • - breaks while the trailer is in motion (statutory break-away function), or
  • - line pressure falls below 310 kPa.
• • Holding all other types of heavy trailer indefinitely, in a fully laden condition, on a 1 in 5 slope or when the "Supply" line air pressure falls below 310 kPa.
• • Being fully released at least three times by means of the auxiliary park brake release control after the trailer has been uncoupled. In the case of air brake systems, the pressure in the supply line must be between 650 and 665 kPa before uncoupling.

4.4.2     The auxiliary park brake release device must be able to be restored automatically to its normal operating state on resumption of the air supply from a towing vehicle.

4.4.3     The brake systems must not compound their individual brake forces.

4.4.4     As an alternative to the system capacity requirements of Appendix E, trailers with air brake systems must have a minimum air reservoir capacity in litres equal to three times the maximum mass in tonnes carried by the trailer axles.

 

5.0     Exemptions for power-driven vehicles which are equipped to tow trailers

5.1     Power-driven vehicles fitted with manually operated push/pull valves are exempt from 4.3.1.a) where the following requirements are met:

• • The valve applying the combination’s park brakes (the button must be coloured yellow).
• • The valves used to apply the park brakes on the towing vehicle or trailer separately are adequately guarded to prevent accidental operation during an emergency.

5.2     If the requirements of clauses A.3.4.a), A.3.4.b), A.3.5.c) and A.8.1 cannot be met, the Certifier may apply to the Director for an exemption.

 

Appendix A

Distribution of braking among the axles of vehicles and requirements for compatibility between towing vehicle and trailer.

A.1.0     General

A.1.1     This appendix relates to the braking forces which are generated by friction in the foundation brake. Those braking forces which are applied through the vehicle’s transmission do not form part of this appendix.

A.1.2     The requirements of this appendix must be met by vehicles when laden to their brake code mass.

A.1.3     A power-driven vehicle that is not permitted to tow a trailer with a GVM of more than 3500 kg, is exempt from the requirements of this appendix provided the vehicle is certified to an alternative standard that is acceptable to the Director and:

• • the distribution of a vehicle’s weight between its axles, when loaded to its GVM, is within 10% of the vehicle’s original certified axle loads; and
• • the vehicle is fitted with load sensing or recognised anti-lock braking devices.

A.1.4     No device must be fitted in a vehicle cab which could allow the driver to alter the vehicle’s braking balance in respect to the requirements of this appendix.

 

A.2.0     Symbols

E = wheelbase (metres)

f_i = T_i/N_i, adhesion utilisation curves for axle i (See note 1)

g = acceleration due to gravity (9.81 m/s²)

h = height of centre of gravity of the laden vehicle (metres)

h_o = height of centre of gravity of drawing vehicle (metres)

h_s = height of the transverse pivot axis of the coupling on which the semi-trailer rests (metres)

i = axle identifier counting from the front of vehicle, e.g., 1 for the front axle, 2 for the second axle, etc

J = deceleration of the vehicle (m/s²)

M = weight of vehicle (BCM) (tonnes)

M_i = reaction normal to road surface on axle i under static conditions (tonnes)

MM = total normal static reaction between road surface and wheels of drawing vehicles for trailer or semi-trailer (tonnes)

MM = M_o + M_so (tonnes)

M_o = unladen mass of vehicle (tonnes)

M_s = M_so (1 + 0.45z) (used only in Section A.3.5.)

M_so = difference between the maximum laden mass of the drawing vehicle and its unladen mass (tonnes)

N_i = vertical reaction of road surface on axle i under normal braking (tonnes)

p_m = pressure at coupling head of control line (kPa)

MR = total normal static reaction normal to road surface on all wheels on laden trailer or semi-trailer (tonnes)

T_i = force exerted by the brakes on axle i under normal braking conditions on the road (kN)

TM = sum of braking forces at the periphery of all wheels of drawing vehicles for trailers or semi-trailers (kN), the expression TM/MM is referred to as a braking ratio

TR = sum of braking forces at periphery of all wheels of a trailer or semi-trailer (kN). The expression TR/MR is referred to as a "Braking Ratio"

z = braking ratio of vehicle = J/g (See note 2)

Note 1     Adhesion utilisation curves of a vehicle are the curves of adhesion utilised by each axle i plotted against the braking ratio of the vehicle for a specific load condition.

Note 2     For semi-trailers, z is the braking force divided by the static weight on the semi-trailer axle(s).

 

A.3.0     Requirements for power-driven vehicles

A.3.1    Two axle vehicles

• a) The following relationship must hold for f_i for values of z between 0.2 and 0.8:
  
  
• b) For two axled vehicles, the curve of adhesion utilisation (f i) for the front axle must be above that of the rear axle, for the range of values of z, between z = 0.15 and z = 0.30. This condition is satisfied when the adhesion utilisation curve for each axle passes between the two lines parallel to f i = z (line of ideal adhesion utilisation) and defined by fi = z ± 0.08, as shown in Diagram 1.
• c) To verify the requirements of A.3.1 and A.3.2, the vehicle manufacturer must produce the adhesion utilisation curves for the front and rear axles, as calculated by the formulas:
  
     
  
• d) Where there are several different loading options for a particular vehicle, the maximum permissable loading on the front axle must be the one used in calculations.

A.3.2     In power-driven vehicles designed to tow trailers and fitted with compressed air brake systems, at each full service brake application, the air line pressure measured at the brake coupling must be:

• • supply line - between 650 and 800 kPa, and
• • control line - between 600 and 750 kPa.

Irrespective of the load of the vehicle, these pressures must be readily measurable at the brake coupling of the towing vehicle.

A.3.3     Vehicles with more than two axles

• a) The curve of adhesion utilisation (f_i) for at least one of the front axles must be above that of at least one of the rear axles, for the range of values of z, between z = 0.15 and z = 0.30. This condition is satisfied when the adhesion utilisation curve for each axle (f_i) passes between the two lines parallel to f_i = z (line of ideal adhesion utilisation) and defined by f_i = z ± 0.08 as shown in Diagram 1.
• b) When calculating the adhesion utilisation (f_i) for individual axles, where:
  • • braking has little effect on axle loadings because of the suspension design (brake reactivity), such transient effects on axle loads may be neglected; and
  • • braking has a significant effect on the axle load distribution, the Certifier must verify that no wheels on the vehicle lock up at a deceleration of 4.5 m/s² during a road test using the service brake, with the vehicle loaded to BCM.

A.3.4     Vehicles other than powered vehicles towing semi-trailers

For vehicles:

• a) Those fitted with an air brake system, the permissible relationship between the ratios TR/MR or TM/MM and the air pressure at the brake coupling (p_m) must be within the shaded area shown in Diagram 2.
• b) Those first registered in New Zealand before 1 July 1991 may be set up to comply with Diagram 3 as an alternative to Diagram 2, only after the consent of the Director has been obtained.

A.3.5     Towing vehicles for semi-trailers

• a) The dynamic load of the semi-trailer on the drawing vehicle is represented by a static weight Ms, which must be applied at the coupling kingpin and be equal to:
  
  Ms = M_so (I + 0.45z)
• b) In calculations of the effect of load transfer, the following value must be taken for h:
  
  
  
  where
  
  M = Mo + Ms
• c) In the case of vehicles fitted with air brake systems, the graph of the required relationship between the braking ratio (TM/MM) and the brake coupling pressure (pm) must be within the shaded area shown in Diagram 3.

 

A.4.0     Requirements for full trailers

A.4.1     The requirements set out in clauses A.3.1 through to A.3.4 inclusive must apply to full trailers.

 

A.5.0     Requirements for semi-trailers

A.5.1     For semi-trailers fitted with compressed air brakes, the graph of the required relationship between the braking ratio (TR/MM) and the brake coupling pressure (pm) must lie within the shaded area shown in Diagram 2.

A.5.2     The requirement of clause A.3.3.b) must be applied to vehicles with more than one axle if the suspension geometry affects the axle load distribution during brake applications (brake reactive suspensions).

A.5.3     If the semi-trailer is itself a towing vehicle for a second semi-trailer (i.e. the first semi-trailer in a B-train), the semi-trailer must meet the requirements specified in clause A 3.5, when laden to its GVM.

 

A.6.0     Requirements for simple trailers

Simple trailers must be subject to the requirements of A.5.

 

A.7.0     Load sensing devices

A.7.1     In any air brake system, it is recommended that the load sensing devices do not modulate the pressure below 70 kPa.

A.7.2     Where a coded vehicle is fitted with a load sensing facility in its braking system:

• • it must meet the Code’s performance requirements; and
• • the Certifier must be satisfied that under normal conditions the braking performance of its braking system will not be adversely affected when operating with a coded vehicle not fitted with load sensing, in both the laden and unladen condition. The Certifier must be able to demonstrate (refer to 3.1.3b) to the Director, if requested, that the braking performance of either vehicle has not been jeopardized.

Where there is doubt as to possible adverse effects on braking performance, the load sensing system should be fixed at the level required by the Code’s calculations for the laden condition.

A.7.3     In the event of a failure, the control of these devices must be capable of meeting the following requirements:

• • Stop the vehicle under the conditions specified for emergency braking.
• • Achieve a pressure at the coupling head of the control line within the range specified in A.3.2. in power-driven vehicles designed to tow a trailer fitted with air brakes.

 

A.8.0     Threshold pressure tests for combination vehicles fitted with air brake systems

A.8.1     The braking at the wheels must commence at a pressure between 55 kPa and 80 kPa, measured in the control line, at the brake coupling.

Braking is considered to have started when a torque of 100 Nm is first achieved at the wheel of least advantage.

For vehicles (including trailers) equipped to tow a trailer(s), the braking at all the vehicle’s wheels must commence at a pressure between 50 kPa and 85 kPa. This pressure measurement must be made at the coupling head of the control line of the towing vehicle.

Exemptions from this clause can only be obtained from the Director.

 

Diagram 1

Adhesion utilisation criteria (See A.3.1)

 

Diagram 2: Towing vehicles, semi-trailers and full trailers

The shaded area defines the permissible relationship between the braking ratio and the air pressure in a towing vehicle’s compressed air braking systems, as measured at the coupling head. (See Clause A.5.1)

 

Diagram 3: Towing vehicles for semi-trailers

The shaded area defines the permissible relationship between the braking ratio and the air pressure in a towing vehicle’s compressed air braking systems, as measured at the coupling head. (See A.3.5.)
Note: This diagram can only be used with the Director’s permission.

 

Appendix B

The standard procedure for measuring the response time on vehicles equipped with compressed air brakes (based on ECE 13 Annex 6).

B.1.0     General

B.1.1     This procedure is not mandatory and should be used only where there is doubt surrounding the timing of a vehicles air brake system. In the event, response times are required to be measured, this procedure should be closely followed.

B.1.2     The response times of the brake system should be determined on the stationary vehicle. The air pressure is to be measured and recorded at the:

• • air inlet to the brake chamber of the least favourably placed brake; and
• • brake coupling, (if fitted).

During the test, the length of free stroke in the brake cylinders on the axles should be that specified by the certifier. The measured response times should be rounded to the nearest tenth of a second.

 

B.2.0     Power-driven vehicles

B.2.1     At the beginning of each test, the reservoir air pressure should be equal
to:

• • for governed compressors, the pressure at which the governor restores the feed to the system; or
• • for compressors not fitted with governors, the pressure in the air reservoir at the beginning of each test should be 90% of the pressure specified by the certifier.

B.2.2     The time taken from the moment of:

• • initiation of a full brake application to when the pressure in the brake chamber reaches 75% of its final value (should not exceed 0.6 seconds); and
• • release of the fully depressed brake pedal to the moment when the brake air pressure reaches 25% of its initial value (should not exceed 0.6 seconds).

B.2.3     In the case of power-driven vehicles being equipped to tow trailers, the response time should be measured at the brake coupling. For this test, a pressure vessel with a capacity of 385 ± 5 cm³ should be connected to the supply and control lines separately, at the brake coupling. The volume of this vessel equates to the internal volume of a pipe 2.5 m long with an internal diameter of 13 mm and under a pressure of 650 kPa.

In the case of towing vehicles of semi-trailers, these should be equipped with flexible pipes (suzies) for connection to the semi-trailers, and the brake couplings should be fitted to the end of these flexible pipes. The measured response times may be rounded up to the nearest one tenth of a second, but should not exceed the following maximum permitted response times:

• • 0.40 seconds from the initiation of a full brake application to the moment when the pressure measured at the brake coupling of the control line reaches 75% of its final value;
• • 0.60 sec. from the initiation of a release of the fully depressed brake pedal to the moment when the brake coupling air pressure reaches 25% of its initial value.

 

B.3.0     Trailers, including semi-trailers

B.3.1     The trailer’s response time should be measured without the towing vehicle being connected. To replace it, a simulator that pneumatically represents the towing vehicle should be provided. The simulator is connected to the trailer’s control line and supply line at the brake coupling.

B.3.2     The air pressure in the supply line should be

B.3.3     The simulator used should:

• a) contain the following features:
  • • a reservoir with a capacity of 30 litres;
  • • an orifice between 4.0 mm to 4.3 mm diameter fitted in the outlet of the braking;
  • • a length of a pipe from the orifice to the brake coupling, with a capacity of 385 + 5 cm³ (equivalent to the volume of air contained in a pipe 2.5 m long and 13 mm internal diameter and pressurized to 650 kPa); and
  • • a brake control valve so designed that its performance is unaffected by the presence of the tester.

The simulator’s reservoir should be recharged to 650 kPa before each test and not during the test.

The control line pressures referred to in B.3.3(b) should be measured immediately downstream of the orifice.

• b) Be capable of being adjusted through the choice of a suitably sized orifice in (refer clause B.3.3(a).) so that when receiver of:
  • • 385 ± 5 cm³ capacity is connected, it will take 0.2 ± 0.01 seconds for the system pressure to increase from 65 to 490 kPa (10% and 75% respectively of the nominal pressure of 650 kPa); or
  • • 1155 ± 15 cm³ capacity is substituted for the smaller one, the pressure should increase from 65 to 490 kPa without further adjustment in 0.38 ± 0.02 seconds.
    
    Between these two pressure values the pressure should increase approximately linearly.
    
    The receivers should be connected to the brake coupling without using flexible pipes and the receivers and pipes should have an internal diameter of not less than 10 mm.
• c) The circuit layouts in Diagram 1 in this Appendix give an example of the correct arrangement of the simulator for setting and use.

B.3.4     The time difference between the pressure in the control line and the trailer actuator should not exceed the following times:

• • 0.40 seconds from the time the rising control line pressure reaches 65 kPa and the pressure in the trailer brake actuator reaches 75% of the asymptotic value;
• • 0.60 seconds from the time the falling control line pressure reaches 490 kPa and the pressure in the trailer brake actuator reaches 25% of its initial value.

B.3.5     In the case of semi-trailers equipped to tow a second semi-trailer and for the purposes of this test, a pressure vessel with a capacity of 385 ± 5 cm³, should be connected to the control line at the rear-most brake coupling. The measured response times may be rounded up to the nearest one tenth of a second, but should not exceed the following maximum permitted times:

• • 0.40 seconds from the time the rising control line pressure reaches 65 kPa and the pressure in the rear-most brake coupling reaches 75% of the asymptotic value.
• • 0.60 seconds from the time the falling control line pressure reaches 490 kPa and the pressure at the rear-most brake coupling reaches 25% of its initial value.

 

B.4.0     Part-pneumatic brake systems

B.4.1     For part-pneumatic brake systems, the requirements of paragraphs B.1, B.2 and B.3 that refer to:

• • the brake coupling should be met; and
• • the least favourably placed actuator should apply to the least favourably placed pneumatic device which acts on the non-pneumatic part of the brake system.

Diagram 4: Typical simulator circuits to determine the response times of a vehicle’s braking system. The key to the abbreviations used:

A = Supply connection with shut off valve

C1 = Pressure switch in the simulator, set at 65kPa and 490 kPa

C2 = Pressure switch to be connected to the brake actuator of the trailer, to operate at 75 of the asymptotic pressure in the brake actuator CF

CF = Brake actuator

L = Line from orifice 0 up to and including its coupling head TC, having an internal volume of 385 + 5 cm³ under a pressure of 650 kPa

M = Pressure gauge

O = Orifice with a diameter of not less than 4.00 mm and not more than 4.30 mm

PP = Pressure test connection

R1 = 30 litre air receiver with a drain valve

R2 = Calibrating receiver including its coupling TC, to be 385 + 5 cm³

R3 = Calibrating receiver including its coupling TC, to be 1155 + 15 cm³

RA = Shut off valve

TA = Supply line coupling

TC = Control line coupling

V = Brake control valve

VRU = Relay valve

Diagram 4

Setting the Simulator

 

Testing the trailer

 

Appendix C

Statement of Compliance with the New Zealand Heavy Brake Code

Vehicle description
Make: _____________________	Model: ______________________
VIN: ____________________________________________________
Vehicle dimensions
Height of vehicle’s unladen COG (m): ___________________________
Height of payload’s COG (m): _________________________________ ________________________________________________________
Wheelbase (m): ____________________________________________ ________________________________________________________
Distance of payload’s COG from front axle: _______________________
Height of fifth wheel*(m): _____________________________________
Vehicle weights
Unladen axle weights
Front axle(s) (kg): ____________	Rear axle(s) (kg): ______________
Suspension details
Front suspension type: _________ (reactive/unreactive)	Rear suspension type: ___________ (reactive/unreactive)
Brake system air pressure
Maximum operating pressure (kPa) [Pm]: ________________________
Governor cut in pressure (kPa) [Pg]:
Time taken for air pressure to rise from Pg to Pm (secs): _____________

 

Statement of Compliance with the New Zealand Heavy Brake Code (continued)

Brake system details
Axle	Pressure at Coupling Producing 100Nm Torque	Brake Force kN/kPa @ Brake Chamber	Tyre size	Friction materials
				Make	Identifier/ Grade	Design coefficient of friction
1
2
3
4
5

 

Axle	Brake type	Drum diameter (mm)	Chamber area (mm)	Length of slack adjuster (mm)	Spring brake force (kN)
1
2
3
4

 

Truck or tractor (towing vehicle)
Valve type	Make	Model
Treadle
Primary Circuit Relay
Secondary Circuit Relay
Trailer Control Relay
Load Sensing
Quick Release
Park Brake
Trailer Hand Control

 

Trailer (towed vehicle)
Valve type	Make	Model
Relay 1
Relay 2
Spring brake
Quick release valve
Pilot 1

 

Statement of Compliance with the New Zealand Heavy Brake Code (continued)

Documentation required to support Statements of Compliance with the New Zealand Heavy Brake Code, to be made available to the Statutory Authority on request, must include all calculations and test reports.

Confirmation of compliance

I confirm that the vehicle identified on page 1 of this Statement of Compliance complies with all relevant requirements of the current New Zealand Heavy Vehicle Brake Code.

Date: _________________________ Signed: _____________________

Certifier’s identification

Name: ___________________________________________________

Phone (bus): ____________________ Fax (bus): ___________________

Postal address: _____________________________________________

________________________________________________________

Position: __________________________________________________

Confirmation of continued compliance of modification

I confirm the brake system of the vehicle identified on page 1 of this Statement of Compliance as modified by myself, continues to comply with all the relevant requirements of the current New Zealand Heavy Vehicle Brake Code.

Date: _________________________ Signed: _____________________

Certifier’s identification: _______________________________________

Name: ___________________________________________________

Phone (bus): ____________________ Fax (bus): ___________________

Postal address: _____________________________________________

________________________________________________________

Position: __________________________________________________

 

 

Appendix D

Pressure test connections for compressed air braking systems

Dimensions of the typical connection.

 

 

valve position	dimension ‘a’
closed	5 mm
open	3 mm

Dimensions not specified are to be chosen according to the application.

Seals and covers shall withstand petroleum products.

 

Appendix E

Provisions for air compressors and air receivers (based on ECE13, Annex 7).

Compressed-air braking systems

E.1.0     Capacity of air receivers.

E.1.1    General

Vehicles on which the braking device requires the use of compressed air must be equipped with air receivers of a capacity that meets the requirements of E.1.2 and E.1.3 below.

However the air receivers are not required to be of a prescribed capacity if the brake system is capable of achieving a braking performance at least equal to the statutory requirement for emergency braking.

In verifying compliance with the requirements of E.1.2 and E.1.3 below, the brakes must be adjusted so that all excessive clearances, within the foundation brakes, has been eliminated as is practical.

E.1.2     Power-driven vehicles

The air brake receivers of power-driven vehicles must be of such a capacity that after eight full-strokes of the service brake control, the pressure remaining in the air brake receiver must be not less than the pressure required to obtain the specified secondary (emergency) braking performance.

For the purposes of this test, the following requirements must be met:

• a) The initial pressure in the air receiver or receivers must be that specified by the manufacturer so that the prescribed performance of the service braking system is achieved.
• b) All auxiliary air receivers must be isolated.
• c) In the case of motor vehicles equipped to tow a trailer or semi-trailer, the feed line must be stopped and a 0.5 litre air receiver must be connected to the control line. This receiver must be vented before each braking operation. After the test referred to in E.1.2. above, the air pressure in the control line must not fall below a level equivalent to one-half of the figure obtained at the first brake application.

E.1.3     Trailers and semi-trailers

The air receivers fitted to trailers and semi-trailers must be of sufficient capacity to allow eight full-strokes of the drawing vehicle’s service brakes (without the air pressure falling below one-half of the pressure measured at the first brake application).

Testing must comply with the following requirements:

• a) The pressure in the air receivers at the beginning of each test must be the maximum pressure specified by the manufacturer.
• b) The air supply line and any auxiliary air receivers must be isolated.
• c) The air receiver must not be replenished during the test.
• d) At each brake application, the pressure in the control line must be the maximum pressure specified by the manufacturer.

 

E.2.0     Capacity of compressors

E.2.1     General

The compressors must meet the requirements set forth in the following paragraphs.

E.2.2     Definitions

p₁ is the pressure in bars, corresponding to 65% of the pressure p₂ defined below

p₂ is the pressure in bars as specified by the manufacturer and referred to above

T₁ is the time required for the relative pressure to rise from 0 to p₁

T₂ is the time required for the relative pressure to rise from 0 to p₂

E.2.3     Conditions of measurement

In all cases the speed the compressor is run at for the purposes of this test must be the same as would be obtained when the engine was running at the speed corresponding to its maximum power or at the speed permitted by the engine governor.

During the tests to determine the time T₁ and the time T₂, the auxiliary air reservoirs must be isolated.

In the case of a power-driven vehicle which was intended to tow a trailer, the trailer must be represented by an air reservoir whose capacity and maximum pressure p is given by:

p.V = 20.R

where:

p = maximum pressure as supplied through the towing vehicle’s air supply (bars)

V = volume of the reservoir simulating the presence of the trailer (litres)

R = sum of the permissible maximum axle load carried by the axles of the trailer or semi-trailer (tonnes).

E.2.4     Interpretation of results

Time T₁ recorded for the least favoured reservoir must not exceed:

• a) 3 minutes for vehicles not fitted to tow a trailer(s) or semi-trailer(s), or
• b) 6 minutes for vehicles fitted to tow a trailer(s) or semi-trailer(s).

The time T₂ recorded for the least favoured reservoir must not exceed:

• a) 6 minutes for vehicles not fitted to tow a trailer(s) or semi-trailer(s), or
• b) 9 minutes for vehicles fitted to tow a trailer(s) or semi-trailer(s).

E.2.5     Additional test

If the power-driven vehicle is equipped with one or more auxiliary air reservoirs having a combined capacity exceeding 20% of the total compressed air storage capacity on the vehicle, an additional test will be required. For the duration of this test no change in the operation of the valves controlling the filling of the auxiliary air reservoirs is permitted.

This test consists of measuring the time, T₃ taken to raise the pressure of the least favoured air reservoir from a pressure of 0 bars to p₂ bars is less than:

• a) 8 minutes for vehicles not fitted to tow a trailer(s) or semi-trailer(s), or
• b) 11 minutes for vehicles fitted to tow a trailer(s) or semi-trailer(s).

E.2.6     The test must be performed in the conditions prescribed in E.2.3.

 

E.3.0     Pressure connections

E.3.1     To facilitate the periodic inspection of vehicles already in use on the road, a pressure connection must be fitted close to the least favourably placed air reservoir.

E.3.2    The pressure connection must comply with Appendix D to this code.