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Technical bulletins

4 Modification thresholds for the Heavy Vehicle Brakes Rule

This technical bulletin replaces the 62 series of memos.
Modifications that may not require an LT400 by an HVEK

Note: Any modifications outside these limits must be referred to a HVSC with the HVEK category. It is the HVEK engineer’s responsibility to confirm that the braking system has not been affected by the modification and issue an LT400 to that effect. If the braking system has been affected, it is the HVEC engineer’s responsibility to ensure that the HVEK engineer certifies the required modifications.

Where the vehicle has an electronic braking system or an integral stability control system the vehicle manufacturer must provide approval, in writing, for the modifications.

Re-bodying a standard-compliant (Note 1) heavy vehicle with change of location of the centre of gravity by no more than +/- 500mm (either horizontally or vertically).

  • The position of the load centre is the responsibility of the original bodybuilder, who must work within the requirements of the manufacturer’s body builders’ manual.

A wheelbase alteration to a standard-compliant (Note 1) heavy vehicle that is not outside the range specified by the original manufacturer (Note 2), provided:

  • no other modifications (eg adding a tag axle, changing an axle, changing a brake component or setting) are performed, and
  • the vehicle must remain within the original manufacturer’s GVM - even if there is a change to the chassis rating. This change of chassis rating must be confirmed by an HVSC with the chassis category (HVEC).
Modifications that always require an LT400 by an HVEK

A heavy vehicle that has been brake-coded to the Heavy Vehicle Brake Code, Second Edition (Schedule 4) and it cannot be established what friction material was used (or the friction material originally used is no longer available).

The vehicle may be re-coded to its original brake code mass using an alternative friction material as long as no other alterations are made. This certification requires the original brake coding confirmed with an LT400 by an HVEK using the NZTA Brake Calculator.

  • This is not available to vehicles that were brake-coded to any of the earlier iterations of the Brake Code (including the Interim Performance Specification for Heavy Vehicle Braking and the Heavy Vehicle Braking Specification of 6 December 1988).

A brake-coded heavy vehicle that has had a change of use, eg tractor to rigid (with or without tow connection) where there are no brake or wheelbase modifications.

If the HVEK certifier can demonstrate (using the NZTA Brake Calculator) continued compliance with the Brake Code as required by Section 8.1(4) of the Rule, then that original brake coding remains valid and is to be confirmed with an LT400.

A brake-coded HV that has had its braking system modified, even if its compliance curves remain within the ‘tramlines’ of the Brake Code.

The vehicle is outside its Brake Code certification and must be re-certified to Schedule 5 and issued an LT400.

Note: When an HVSC considers a modification ‘minor,’ they can apply for an exemption from the requirements of clause 8.1(4).

A heavy vehicle that has had its braking system modified in any way other than those specifically allowed by the vehicle’s manufacturer in their body builder’s manual. The braking system must be certified by a HVSC with the brakes category HVEK (or HVKD supported by a design certificate (DC) from an HVEK) and issued an LT400.

An air-operated spring parking brake that has been retrofitted to a vehicle to replace a wind-on parking brake must be certified by an HVSC with the brakes category HVEK.

Note: Provided the replacement spring brake chamber has the same service brake performance as the original and no other modification is made to the service brake, compliance to Schedule 5 is not required.

Note 1

Standard compliant means a vehicle which, when it went through entry certification on or after 1-July-2008, was certified to one of the international standards approved in clause 2.5(2) of the Heavy-vehicle Brakes Rule, or, being a vehicle manufactured or modified in New Zealand after 1 March 2007, was certified to Schedule 5 of the Rule.

Note 2

Original manufacturer means the state at manufacture, not the state after any subsequent modification/certification.

Page amended 1 October 2020 (see amendment details)