NHVR VSG38 sets approval path for longer semitrailer builds and modifications

Trailer builders and modification workshops now have a clearer approval path for semitrailers designed to operate in qualifying 20-metre combinations, following the NHVR’s publication of Vehicle Standards Guide 38.

The guide deals with the gap between the amended Heavy Vehicle (Mass, Dimension and Loading) National Regulation, which took effect on 1 August 2026, and the existing semitrailer limits in Australian Design Rule 43/04.

Dimensions for qualifying combinations

For semitrailers used in combinations longer than 19 metres and no longer than 20 metres, the amended road rules allow rear overhang of up to 4.0 metres instead of 3.7 metres, subject to the 60 per cent limit; up to 10.5 metres from articulation point to rear-overhang line, subject to the relevant geometry; and up to 14.5 metres from articulation point to trailer rear, compared with 12.3 metres previously.

Those dimensions do not remove the need to meet braking, vehicle-standards and other applicable combination requirements.

New builds: federal approval still required

Manufacturers seeking to use the larger dimensions must apply for a Non-Standard Vehicle Type Approval or a Concessional Register of Approved Vehicles entry through the Commonwealth department. The NHVR says VSG38 itself provides the necessary in-principle support for applications relating solely to the new 20-metre semitrailer provisions.

Applicants must include the guide, select the non-standard option for ADR 43/04 and explain that the application relates to the amended 20-metre combination provisions.

Modifications: exemption before certification

For semitrailers already in service, the NHVR directs modifiers to Vehicle Standards Bulletin 6 and approval by an Approved Vehicle Examiner. Where the proposed work exceeds an ADR dimension, an in-service vehicle-standards exemption is required before the modification is certified. Changes outside VSB6 must go through the NHVR’s complex-modification process.

For builders, the practical distinction is between the dimension now allowed on the road and the approvals needed to deliver a compliant trailer. Operators should confirm those approvals before committing to fabrication, conversion or fitment.

Source: NHVR Vehicle Standards Guide 38.