Have your say on the draft DZ 5446 On-road heavy vehicle towing connections – drawbeams and drawbars

A truck in New Zealand towing multiple trailers

A note from Jim Williamson, the chair of the P5446 committee

I am pleased to inform you that after 12 months of discussions and debates, the draft revised NZS 5446 is now ready for public consultation. The document has been prepared by a committee of eight industry representatives, who have worked with great care and perseverance to ensure the document reflects the interests of the many NZ transport operators, their industry and related transport engineering, certification, and regulatory organisations.

About NZS 5446

NZS 5446 On-road Heavy Vehicle Towing Connections – Drawbeams and Drawbars establishes design, manufacture, installation, testing, maintenance, repair, and certification criteria necessary to ensure that a secure connection can be maintained between towing vehicles and drawbar trailers for use in heavy road vehicles in normal use on both sealed and unsealed roads. Although primarily covering applications incorporating pin or hook couplings, this standard also applies to other types of couplings covering both rigid and hinged drawbars. This standard covers drawbeams, drawbars, and couplings, and the method of attachment to towing vehicle chassis and main structural member of the trailer chassis or steering axle assembly.

We welcome your views on the draft through our Citizen Space public consultation hub. The deadline for submissions is Monday 12 February:

Have your say on NZS 5446(external link)

What is new in this revision?

The draft document includes important changes to the drawbars on simple trailers, and whilst the initial focus was on fixing an unintended interpretation on the height of the centre of gravity, it became apparent that the formulas used to establish the vertical load on the drawbar had been over simplified and did not properly reflect the actual loads seen in real life, resulting in overly complicated design solutions.

This standard revision has built on the original research done on towing connections, and more recent work to better define the tyre adhesion factors across a range of road surfaces, as well as the variations of tyre and retread construction.

The P5446 committee has also examined this document for consistency and have updated the referenced standards for couplings and design standards, and have made minor changes throughout the standard, as well as updates to some of the diagrams. 

We have taken into account the many comments provided from nominating organisations and stakeholders over the years, and whilst some were deemed not to be within the scope of this standard, we have listened and incorporated as many of the comments as possible.

Created together

We have reached an important milestone with the release of the draft for public consultation. We would like to thank all the committee members for their efforts, their nominating organisations, and the commissioner for its ongoing support. It is with a sense of accomplishment and relief that all members recently signed off on the release of the draft for public consultation.

We look forward to hearing your feedback and encourage you to take part in the public consultation process and have your say. We understand that there is a lot of information to digest and to consider in the new draft standard, but your view is both encouraged and appreciated.

Ngā mihi nui,

Jim Williamson, P5446 committee chair