Tow Structure Certifications

Strength Requirements

Tow structures must be designed and constructed with sufficient strength and must comply with Australian Design Rule 62/xx “Mechanical Connections Between Vehicles”, relevant to the laden mass of the towed vehicle.

Coupling manufacturers and installers need to consider the strength of towbar/drawbar structures as well as the rating and certification of couplings (e.g. fifth wheels, pintle hooks, etc.) before installation. These strength ratings must exceed the towing rating, otherwise the vehicle towing rating should be downrated to match the rating of the coupling/towbar/drawbar being fitted.

VSB6 Section P relates to the fitting of Tow Couplings and/or Fifth Wheels to heavy vehicles. It states as follows:
The following activities constitute a modification under this code:
• Initial fitment of a Tow Coupling/Fifth Wheel;
• Change of a Tow Coupling/Fifth Wheel;
• Relocation of a Tow Coupling/Fifth Wheel;
• Change of “D-Value”;
• Change to Chassis Rear Overhang;


• Change of Trailer Type;
• Change of Operational Requirements;
• Fitment of Additional Axle;
• Wheelbase Modification;
• Fitment of Sleeper Compartment;
• Axle(s) Change;
• Axle Mass Limit Regulation Change;
• Refurbishment Requiring Welding or Change of Design.
This Section applies to modifications to all vehicles regardless of whether or not they were initially manufactured to comply with ADR 62/xx

Marking Requirements

A towbar fitted to a vehicle built after 1992 must be marked with its load capacity and the towbar manufacturer’s part number. The tow coupling must also be fitted with an ID plate stating its D-Value and any other relevant ratings. Aside from the safety aspect (and any warranty issues) tow structures that do not have evidence of certification could be deemed non-compliant by Insurance Companies and Statutory Authorities.

Heavy Vehicle Certifications can design and certify vehicle-specific tow structures to suit your individual requirements. Feel free to contact us for any enquiries.