Mechanical Connections between Vehicles

Main Roads Transport Inspectors have recently highlighted the significant use of “collars” in the connection of vehicle combinations between prime movers, dollies and trailers, to increase the size of the king pin from 50 mm to 75 mm when using a Fifth Wheel with
75 mm jaws.

The use of collars does not comply with Part 13, Rule 151 of the Road Traffic (Vehicle Standards) Rules 2002, as listed below:

“Division 1 – Couplings on all types of vehicles

151.  General coupling requirements

(1) A fifth wheel coupling, the mating parts of a coupling, a king pin or a tow bar must not be used for a load more than the manufacturer’s load rating.

(2) A king pin must be used only with a fifth wheel coupling that has a corresponding jaw size.”

This Update brings this issue to the attention of industry, and advises that operators using this practise do so illegally. 

Therefore Main Roads reminds industry that vehicles not complying with the above standard will be issued with a Vehicle Defect Compliance Notice.  

Doug Morgan
Acting Director Heavy Vehicle Operations
12 May 2008