The NZ Transport Agency Waka Kotahi has issued an industry alert warning of the risk of drawbar trailers disconnecting due to incorrect coupling and damaged towing equipment, following recent incidents.
The alert says inspections are needed after cases where drawbar trailers failed to couple correctly, causing them to disconnect or damage the coupling.
Truck tow couplings that use a dropping pin must be checked and inspected regularly, with drivers required to check the trailer coupling at every connection and at least once a day before driving.
The agency says trailer coupling dropping pins must be able to drop to the fully locked position and lock without being blocked by dirt or other obstructions. Trailer coupling devices must be safe, effective and able to ensure a secure connection between the towing and towed vehicles under all conditions, and towing connections must not be modified.
Industry inspections have found damaged and heavily worn couplings caused by the dropping pin not being in the correct position when towing.
The alert warns that if a dropping pin is blocked, held up or obstructed from its fully down and locked position, the coupling is not secure and is unsafe. This can cause excessive stress on other parts, leading to high wear and damage, and in some cases the trailer can unexpectedly disconnect.
“Towing with a coupling improperly locked causes excessive wear, and can cause loose and damaged dropping pins, their bushes and receivers,” the alert says. It adds that this can occur due to modifications or contamination that stops the dropping pin from correctly locating and properly locking.
To prevent failures, the agency says couplings should be regularly inspected, maintained, lubricated and kept clean.
The alert also highlights the importance of checking coupling lock indicators, also known as secondary safety devices, which must clearly show whether the coupling is open or closed. Operators are warned not to use a coupling if the indicator is inaccurate, damaged or unreadable, and to always physically confirm the coupling is locked before driving.
Specific guidance is provided for operators, inspectors, certifiers and repairers, including stopping the use of vehicles with damaged couplings, ensuring release handles are not obstructed, and never operating a vehicle with an excessively worn or damaged trailer coupling.
*Click here to read the full alert.
