NZ Transport Agency (NZTA) is issuing a safety alert following an incident where a logging truck’s trailer separated from the truck and continued along the road, crashing, and spilling its load across the road.

Other vehicles subsequently collided with the logs causing damage. Fortunately, no major injuries were sustained by any occupants of the vehicles involved, however the incident has highlighted a major risk that must be addressed.

The initial investigation carried out with NZTA found the truck was fitted with an air operated automatic coupling device. This device had been unintentionally activated causing the locking drop pin to release the drawbar of the trailer. The operating system for the device, which has a two-step release procedure, had instead been fitted with a simple switch and therefore, a single action allowed the disconnection to occur.

The safety alert provides critical advice to all heavy vehicle operators, heavy vehicle specialist certifiers and heavy vehicle service providers about the safe installation and operation of automatic de-coupling devices.

Any affected vehicles must be removed from service until key actions described in the safety alert are completed.

The key points of the alert are:

• Air operated automatic tow coupling devices must be installed either according to the manufacturer’s instructions including all safeguards, or with a safety mechanism that ensures that unintentional trailer disconnection is not possible while the vehicle is moving.
• Where the air supply to operate an automatic tow coupling device is drawn from the brake system supply, protection of the brake system supply must be fitted and be certified by a heavy vehicle specialist brake certifier (HVEK category).
• Signage, instructions, and training should be provided to alert the operator of the device and ensure its correct operation.