Truck tow couplings with a dropping pin must be checked and inspected regularly. Drivers must check the trailer coupling at every connection and at least once a day (before driving).

Inspection is needed after recent incidents of drawbar trailers failing to couple correctly, causing them to disconnect or damage the coupling. Trailer coupling dropping pins must be able to drop to the fully locked position and lock without being blocked by dirt or anything else. Trailer coupling devices must be safe, effective and ensure a secure connection between the towing and towed vehicles under all conditions. Towing connections must not be modified.

Checking locking indicators - Coupling lock indicators (also called secondary safety devices) must clearly show whether the coupling is open or closed (locked). Don’t use a coupling if the indicator is inaccurate, damaged, or unreadable. Always check and physically confirm the coupling is closed (locked) before driving.

Dropping pin failures - Industry inspections found damaged and heavily worn couplings caused by the dropping pin not being in the correct position when towing. If a dropping pin is blocked, held-up or obstructed from its fully down and locked position, it isn’t secure, and the coupling isn’t safe. It can cause excessive stress on other parts, causing high wear and damage. 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. This can happen due to modifications or contamination that stops the dropping pin from correctly locating and properly locking. To prevent this, make sure couplings are regularly inspected, maintained, lubricated and kept clean.

Key points - Do not use modified or damaged couplings. Look out for release handles which have been bent or shifted from their original position (sometimes referred to as, ‘clocked’ on the spline). Keep coupling bottom bushes clean and free of debris. Do not drive with the dropping pin in the raised position, it allows dirt and debris to enter the lower pin bush.