Trailer Coupling Accident Scenarios

A driver may back up to the trailer and the king pin not correctly engage. They then climb up to the back of the tractor unit, connect the red emergency line and the trailer brakes instantly release as the park valve has not been operated. At which point the trailer could roll forward crushing the driver or roll backwards possibly injuring another person.

With close coupled trailers, most drivers are forced to connect trailer services with the tractor just in front of the trailer, while they stand between the two. Without the park valve applied this unavoidable practice is an accident just waiting to happen! The trailer could roll backwards causing damage or roll forwards crushing the driver.

Should the driver have forgotten to apply the tractor and trailer park brake, the whole rig could roll away when the red line is connected. At this point the driver is out of the cab, between the rear of the tractor unit and front of the trailer, unable to apply the brakes.

When a vehicles air tank is depleted and the driver leaves the vehicle with the engine running, not realising the handbrake is off, as air pressure builds up, the spring brake actuators release and the vehicle becomes unbraked and free to roll.A vehicle can have low air tank pressure following a damaged Red Suzie line; coupling to a trailer with a depleted air reservoir; or by leakage.

*A park brake alarm, if fitted, may not operate if the air pressure is below its operating threshold. Please refer to the Sentinel Low Air Interlock valve as a solution to this problem.

REAL LIFE INCIDENT 1

A driver backed under a trailer, applying the tractor handbrake as he exited the cab. After coupling, he attempted to drive away and found the park brakes would not release due to low air. Leaving the engine running, he exited the cab forgetting to re-apply the handbrake*. As air pressure built up, the spring brake actuators released allowing the rig to roll away.

REAL LIFE INCIDENT 2

Having just had his red Suzie line replaced following a broken line, the driver exited the cab leaving the engine running to talk to the fitter. As they talked, the rig started to roll away. he had forgotten to apply the handbrake*.