Trailer Rollaway is any situation where either the trailer or trailer & tractor unit do not have applied brakes and the trailer or combination is free to move. This is an extremely hazardous risk that all operators should be aware of and prevent.
All drivers should be familiarised with the operation of the park and shunt valves on a trailer, but when they apply the trailer park brakes, are they fully aware of why this is so critical?
To be clear, there are situations where a trailer can roll either backwards or forwards with potentially fatal consequences. The situation can arise from the potential assumption that, when the air lines are disconnected, the trailer brakes apply automatically. Whilst this is strictly true, it should not be relied upon due to the way that the trailer air/spring brakes work. If a trailer is left for any length of time and the trailer park brake has not been applied, rollaway can occur when re-coupling if the driver does not apply the tractor park brakes (hand control) or carries out split coupling.
Don-Bur has produced an useful infographic to explain how trailer air brakes work and how this situation could arise.
Drivers should always follow the correct coupling and procedures.
Published: Fri 17 Nov 2023
Updated: Tue 09 Jan 2024