This technical advisory procedure provides trucking operators with essential checks to make sure the park brakes on their trucks restrain their trailers safely.
In Australia, the standard practice is that trailers are parked using the mechanical force of their spring brakes. Applying the park brake in the cab of a prime mover should apply these spring brakes on all connected trailers.
Under the Australian Design Rules, trucks and prime movers that meet the European brake standard, UNECE R13, are deemed to meet the Australian standard as long as they also meet a performance specification. However, some of these units use park brakes that only apply service air to the brakes on connected trailers, rather than spring brakes.
This is less safe, because the brakes would release if the air leaked out or a driver accidentally disconnected the air lines in the wrong order. If a trailer is parked on spring brakes, the brakes remain on even if air pressure is lost – the brakes fail to safe.
The European standard only requires the brakes to maintain pressure for 15 minutes, because their drivers routinely fit wheel chocks. Because Australian operating practices don’t include the use of wheel chocks in these situations, there’s a real danger that these braking systems could contribute to a trailer rolling away, or its landing legs being damaged.”
This advisory procedure, developed by the ATA’s Industry Technical Council, provides procedures to help find out what kind of park brakes are installed in a vehicle.