Ways to stop vehicles from moving

Key messages

To protect people working on or near them, vehicles must not move when they are parked and during loading, unloading and other operations.


Vehicles should have suitable and effective brakes.

Some tanker vehicles have a safety system that prevents the vehicle brakes from being released until the delivery hose has been stored. These systems prevent the driver from driving off while the delivery is still under way. Workers should not use a site-based hose to shortcut this system.

On some vehicles, the handbrake only secures the rear wheels. Fully extending the outriggers on some vehicles may raise the rear wheels off the ground, which might mean the handbrake does not work.

Consider fitting four-wheel braking systems or other effective methods to make sure the vehicle cannot move during loading.

Outriggers and chocks

If it is reasonable, fit outriggers with plates instead of wheels, to increase contact with the ground.

If manufacturers provide wheel chocks, always use these when vehicles are stationary. There should be Information on chocking with the vehicle operating instructions.

Instruct drivers to make sure the wheels remain in contact with the ground when operating outriggers, and to use chocks where provided.

Semi-trailers and tractive units

The 'fail-safe' emergency air brakes on semi-trailers lock the trailer wheels when the air hose connection with the trailer (the 'suzie') is disconnected. If the trailer breaks away from the tractive unit (for example, in a crash), the line is broken and the brakes are applied to stop the trailer.

Drivers sometimes use the emergency brakes as parking brakes when they uncouple the tractive and semi-trailer units, because they have to disconnect the suzie anyway. This should never happen. Air brakes should never be applied solely by disconnecting the suzie hose. The emergency brakes should not be relied on to secure a semi-trailer.

Although the brakes on this system are the same for both the parking and emergency brakes, the control mechanism is different, and emergency brakes should never be relied on to secure a semi-trailer.

Reconnecting the hose will free the brakes immediately, leaving the vehicle free to move with the driver away from the cab. These 'vehicle runaway' accidents are preventable.

When vehicle runaway accidents happen, they often cause serious injuries because there are usually people around the vehicle (for example, the driver). Even if nobody is hurt, there is likely to be significant and expensive damage to the vehicle, buildings or other plant.

The most effective way to prevent vehicle runaways is to make sure that both the tractive unit and semi-trailer parking brake controls are used.

Alarm systems that go off if the driver tries to leave the vehicle cab without applying the handbrake may help to make vehicle runaway accidents less likely, but drivers still need to make sure that semi-trailer parking brakes have been applied.

Relying on the tractive unit handbrake to secure a semi-trailer is not safe. These brakes are not designed to hold the combined weight of the tractive unit and a semi-trailer. A different tractive unit might be involved, which may not be fitted with the same sort of alarm system.

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Updated 2022-05-21