A Safety Alert from Qld Workplace Health & Safety

Vehicle Stabilisers and Outriggers

Issued: 10 February 2014

Last updated: 26 May 2016



The purpose of this safety alert is to highlight the risks associated with stabilisers and outriggers on trucks and trailers when travelling on public roads.



In 2013 a manually-operated stabiliser on a truck, fitted with a vehicle load crane, unintentionally extended while travelling on a public road and killed a cyclist.

In the most recent incident, an outrigger on an amusement ride trailer swung out while being driven on a public road and hit a vehicle heading in the opposite direction, killing the driver. Similar incidents have occurred elsewhere in Australia and internationally.

Stabilisers and outriggers have many configurations depending on the application and are used to minimise the risk of toppling when the centre of gravity of the combined load and vehicle is outside the support base of the vehicle. Outriggers lift the vehicle’s wheels off the ground while stabilisers do not.

Examples of mobile plant using stabilisers or outriggers include:

  • mobile cranes
  • truck mounted elevating work platforms
  • vehicle loading cranes
  • mobile concrete placement booms
  • mobile amusement rides.

Contributing factors 

Manually operated stabilisers rely solely on the locking mechanism to ensure the stabiliser remains in the travel position.

The stabiliser can extend due to:

  • the stabiliser not being returned to and effectively locked into the travel position
  • the stabiliser restraining mechanism failing
  • incidental forces, such as, when the truck goes over a bump or around a corner.

Hydraulically operated stabilisers still require effective restraint during road travel, but they are less likely to extend due to the resistance afforded by the hydraulic system.


Action required 

For safety, make sure:

  • components of the stabiliser or outrigger travel restraint locking mechanism are fit for purpose, inspected and maintained in accordance with the manufacturer’s recommendations and/or guidance provided in relevant technical codes and standards
  • workers who drive the vehicles are provided with appropriate instruction, training and supervision regarding the proper use of the stabiliser or outrigger and the associated locking mechanism. The training should relate to the specific make and model of plant and be documented
  • management consider installing a warning system (e.g. a warning light in the cab) to indicate the retracted or extended position of stabilisers.

Further information 

Mobile crane code of practice 2006 (PDF, 1019.09 KB)

Managing risks of plant in the workplace code of practice 2013 (PDF, 1072.88 KB)

How to manage work health and safety risks code of practice 2011 (PDF, 593.82 KB)