This alert focuses on trailers but similar risks and control measures may apply to other wheeled vehicles. However, this alert does not cover the safety issues involved when loading and unloading trailers with forklifts.
This alert highlights the potential risks when:
- releasing the brakes of a trailer when it is not connected to a prime mover
- towing a trailer with plant that is not designed to tow
- designing and using landing legs.
In 2012, a man died when crushed by a trailer while working under it. He intended to tow the trailer using a crane, by suspending the front of the trailer from the crane using chains. While under the trailer, the brakes were released and the trailer moved forward causing the landing leg to fold back to its travelling position. As a result, the front of the trailer crashed down on the man, fracturing his leg and spine, and crushing his chest.
The major hazards involved in this task include:
- The possibility of being crushed by moving wheels, between the trailer and another object, or under the trailer if the landing legs give way.
- Uncontrolled movements of the trailer or the towing vehicle due to inadequate braking force to control both units.
- Instability when either the trailer or towing vehicle move relative to the other.
- The capacity of the landing legs is exceeded – eg the landing legs don't have the capacity to support the trailer with a full load.
- The landing leg can't be secured into a fixed vertical position.
- The brakes of the trailer were released before ensuring the trailer could not move.
- The air receiver was connected directly to the brake system to release the brakes and there was no way to control the air pressure and supply to the braking system – eg dumping the air in case of an emergency.
- The landing gear was not secured in a vertical position, which allowed it to fold to its travelling position.
- The landing gear was not designed to lock into a vertical position.
- Identify and eliminate the hazards, or control the risks if they can't be eliminated.
- To manage risks, use information from the manufacturers, safety alerts, technical standards, knowledge gathered through experience, and site specific safety issues.
- Consult with all relevant parties, including workers.
- A person with management or control must take all reasonable steps to ensure that plant is used only for the purpose for which it was designed, unless the person has determined the proposed use does not increase the risk to health or safety.
- Trailers should be parked on level ground, or within the slope the manufacturer of the trailer has allowed.
- Trailers that are not connected to a purpose-built towing vehicle should be secured against unwanted movement at all times, by using fail-to-safe-state braking system or chokes.
- Before using plant that is not designed to tow a trailer, consider whether such action is necessary – eg bring the equipment required to repair the trailer rather than tow the trailer to the workshop.
- Towing arrangements that require trailer wheels to freewheel – ie move with the braking system bypassed – using an item of plant not designed for the purpose presents many risks, including:
- lack of braking capacity to serve both units
- jack-knifing when the brake is applied
- likelihood of uncontrolled movement of the trailer beneath the suspension point
- swinging movement of the towed load under the suspension point
- increasing the working radius of the crane causing structural or stability hazards.
Therefore plant not designed to tow should not be used for towing unless the use of purpose built plant is not reasonably practicable.
- Landing legs should be able to be locked in a desired position.
- Landing legs that can't be locked in the vertical position should be retrofitted with a locking mechanism. The new system should be designed in consultation with the trailer manufacturer by a competent person who has experience in trailer designs. Welding on the trailer should not be undertaken without assessing for the effects of heat on the strength of the section to be welded.
- The locking mechanism on landing legs should be capable of handling the designed loads.
- The design of landing legs should take into account reasonably foreseeable misuse.
Note: The above recommendations do not preclude a mobile crane towing trailer being designed for towing by the crane.
- AS2550 Part 1 Cranes, hoists and winches
- AS2550 Part 5 Cranes, hoists and winches
- Managing the risks of plant in the workplace: Code of practice.
- How to manage work health and safety risks: Code of practice.