Motor accidents involving a trailer, who is the insurer?

In 2024, there were 1,164,371 trailers registered with the Queensland Department of Transport and Main Roads, being around 19% of all vehicle types.1 The number of trailers registered in Queensland has been on the rise since 1992 and in particular, there were an additional 24,320 trailers registered since 2023.2 With this in mind, it is not difficult to explain why motor accidents involving trailers are increasingly common in Queensland.  

One key difference that makes motor accidents involving trailers unique is that each trailer carries a different Queensland registration number from the vehicle towing it. By reason of this, it is possible for the trailer and the vehicle towing it to be covered by two different Compulsory Third Party (‘CTP’) insurers.  

The question then is: Which CTP insurer answerable? On one hand, the trailer is incapable of independent movement and without the vehicle towing it, it could not have been in a position to cause the motor accident. On the other hand, the vehicle towing the trailer may not, in and of itself, have been responsible for the causing of the motor accident.  

Luckily for Queenslanders, the primary legislation governing motor accidents, being the Motor Accident Insurance Act 1994 (Qld) (the ‘Act’), does indeed contemplate scenarios of this nature. On this issue, section 31(3) and (4) of the Act provides the relevant principles to be applied when facing the question of who the relevant CTP insurer is. 

The structure of section 31(3) of the Act is such that if at the time of the collision: 

the trailer causative of the collision was attached to the vehicle towing it, then the trailer is regarded as part of the vehicle and the same CTP insurer insures against both the vehicle and the trailer;  

the trailer causative of the collision becomes detached from the vehicle towing it and runs out of control, then the trailer is regarded as part of the vehicle and the same CTP insurer insures against both the vehicle and the trailer; or  

in scenarios other than those described at paragraphs [1] and [2] above, the Nominal Defendant is taken to be the insurer of the Trailer, as if it had separate CTP insurance. 

Section 31(4) of the Act qualifies the preceding subsection and provides that irrespective of the principles set out in section 31(3) of the Act, if: 

the trailer: (1) has a GVM of more than 4.5 tonnes; and (2) the motor accident happened outside of Queensland, then the Nominal Defendant cannot be the CTP insurer of the trailer; and  

the trailer has separate CTP insurance (other than a supplementary policy), then the CTP insurer under the relevant policy answers to claims relevant to the trailer.   

In practical terms, the typical scenario involving a trailer being causative of the motor accident is almost always captured by the circumstances described at paragraphs [1] and [2] above. Assuming this to be the case, the short answer is that the relevant CTP insurer is the same as the vehicle towing it.  

Indeed, this is reflected in practice, when completing a point-in-time search for the trailer’s registration number, it is often the case that the return reveals that no CTP insurer is associated with the trailer. 

However, in the less common situation where the trailer has its own separate CTP insurance policy, the insurer under the separate policy becomes the CTP insurer answerable to a claim, as discussed at paragraph [5] above.