An agreement was reached in 1998 by the Ministers of Transport encompassing all states, is now our current national towing laws. The regulations regarding any motor vehicle with a Gross Vehicle Mass, G.V.M, exceeding 4.5 tonnes are very specific. You cannot, without first seeking approval from an authority, tow any trailer which has a mass, including the load, that exceeds the recognised capacity of any towing equipment fitted to their vehicle. Neither can it exceed the maximum mass which has been specified by the manufacturer of the vehicle.
In simple terms; the maximum weight you are allowed to tow by law is either the towbar’s capacity or the amount that has been specified by the manufacturer of the vehicle; whichever is the least. It is easy enough to find out exactly what you vehicle is allowed to tow. First of all, you should check the manufacturer’s recommendations for towing in your owner’s manual or in the sales brochure. Next, you should ensure that you have a towing capacity that is at least, but preferably more, that the trailer’s mass including load. If you aren’t sure how strong your towbar is, it worth having a chat with a specialist in towing equipment.
There are cases, however, where a vehicle manufacturer hasn’t specified a maximum weight for towing, but this is covered in the regulations as follows;
• If the trailer has brakes you can legally tow a weight that is 1.5 times the kerb weight, or unladen mass of the trailer
• If the trailer does not have brakes then you are allowed to tow the unloaded weight of the vehicle itself.
Please note however, that the above rules rarely come into play as apart from when you are using a truck. Almost every other vehicle that can be used to tow a boat trailer, horse float, caravan etc will come with a towing recommendation from the manufacturer.
Owners of light commercial vehicles and 4WD’s should be very careful that they don’t exceed the GCM, or Gross Combined Mass, of their vehicle. The GCM is the maximum the vehicle combined with its load or trailer is allowed to weigh. It is very possible that when you load your vehicle, for example, with 5 adults, camping gear and luggage the allowance for the trailer mass must be reduced to ensure the whole thing doesn’t exceed its GCM. Do not ignore this as it must be done in order not to invalidate your insurance or warranty.
Since the law was passed in December 1998, trailers are allowed to be towed on the particular roads speed limit everywhere except Western Australia. You need to remember that vehicle manufacturers will, occasionally, place a speed restriction on a vehicle if it is towing over a certain weight. Ford only allows you to travel at 100km/h if your load is below 1200kg. If you are towing 1600kg this falls to 90km/h, and 2300kg will see you only being allowed to travel at 80km/h. Holden take a similar stance but also restricts the speed of the vehicle depending on the kind of towing equipment you have fitted. It is highly recommended that you spend a short time reading the section on trailer towing in your owner’s manual.
Agreements between states
In different states there are some variations in these regulations, but on the whole they agree with these safety aspects;
• The trailer cannot be larger or heavier than can be safely controlled by the driver
• The laden or total mass of the trailer cannot be more than;
The ATM, maximum mass, which is determined by the manufacturer of the trailer and is stated on its trailer plate
The weight must not exceed the stated load of the coupling attached to trailer which goes onto the towbar fitted to the vehicle or the permissible weight of the tyres.
The towing vehicle and the trailer must be set up properly to ensure the combination weight is correct. This effectively means that there will be a load weight of around 10% of the total trailer on the towbar.