In December 1998, a national regulation came into effect that limits the mass a vehicle can tow. So if you are going to purchase a trailer or caravan, it is critical that you give careful consideration to your vehicle's towing mass and construction prior to making your purchase.

You will find the towing mass (or towing rating) under the towing section in the vehicle manufacturer's handbook. The rating will include a trailer weight capacity and a trailer ball weight capacity, both of which must be adhered to.

As previously mentioned, if the manufacturer has not stipulated a recommended tow mass, then the vehicle may tow one and a half times its unladen mass if the trailer has brakes. If no brakes are fitted, then the one to one ratio applies.

With regards to the construction of the tow vehicle, its body must be sturdy enough to attach a towbar of suitable capacity for the trailer you intend to tow. Some vehicles may require structural reinforcement and/or special suspension and load distribution devices before they can satisfactorily tow heavier trailers. You may also need to make other modifications to your vehicle, which could include:

• Fitting levelling equipment (frequently called weight distributing sets or level rides).
• Fitting electrical sockets for lighting: a seven pin electrical connector (which is compulsory in Australia) provides the electrical power to operate the trailer lights as well as the electrical brakes that are fitted to all later model caravans.
• Fitting a suitable brake controller and connection: all trailers of 750kgs GTM or more must be fitted with brakes. Electrical brakes are the most commonly used and require a brake controller, with appropriate connections to the trailer, to be fitted in the tow vehicle.
• Extra mirrors may need to be added to the tow vehicle when towing large trailers. It is a legal requirement that the driver has a clear and unobstructed view of the road at all times.
• Fitting an extra transmission oil cooler for vehicles with automatic transmission. (these are standard on some late model vehicles).
• As some motor vehicle manufacturers limit the speed at which you can tow a trailer always refer to the vehicle handbook.

Remember that towing a trailer or caravan will decrease your vehicle's acceleration and braking performance. It will also reduce vehicle control and manoeuvrability, while increasing fuel consumption.

Your vehicle's towing capacity is a factor of its engine size, brakes, weight, transmission, tyres, chassis etc. After taking these variables into account, the vehicle's manufacturer establishes a recommended towing capacity, which must be adhered to.