GVM, GCM and ATM explained: which truck licence do you need?

The three numbers that matter

GVM (Gross Vehicle Mass) is the maximum the truck can weigh fully loaded, including the body, fuel, driver and cargo. It is stamped on the compliance plate and it is the number that decides your licence class.

GCM (Gross Combination Mass) is the maximum combined weight of the truck plus anything it is towing. If GCM minus GVM is less than the trailer you want to pull, the combination is illegal even if the tow bar is rated.

ATM (Aggregate Trailer Mass) applies to trailers: the maximum the trailer can weigh when loaded and uncoupled. GTM (Gross Trailer Mass) is the weight on the trailer's own axles when coupled, so it is always a little less than ATM.

NSW licence classes by GVM

• C (car licence) – any vehicle up to 4.5 t GVM. This is why 4.5 t trucks like the Isuzu NPR and Fuso Canter are so popular: anyone with a car licence can drive them, and they can tow a trailer up to 9 t GCM.
• LR (Light Rigid) – rigid trucks over 4.5 t and up to 8 t GVM, and buses up to 8 t.
• MR (Medium Rigid) – rigid trucks over 8 t GVM with two axles.
• HR (Heavy Rigid) – rigid trucks with three or more axles, including those towing a trailer up to 9 t GVM.
• HC (Heavy Combination) – prime mover plus semi-trailer, or a rigid truck towing a trailer over 9 t GVM.
• MC (Multi Combination) – B-doubles and road trains.

Most classes also require you to have held the class below for a minimum period, usually 12 months. Transport for NSW publishes the exact rules.

Payload is what you actually get

Payload = GVM minus tare (the empty weight with body fitted). A 4.5 t GVM pantech with a 2.9 t tare carries about 1.6 t. Add a tailgate loader (roughly 300 kg) and you lose that from payload. Always ask for the tare with the body on, not the cab-chassis tare from the brochure.

Overloading is expensive

Chain of Responsibility law means the driver, the business and sometimes the customer can all be fined for an overloaded truck. If you regularly carry near the limit, step up a GVM class rather than hoping.

Still not sure?

Call us with what you carry and where you drive it. We will tell you honestly whether a car-licence truck will do the job or whether you are better off with an LR or MR unit.