GVM (GROSS VEHICLE MASS) & GCM (GROSS COMBINATION MASS)

GVM (Gross Vehicle Mass)

Definition: The maximum legal weight of a vehicle when fully loaded, as specified by the manufacturer or regulator.

Includes:

• The vehicle itself (tare weight)
• Passengers
• Fuel, fluids, accessories
• Cargo/load

Why it matters: Licence classes in Australia are set by GVM thresholds.

• LR (Light Rigid): 4.5–8 tonnes GVM
• MR (Medium Rigid): More than 8 tonnes GVM with two axles
• HR (Heavy Rigid): More than 8 tonnes GVM with three or more axles
• HC (Heavy Combination): Prime mover + trailer with GVM over 9 tonnes
• MC (Multi-Combination): Road trains/B-doubles

Essentially, GVM tells you what vehicle class licence you need.

GCM (Gross Combination Mass)

Definition: The maximum legal weight of a vehicle and anything it tows combined.

Includes:

• The GVM of the towing vehicle
• The weight of trailers/semi-trailers/dollies
• The load carried in all of them

Why it matters: GCM sets the legal and safe limit when towing.

Example: A prime mover may have a GVM of 22.5t but a GCM of 70t, meaning it can tow a trailer or trailers so long as the combined weight doesn’t exceed 70t. For licensing, once you’re towing a trailer over 9 tonnes GVM, you’re into HC or MC territory.   

Why it Matters for Licensing

Licence Class Boundaries:

• GVM defines the base vehicle licence class (LR/MR/HR).
• GCM determines if you need a combination licence (HC or MC).

Compliance & Safety: Driving a vehicle combination over your licensed GVM/GCM is illegal and unsafe, it can void insurance, attract heavy fines, and breach Chain of Responsibility obligations.

Practical Skills: Larger GVM and GCM vehicles handle very differently, braking distances, turning space, rollover risk, load restraint, and fatigue are all impacted. This is why training and assessments escalate with licence class.

Quick way to remember:

• GVM = the truck itself loaded
• GCM = the truck + whatever it’s towing