Vehicle Loading, Mass and Dimension Limits
Mass and Dimension Limits
Heavy vehicle operators must comply with mass and dimension limits set by the Heavy Vehicle National Law (HVNL) as applied in the ACT. Key limits include: maximum width of 2.5 metres, maximum height of 4.3 metres, and maximum length of 12.5 metres for a rigid vehicle. For combinations, length limits vary: 19 metres for a B-double, and up to 53.5 metres for road trains in certain areas. Mass limits are based on axle groups: steer axle typically 6 tonnes, tandem axle group 16.5 tonnes, and tri-axle group 20 tonnes. Gross mass limits depend on the number of axles and configuration.
Traps in Questions
A common trap is confusing gross mass with payload. Payload is the difference between GVM and tare mass. Another trap is the requirement for load restraint: loads must be secured so they cannot move and affect vehicle stability. Also, be aware of overloading penalties: exceeding mass limits can result in fines and demerit points. Questions may ask about the need for a permit for oversize loads; any load exceeding standard dimensions requires a permit.
Worked Example
A rigid truck has a GVM of 15 tonnes and a tare mass of 7 tonnes. The maximum payload is 8 tonnes. If the truck is loaded with 9 tonnes of cargo, it is overloaded by 1 tonne. A rule of thumb: always check axle loads individually, not just total mass, because overloading a single axle can be illegal even if total mass is within limits.