Mass & Dimension
Mass & Dimension Limits Explained
General mass limits, concessional and higher mass limits, axle groups, dimension limits and permits — explained for Australian owner-drivers who need to stay legal and loaded.
6 min read
The short version
- Gross mass and axle group mass are separate tests — you must pass both.
- Higher mass limits require accreditation and approved routes.
- Oversize or over-mass travel needs the correct notice or permit carried in the vehicle.
The three mass schemes
- General Mass Limits (GML) — the default, available to any compliant vehicle.
- Concessional Mass Limits (CML) — a modest increase for accredited operators under the mass module.
- Higher Mass Limits (HML) — larger increases requiring accreditation, compliant suspension and approved routes.
Legal gross, illegal axle
A trailer loaded nose-heavy can sit under its gross limit while the drive group is well over. Distribute the load, then confirm on a weighbridge.
Dimensions and access
- Height, width, length and rear overhang each have prescribed limits.
- Exceeding a limit requires a notice or permit, and the route conditions must be followed.
- Route access differs by vehicle class — check the NHVR route planner before you commit to a lane.
Payload is revenue
Every tonne you cannot legally carry changes your rate per kilometre. Model the payload you can actually and legally carry in the TruckProfit calculator.
Official source
Always refer to the NHVR for official legal requirements. This guide is general information for Australian owner-drivers, not legal advice.
Frequently asked questions
What is the difference between GML, CML and HML?
General Mass Limits apply by default, Concessional Mass Limits offer a small increase for accredited operators, and Higher Mass Limits offer a larger increase but require accreditation, compliant suspension and approved route access.
Do I need a permit for an over-height load?
Yes. Travel above the prescribed dimension limits requires the applicable notice or permit, which must be carried and complied with.
Always refer to the NHVR for official legal requirements.