Heavy Vehicle Mass Limits in Australia: GML, CML and HML Explained
Australian truck mass limits are not a single number. They vary by vehicle type, axle configuration, road class, and road manager approval. This guide covers General Mass Limits, Concessional Mass Limits, Higher Mass Limits, axle group rules, and how Truck Me keeps you within the right limits on every route.
The NHVR's role in setting and enforcing mass limits
The National Heavy Vehicle Regulator (NHVR) is the single national body responsible for regulating heavy vehicles over 4.5 tonnes gross vehicle mass in Australia (excluding WA and NT). Mass limits under the Heavy Vehicle National Law (HVNL) are part of the NHVR's regulatory framework, and the NHVR publishes approved network data for each mass tier through its API.
Mass limit tiers determine not just how much a vehicle can weigh, but which roads it can legally travel on at that weight. A vehicle within GML can use the general road network. A vehicle seeking HML masses must travel on the designated HML network. The road and the vehicle must both be approved for the mass tier being used.
Road managers, which include local councils, state road authorities, and private road owners, set access decisions for their roads and submit them to the NHVR. Those decisions can include mass conditions that are lower than the national tier limits. The NHVR publishes the combined dataset, which Truck Me reads to determine what your combination can carry on any given road.
The three mass limit tiers
Each tier has different vehicle eligibility criteria and road network requirements. Higher tiers require more from both the vehicle and the road.
General Mass Limits (GML)
The default mass limits that apply on all roads unless a higher limit is specifically approved. GML applies to all heavy vehicles automatically. For a standard semi-trailer, the GML gross combination mass (GCM) is typically 42.5 tonnes. Individual axle group limits also apply under GML.
Concessional Mass Limits (CML)
Higher than GML and available to vehicles that meet specific vehicle standards, often relating to axle spacing and tyre specifications. CML access is not universal. It applies only on roads where the road manager has approved CML access, and the vehicle must meet the CML vehicle standards.
Higher Mass Limits (HML)
The highest tier of approved mass, available on a designated network of roads capable of supporting the additional load. HML allows gross combination masses up to 68.5 tonnes for eligible vehicles. HML road access is strictly controlled and not available everywhere.
Mass Management Agreements
An accreditation pathway for operators who want to carry loads above GML without requiring per-trip permits. Operators demonstrate they have systems to manage vehicle mass within approved limits. The vehicle, road, and operator accreditation must all align.
Axle group limits: GML vs HML
Gross combination mass is only part of the compliance picture. Each axle group on the vehicle is independently limited. A vehicle can be under its GCM limit and still be non-compliant because one axle group is overloaded. Load placement on the trailer matters as much as total weight.
| Axle group | GML limit | HML limit |
|---|---|---|
| Single axle | 9.0 t | 10.0 t |
| Tandem axle group | 16.5 t | 18.0 t |
| Tri-axle group | 20.0 t | 22.5 t |
| Quad-axle group | 23.0 t | 26.0 t |
These are standard axle group limits under the HVNL. Some roads carry local conditions with lower limits set by the road manager. Always check the NHVR network data for the specific road before travelling.
Penalties for exceeding mass limits
Mass non-compliance is one of the most commonly detected offences at weigh stations and mobile enforcement operations. The HVNL uses a tiered penalty structure based on the percentage excess:
- Minor risk: up to 5% excess mass. Infringement notice, moderate fine.
- Substantial risk: 5-20% excess. Higher fines, potential court action.
- Severe risk: over 20% excess. Court-only offence, major fines, possible licence action.
- Chain of responsibility: consignors, packers, and loaders can also be liable even if they are not driving.
- Road damage liability: operators can be held liable for infrastructure damage caused by overloading.
How Truck Me handles mass limits
Vehicle-specific mass checking
Truck Me stores your vehicle profile, including GCM and axle configuration. Routes are calculated against the approved mass limits for your combination on every segment.
HML network awareness
HML roads are a separate designated network. Truck Me reads NHVR network data to determine which roads on your route are HML-approved and which are GML-only.
Mass condition warnings
Conditional road segments often carry mass-related conditions such as reduced axle limits on local roads. Truck Me surfaces those conditions before you depart.
Saved route monitoring
If a road on a saved route loses HML or CML approval, Truck Me sends a notification before your next trip so you can adjust your load or find an alternative.
Multiple vehicle profiles
Different runs use different trucks. Save multiple vehicle profiles with their mass limits and switch between them before calculating a route.
Permit requirement flags
Some mass limit tiers require operator accreditation or a road manager permit. Truck Me flags when a route segment has these requirements so you know before you arrive.
Common questions about mass limits
What is the difference between GML, CML, and HML?
GML (General Mass Limits) is the baseline that applies everywhere by default. CML (Concessional Mass Limits) allows slightly higher masses for vehicles meeting specific design standards, on roads where road managers have approved CML access. HML (Higher Mass Limits) is the highest tier, allowing GCMs up to 68.5 tonnes on a designated network of roads that have been assessed as structurally capable of supporting that load. Each tier stacks higher requirements on both the vehicle and the road.
How do axle group limits work?
Mass limits in Australia apply at two levels: the gross combination mass (the total weight of the vehicle and load) and the per-axle-group limit. Even if your GCM is within the road's limit, you can still be in breach if any individual axle group exceeds its limit. Under GML, a tandem axle group is limited to 16.5 tonnes. Under HML, the same axle group is limited to 18.0 tonnes. Both limits apply simultaneously, so a vehicle can be compliant on GCM but non-compliant on an axle group.
Do mass limits change on different roads?
Yes. Road managers, which include local councils and state road authorities, can apply reduced mass limits on specific roads. These are called local area access restrictions and they override the network-level limits. A road in the HML network may still have a local bridge with a 5.5 tonne axle limit posted by the local council. Those local restrictions are part of the NHVR network data and are reflected in Truck Me routing.
What is a mass management agreement and who needs one?
A mass management agreement (MMA) is an accreditation under the National Heavy Vehicle Accreditation Scheme (NHVAS) that allows operators to carry loads above GML without applying for individual trip permits. To qualify, operators must demonstrate documented systems for weighing vehicles, training drivers, and maintaining records. The vehicle must still comply with the mass limits for the network it is travelling on, and the operator must hold current NHVAS accreditation.
Are mass limits the same in every state?
Australia's mass limits are set by the Heavy Vehicle National Law, which applies uniformly in Queensland, New South Wales, Victoria, South Australia, Tasmania, and the ACT. Western Australia and the Northern Territory are not party to the HVNL and maintain their own legislation, so limits can differ. For WA and NT routes, always verify the current state-specific limits with the relevant road authority.
What happens if you exceed the mass limits?
Exceeding mass limits is an offence under the Heavy Vehicle National Law. Penalties are scaled to the severity of the excess. Minor overloads attract infringement notices. Severe excess mass (typically more than 20 percent over the limit) can result in major penalties, vehicle defect notices that ground the vehicle, and chain of responsibility liability extending to the consignor and loader. Road damage liability can also follow from overloading.
Related guides
NHVR Access Codes
What the approved, conditional, and restricted access codes mean on the map and for your compliance obligations.
Heavy Vehicle Compliance
HVNL obligations for operators and drivers, NHVR enforcement, and how Truck Me helps keep every trip compliant.
NHVR Approved Roads
How road approvals work per vehicle class and what conditional roads actually require from drivers.
Know your limits before you leave
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