Three limits that apply at once
Schedule 1 section 2 says the mass of a single vehicle or combination "must not be more than the lowest of" (a) a fixed cap by vehicle type, (b) "the sum of the mass limits stated in Table 1 of Part 2 in relation to each of the axle groups and single axles", and (c) for non-buses, a reduced-mass calculation using the deduction table in Part 3. On top of that, section 4 caps each axle or group individually, and section 5 caps the mass carried within any axle spacing by the distance between the axles. "A vehicle is not within the amount ... if any single axle or axle group fitted to the vehicle has a mass in excess of the mass limits applying to the single axle or axle group": you cannot offset an overloaded drive group against a light trailer.
Table 1: the axle limits (general mass limits)
| Axle or group | Limit |
|---|---|
| Steer axle, ordinary motor vehicle | 6.0 t |
| Steer axle, complying steer axle vehicle (Euro IV-plus engine and other conditions), or Euro VI single steer | 6.5 t (7.0 t for a Euro VI complying steer axle on 315 mm-plus tyres) |
| Twinsteer group | 10.0 t without load-sharing suspension, 11.0 t with; 11.5 t Euro VI twinsteer |
| Single axle, single tyres | 6.0 t under 375 mm; 6.7 t from 375 to 450 mm; 7.0 t from 450 mm |
| Single axle, dual tyres | 9.0 t (8.5 t on a pig trailer; 10.0 t on a complying bus) |
| Tandem group, single tyres | 11.5 t under 375 mm; 13.8 t from 375 to 450 mm; 14.5 t from 450 mm |
| Tandem group, single tyres on one axle and dual on the other | 13.5 t (14.0 t complying bus) |
| Tandem group, dual tyres | 17.0 t (15.0 t on a pig trailer) |
| Tri-axle group, narrow single tyres (under 375 mm) on any axle | 15.5 t |
| Tri-axle group, dual tyres or wide singles (375 mm-plus) | 21.0 t (18.0 t on a pig trailer) |
| Quad-axle group | 15.5 t narrow singles; 21.0 t wide singles or duals |
Tyre section width decides most rows: wide single tyres of 375 mm or more are treated like duals, narrow singles are not. A tri-axle semi-trailer on super singles under 375 mm is limited to 15.5 t, not 21 t.
The total mass caps
Schedule 1 section 2(1)(a) sets a ceiling by vehicle type regardless of axles, for vehicles that are neither B-doubles nor road trains: 43.5 t for an ordinary vehicle, 44 t for a complying steer axle vehicle or a Euro VI single-steer vehicle, 44.5 t for a Euro VI complying steer axle vehicle, 47.5 t for a twinsteer prime mover with a tri-axle semi-trailer (48 t Euro VI). Complying buses have their own figures (16 t, 20 t, 22.5 t by axle configuration). B-doubles and road trains are governed by their own spacing tables (Tables 3 and 4) rather than a single cap.
Axle spacing: Table 2
Section 5 limits "the sum of the mass on each axle group or single axle within the heavy vehicle’s axle spacing" by the distance between the outermost axles concerned, on a sliding scale in Table 2: 15.0 t under 2.5 m, 23.0 t from 2.5 m, 30.0 t at 6.0 m, 36.0 t at 8.0 m, 42.0 t at 10.0 m, 42.5 t from 10.0 to 10.5 m, 43.0 t at 11.0 m, rising to 46.5 t at 14.0 m and beyond. A complying steer axle or Euro VI single-steer vehicle gets 0.5 t more and a Euro VI complying steer axle vehicle 1.0 t more when the steer axle is one end of the spacing. Section 3 adds a blunt rule for short vehicles: any two axles not in the same group closer than 2.5 m cap the whole vehicle at 15 t.
Worked example. A six-axle semi: steer 6 t, tandem drive 17 t, tri-axle trailer 21 t, sum 44 t. The general cap is 43.5 t, and the spacing from the steer to the last trailer axle, typically just over 10 m, gives 42.5 t from Table 2. The lowest applies: 42.5 t. With a complying steer axle vehicle the steer rises to 6.5 t, the cap to 44 t and the spacing figure by 0.5 t, so 43 t. That is why "42.5" and "43" are the numbers drivers know for a standard semi.
Higher mass limits (HML)
Schedule 5 lets particular axle groups run above GML "as an exception to the general mass limits": a single-drive axle on a bus 10 t instead of 9 t; a tandem group 17 t (unchanged, but qualifying); a six-tyred tandem 14 t instead of 13.5 t; a tri-axle group 22.5 t instead of 21 t. The conditions: the group must qualify for the base GML figure (at least 9 t, 17 t, 13.5 t or 21 t respectively), be "fitted with a certified road-friendly suspension system" under Vehicle Standards Bulletin 11, be on a vehicle that is not a class 1 vehicle, not a rigid towing a dog trailer, not a truck and tag trailer, and, for a tri-axle group outside the Northern Territory, "is being operated by a person who holds mass alternative compliance accreditation for the vehicle". HML applies only within an HML area or on an HML route declared by notice or permit. NHVR adds that NSW and Queensland require telematics enrolment for HML operation. The accreditation route is the NHVR’s Heavy Vehicle Accreditation scheme (mass alternative compliance accreditation), which replaced the NHVAS mass management module during the 2026 transition.
Concessional mass limits
Older guidance describes a third tier, concessional mass limits (CML), a small increment above GML on certain axle groups for accredited operators. The current regulation shows the definitions of "concessional mass limits" and "CML heavy vehicle" as omitted by the 2026 amending regulation (SL No. 100 of 2026), which restructured mass concessions around the new accreditation scheme. Operators who relied on CML should check the NHVR’s transition material for how their accreditation and notices now apply; this page describes the regulation as in force when it was written.
Enforcement and the chain
Mass is checked at weighbridges, by portable scales at roadside intercepts and, increasingly, by weigh-in-motion. Overloading is a breach by the driver and operator and, through the Chain of Responsibility, by the loader, packer and consignor whose conduct caused it; container weight declarations exist for that reason. Route access for HML and for combinations above general access is through NHVR notices and permits, which the NHVR route planner summarises. Rest areas where a load can be checked and re-secured are in the rest area directory, and the hours available to do it are on the fatigue rules page.
Common mistakes
- Adding up the axle limits and calling it the legal mass. The cap and the spacing table usually bring it lower.
- Running super singles under 375 mm at dual-tyre limits.
- Assuming road-friendly suspension alone gives HML. Accreditation and an HML route are also required for tri-axle groups.
- Balancing an overloaded drive group against a light trailer group. Section 2(2) forbids it.
- Treating a permit as national. HML and access notices vary by state.