NHVR General Mass Limits Explained in Plain English

General Mass Limits are the default legal masses for heavy vehicles on Australian roads under the Heavy Vehicle National Law: how much weight each axle group may carry, and how much the whole vehicle or combination may weigh, before you need an accreditation scheme, a notice or a permit. The rules changed on 1 August 2026, when the NHVR's amended Mass, Dimension and Loading Regulation lifted GML to the levels that used to require Concessional Mass Limits accreditation: the tandem axle group limit is now 17.0 tonnes and the tri-axle group limit 21.0 tonnes, with the separate CML category removed entirely. The catch that trips people is that mass limits stack: you can be under your GVM and still be overloaded on one axle group, because the lowest applicable limit always governs.

Everything in this post is drawn from the NHVR's published guidance at nhvr.gov.au and its Mass, Dimension and Loading changes fact sheets, checked on 6 August 2026.

What General Mass Limits are and who they apply to

The Heavy Vehicle National Law covers vehicles over 4.5 tonnes gross vehicle mass, and the Heavy Vehicle (Mass, Dimension and Loading) National Regulation under it sets the mass and dimension rules. General Mass Limits are the regulation's baseline, set out in Schedule 1 Part 2: no accreditation, no special suspension certification, no permit, just the masses any compliant heavy vehicle may run at on general access roads.

One important boundary, straight from the NHVR's own fact sheet: the HVNL does not apply in Western Australia or the Northern Territory. If you operate there, your mass rules come from Main Roads WA or the NT road transport authority, and you should read this post as background only.

Three ceilings, all of which apply

Three different limits constrain any loaded heavy vehicle, and you comply with all of them simultaneously, not whichever is most convenient.

First, the manufacturer's ratings: GVM for a single vehicle and GCM for a combination. The NHVR is explicit that loaded mass must not exceed the manufacturer's rating regardless of what the regulation would otherwise allow.

Second, the regulated axle group limits: each individual axle or axle group has its own maximum.

Third, the regulated total for the vehicle or combination.

The lowest of these governs. A prime mover with a generous GCM still cannot put more than the regulated mass on its drive group, and a combination whose axle limits sum to a big number is still capped by the combination total.

The axle groups

An axle group is a set of closely spaced axles the regulation treats as one unit: a single steer axle, a single axle with dual tyres, a twinsteer, a tandem, a tri-axle group, and quad or larger groups.

The two figures most buyers and operators care about, confirmed against the NHVR's Mass, Dimension and Loading changes fact sheet: from 1 August 2026, a tandem axle group may carry up to 17.0 tonnes, and a tri-axle group up to 21.0 tonnes. The same fact sheet aligns quad axle groups and groups of five or more with the tri-axle figure at 21.0 tonnes.

For steer axles, single axles and twinsteer groups, we are deliberately not printing figures, because we could not re-confirm them against NHVR's tables on the day of writing and this is not a topic to publish from memory. The exact numbers, including the tyre width conditions that attach to some of them, are in Schedule 1 Part 2 of the MDL Regulation and in the NHVR's General Mass Limits fact sheet at nhvr.gov.au. One steer axle change we can confirm from the 1 August 2026 fact sheet: eligible Euro VI (ADR 80/04) prime movers in road trains gained a steer axle concession of an extra 0.5 tonnes up to 7.0 tonnes with tyres at least 315 millimetres wide, and eligible twinsteer groups an extra 0.5 tonnes up to 11.5 tonnes with load-sharing suspension and tyres at least 275 millimetres wide.

How the limits combine across a combination

Here is the part the regulation-speak obscures. You might expect a combination's legal total to be the sum of its axle group limits. It is not: the combination total is capped separately, and from 1 August 2026 the cap works like this, per the NHVR fact sheet: the general limits rose to the old concessional levels, with overall increases capped at 1 tonne for combinations up to 55 tonnes and 2 tonnes above 55 tonnes, while the old 5 per cent gross mass restriction and the one-tonne tri-axle mass transfer allowance were both removed.

Worked example: a common six-axle semi

Take the classic single articulated combination: prime mover with a steer axle and tandem drive, semi-trailer with a tri-axle group.

Sum the big groups under the new limits and you get 17.0 tonnes on the drive tandem plus 21.0 tonnes on the trailer tri-axle, plus the steer allowance. That arithmetic lands above what the combination may actually gross, because the capped increase governs: the long-standing GML total for this combination was 42.5 tonnes, and the 1 August 2026 change adds the capped 1 tonne, taking a six-axle semi to 43.5 tonnes. The lesson generalises: axle group limits tell you how the load must be distributed, the combination total tells you how much you may carry, and the tighter constraint wins. Confirm the current total for your configuration against NHVR's tables before you load to it.

The same logic applies to a rigid. A tandem drive rigid might have a GVM plate reading higher or lower than the sum of its steer and tandem limits; whichever is lowest is your ceiling, and getting the load too far rearward can overload the tandem while the weighbridge total still looks fine.

What changed on 1 August 2026

The amendments commenced alongside the updated HVNL on 1 August 2026. In summary, per the NHVR:

Note what did not change: Higher Mass Limits. HML still sits above GML for road-friendly suspension vehicles on approved networks, and the trade-offs are covered in CML versus HML.

Steer axles and the practical loading consequences

Steer axle mass matters beyond compliance: it is steering feel, tyre life and braking. The new tag trailer rules make the point explicitly, requiring steer axle mass to be at least the greater of 20 per cent of the sum of the towing vehicle's axle limits or the manufacturer's minimum. Load too far back to protect a drive group and you can starve the steer; too far forward and you overload it. If you are speccing a truck and trailer combination around these rules, the mass story should drive the axle configuration you buy, whether that is a truck or the trailer behind it, and how you restrain what you carry is its own legal topic, covered in load restraint basics.

Where to look it up yourself

Go to the source, not a forum thread: the NHVR's mass limits pages and General Mass Limits fact sheet at nhvr.gov.au, and Schedule 1 Part 2 of the Heavy Vehicle (Mass, Dimension and Loading) National Regulation for the legal text. Dimensions have their own rules and their own 1 August 2026 changes, covered in heavy vehicle dimension limits. If the mass rules have you re-thinking your fleet mix, the market is the other half of the answer: browse trucks, or if the changes have left a vehicle in your yard surplus, list it free while the productivity story is fresh.

Checked against NHVR guidance on 6 August 2026, including the Mass, Dimension and Loading changes fact sheet for the amendments commencing 1 August 2026. Mass rules change; confirm current limits with the NHVR before relying on this, and with Main Roads WA or the NT authority outside the HVNL states.