10.2 Ratings, Current Axle Limits and Distribution

Distinguish ratings from measured mass

GVM is the manufacturer’s maximum loaded vehicle rating. GCM is the manufacturer’s maximum for the towing vehicle and combination. Gross mass is what the vehicle actually weighs in its current condition. Gross Trailer Mass (GTM) concerns the trailer mass supported through its axles, while trailer ratings and definitions must be read correctly for the configuration.

A payload estimate from GVM minus an unladen figure is only a starting point. Fuel, driver, accessories and operating equipment can change the mass available for cargo. Use an accurate operating mass and check each axle. A vehicle can be below GVM and still overload a steering axle, trailer group, tyre, coupling or bridge.

Current general axle references

The August 2026 reform raised common General Mass Limits (GML) to the former concessional allowances. Do not use the old 16.5 t tandem and 20 t tri-axle figures as the unchanged current general figures for the qualifying groups below.

These are not a complete table for every tyre width, bus, special vehicle or axle spacing. Current GML guidance and the regulation supply those details. Manufacturer component ratings can be lower. The vehicle’s total or axle-spacing limits can also prevent simply adding each group’s maximum to obtain an unrestricted allowable combination mass.

GML, accreditation and higher mass

Concessional Mass Limits (CML) were removed on 1 August 2026 because the relevant allowances became part of GML. Do not teach CML as a separate current entitlement that every new operator must obtain for those same masses. Existing accreditation and transition arrangements should be checked through current NHVR guidance.

Higher Mass Limits (HML) remain conditional. Relevant road-friendly suspension, accreditation or approval, network and other operating conditions must be met. The qualifying tri-axle HML reference is 22.5 t; the common dual-tyred tandem reference is now 17 t under both GML and HML. An HML route does not authorise exceeding a manufacturer’s rating or every bridge sign. Check the actual notice, permit and vehicle requirements rather than assume one monitoring system is mandatory in every case.

How position changes axle loading

A load applies weight to supports according to its position. Moving cargo rearward can reduce steering-axle load while increasing rear-group load. Moving it forward does the reverse. The gross mass stays the same, so a gross weighbridge result alone cannot establish distribution.

For a simplified static example, assume a rigid truck’s front axle and rear-group support centres are 5 m apart. Before the cargo, the front carries 3 t and the rear group 6 t. Add a 10 t load whose centre is 3 m behind the front axle. Its added rear reaction is 10 multiplied by 3 divided by 5, or 6 t. Its added front reaction is 4 t. Final loads are therefore 7 t front and 12 t rear, with gross mass 19 t.

If the assumed front limit is 6 t and the qualifying rear tandem limit 17 t, the front is overloaded even though the rear and an assumed 23 t GVM are not. Moving the same load centre to 3.5 m gives 7 t added rear and 3 t added front, for final loads of 13 t rear and 6 t front. The gross mass remains 19 t. This model assumes a level static vehicle and concentrated load; actual distribution must be measured and verified.

Stability and load shift

Keep heavy items low, distribute laterally to avoid an off-centre load and position them within the permitted mass envelope. A high centre of gravity increases rollover risk. A liquid or livestock load can move dynamically, so a static weighbridge result does not eliminate stability concerns. Use suitable tanks, compartments, loading methods and restraint rather than an invented universal fill-percentage rule.

After partial unloading, check both restraint and distribution. Removing cargo from one end can increase the proportion carried by another axle or expose remaining goods to movement. A multi-drop plan should anticipate each stage, including how equipment and axle load change. Secure the new load arrangement before leaving.

Weigh the correct configuration using suitable equipment and retain useful records. If an axle is overloaded, reposition or reduce the load and recheck; do not assume a permit for dimensions also authorises excess mass. Communicate accurate cargo weights through the transport chain.

Key decisions

Check all ratings and legal limits together, verify axle distribution and use current GML/HML rules. A legal gross total alone is never a complete loading check.

Official sources

NHVR current GML; HML; current national MDL Regulation. Sources checked 10 October 2026.