Heavy vehicle rules: the main duties

If you operate vehicles over 4.5 tonnes anywhere except Western Australia or the Northern Territory, the Heavy Vehicle National Law applies to you. Day to day it comes down to four duties: keep vehicles roadworthy, manage driver fatigue, stay within mass and loading limits, and meet the Chain of Responsibility duty that wraps around all of it.

Does the HVNL apply to you?

The line is 4.5 tonnes gross vehicle mass, the manufacturer's rated maximum, not what the vehicle happens to weigh today. A council with two tippers and a bus is a heavy vehicle operator. WA and the NT run their own rules; fleets crossing those borders live under both.

Duty one: roadworthiness

Heavy vehicles must meet the Heavy Vehicle Standards and be maintained to them. In practice that means scheduled maintenance actually happening, daily checks before vehicles move, and defects tracked to repair. Inspection regimes vary by state and vehicle class.

Duty two: fatigue

Fatigue rules apply to vehicles over 12 tonnes and to buses over 4.5 tonnes with more than 12 seats. Work and rest limits, work diaries and record-keeping are covered in the fatigue and work diaries guide.

Duty three: mass, dimension and loading

Every vehicle and combination has legal mass limits, per axle group and gross:

  • General Mass Limits (GML) apply by default to everyone.
  • Concessional Mass Limits (CML) allow a small increase in return for NHVAS mass accreditation.
  • Higher Mass Limits (HML) allow more again on approved routes, and on many routes require telematics-based monitoring through schemes such as the Intelligent Access Program.

Loads must also be restrained to the performance standards in the Load Restraint Guide. Overloading and poor restraint are Chain of Responsibility offences for everyone in the chain.

Access: where heavy vehicles may travel

Restricted-access vehicles need to stay on approved networks or hold permits. The NHVR publishes gazetted networks, and route planning should treat network restrictions as a first-class input. IntelliTrac's route planning flags NHVR network restrictions for review; a person confirms the route, which is how it should be.

Accreditation in one paragraph

The National Heavy Vehicle Accreditation Scheme (NHVAS) has three modules: Mass, Maintenance and Fatigue (BFM and AFM). Accreditation is voluntary, but it is the entry ticket to concessions such as CML, HML and flexible fatigue hours. The price is documented systems, records and audits, which is exactly what a good digital operations trail makes cheap.

This guide is general information, not legal advice.

The heavy vehicle operator basics

  • Every vehicle over 4.5 tonnes GVM is identified, with its mass limits documented.
  • Maintenance schedules exist per vehicle and completed work is logged.
  • Pre-start checks run before movements and failures escalate.
  • Fatigue-regulated drivers keep work diaries and records are retained.
  • Loading follows documented mass and restraint procedures.
  • Restricted-access vehicles run on approved networks or hold permits.
  • Any NHVAS accreditation obligations have named owners and audit-ready records.

Official sources

Last updated 10 July 2026. General information, not tax or legal advice.

IntelliTrac provides fleet, telematics and field-operations software in Australia. Call 1300 767 492.