General mass and dimension limits

The National heavy vehicle mass and dimension limits fact sheet (PDF, 1.4MB) illustrates the information below in more detail. 

General Mass Limits

General Mass Limits (GML) apply to all heavy vehicles. The GML state the allowable mass for all types of heavy vehicle axle groups unless the vehicle is operating under an accreditation or an exemption under the Heavy Vehicle National Law (HVNL).

1-Tonne Tri-Axle Mass Transfer Allowance (1TMTA)

The 1TMTA provides heavy vehicle operators with flexibility in loading certain heavy vehicle combinations. The 1TMTA allows increased mass on tri-axle groups so that they may be loaded by up to 1 tonne (t) above the normal tri-axle group 20t General Mass Limit (GML) provided any additional mass loaded onto each tri-axle group is offset onto other non-steer axle or axle groups.

Prescribed dimensions

The prescribed dimension requirements for heavy vehicles are set out under the Heavy Vehicle (Mass, Dimension and Loading) National Regulation.

Width

The width limit for vehicles is 2.5 metres, excluding:

  • rear vision mirrors, signalling devices and side-mounted lamps and reflectors
  • anti-skid devices mounted on wheels, central tyre inflation systems, tyre pressure gauges
  • permanently fixed webbing-assembly-type devices, such as curtain-side devices, provided that the maximum distance measured across the body including any part of the devices does not exceed 2.55 metres.

Height

The height limit for heavy vehicles is 4.3 metres unless it is a:

  • vehicle built to carry cattle, horses, pigs or sheep - 4.6 metres
  • vehicle built with at least 2 decks for carrying vehicles - 4.6 metres
  • double-decker bus - 4.4 metres

Length

  • General access vehicles - The length of a heavy vehicle is:
        • for a combination other than a B-double, road train or a car carrier—19 metres
        • for a B-double—25 metres
        • for a road train—53.5 metres
        • for a car carrier —25 metres
        • for an articulated bus—18 metres
        • for a bus other than an articulated bus—14.5 metres
        • for another vehicle—12.5 metres
  • Trailers - On a semi-trailer or dog trailer the distance from the front articulation point to the rear over hang line must not be more than 9.5 metres and the distance from the front articulation point to the rear of the trailer must not be more than 12.3 metres. The maximum forward projection of a semi-trailer, or anything attached to a semi-trailer must not protrude beyond a 1.9-metre arc from the towing pivot pin (King pin). The articulation point to the rear of a semitrailer may be up to 13.2 metres if the trailer has a distance of not more than 9.5 metres from the front articulation point to the rear overhang line, does not operate in a B-double or road train combination and otherwise complies dimensionally.
  • Refrigerated van trailers - The distance from the articulation point to the rear of a semi-trailer may be up to 13.6 metres if the trailer is designed and constructed for the positive control of temperature through the use of refrigerated equipment, has a distance from the articulation point to the rear overhang line of no more than 9.9 metres and does not operate in a B-Double or road train combination and otherwise complies dimensionally. Also, the distance from the front articulation point to the rear overhang line of not more than 9.9 metres; and the vehicle must not operate in a B-Double or Road Train combination.
  • Car carriers - The distance measured at right angles between the rear overhang line of a trailer carrying vehicles on more than one deck and the rear of the rearmost vehicle on the trailer must not exceed 4.9 metres.
  • Livestock carriers - A trailer built to carry cattle, horses, pigs or sheep on two or more partly or completely overlapping decks must not have more than 12.5 metres of its length available to carry cattle, horses, pigs or sheep. In a B-double built to carry cattle, horses, pigs or sheep, the two semitrailers must not have more than 18.8 metres of their combined length available to carry cattle, horses, pigs or sheep. Note - the length available for the carriage of cattle, horses, pigs or sheep on a trailer is measured from the inside of the front wall or door of the trailer to the inside of the rear wall or door of the trailer, with any intervening partitions disregarded.

Rear overhang and rear overhang line

The rear overhang of a vehicle is the distance between the rear of the vehicle and the rear overhang line of the vehicle.

  • If a vehicle’s rear axle group comprises of only 1 axle, the rear overhang line is the centre-line of that axle.
  • If a vehicle’s rear axle group comprises of 2 axles, 1 of which is fitted with twice the number of tyres as the other, the rear overhang line is located at one-third the distance between the 2 axles and is closer to the axle with the greater number of tyres.
  • If a vehicle’s rear axle group comprises of 3 or more axles, the rear overhang line is the centre-line of the axle group.

Rear overhang on rigid trucks - Lesser of 3.7 metres or 60% of wheelbase.

Rear overhang on a semi-trailers and dog trailers - Lesser of 3.7 metres or 60% of ‘S’ dimension.

Rear overhang on a pig trailer - Rear overhang on a pig trailer must not exceed the lesser of the length of the load-carrying area, forward of the rear overhang line or 3.7 metres.

Dimensions relating to specific trailer types

Livestock carriers

  • A trailer built to carry cattle, horses, pigs or sheep on two or more partly or completely overlapping decks must not have more than 12.5 metres of its length available to carry cattle, horses, pigs or sheep.
  • In a B-double built to carry cattle, horses, pigs or sheep, the two semi-trailers must not have more than 18.8 metres of their combined length available to carry cattle, horses, pigs or sheep.

Note - the length available for the carriage of cattle, horses, pigs or sheep on a trailer is measured from the inside of the front wall or door of the trailer to the inside of the rear wall or door of the trailer, with any intervening partitions disregarded.

Refrigerated van trailers

The front articulation point to the rear of a semi-trailer may be up to 13.6 metres if the trailer is designed and constructed for the positive control of temperature through the use of refrigerated equipment. Also, the distance from the front articulation point to the rear overhang line of not more than 9.9 metres does not operate in a B-double or road train combination and otherwise complies dimensionally.

Car carriers

The distance measured at right angles between the rear overhang line of a trailer carrying vehicles on more than one deck and the rear of the rearmost vehicle on the trailer must not exceed 4.9 metres.