This page discusses the regulatory criteria for heavy rigid trucks as outlined in the Land Transport Rule: Vehicle Dimensions and Mass 2016.
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What is a heavy rigid vehicle?
Heavy vehicles have a maximum gross vehicle mass (GVM) of more than 3500 kilograms (kg), as determined by the manufacturer.
A rigid vehicle is comprised of two axle sets, a driver's position, a steering system, motive power, and a single rigid chassis. A restricted variety of unusual vehicles, such as an articulated bus, with a chassis divided into two dependent pieces and joined by a permanent steering pivot, are also legally rigid vehicles.
Heavy rigid vehicles (classes NB and NC), heavy buses (classes MD3, MD4, and ME), large mobile homes, mobile cranes, fire engines, heavy forklifts, heavy tractors, heavy self-powered agricultural and construction machines, and vehicles with pivot steering are examples of heavy rigid vehicles.
What are the maximum dimension limits?
Width
The maximum width (including any load) is 2.55 metres, or 1.275 metres from each side of the vehicle's longitudinal centre line (excluding side marker lights, direction indications and the bulge at the bottom of a tyre).
The only additional width permitted is:
- Direction indicators and side marker lamps
- foldable mirrors that extend no more than 240 mm beyond the vehicle's or trailer's side, and 1.49m when measured from the vehicle's longitudinal centre line
- central tyre inflation system hoses that extend no more than 75 mm beyond the exterior of the tyre on a heavy motor vehicle's drive axles
- a hubodometer that extends no more than 50mm beyond one side of a vehicle from a non-lifting, non-steering axle with light-colored outer casings, provided the hubodometer is installed on the axle with the least overwidth.
- cab exterior grabrails that extend no further than 1.325m from the vehicle's longitudinal centerline
- a bulge around the bottom of a tyre
- Close-proximity monitoring systems or cameras set on the side outside of a vehicle that reach no more than 70mm from the car's side wall
- Devices for improving a vehicle's aerodynamic performance that extend no more than 25mm from either side of the vehicle.
Height (including load)
The highest point above ground is 4.3 metres.
Stability restrictions, particularly the requirement for the vehicle to have a minimum static roll threshold (SRT), may limit the height of the body or load of class NC trucks (goods service vehicles with a GVM greater than 12 tonnes) or their operating gross mass.
Maximum length (excluding collapsible mirrors)
Except for buses, the maximum length (including weight) of a heavy rigid vehicle is 12.6 metres; for further information, see heavy buses. If the vehicle is hauling a trailer or another motor vehicle, the maximum length cannot exceed 11.5 metres. (For the maximum allowable overall length of a specific heavy combination vehicle, see heavy trailers and combinations.)
Forward distance
For a rigid vehicle, forward distance is defined as the distance from the rear axis to the front of the vehicle or its load, whichever comes first (excluding collapsible mirrors).
For big rigid vehicles without a tow coupling, the maximum forward distance is 9.5 metres. Heavy rigid trucks equipped with a tow link have a maximum forward distance of 8.5 metres.
Rear overhang
The distance from the rear axis to the rear of the vehicle or its load, whichever is greater, is referred to as the rear overhang. It is determined by the definitions of the rear axis and wheelbase.
- The maximum rear overhang for a large rigid vehicle with a non-steering axle is the lesser of four metres or 70% of the wheelbase. (In the diagram above, the rear axis is in the midway of the two or more axles).
- The maximum rear overhang for a large rigid vehicle with a steering axle is the lesser of 4.25 metres or 70% of the wheelbase. (In the diagram above, the rear axis is in the midway of the two or more axles).
- The maximum rear overhang for a heavy rigid bus longer than 12.6 metres (that must have a rearmost steering axle) is the lesser of 4.5 metres or 72 percent of wheelbase.
Front overhang
The maximum front overhang is three metres (four metres for agricultural motor vehicles). It is measured from the front edge of the driver's seat (in its rearmost position) to the foremost point of the vehicle or its cargo.
Ground clearance
The ground clearance must be at least 100mm. In addition, the ground clearance must be at least 6% of the distance between the nearest axle and the place where the ground clearance is measured (unless when loading or unloading). Flexible mudflaps, wheels, tyres, and devices meant to discharge static electricity are not included in the ground clearance requirement.
Outside turning circle
A vehicle (including projections) must be able to turn 360 degrees to the left and right within a circular with a kerb-to-kerb diameter of 25 metres. Only foldable mirrors can be projected outside of this circle.
