Factsheet 13 — June 2005

Vehicle dimensions and mass — guide to the factsheet 13 series

The information in the factsheet 13 series applies to all vehicles first registered anywhere in the world after 1 July 2002 and using New Zealand's public roads.

Most vehicles first registered in New Zealand before 1 July 2002 will comply with Land Transport Rule: Vehicle Dimensions and Mass, which came into effect on 1 July 2002. Those that have different dimension or weight limits may continue to operate under the dimension and weight limits that were specified in the legislation, or under specific permits issued before 1 July 2002 and that applied when the vehicle was first registered.

Existing heavy vehicles, however, need to comply with the trailer:truck mass ratio and static roll threshold requirements set out below.

Guide to the factsheet 13 series

No.	Title
13	Vehicle dimensions and mass
13a	Heavy rigid vehicles
13b	Light rigid vehicles
13c	Trailers (full, semi, simple, pole, A- and B-train)
13d	Trailers (light simple trailers)
13e	Static roll thresholds

Overdimension vehicles or loads

The dimensions in the factsheet 13 series apply to the load of the vehicle and the trailer (including its load). If you want to carry a load that exceeds these dimensions (ie, an over dimension load) on a legally dimensioned vehicle, or to operate a special over dimension vehicle, read Factsheet 53 or contact the Over dimension Permit Issuing Agency on 0800 OVERSIZE (0800 683 774).

Overweight vehicles or loads

If the vehicle or load exceeds the maximum permitted weights described in this factsheet, and you believe you're eligible for an overweight permit, contact your nearest Transit New Zealand regional office.

Mass on front axles

In order to retain sufficient grip on the road surface when turning, it's recommended that buses and trucks have a minimum mass (weight) on their front axle(s). This mass shouldn’t go below 20 percent (one fifth) of the total mass on the axles of that vehicle. Drivers need to be aware of this at all times. The vehicle needs to be loaded in an appropriate way so this is achieved. Placing all the load behind the rear axles of the vehicle isn't recommended.

This recommendation has been introduced to make sure that vehicles with an increased rear overhang (which is now allowed) retain front traction and steering and remain stable.

Heavy rigid vehicles first registered on or after 1 July 2002 must have at least 20 percent of their mass on the front axles at all times.

Drivers of vehicles which tow simple trailers (those with one axle set which aren’t semi-trailers) also need to be aware that the simple trailer can impose a large weight on the rear of the towing vehicle. This imposed weight can (by lever action through the chassis of the vehicle) reduce the effective mass bearing on the front axle(s) of the towing vehicle. Simple trailers therefore need to be loaded carefully so that their load is distributed centrally over the axle(s) of the trailer. This will allow the towing vehicle to maintain front wheel traction.

Note: There needs to be a small downward force on the tow coupling, to make sure a simple trailer remains stable while it's being towed.

Trailer:truck mass ratio

Heavy trailers have been identified as more likely to show stability problems than buses or trucks. For this reason the maximum mass on the axles of a heavy trailer is limited, and can't be more than 50 percent higher than the mass of the vehicle which tows it. Trailers within this limit are easier to control when braking and during emergency manoeuvres. This limitation on the mass of a heavy trailer applies at all times when heavy trailers are being moved in areas open to public access.

Operators will need to ensure that the vehicle which moves a loaded heavy trailer has sufficient mass for the purpose. It may be necessary to change loading practices so this can be achieved. This requirement mainly affects the movement of full and simple trailers. Semi-trailers and B-trains are less likely to be affected because part of the mass of these trailers is borne by the towing vehicle.

Assessing stability by static roll threshold

Trailers

If their load or body is over 2.8 metres high, the heaviest class of trailers (Class TD, with GVM over 10 tonnes) will, in addition, need to be assessed for their tendency to roll over when loaded. This assessment is mandatory for all of these vehicles.

Trailers that don't meet the required level of stability will have their capacity to carry their existing load type reduced, or could be re-certified to carry a different type of load, or will need to be adjusted or modified to improve their stability.

Trucks

The heaviest class of trucks (Class NC with GVM over 12 tonnes) must meet a minimum SRT of 0.35 g. They aren't, however, required to be certified. Factsheet 13e contains further information on static roll thresholds.

Dimension and axle changes

During consultation over the development of the Vehicle Dimensions and Mass Rule, the road transport industry requested that various restrictions on dimension limits and axle types be modified to allow a wider range of vehicles. Land Transport New Zealand drafted a set of dimension limits that were assessed by specialist engineering consultants and found to meet stability and fit-on-the-road requirements. These dimensions and their conditions are set out in the factsheet 13 series.

Key points of the dimension limits are:

• Retracting axles are now permitted on many heavy vehicles. They may only be lifted off the ground when the vehicle carries no load.
• Some rear axles on some heavy vehicles will be permitted to steer. These vehicles are:
  1. buses and trucks (except those which can tow a heavy trailer), and
  2. semi trailers (except those in A-trains and B-trains).
• A truck and semi-trailer combination may have an overall length of 18 metres.
• Semi-trailers (except those in A-trains or B-trains) may have a quad (four) axle set.
• A truck and simple trailer combination may have an overall length of 20 metres. The maximum gross mass of this combination is 32 tonnes. Stinger Steer Transporters are included in this category.
• A heavy truck may tow two trailers (excluding A-trains and B-trains) if the trailer at the rear is a light trailer and the gross mass of the combination is up to 20 tonnes.

Projecting loads

Vehicles may carry loads which are higher, longer or wider than the dimensions of the vehicle itself provided that the load doesn’t exceed the maximum permitted dimensions for that class and type of vehicle, and the vehicle can be moved safely when so loaded. It’s the operator’s responsibility to ensure the load is properly secured to the vehicle so that the vehicle remains stable at all times.

Please note: You need to read Factsheet 53 if the load exceeds any of the standard dimension limits.

Loads that overhang the outside of the body or deck of the vehicle by more than one metre to the front or rear, or more than 200 millimetres to the left or right side, need to carry special warning devices attached to the overhanging end(s) of the load.

During the hours of daylight, there must be either:

• a clean white, or fluorescent red, orange or yellow flag, at least 400mm long by 300mm wide, or
• a frangible hazard warning panel, at least 400mm long by 300mm wide showing an orange diagonal stripe (200mm wide) against a yellow green background, facing forwards or rearwards (see diagram below).
  
  
  Minimum dimensions of hazard warning panels, which can be used instead of flags on projecting loads

During the hours of darkness, the flags or hazard panels must be replaced with lights attached to the load as follows:

• For loads over one metre wide and extending more than one metre from the rear of the vehicle, one red lamp (facing toward the rear) on each side of load
• For loads up to one metre wide and extending more than one metre from the rear of the vehicle, one red lamp (facing toward the rear) at the centre of load
• For loads over one metre wide and extending from the front of the vehicle, one white or amber lamp (facing toward the front) on each side of load
• For loads up to one metre wide and extending more than one metre from the front of the vehicle, one white or amber lamp (facing toward the front) at the centre of load
• For loads extending more than 200mm beyond the side of the body of the vehicle, one red lamp (facing toward the rear) on each side of the load at the rear and one white or amber lamp (facing toward the front) on each side of the load at the front.

These lights need to be clearly visible in clear weather at a distance of at least 200 metres during the hours of darkness.

This applies to all vehicles, no matter when they were first registered.

Please note: Goods service vehicles parked on a roadway must have a red light on projecting loads that extend more than 1.5 metres behind the vehicle (see Traffic Regulation 37[5]).

Mass weight limits for heavy vehicles

To preserve the strength of roads and bridges, we need to set limits on the weight of vehicles that use them. Most New Zealand roads and bridges have been designed and are maintained to a level called 'Class 1'.

Note: Some roads and bridges have lower weight limits than Class 1. These lower limits have been imposed by the road controlling authority to protect particular bridges or roads from damage. These special limits are indicated on road signs that read 'Class C' or 'Heavy Vehicle Axle Limit' or 'Heavy Vehicle Bridge Limits'. Only vehicles within the specified limits can use these roads or bridges.

Heavy vehicles need to meet four mass limits:

• the individual axle limit, and
• the axle set limit, and
• the combined axle set limit, which depends on the distance from the first axle in any set to the last axle in any other set, and
• the ratings specified by the vehicle manufacturer for chassis, axles, tyres and other components of the vehicle.

The following mass limits indicate the maximum mass (weight) allowed on Class 1 roads.

	Single standard tyred axle (includes 2 axles spaced less than 1 metre apart)
	Single large tyred axle — tyres at least 330 mm (13 inch) width by 24 inch diameter or 355 mm (14 inch) width by 19.5 inch diameter (includes 2 axles spaced less than 1 meter apart).
	Twin-tyred axle.

Maximum allowable mass (weight) on axle sets (kilograms)

Single axle set:

Tandem axle set:

Tri-axle set:

Quad axle set:

Please note: For weights on oscillating axles and other axle combinations not shown here, see the Vehicle Dimensions and Mass Rule.

As well as having a mass on their axle sets within the limits shown in the diagrams on the previous page, heavy vehicles need to have a total mass that is within the limits set out below, when the distance from any axle in any set is measured to any other axle in another set.

Vehicles over 39,000 kg are subject to additional conditions as set out in the heavy trailers factsheet (Factsheet 13c) and to brake coding (see the Heavy Vehicle Brake Code [1997], available from Land Transport New Zealand's Vehicle Certification Unit, telephone 04 495 5489).

Maximum vehicle and axle mass (kilograms)

Maximum sum of mass on any two or more axles that together do not constitute a single tandem axle set, single triaxle set or single quad axle set, where the distance from centre of first axle to centre of last axle is 1.8m or more (including maximum gross weight).

1.8 m but less than 2.5 m	15,500 kg
2.5 m but less than 3.0 m	17,500 kg
3.0 m but less than 3.3 m	19,000 kg
3.3 m but less than 3.6 m	20,000 kg
3.6 m but less than 4.0 m	21,000 kg
4.0 m but less than 4.4 m	22,000 kg
4.4 m but less than 4.7 m	23,000 kg
4.7 m but less than 5.1 m	24,000 kg
5.1 m but less than 5.4 m	25,000 kg
5.4 m but less than 5.8 m	26,000 kg
5.8 m but less than 6.4 m	27,000 kg
6.4 m but less than 7.0 m	28,000 kg
7.0 m but less than 7.6 m	29,000 kg
7.6 m but less than 8.2 m	30,000 kg
8.2 m but less than 8.8 m	31,000 kg
8.8 m but less than 9.4 m	32,000 kg
9.4 m but less than 10.0 m	33,000 kg
10.0 m but less than 10.8 m	34,000 kg
10.8 m but less than 11.6m	35,000 kg
11.6 m but less than 12.0 m	36,000 kg
12.0 m but less than 12.5 m	37,000 kg
12.5 m but less than 13.2 m	38,000 kg
13.2 m but less than 14.0 m	39,000 kg
14.0 m but less than 14.8 m	40,000 kg
14.8 m but less than 15.2 m	41,000 kg
15.2 m but less than 15.6 m	42,000 kg
15.6 m but less than 16.0 m	43,000 kg
16.0 m or more	44,000 kg

Summary table of dimension limits

All dimension limits are maximums, in metres (m) or millimetres (mm), unless otherwise stated. For more detailed information see the appropriate vehicle factsheet (f|s).

	Rigid vehicles
	Light vehicles (F|s 13b)		Heavy vehicles (F|s 13a)
	Not towing	Towing	Not towing	Towing
Width	2-wheeled vehicles (classes AA, AB, LA, LC); 1.0 m All others: 2.5 m
Height	4.25 m
Forward distance	9.5 m	8.5 m	9.5 m	8.5 m
Rear overhang	4 m from rear axis		With non-steering rearmost axle, the lesser of 4 m from rear axis or 70% of foremost axle to rear axis. With steering rearmost axle, the lesser of 4.25 m from rear axis or 70% of foremost axle to rear axis.
Front overhang	3 m ahead of front of driver's seat when in its rearmost position.
Length of vehicle	12.6 m	11.5 m	12.6 m	11.5 m
Overall length	N|A	20 m	N|A	20 m
Ground clearance	Light: No required minimum, but if light motor vehicles and trailers have their suspension modified so ground clearance is less than 100 mm, then that suspension must be approved by a Low Volume Vehicle Certifier. Heavy: Minimum is the greater of 100 mm OR 6% of the distance from the nearest axle to the point where the ground clearance is measured.
Turning circle	25 m diameter from wall to wall, excluding collapsible mirrors.
Intervehicle spacing	N|A	4m	N|A	4m
SRT	N|A		0.35g (class NC only — over 12 tonnes GVM)

	Trailers (F|s 13c)
	Trailer with 1 axle set			Trailer with 2 axle sets
	Semi	Simple	Pole	Full	Pole
Width	2-wheeled vehicles (classes AA, AB, LA, LC); 1.0 m All others: 2.5 m
Height	4.25 m
Forward distance	8.5 m	8.5 m	8.5 m with fully extended drawbar	8.5 m	8.5 m with fully extended drawbar
Rear overhang	Light: 4 m from rear axis
	Heavy: Lesser of 4 m from rear axis or
	50% of forward distance	50% of tow coupling to rear axis		50% of front axis to rear axis
Front overhang	2.04m radius arc ahead of centre of kingpin	2.04 m radius arc ahead of centre of tow coupling	2.04 m radius arc ahead of centre of turntable on tow vehicle	2.04 m radius arc ahead of centre of turntable	2.04 m radius arc ahead of centre of turntable on tow vehicle
Length of vehicle	N|A	11.5 m	11.5 m excl. load	11.5 m	11.5 m excl. load
Overall length	18 m	20 m (includes A-trains and B-trains and heavy rigid vehicles towing two trailers)
Ground clearance	Light: No required minimum, but if light motor vehicles and trailers have their suspension modified so ground clearance is less than 100 mm, then that suspension must be approved by a Low Volume Vehicle Certifier. Heavy: Minimum is the greater of 100 mm or 6% of the distance from the nearest axle to the point where the ground clearance is measured.
Turning circle	25 m diameter from wall to wall, excluding collapsible mirrors
Intervehicle spacing	N|A	4 m	N|A	4 m max, 1 m min (F/s 13c)	N|A
SRT	Light: N/A. Heavy (Class TD only - over 10 tonnes GVM): 0.35 g (those with load or body height over 2.8m above ground to be certified for SRT)

Where you can find out more

See:

• Factsheets 13a, 13b, 13c, 13d and 13e
• Factsheet 53 Overdimension vehicles and loads
• The glovebox guide to safe towing and loading
• Land Transport Rule 41001: Vehicle Dimensions and Mass.

You can also contact Land Transport New Zealand:

• Email us: info@nzta.govt.nz.
• Phone our Helpdesk: (freephone) 0800 699 000.
• Write to us: Land Transport New Zealand, PO Box 2840, Wellington.