Source: https://www.nzta.govt.nz/resources/rules/vehicle-dimensions-and-mass-2002/
Timestamp: 2019-03-22 06:23:03
Document Index: 294081857

Matched Legal Cases: ['art 2', 'art 2', 'art 1', 'art 1', 'art 2', 'art 1']

Note: This Rule should be read in conjunction with Land Transport Rule: Vehicle Dimensions and Mass Amendment 2005.
1.5 Objective of the rule
Section 2 General requirements for all vehicles
Section 3 Static Roll Threshold (SRT) performance requirements
3.2 Minimum SRT values
3.4 Methods for determining SRT
3.5 Determining the appropriate loading of a vehicle
3.6 Certifying results of SRT test
Section 4 Requirements for specific types of vehicle and vehicle configuration
4.1 General requirements for dimension and mass limits
4.2 Axle requirements for heavy motor vehicles
4.3 Gross mass limits
4.4 Trailer:truck mass ratio for heavy combination vehicles
4.5 Road mass limits
4.6 Towing requirements
Section 5 Permits for overweight vehicles
Section 6 Overdimension motor vehicles and overdimension loads
6.1 Scope of this section
6.2 Standard motor vehicles transporting overdimension loads
6.3 Specialist overdimension motor vehicles
6.4 Motor vehicles designed primarily to transport overdimension and overweight loads
6.5 Dimension requirements for overdimension motor vehicles
6.6 General operating requirements for overdimension vehicles
6.7 Lighting requirements for overdimension motor vehicles
6.8 Permits
6.9 Hazard warning flags
6.10 Hazard warning panels
6.11 'OVERSIZE' signs
6.12 Travel times
Section 7 Piloting requirements
7.1 Piloting of overdimension vehicles and overdimension loads
7.2 Responsibilities of operators of pilot vehicles
7.3 Pilot vehicles
7.4 Enforcement officers' vehicles
Section 8 Responsibilities
8.1 Responsibilities of operators
8.2 Responsibilities of modifiers
8.3 Responsibilities of vehicle inspectors and inspecting organisations
8.4 Responsibilities of manufacturers
8.5 Functions of the Director
Schedule 1 SRT calculations
Schedule 2 Maximum mass for heavy motor vehicles
Schedule 3 Permit to exceed mass limits
Schedule 5 Prohibited travel
Schedule 6 Zones for restricted travel
Schedule 7 Specific route restrictions
Schedule 8 Swept path performance measures for maximum standard-sized vehicle
Schedule 9 Swept path performance measure for maximum Category 1 overdimension vehicle
Land Transport Rule: Vehicle Dimensions and Mass 2002 specifies requirements for dimension and mass limits for vehicles operating on New Zealand roads. The rule sets in place a regulatory regime so that vehicles, in particular, heavy truck and trailer combinations, are operated safely.
This rule clarifies, consolidates and rationalises the existing requirements for vehicle dimension and mass limits. It addresses the risks to land transport safety arising from the demands that the road network and the traffic environment place on the manoeuvrability and stability of vehicles. The rule includes new requirements aimed at improving vehicle stability and, thereby, reducing the incidence of rollover and loss-of-control crashes among heavy vehicles. The rule reduces the trailer:truck mass ratio so as to address the tendency of heavy vehicles with trailers to jack-knife while undertaking emergency manoeuvres, in particular, when braking into corners. The rule’s provisions take into account recommendations of the 1996 Parliamentary Inquiry into Truck Crashes.
The rule largely carries over from the previous legislation the maximum envelope of dimensions and mass limits, namely, 20 metres and 44 tonnes respectively. It reduces the complexity of, and removes anomalies in, the limits and how they are administered. The overdimension policy has been rationalised in relation to road-space requirements, hazard warning systems, piloting and travel times for heavy vehicles. Where possible, requirements for overdimension and overweight vehicles that have been allowed to operate outside the limits prescribed by the legislation, by way of a special-permit regime, have been brought into the rule, and the special permit regimes have been ended.
The rule requires compliance with two approved standards. One of these relates to testing for Static Roll Threshold (which is used to determine the stability of a vehicle). The other is an approved standard with which retroreflective materials used for ‘OVERSIZE’ signs and hazard warning panels must comply if the overdimension vehicle is operated at night. The approved vehicle standards are ‘incorporated by reference’ in accordance with section 165 of the Land Transport Act 1998 so that they are effectively part of the rule.
This rule applies to all vehicles in Table A in the rule, as well as to motor vehicles that are not in the table (such as motor scrapers and other vehicles that may operate on public roads) regardless of when they were manufactured or registered.
The rule states who is responsible for ensuring compliance with its requirements: operators, modifiers, vehicle inspectors and inspecting organisations, and manufacturers. This ensures that the rule is linked to relevant provisions of the Land Transport (Offences and Penalties) Regulations 1999.
Consultation on Land Transport Rule: Vehicle Dimensions and Mass 2002 began formally with the release, on 30 June 2000, of the red draft for comment by industry and other interested organisations and individuals. Thirty-nine submissions were received.
The Land Transport Safety Authority (LTSA) released the public consultation (yellow) draft of the rule on 2 July 2001 and sent copies to around 600 organisations and individuals who had expressed an interest, or who were considered likely to be interested, in the rule. The availability of the yellow draft was publicised in metropolitan newspapers and in selected regional newspapers, the New Zealand Gazette, Te Maori News and in various industry publications. The draft rule and associated material were accessible on the LTSA’s website and were sent to transport authorities and libraries overseas. 134 submissions were received on the yellow draft.
To assist with the production of the rule, the LTSA appointed a technical advisory group of experts, drawn from the New Zealand Police, Transit New Zealand, the Road Transport Forum of New Zealand, Transport Engineering Research New Zealand Ltd, the Truck Trailer Manufacturers Federation, the Motor Industry Association, bus chassis importers and specialist heavy vehicle certifiers. The members of the technical advisory group provided advice as technical experts rather than as representatives of their respective organisations. They provided the LTSA with useful comments that were taken into account in drafting the rule.
Issues identified in submissions were taken into account in redrafting the rule, and when required, were resolved through discussion with the affected industry group, before the rule was submitted to Cabinet, and to the Minister of Transport for signature.
This rule is Land Transport Rule: Vehicle Dimensions and Mass 2002.
1.2(1) This rule applies to:
(a) all motor vehicles, including motor vehicles in Table A in Part 2; and
(b) vehicles of Class AA in Table A.
1.2(2) Except as otherwise provided in this rule, reference to the dimensions and mass of a vehicle includes reference to its load, load restraints, fittings, attachments, equipment and accessories.
1.2(3) Except as provided in sections 3, 6 and 7 and 4.4, a vehicle that was first registered in New Zealand before the date on which this rule comes into force and that complies with dimension and mass limits imposed by or under any enactment in force before the commencement of this rule, may continue to operate under the dimension and mass limits imposed by or under that enactment.
This rule comes into force on 1 July 2002, except for those provisions with different dates specified in the rule.
1.5(1) The objective of the rule is to manage the risks to road safety resulting from the dimensions and mass of vehicles, and, in particular, to achieve a reasonable balance between the risks that heavy motor vehicles present to public safety, and the efficient operation of the heavy motor vehicle fleet within the constraints imposed by the road network.
1.5(2) The rule aims to achieve its objective by:
(a) specifying performance requirements with which vehicles must comply so as to operate on a road; and
(b) specifying dimension and mass limits for vehicles, and their towing requirements; and
(c) allowing vehicles and their loads that exceed the specified limits in section 4, to operate on a road under conditions imposed by section 5 or section 6, as applicable, provided that the safety of road users and the protection of the road network are not compromised.
[Note: In this rule, dimensions less than one metre are expressed in millimetres (mm). Dimensions of one metre or more are expressed in metres (m).]
2.1(1) A vehicle and its load must comply with dimension requirements in this rule and must be manoeuvrable, fit safely on a road and interact safely with road users.
2.1(2) The distribution of the gross mass of a motor vehicle over its axles, and the position of the centre of gravity of the vehicle, must ensure that the dynamic handling characteristics of the vehicle remain safe in terms of stability and steering manoeuvres for the design speed of the road.
2.1(3) A vehicle must not be operated on a road if the vehicle or its load is likely to damage any wires, cables or construction lawfully on, over or alongside that road, unless the vehicle is an overdimension motor vehicle of excess height, in which case the operating requirements in Table 6.2 must be complied with.
2.1(4) A load that is being transported on a motor vehicle and that extends more than 1 m to the rear, or more than 1 m forward from, or more than 200 mm out from the side of, the body of the vehicle must be indicated by:
(a) a clean white flag, or a red, orange or yellow fluorescent flag, which must be at least 400 mm long and 300 mm wide; or
(b) a frangible hazard warning panel, which must comply with the dimensions in Figure 1 in Schedule 4.
2.1(5) A motor vehicle that is transporting a load specified in 2.1(4) during the hours of darkness must, instead of a flag or frangible hazard warning panel, be fitted, and be operated, with the following lights:
(a) for a load exceeding 1 m in width extending from the rear of the vehicle, one red lamp fitted on each side of the load at the rear of the load;
(b) for a load that is 1 m in width or less extending from the rear of the vehicle, one red lamp fitted centrally at the rear of the load;
(c) for a load exceeding 1 m in width extending from the front of the vehicle, one white or amber lamp fitted on each side of the load at the front of the load;
(d) for a load that is 1 m in width or less extending from the front of the vehicle, one white or amber lamp fitted centrally at the front of the load;
(e) for a load that extends more than 200 mm beyond the side of the body of the vehicle:
(i) one red lamp fitted on each side of the load at the rear; and
(ii) one white or amber lamp fitted on each side of the load at the front.
2.1(6) A lamp in 2.1(5) must be clearly visible in clear weather at a distance of at least 200 m during the hours of darkness.
2.1(7) Subclause 2.1(4) is subject to 2.1(5), 6.9 and 6.10.
2.1(8) Subclause 2.1(5) is subject to 6.7.
This section sets out Static Roll Threshold (SRT) performance requirements for heavy motor vehicles. These requirements are intended to ensure the stability of heavy motor vehicles when negotiating corners within posted advisory speeds, and when undertaking evasive manoeuvres to avoid a collision.
Subject to 3.3(4), a vehicle of Class NC or Class TD, whether laden or unladen, must comply with an SRT of at least 0.35 g.
3.3(1) A vehicle of Class TD, other than a vehicle in 3.3(4), that was first registered before 1 July 2002 must, by the first date of renewal of a certificate of fitness occurring after 1 July 2003:
(a) comply with the SRT specified in 3.2; and
(b) if it has a body height or load height above the ground that exceeds 2.8 m, be certified for SRT in accordance with 3.4 to 3.6.
3.3(2) A vehicle of Class TD, other than a vehicle in 3.3(4), that is first registered on or after 1 July 2002 must, by the first date of renewal of a certificate of fitness occurring on or after 1 January 2003:
3.3(3) A vehicle of Class NC, other than a vehicle in 3.3(4), must:
(a) on or after 1 January 2003, comply with the SRT specified in 3.2; and
(b) if checked for compliance with SRT, have the SRT determined by one of the methods specified in 3.4.
3.3(4) The following vehicles of Class NC and Class TD do not have to comply with the minimum SRT requirements:
(b) a vehicle operating under section 6, or with a vehicle axle index above 1.1 and operating under an overweight permit, or both, provided that the operator of the vehicle complies with the conditions of the permit and the applicable requirements in section 6;
(d) a vehicle that is being used on a road or portion of a road that is a roadworks zone approved by the road controlling authority;
(i) a vehicle first registered before 1 January 1940.
SRT must be determined by one of the following methods:
(b) a calculation using the ‘SRT Calculator’ computer program approved by the Director; or
(c) a calculation using the method in Schedule 1; or
(d) a procedure, approved by the Director, other than that in (a).
3.5(1) The following procedures must be applied to determine the appropriate vehicle loading:
(i) if the vehicle is loaded to the maximum internal body height or to the maximum height specified in section 4, the maximum allowable gross mass must be determined;
(ii) if the vehicle is loaded to the maximum allowable gross mass specified in section 4, the maximum allowable load height must be determined;
3.5(2) The combination of load height and load mass in 3.5(1) applies for a particular standard type of loading that must be appropriate for the particular type of deck or body with which a heavy motor vehicle is fitted, and must be one of the following types of load:
(c) ‘other loads’, where the height above ground of the centre of gravity of the load is entered in the calculation.
3.5(3) If the deck or body fitted on a heavy motor vehicle is changed to allow a different type of load to be carried, the SRT must be determined, and the vehicle recertified, for the new loading.
3.5(4) A motor vehicle with a retractable axle or axles must be assessed under the procedures in 3.5(1) with its axles in a non-retracted position.
3.6(1) SRT test results must be:
(a) verified for compliance with loading and mass specifications by a vehicle inspector or an inspecting organisation; and
(b) specified in a document of compliance that complies with a form approved by the Director.
3.6(2) SRT test results must be displayed on a vehicle’s certificate of loading with the options for load height and gross mass specified on the certificate as follows:
‘SRT 0.35 g X1/Y1, Y2/X2
X2 = maximum safe load height above ground in metres to two decimal places to meet SRT of 0.35 g’
[Note: X1/Y1 represents the maximum allowable load height (X1) of the vehicle that is used to calculate the maximum safe gross mass (Y1) of the vehicle to meet an SRT of 0.35 g.
Y2/X2 represents the maximum allowable gross mass (Y2) of the vehicle when loaded that is used to calculate the maximum safe load height (X2) of the vehicle to meet an SRT of 0.35 g.
The procedure is fully explained in 3.5.]
4.1(1) Except as otherwise provided in this section and in 1.2(3), a vehicle must comply with the applicable requirements in Table 4.1, and with other applicable requirements in this section.
4.1(2) An overdimension motor vehicle that does not comply with a dimension requirement in Table 4.1 may comply instead with the equivalent requirement in Table 6.1 or Table 6.2, and:
(a) if the width limit in Table 4.1 is exceeded, the inter-vehicle spacing requirement in 4.1(8) does not apply;
(b) if the length limit in Table 4.1 is exceeded, the rear trailing unit distance requirement in that table may also be exceeded;
(c) if the width, forward distance or length limit in Table 4.1 is exceeded, the outside turning circle for a 360-degree turn requirement in Table 4.1 may also be exceeded.
4.1(3) A vehicle designed principally to transport overdimension or overweight loads, or both, does not have to comply with the ground clearance requirements in Table 4.1 when the vehicle’s suspension is lowered temporarily to enable the vehicle to clear an overhead obstruction.
Table 4.1 Dimension requirements1 for vehicles and vehicle combinations
Distance (metres except where
Two-wheeled vehicles of Classes AA, AB, LA, and LC 1.0
All other vehicles 2.5, or 1.25 from each side of the
longitudinal centre-line of the vehicle
Overall length (excluding collapsible
Towing vehicle, full trailer, simple trailer, pole
trailer (excluding load) 11.5
Towing vehicle and semi-trailer, articulated
bus 18.0
Towing vehicle and full trailer, towing vehicle
and simple trailer, towing vehicle and pole
trailer, A-train, B-train, towing vehicle and two
trailers, towing vehicle in combination with a
motor vehicle other than a trailer 20.0
All vehicles 4.25
Forward distance (excluding collapsible
8.5 if fitted with tow coupling; 9.5
Full trailer, simple trailer, pole trailer with
drawbar at full extension, articulated bus (both
front and rear sections), semi-trailer 8.5
Heavy rigid vehicle 4.0 or 70% of wheelbase (whichever
is less) for a vehicle whose rearmost
axle is a non-steering axle
4.25 or 70% of wheelbase
(whichever is less) for a vehicle
whose rearmost axle is a steering
Articulated bus, heavy semi-trailer, heavy
simple trailer, heavy pole trailer with one axle
set 4.0 or 50% of forward distance
Heavy full trailer, heavy pole trailer with two
axle sets 4.0 or 50% of wheelbase (whichever
Heavy motor vehicle The greater of 100 mm or 6% of the
distance from the nearest axle to the
point where the ground clearance is
measured (except when vehicle is
loading or unloading)
Semi-trailer 2.04 radius arc ahead of kingpin
Simple trailer 2.04 radius arc ahead of tow
coupling centre
Full trailer 2.04 radius arc ahead of turntable
Pole trailer 2.04 radius arc ahead of turntable
centre on towing vehicle
(excluding articulated buses) No further rearward than the
rearmost axle of the towing vehicle
or rearmost axle of the leading
trailer, and if the towing vehicle is a
rigid vehicle and has more than one
axle in its rear set, not more than
300 mm rearward of the rear axis of
Tow coupling position5 (for towing heavy
Full trailer 40% of wheelbase of towing vehicle
Simple trailer At least 700 mm rearward of the rear
axis of the towing vehicle and not
more than a distance equal to 50%
Articulated bus 40% of wheelbase of the leading unit
Inter-vehicle spacing (between towing
vehicle and trailer, except for a laden pole
trailer)7 4.0
Outside turning circle in either direction for
360-degree turn8 25.0 diameter (wall to wall, excluding
collapsible mirrors)
1 Unless otherwise stated, the dimensions in Table 4.1 are maximum dimensions.
2 For items not included in determining whether a vehicle complies with width restriction, see 4.1(4).
3 For restrictions on height, see 4.1(5); for items not included in determining whether a vehicle complies with height restrictions, see 4.1(6).
4 For items not included in determining the ground clearance for a heavy motor vehicle, see 4.1(7).
5 The tow coupling position is the distance rearward from the motor vehicle’s rear axis to the centre of the tow coupling.
7 For other requirements relating to the inter-vehicle spacing between a towing vehicle and a full trailer, see 4.1(8).
8 Includes all attachments to vehicles except collapsible mirrors. For requirements relating to turning circle, see 4.1(9) and 4.1(10).
4.1(4) The following items are not included in determining whether a vehicle complies with the width requirements in Table 4.1:
(a) side marker lamps and direction indicators;
(b) collapsible mirrors that extend not more than 240 mm beyond the side of the vehicle or its trailer;
(c) ropes, lashings, straps, chains, and related connectors or tensioning devices that extend not more than 25 mm from either side of the vehicle and are neither permanently nor rigidly fixed to the vehicle;
(d) J-hook assemblies that extend not more than 25 mm from either side of the vehicle, not more than 1.275 m when measured from the vehicle’s longitudinal centre-line, and that comply with the ratings specified on the manufacturer’s plate affixed to the stockcrate or bin that is being secured;
(e) central tyre inflation system hoses that extend not more than 75 mm beyond the outside of the tyre on the drive axles of a heavy motor vehicle;
(f) hubodometers that extend not more than 75 mm beyond the 2.5-m width limit from a non-lifting, non-steering axle whose outer casings are of a light colour, provided the hubodometer is fitted on the axle that causes the least overwidth;
(g) cab exterior grabrails that extend not more than 50 mm from either side of the vehicle;
(h) the bulge towards the bottom of a tyre;
(i) trolley bus poles and their safety cables, when extended to collect electric power from overhead conducting wires, provided there is a 2.5-m ground clearance outside the body of the bus.
4.1(5) The load height of a towing vehicle and of a trailer with an open deck may be restricted for reasons of stability, as specified in 3.5(1)(a)(ii).
4.1(6) The following items are not included in determining whether a vehicle complies with the height requirements in Table 4.1:
(a) load-restraining devices, such as ropes, lashings, straps, chains, covers and related connectors and tensioning devices, that extend not more than 25 mm above the body or load of the vehicle, and that are neither permanently nor rigidly fixed to the vehicle;
(b) trolley bus poles, when extended to collect electric power from an overhead conducting wire.
4.1(7) Ground clearance for a heavy motor vehicle does not include flexible mudflaps, wheels, tyres or devices designed to discharge static electricity.
4.1(8) The inter-vehicle spacing between a towing vehicle and a full trailer, when in a straight line, must not be less than the greater of 1 m or half the width of the foremost point of the trailer (including its load but excluding the drawbar and front dolly assembly).
4.1(9) An articulated bus must be able to complete a 360-degree turn in either direction without any part of the vehicle, except for collapsible mirrors, encroaching within a concentric internal radius of 5.3 m.
4.1(10) In carrying out a 360-degree turn at the 25-m diameter, as specified in Table 4.1, no part of a vehicle in a combination, other than its articulation mechanism, may come into contact with the other vehicle in the combination.
4.1(11) Subclauses 4.1(12) to 4.1(15) apply to a drawbar or a drawbeam between a towing vehicle and a full trailer.
4.1(12) A drawbar may have only one operating position and must not be extendable, except if 4.1(13) or 4.1(14) applies.
4.1(13) A drawbar may be retractable only to facilitate the through loading or unloading of livestock or goods, provided that the drawbar has only one set of holes for locking pins and that the holes are positioned so that the drawbar is fully extended when locked.
4.1(14) A trailer that is used to transport logs may have a drawbar with up to three fixed positions and one sliding position, provided that the drawbar has:
4.1(15) A drawbeam must not be sliding or adjustable.
4.2(1) A heavy rigid motor vehicle must be supported by:
(b) one axle set towards the rear of the vehicle, which must be a single axle set, a tandem axle set or a tri-axle set.
4.2(2) Except as provided in 4.2(3), 4.2(4) and 4.2(11), a heavy motor vehicle must not have any rear steering axles.
4.2(3) A forklift, the rear unit of an articulated bus, or a mobile crane may have one or more rear steering axles.
4.2(4) A rigid vehicle without a heavy tow coupling or a semi-trailer (other than a semi-trailer in an A-train combination or a B-train combination) may have steering axles in the rear axle set, if no more than half of the axles within the axle set steer at any time.
4.2(5) A mobile crane must have at least one rear axle locked so that it is non-steering, when the mobile crane is being operated on a road.
4.2(6) A rigid motor vehicle or semi-trailer, fitted with rear steering axles, must comply, in all configurations, with the rear overhang requirements and forward distance requirements in Table 4.1.
4.2(7) The axle sets, except a twin-steer axle set, of a heavy motor vehicle must be load sharing.
4.2(8) If a tandem axle set has a large single-tyred axle with a load-share ratio of 60%:40% or 55%:45%, the manufacturer of the vehicle must securely affix to the vehicle an indelible plate, so that it is clearly visible to the person who is weighing the vehicle, that specifies the:
4.2(9) An A-train must have two motor-driven axles in a tandem axle set or a tri-axle set, or three motor-driven axles in a tri-axle set.
4.2(10) A semi-trailer must be supported by one axle set only, which must be set towards the rear of the vehicle and must be:
(d) a quad-axle set (except if the semi-trailer is in an A-train combination or a B-train combination).
4.2(11) A semi-trailer with a quad-axle set must have two steering axles within the quad-axle set, provided that they are either:
(a) the two rearmost axles, which must be capable of turning in the same direction through an angle of at least 15 degrees; or
(b) the foremost axle and the rearmost axle, which must be capable of turning in opposite directions through an angle of at least 15 degrees.
4.2(12) A steering axle in 4.2(11) must be certified for compliance with 4.2(11)(a) or (b) by a vehicle inspector or inspecting organisation.
4.2(13) The axle set towards the front of a full trailer must connect all wheels for that part of the trailer to the drawbar steering system, and must be either a single axle set or a tandem axle set.
4.2(14) The axle set towards the rear of a full trailer must be one of the following:
(a) a single axle set;
(b) a tandem axle set;
(c) a tri-axle set, provided that the front axle set is a tandem axle set.
4.2(15) A simple trailer must be supported by one of the following:
(c) a tri-axle set.
4.2(16) A pole trailer with one axle set may only carry poles or long loads that are not part of the trailer, and must be supported by a single axle set, a tandem axle set or a tri-axle set.
4.2(17) For a pole trailer with two axle sets, the axle set towards the front of the trailer must connect all wheels for that part of the trailer to the drawbar steering system, and must be either a single axle set or a tandem axle set.
4.2(18) The axle set towards the rear of a pole trailer with two axle sets must be one of the following:
4.2(19) A heavy motor vehicle, other than an A-train or a B-train, may have a retractable axle, provided that the following requirements are complied with:
(a) the retractable axle is in a rear axle set;
(b) the retractable axle has an automated control that ensures the remaining axle or axles and axle set or axle sets in contact with the ground remain within the mass limits in Schedule 2 and within all manufacturer’s component ratings for all retracted axle configurations;
(c) the forward distance requirements and rear overhang requirements in Table 4.1 are complied with, whether the axle is in contact with the road or is in a retracted position.
4.2(20) A retractable axle must be certified for compliance with 4.2(19) by a vehicle inspector or inspecting organisation.
4.2(21) A specialist overdimension motor vehicle, or a motor vehicle designed principally to transport an overdimension load or an overweight load, or both, must comply with 4.2(7), but does not have to comply with other requirements in 4.2.
4.3(1) The mass on the front axle set or twin-steer axle set of a heavy rigid vehicle must, at all times, be at least 20% of the sum of the axle mass of the heavy rigid motor vehicle.
4.3(2) The combined gross mass of an A-train must not exceed 39,000 kg.
4.3(3) The combined gross mass of a towing vehicle and a pole trailer, a towing vehicle and a semi-trailer, or a B-train must not exceed 39,000 kg, except if the towing vehicle has two motor-driven axles in a tandem axle set or tri-axle set, or three motor-driven axles in a tri-axle set.
4.3(4) The combined gross mass of a towing vehicle and a full trailer must not exceed 39,000 kg, except if the towing vehicle has:
(a) a twin-steer axle set, or a wheelbase of at least 4.25 m; and
4.3(5) The combined gross mass of a towing vehicle and a full trailer must not exceed 42,000 kg, except if:
(c) the trailer is a five-axle trailer.
4.3(6) The combined gross mass of a towing vehicle and a simple trailer must not exceed 32,000 kg.
4.4(1) For an A-train, a B-train or a rigid vehicle towing two trailers, the gross mass of the rearmost trailer must not exceed 1.5 times the gross mass of the towing vehicle and front trailer, that is:
4.4(2) For all other heavy combination vehicles, except those operating under an overweight permit with a VAI exceeding 1.1, or those restricted to an operating speed of 40 km/h or less, the gross mass of the trailer must not exceed 1.5 times the gross mass of the towing vehicle, that is:
4.5(1) A heavy motor vehicle, other than a vehicle that is operating in accordance with section 5, must not exceed the mass limits for road and bridge preservation applicable to axles, axle sets and gross mass in the relevant tables in Schedule 2.
4.5(2) For the avoidance of doubt, the road mass limits and the mass limits for axles, axle sets and gross mass in this rule import the equivalent weight limits.
4.6(1) A trailer must be of one of the following types:
4.6(2) Except as provided in 4.6(3), a light motor vehicle may not tow more than one trailer.
4.6(3) Despite 4.6(2), a tractor may tow two light trailers, provided that the tractor manufacturer’s ratings are not exceeded.
4.6(4) A heavy motor vehicle may not tow more than one trailer, except if that vehicle is:
(e) a vehicle operating under section 5 and section 6.
4.6(5) Except as specified in 4.6(6), a light motor vehicle may tow a trailer, provided that, if the light motor vehicle is towing a heavy trailer, the gross mass of the trailer does not exceed 1.5 times the gross mass of the towing vehicle or the maximum towed mass specified by the manufacturer.
4.6(6) A light passenger service vehicle may not tow a trailer that has a gross vehicle mass of 2000 kg or more.
4.6(7) A heavy passenger service vehicle may not tow a trailer that has a gross vehicle mass exceeding 3500 kg.
4.6(8) An articulated bus may not tow a trailer.
5.1(1) A road controlling authority may issue a permit to the operator of a heavy motor vehicle that exceeds the mass limits in section 4, with due consideration for the safety of the vehicle, road users and the durability of roads and bridges.
5.1(2) A vehicle in 5.1(1) may not exceed the gross vehicle mass or maximum towed mass specified by the manufacturer of the vehicle.
5.1(3) A vehicle to which 5.1(1) applies that is required under the Road User Charges Act 1977 to have a road user licence must have a current licence issued under that Act, for the correct weight of the vehicle as specified in the permit.
5.1(4) A permit issued under this section must be issued in Form 1 in Schedule 3, or in a form having the same effect, and must be signed by a duly authorised officer of the appropriate road controlling authority.
5.1(5) A permit issued by a road controlling authority must be for a road that is:
(a) under the control of that road controlling authority, or of another road controlling authority, if written permission to operate has been granted by the other road controlling authority; and
(b) classified as being unavailable for use by that heavy motor vehicle under normal operating conditions.
5.1(6) If a permit covers a journey on a road or roads under the control of more than one road controlling authority, the road controlling authority that issues the permit must obtain the consent of all the relevant road controlling authorities for travel on roads under their control. The provisions of this section apply to that permit.
5.1(7) If a road controlling authority issues a permit for a heavy motor vehicle to transport a divisible load for a continuous period exceeding three days, the road controlling authority must:
(a) publish in a newspaper circulating in the relevant district a notice in Form 2 in Schedule 3 within seven days after the permit has been issued; and
(b) on receiving an application from a person, issue a permit to allow that person to transport the same commodity on the same road and subject to the same conditions.
5.1(8) A permit issued under this section may specify conditions including the following:
(a) the heavy motor vehicle’s maximum gross mass and axle mass;
(b) the period of travel;
(c) the number of trips the vehicle is allowed to make;
(d) restrictions on the vehicle’s speed;
(e) restrictions relating to weather conditions;
(f) the roads or types of road on which the vehicle may operate;
(g) the type and amount of the load transported;
(h) the times of the day during which the vehicle may be operated;
(i) the circumstances under which the vehicle may be operated;
(j) any other condition the road controlling authority considers necessary.
5.1(9) The fee for the issue of a permit under this section is prescribed under regulation 7(1A) of the Heavy Motor Vehicle Regulations 1974, and specified in Schedule 4A of those regulations.
5.1(10) A road controlling authority may revoke a permit immediately because of adverse weather conditions, if, in its opinion, the continued operation of the heavy motor vehicle may cause extraordinary damage to the road.
5.1(11) The Director may revoke a permit, or may authorise the Commissioner to do so, if the Director considers there is a significant risk to public safety.
5.1(12) A road controlling authority may revoke a permit if it considers that any of the conditions of the permit have not been complied with.
5.1(13) A revocation under 5.1(11) or 5.1(12) must be made by notice in writing to the operator of the heavy motor vehicle as soon as is practicable, giving reasons for its revocation, and the revocation takes effect immediately.
This section applies to motor vehicles that exceed the dimension limits in section 4 or to standard motor vehicles that transport overdimension loads. It specifies the criteria with which those vehicles must comply so as to operate on a road. They may be one of the following:
(a) a standard motor vehicle transporting an overdimension load;
(b) a specialist overdimension motor vehicle;
(c) a motor vehicle designed primarily to transport an overdimension load.
6.2(1) A standard motor vehicle may transport an overdimension load that exceeds the dimension limits specified in section 4, provided that the load:
6.2(2) A standard motor vehicle may transport an overdimension load as well as a divisible load, provided that the divisible load does not exceed:
(a) a width of 2.5 m;
(b) a height of 4.25 m;
(c) the appropriate requirements for length or rear overhang in section 4.
6.2(3) A standard motor vehicle may transport more than one overdimension load, provided that the loads:
(a) if loaded side-by-side, do not exceed a width of 2.5 m;
(b) if loaded one above the other, do not exceed a height of 4.25 m;
(c) if loaded one behind the other, do not exceed the appropriate requirements for length or rear overhang in section 4.
6.2(4) Despite 6.2(1), a standard motor vehicle may transport:
(a) a divisible load of hay bales or wool bales, provided that the load does not exceed a width of 2.7 m; or
(b) concrete pipes with a minimum diameter of 400 mm that are loaded transversely on the deck, provided that the load does not:
(i) exceed a width of 2.7 m; and
(ii) project more than 1.35 m beyond either side of the longitudinal centre-line of the vehicle.
6.2(5) The following combination motor vehicles may not exceed the rear overhang or overall length limits in Table 4.1 when transporting an overdimension load:
6.3(1) A motor vehicle that is not designed primarily to transport overdimension or overweight loads may exceed the dimension limits in section 4, if the vehicle’s primary purpose is to carry out a specialist function that requires overdimension equipment, and:
(b) it would take more than four hours to dismantle the vehicle’s equipment.
6.3(2) A specialist overdimension motor vehicle of a type specified in 6.3(1) that is transporting a divisible load may not exceed the dimension limits in section 4, if those limits can be complied with by reducing the vehicle’s divisible load.
6.3(3) A motor vehicle that is being operated on a road or a portion of a road that is designated as a road construction zone under regulation 12 of the Heavy Motor Vehicle Regulations 1974, or that is a road works zone operated under a traffic management plan approved by a road controlling authority, may exceed the limits in section 4.
6.3(4) A motor vehicle that is being operated in accordance with 6.3(3) does not have to comply with the requirements of section 6 or section 7.
6.4(1) A motor vehicle designed primarily to transport an overdimension or overweight load, or both, may transport a load that exceeds the dimension limits in section 4, provided that the load:
6.4(2) A motor vehicle in 6.4(1) may transport more than one overdimension load, provided that the loads:
(c) if loaded one behind the other, do not exceed the appropriate requirements for length, front overhang or rear overhang in section 4, unless they comply with 6.4(3).
6.4(3) If two or more overdimension loads have the same departure and destination points, and one of the loads exceeds 5 m in width, the loads may be carried one behind the other on a semi-trailer, provided that:
6.4(4) A motor vehicle in 6.4(1) must be reduced to the smallest dimension practicable, if it is not transporting an overdimension load.
6.4(5) A motor vehicle in 6.4(1) may not transport a divisible load, except if:
(a) one direction of the vehicle’s journey requires an overdimension vehicle to transport an indivisible load; or
(b) the weight or instability of the divisible load requires the use of an overdimension motor vehicle.
6.4(6) A motor vehicle to which 6.4(5) applies may transport divisible loads provided that the loads, if loaded:
(b) one above the other, do not exceed a height of 4.25 m;
6.4(7) Two motor vehicles to which 6.4(1) applies that have the same point of departure and the same point of destination may travel together, provided that:
Table 6.1 Overdimension requirements dependent on width, length, forward distance, front overhang and rear overhang (Ref. 6.6(2))
Size limits1
Category 11 Width/forward
distance2:
limits in section
4 up to and
2.5 m/11.4 m,
3.1 m/10.5 m
and up to and
3.7 m /8.5 m
overhang: up
overhang3: up
7 m Operations
flags or panels
(see 6.9 and
‘OVERSIZE’ sign,
if width exceeds
3.1 m and vehicle
is piloted (see
(see 6.12)
One Class 2
pilot required,
3.1 m in
40 km/h; or
during hours of
Revolving amber
light (see also
(see 6.10)
3.1 m Operations
pilot, if width
exceeds 3.1 m
Category 2(a)1 [Width/forward
3.1 m/10.5 m,
3.7 m/8.5 m up to
2.5 m/13.3 m and
4.5 m/8.5 m
25 m, up to and
including 35 m
exceeding 7 m,
including 10 m]
[Rear overhang4:
including 10 m] Excess
panels (see
sign, if width
(see 6.11)
amber light, if
width exceeds
3.7 m or
travelling during
hours (see also
6.7) Restriction
(see 6.12) One Class 2
Category 2(b)1 [Width/forward
3.7 m/8.5 m up
2.5 m/13.3 m
overhang4:
3.1 m (see 6.11)
light, if width
exceeds 3.7 m or
beam during
(see also 6.7) Restriction
(see 6.12) Two Class 2
Category 3(a)1 Width/forward
4.5 m/8.5 m up
2.5 m/20 m, up
5 m/20 m and
5 m/8.5 m
Length3: up to
overhang4: up
7 m Excess
panels (see 6.10)
‘OVERSIZE’ sign
One Class 1
pilots if required
Category 3(b)1 [Width/forward
10 m]
under section 7)
Category 41 Width/forward
5 m/8.5 m up to
11 m/20 m and
11 m/8.5 m
10 m Excess
(see 6.12) Loads up to
5 m wide and
up to 7 m rear
exceeding 5 m
wide and/or
7 m rear
Two Class 2
1 See Figure 6.1.
2 Forward distance is defined in Part 2. However, for forward-distance requirements for vehicle combinations including a load-sharing trailer or a manned steering jinker, see 6.5(4) and 6.5(5).
3 For requirements for loads exceeding 25 m and 30 m in length, see 6.5(1) and 6.5(2).
4 Centre of gravity of the load must be forward of the rear axis. For rear overhang requirements for vehicle combinations including a manned steering jinker or pole trailer, see 6.5(3).
Figure 6.1 Swept path requirements for width/forward distance thresholds1
1 Refer to Table 6.1 for limits and operating requirements.
2 The piloting requirements are minimum requirements. Sufficient pilots must be used to comply with section 7.
Table 6.2 Overdimension requirements for excess height
4.25 – up to and
including 5 Written permission from the owner of an overhead
obstruction that the vehicle cannot clear safely.
Written approval from the relevant rail service operator, if the
vehicle travels over a level crossing that does not cross a
State Highway, and the vehicle exceeds the height shown on
an electrified railway safe height sign.
For loads exceeding 4.8 m, a vehicle with a deck height less
than 1.3 m above the road must be used.
Greater than 5 – up
to and including 6.5 A vehicle with a deck height less than 1.3 m above the road
Written permission from the owner of overhead wires or
cables that the vehicle travels under.
Greater than 6.5 Written approval from the Director.
6.5(1) The operator of an overdimension motor vehicle must obtain written permission from the rail service operator, if the vehicle is to travel over a level crossing and its overall length exceeds 25 m.
6.5(2) A rear steering facility must be used on an overdimension motor vehicle transporting a load that exceeds 30 m in length.
6.5(3) If an overdimension motor vehicle is operated with a manned steering jinker or a pole trailer, the rear overhang is measured between the centre of the rear turntable load support and the rearmost part of the load.
6.5(4) If the vehicle combination includes a load-sharing trailer, the load-sharing trailer does not have to be included in forward-distance calculations if the forward distance is 3.5 m or less. If the forward distance exceeds 3.5 m, this distance must be added to the forward distance of the main trailer, less 3.5 m.
6.5(5) If the vehicle combination includes a manned steering jinker, the forward distance used for determining operating requirements in Table 6.1 is half the distance between the two turntables supporting the load.
6.6 General operating requirements for overdimension motor vehicles
6.6(1) An overdimension motor vehicle must:
(b) comply with the route restrictions in Schedule 7.
6.6(2) An overdimension motor vehicle must comply with the relevant requirements in Table 6.1 for hazard warning equipment, travel times and piloting requirements, unless 6.6(11) or 6.6(12) applies.
6.6(3) A motor vehicle that exceeds 4.25 m in height must comply with the relevant requirements in Table 6.2.
6.6(4) Subject to 6.6(5), an overdimension motor vehicle must not interfere with or damage a traffic control device, bridge, tunnel or other structure, or trees or other foliage, without the road controlling authority’s or owner’s permission.
6.6(5) A traffic control device may be removed temporarily, with the road controlling authority’s or owner’s permission, to allow safe passage of an overdimension motor vehicle, provided that, when the vehicle has passed by the point on the road from which the traffic control device was removed, the traffic control device is immediately re-erected in its original position.
6.6(6) An overdimension motor vehicle must not travel on a road if fog, heavy rain, hail or any other factor restricts ambient visibility to less than 500 m. If, after the vehicle has begun its journey, ambient visibility is reduced to less than 500 m, the vehicle must, at the earliest opportunity, be stopped clear of moving traffic until ambient visibility is no longer less than 500 m.
6.6(7) An overdimension motor vehicle must be operated with due consideration for other road users and where it is safe to do so, other road users must be allowed to pass the vehicle at the earliest opportunity.
6.6(8) The operator of an overdimension motor vehicle must notify emergency services personnel who are operating in the area where the vehicle or its load is likely to restrict a route in a way that would significantly delay emergency services personnel.
6.6(9) An enforcement officer, the Director or a road controlling authority may prohibit the use of a road by an overdimension motor vehicle at any time if that person believes on reasonable grounds that:
(a) the vehicle does not comply with a condition imposed under section 6; or
(b) a prohibition is necessary in the interests of safety or traffic management.
6.6(10) A person in 6.6(9) may impose special conditions for an overdimension motor vehicle to be operated on a road, so as to minimise adverse safety effects on other road users.
6.6(11) A Category 1 motor vehicle whose performance dimensions have been verified by a person or organisation approved by the Director as meeting those of a maximum-sized standard motor vehicle, as specified in Schedule 8, does not have to comply with the travel time requirements specified in 6.12(3), provided it does not project outside the lane in which the vehicle is travelling.
6.6(12) A Category 2 motor vehicle whose performance dimensions have been verified by a person or organisation appointed by the Director as meeting the requirements of a Category 1 overdimension motor vehicle, as specified in Schedule 9, may be operated in accordance with the operating requirements for a Category 1 overdimension motor vehicle.
6.7(1) The headlights of an overdimension motor vehicle must be operated on low beam during daylight hours.
6.7(2) During the hours of darkness, the lamps in 6.7(3) must be fitted to, and operated on, an overdimension motor vehicle, and must be clearly visible in clear weather at a distance of at least 200 m during the hours of darkness.
6.7(3) The lamps to which 6.7(2) refers are:
(a) steady white or amber lamps at the front, and steady red or amber lamps at the rear, of the vehicle’s load that:
(i) have an area of at least 50 cm2;
6.7(4) A revolving amber light must be fitted to the cab roof of an overdimension motor vehicle and must operate:
(a) during the hours of darkness, if the vehicle’s load is 3.7 m in width or less;
(b) at all times, if the vehicle’s load exceeds 3.7 m in width;
6.7(5) During the hours of darkness, two or more white scene lamps, each with a minimum power output of 100 W, must be fitted to, and operate on, an overdimension motor vehicle whose load exceeds 5 m in width.
6.7(6) The scene lamps in 6.7(5) must illuminate the front of the load, but must not be visible to following traffic.
6.8(1) This clause applies to any of the following:
(a) a motor vehicle with a width and forward distance combination within Category 3 or Category 4 in Table 6.1;
(e) a motor vehicle whose dimensions exceed the limits specified in Category 4 in Table 6.1;
(f) a motor vehicle that, although complying with the size limits in Table 6.1, is unable, for a particular reason, to comply with the operational requirements in that table.
6.8(2) If travelling on a road, the operator of a motor vehicle to which this clause applies must:
(a) apply for, and be issued with, a permit by the Director; and
(c) if the vehicle or load exceeds 5 m in width, notify the Director at least 30 minutes before the journey is to begin.
6.8(3) The Director may include, in a permit, special conditions that the Director considers necessary for the safety and convenience of road users.
6.8(4) The Director may revoke a permit if the Director considers there is a significant risk to public safety.
6.8(5) A revocation under 6.8(4) must be made in writing to the operator of the motor vehicle as soon as is practicable, giving reasons for the revocation, and the revocation takes effect immediately.
6.8(6) If aware of the presence on the road of another overdimension vehicle that may create a hazardous situation, or if advised by the Director of this, the operator of each overdimension vehicle must manage the operation of their vehicle’s movement in relation to that other vehicle.
6.8(7) A road controlling authority may issue a permit only for the operation of a motor vehicle transporting an overdimension load that cannot otherwise be transported within the limits in section 4.
6.8(8) Evidence of permission given under 6.5(1) and 6.6(4) or a verification under 6.6(11) and 6.6(12) or a permit issued under 6.8(2) or 6.8(7) must:
6.8(9) The Director may not issue a permit under 6.8(2), if a road controlling authority notifies the Director that it objects to the permit being issued.
6.8(10) Despite 6.8(2), an enforcement officer may:
(b) impose any safety conditions that ensure that the overdimension vehicle is operated safely.
6.9(1) A hazard warning flag displayed on an overdimension motor vehicle as required in Table 6.1:
(ii) at the front of a load with excess front overhang;
(iii) at the rear of a load with excess rear overhang;
(iv) at the rear of a load with excess length; and
6.9(2) An overdimension motor vehicle in Category 1 in Table 6.1 that is required to display a hazard warning flag during daylight hours must display instead warning panels as specified in 6.10, if it is travelling during the hours of darkness.
6.9(3) A motor vehicle or its load may not display a hazard warning flag in 6.9(1) unless the vehicle is overdimension and is required under Table 6.1 or 2.1(4) to display the flag.
6.10(1) A hazard warning panel required in Table 6.1 to be displayed on an overdimension motor vehicle must:
(i) on each side of an overwidth load or vehicle at its front and rear, in the position specified in Figure 2 in Schedule 4;
(iv) at the rear of a load for excess length; and
(b) comply with AS/NZS 1906.1.1993, Retroreflective materials and devices for road traffic control purposes, Part 1: Retroreflective materials; and
(c) consist of retroreflective material with a 200-mm-wide chevron pattern with alternate yellow-green, and orange retroreflective sheeting as specified in Figure 1 in Schedule 4; and
(d) comply with the dimensions in Figure 1 in Schedule 4; and
(e) be frangible.
6.10(2) A motor vehicle may not display a hazard warning panel unless the vehicle or its load is overdimension and is required under Table 6.1 or 2.1(4) to display the panel.
6.11 ‘OVERSIZE’ signs
6.11(1) An overdimension motor vehicle exceeding 3.1 m in width that is escorted by a pilot vehicle must display an ‘OVERSIZE’ sign that complies with 6.11(2).
6.11(2) An ‘OVERSIZE’ sign that is displayed on an overdimension motor vehicle as required in Table 6.1 must:
(c) may be split into two parts, provided that:
(i) the word ‘OVER’ and the word ‘SIZE’ are on separate parts; and
(ii) both parts of the sign are mounted at the same height; and
(iii) the combined length of the parts is at least 1.1 m; and
(d) be frangible; and
(e) during daylight hours, have matt black lettering on a yellow-green background with a matt black border; or
(ii) comply with AS/NZS 1906.1.1993, Retroflective materials and devices for road traffic control purposes, Part 1: Retroreflective material.
6.11(3) A motor vehicle may not display an ‘OVERSIZE’ sign in 6.11(2) unless the vehicle is overdimension and is required by Table 6.1 to display the sign.
6.12(1) For the purposes of this clause and for Schedule 6, ‘city area’ means the urban areas of Auckland (between Albany and Drury), Christchurch, Dunedin, Hamilton, Hastings, Invercargill, Napier, Nelson, New Plymouth, Palmerston North, Tauranga, Wanganui, Wellington (including all areas south of McKay’s Crossing on State Highway 1 and Te Marua on State Highway 2) and Whangarei.
‘Level 1’ restricted travel times
6.12(2) Except as provided in 6.6(11) and subject to 6.12(9) and 6.12(10), a motor vehicle whose dimensions are within Category 1 in Table 6.1 must comply with the travel restrictions in 6.12(3).
6.12(3) A motor vehicle in 6.12(2) must not travel:
(b) at times (other than those specified in 6.12(3)(a)), when there are unusually heavy traffic volumes.
‘Level 2’ restricted travel times
6.12(4) Except as provided in 6.6(12) and subject to 6.12(9) and 6.12(10), a motor vehicle whose dimensions are within Category 2 in Table 6.1 must comply with the travel restrictions in 6.12(5) and 6.12(6).
6.12(5) A motor vehicle in 6.12(4) must not travel:
(c) in a province on its provincial anniversary holiday, or after 1600 hours on the day preceding that anniversary holiday.
6.12(6) A motor vehicle in 6.12(4) must not travel:
(b) at times (other than those specified in 6.12(5) and 6.12(6)(a)) when there are unusually heavy traffic volumes, or when travel is likely to cause significant delay to other road users.
‘Level 3’ restricted travel times
6.12(7) Subject to 6.12(9) and 6.12(10), a motor vehicle whose dimensions are within Category 3 or Category 4 in Table 6.1:
(a) must comply with the travel restrictions in 6.12(8); and
(b) may not travel at the times specified in Schedule 5 within the areas specified in Schedule 6.
6.12(8) A motor vehicle in 6.12(7) must not travel:
(d) at times (other than those specified in 6.12(7) and 6.12(8)(a) to (c)) when there are unusually heavy traffic volumes, or when travel is likely to cause significant delay to other road users.
6.12(9) If there is an unforeseen delay in a journey for an overdimension vehicle to which travel restrictions in 6.12(8) apply, and there is no place to safely park, the vehicle may continue its journey provided that the Police are notified and agree to the extended travel time.
6.12(10) An extended travel time in 6.12(9) must not exceed 30 minutes, unless an extended travel time greater than 30 minutes is necessary for the vehicle to reach a destination where it can safely park, and the Police agree to this.
7.1(1) The operator of an overdimension motor vehicle must ensure that there is an adequate number of pilot vehicles to accompany the vehicle so as to provide adequate warning to approaching traffic throughout the journey.
7.1(2) An overdimension motor vehicle must be escorted by at least one Class 2 pilot vehicle, if:
(a) the overdimension vehicle or its load encroaches over the centre-line of the road by 500 mm or more, or over half the available road space where a centre-line is not marked; and
(b) the overdimension vehicle or its load does not allow sufficient remaining road space for another standard motor vehicle travelling in the opposite direction to pass without a significant reduction in speed; and
(c) the overdimension vehicle travels on a road where, without a pilot vehicle, there would be inadequate warning to approaching road users of the overdimension hazard.
7.1(3) Subclause 7.1(2) does not apply if the overdimension motor vehicle is travelling less than 500 m during daylight hours and the vehicle can travel safely without impeding other traffic.
7.1(4) An overdimension motor vehicle or overdimension load whose dimensions are within Category 1 in Table 6.1, and whose width exceeds 3.1 m, must be escorted by at least one Class 2 pilot vehicle, if operated:
7.1(5) A motor vehicle whose dimensions are within Category 1 in Table 6.1 and whose width does not exceed 3.1 m does not have to be escorted by a Class 2 pilot vehicle, provided that the vehicle’s compliance with the swept path performance measures in Schedule 8 has been verified by a vehicle inspector or inspecting organisation.
7.1(6) An overdimension load or overdimension motor vehicle whose dimensions are within Category 2 in Table 6.1 must be escorted by at least one Class 1 pilot vehicle and one Class 2 pilot vehicle, if it is travelling on a road during the hours of darkness.
7.1(7) A motor vehicle in 7.1(6) that has been certified as complying with the swept path performance measure in Schedule 9 must be escorted by at least one Class 2 pilot vehicle.
7.1(8) An overdimension load or overdimension motor vehicle that is travelling in the lane for opposing traffic on a median-divided road or at a controlled intersection must be escorted by at least one Class 1 pilot vehicle and must have road controlling authority permission.
7.2(1) A person who, immediately before 1 July 2002, operated as an A-Grade or B-Grade certified pilot may continue to operate as a Class 1 certified pilot on or after 1 July 2002, provided that the person complies with the requirements in 7.2(3).
7.2(2) A person who, immediately before 1 July 2002, operated as a C-Grade certified pilot may continue to operate as a Class 2 certified pilot on or after 1 July 2002, provided that the person complies with the requirements in 7.2(3).
7.2(3) The requirements are:
(a) the completion of a pilot driver’s course, approved by the Director, by 31 January 2004; and
(b) compliance with the requirements in this section.
7.2(4) The operator of a pilot vehicle must either be an enforcement officer or have completed a Class 1 or Class 2 pilot driver’s course approved by the Director.
7.2(5) A pilot vehicle must display adequate warning and information concerning the overdimension hazard to approaching drivers.
7.3(1) A pilot vehicle must have sufficient manoeuvrability and dynamic performance to enable it to carry out its primary duty of providing adequate warning to road users.
7.3(2) A pilot vehicle must be clearly identifiable as a vehicle that is providing a warning of the overdimension motor vehicle that it is escorting.
7.3(3) A pilot vehicle may not carry an overdimension load or tow a trailer with an overdimension load.
7.3(4) All pilot vehicles and overdimension motor vehicles in a convoy must be in radio communication with each other.
7.3(5) A Class 1 pilot vehicle must be substantially white in colour.
7.3(6) A Class 1 pilot vehicle must be a motor vehicle with a gross vehicle mass not exceeding 3500 kg.
7.3(7) A Class 2 pilot vehicle at the front of an overdimension motor vehicle must be a motor vehicle with a gross vehicle mass not exceeding 7000 kg and a wheel rim diameter not exceeding 17 inches.
7.3(8) A pilot vehicle at the front of an overdimension motor vehicle may not tow another vehicle.
7.3(9) A pilot vehicle at the front of an overdimension motor vehicle must display above its roof a warning sign as specified in Schedule 4 describing the load behind it.
7.3(10) Except as provided in 7.3(11), a pilot vehicle at the rear of an overdimension motor vehicle must be a rigid motor vehicle with not more than three axles.
7.3(11) A pilot vehicle at the rear of an overdimension motor vehicle may tow a simple trailer with a maximum of two axles.
7.3(12) A pilot vehicle (or its trailer) at the rear of an overdimension motor vehicle must display a warning sign as specified in Schedule 4 that faces towards the rear of the vehicle (or the trailer, if the pilot vehicle is towing a trailer) and describes the load ahead of it.
7.3(13) The operator of an overdimension motor vehicle must ensure that appropriate measures are taken to minimise the risks to the safety of road users presented by a pilot vehicle that is operating at the rear of an overdimension vehicle, particularly when the pilot vehicle has stopped.
7.3(14) A Class 1 pilot vehicle must clearly display on its front doors a pilot logo that is approved by the Director.
7.3(15) A Class 2 pilot vehicle may display on its front doors a pilot logo that is approved by the Director.
7.3(16) A pilot warning sign must comply with the size and colour specifications in Schedule 4, and must be frangible.
7.3(17) The pilot warning sign specified in Schedule 4 may be displayed only when the vehicle is escorting an overdimension vehicle.
7.3(18) Except as provided in 7.3(23), the headlamps of a pilot vehicle must be operated on low beam when the pilot vehicle is escorting an overdimension motor vehicle during daylight hours.
7.3(19) The lighting in 7.3(20) to 7.3(24) may be operated only when a pilot vehicle is escorting an overdimension motor vehicle.
7.3(20) Except as provided in 7.3(21), a Class 2 pilot vehicle must have fitted to its roof one or two flashing or revolving amber beacons.
7.3(21) An overdimension motor vehicle whose load exceeds 5 m in width must be escorted by at least one Class 1 pilot vehicle and at least two Class 2 pilot vehicles, each of which has fitted to its roof and operates:
7.3(22) In addition to the beacons required under 7.3(21), the pilot vehicle that is travelling furthest ahead of an overdimension motor vehicle whose width exceeds 5 m must display one pair of alternately flashing auxiliary lamps that emit a purple light.
7.3(23) During daylight hours, the pilot vehicle travelling furthest ahead of an overdimension motor vehicle whose width exceeds 5 m may operate with one pair of alternately flashing headlamps, which must be operated on low beam.
7.3(24) During the hours of darkness, a pilot vehicle must be fitted with one or two lamps that emit a white light to illuminate a roof-mounted warning sign, provided that the light is not directly visible from the rear of the vehicle.
7.4 Enforcement officers’ vehicles
Nothing in 7.2 or 7.3 applies to an enforcement officer piloting an overdimension vehicle and load, provided the pilot vehicle displays blue and red flashing lights.
8.1(1) A person who operates a vehicle must ensure that the vehicle complies with this rule.
8.1(2) A person who operates an overdimension motor vehicle must comply with the applicable operating requirements in section 6.
8.1(3) A person who operates a motor vehicle under a permit that is issued under section 5 must comply with all the requirements of that permit.
8.1(4) A person who operates a motor vehicle under a permit that is issued under 6.8 must comply with all the requirements of that permit.
(b) notify the operator if the vehicle must be inspected, and, if necessary, certified, because there is reason to believe it is:
(ii) a heavy motor vehicle that has been modified to affect its safety performance or compliance with this rule.
A vehicle inspector or inspecting organisation must not certify a motor vehicle under Land Transport Rule: Vehicle Standards Compliance 2002 if they have reason to believe that the vehicle does not comply with sections 3, 4 and 6 of this rule.
[Note: In addition to the functions of the Director as summarised in 8.5, the Director has the authority under section 166 of the Land Transport Act 1998, where circumstances justify this, to grant an exemption from a specified requirement in this rule.]
(a) issue a permit, as specified in 6.8, to allow the operation of a motor vehicle that exceeds the dimension or load limits in section 4;
(b) set conditions in a permit issued under 6.8;
(c) revoke a permit issued under section 5 if the Director considers that there is a significant risk to public safety;
(d) revoke a permit issued under 6.8 if the Director considers that the conditions of the permit have not been complied with or there is a significant risk to public safety;
(e) approve computer programs and procedures, as specified in 3.4, for testing the performance of a motor vehicle;
(f) approve a pilot driver’s course for a Class 1 or Class 2 certified pilot;
(g) approve pilot logos for use on a Class 1 or Class 2 pilot vehicle;
(h) issue a permit, with any conditions to ensure the safety and convenience of road users, for a vehicle that exceeds the dimension limits in section 4 and section 6;
(i) approve a form for the purposes of 3.6(1)(b), 6.6(11) and 6.6(12);
(j) define the rear axis of a vehicle for the purposes of paragraph (f) of the definition of ‘rear axis’ in Part 2.
(b) if the longitudinal centre-line of an axle of a motor vehicle is less than 1 m distant from the longitudinal centre-line of another axle, the two axles are to be treated as one axle (‘a dual axle’);
(c) for the purposes of measuring the distance of a dual axle from any other axle, the measurement is taken from the longitudinal centre-line of the axle that is nearer to the axle from which the distance is to be measured.
means a single axle set, a tandem axle set, a twin-steer axle set, a tri-axle set, or a quad-axle set.
means a motor vehicle comprising a towing vehicle and two semi-trailers connected at two points of articulation where the forward distance of the longer trailer divided by the forward distance of the shorter trailer does not exceed 1.3.
means an individual trailer unit with a fifth wheel coupling used to convert a semi-trailer to a full trailer. A dolly must have either:
(b) a tandem axle set with a hinged drawbar with a fixed fifth wheel.
means a lamp used for signalling an intention to change direction to the right or to the left.
means the person who is the Director of Land Transport Safety appointed under section 186 of the Land Transport Act 1998.
means any member of the New Zealand Police, New Zealand Fire Service or an ambulance service.
(c) a person who is appointed to that office by warrant under section 208 of the Land Transport Act 1998 or who holds that office by virtue of the Land Transport Act 1998.
means first registered in New Zealand.
(f) for a pole trailer having two axle sets, the distance, excluding load, from the trailer’s front axis to the centre of the point of attachment on the towing vehicle with the drawbar fully extended.
means breakable or readily deformable.
(b) the centre of the foremost axle of a rigid vehicle with motive power.
(e) for the load of a pole trailer combination, the centre of the turntable on the towing vehicle.
means a trailer with two axle sets, the foremost of which is steered by a drawbar; and includes a semi-trailer with non-steering axles coupled to a converter dolly.
(b) if a person approved for the purpose by the Director determines that the gross vehicle mass of a vehicle should differ from that specified by the manufacturer, taking into account evidence on the capability of the systems and components of the vehicle, or the effects of any modification, that mass determined by that person.
Heavy passenger service vehicle
means a passenger service vehicle whose gross vehicle mass exceeds 3500 kg.
(b) any other time when there is not sufficient daylight to render clearly visible a person or a vehicle at a distance of 100 m.
means a load that cannot reasonably (without disproportionate effort, expense or risk of damage to the load) have its size reduced or be divided into two or more sections for road transport; and includes customs-sealed import/export ISO containers.
(a) consists of a bush, fastener, associated washer or washers, and ‘J’-shaped bar including its threaded portion; and
(b) is used for the retention of a stockcrate or detachable bin to the vehicle load platform; and
(including reasonably level surface) in relation to a road, means a road or weigh platform including weigh scale surfaces of such a minimal gradient that the heavy motor vehicle or combination vehicle on it does not move in a forwards or backwards direction after the enforcement officer has requested all brakes on such vehicle be released. The vehicle should not otherwise be restrained by any artificial restraining force, such as chocks, when the enforcement officer requests that the brakes be released.
Light passenger service vehicle
means a passenger service vehicle whose gross vehicle mass is 3500 kg or less.
Load-sharing trailer
means a type of short, load-sharing semi-trailer, that is not designed to directly carry any goods, and that has one or more axles equipped with a kingpin, a fifth wheel and other parts necessary for attaching it to the rear end of a towing vehicle and the front portion of a second gooseneck trailer.
Manned steering jinker
means a specialised load-bearing vehicle that is steered by an operator and that is used to carry the rear of a long load.
means a motor vehicle drawn or propelled by mechanical power; and includes a trailer; but does not include:
(d) a trailer running on one wheel and designed exclusively as a speed-measuring device or for testing the wear of vehicle tyres;
means any axle of a vehicle the wheels of which remain substantially parallel with the longitudinal centre-line of the vehicle while the vehicle is turning.
(c) the centre of each such wheel is at least 500 mm distant from the centre of every other wheel fitted to the motor vehicle.
means the length of a vehicle or vehicle combination measured in a straight line; and includes:
means an indivisible load on a motor vehicle that exceeds the dimension limits in section 4.
means a motor vehicle or combination vehicle (including any load) that exceeds one or more of the dimension limits in section 4.
means a motor vehicle that escorts an overdimension and/or overweight motor vehicle, and that warns road users of the potential hazard created by the overdimension and/or overweight motor vehicle, or its load, or both.
means a set of four axles where:
(a) the centres of the first and fourth axles are spaced not less than 3.75 m, and not more than 4 m, apart; and
(b) all axles contain an equal number of tyres of the same size; and
(c) none of the axles is a single standard-tyred axle; and
(d) the axles are a load-sharing set.
Rail service operator
has the same meaning as in the Transport Services Licensing Act 1989.
(i) midway between those axles, if each axle has an equal number of tyres on it;
(d) in relation to a vehicle whose rear axle set includes one or more steerable axles in conjunction with one or more non-steering axles, means midway between the extreme non-steering axles of the set;
(e) in relation to a vehicle whose rear axle set includes one or more retracted axles in conjunction with one or more non-retracted axles, means midway between the extreme non-retracted axles of the set;
(f) in relation to a vehicle that does not have an axle arrangement that is in paragraphs (a) to (e), means a position determined by the Director.
(a) for pole trailers transporting a long load, means the distance from the rear axis or centre of the bolster to the rear of the vehicle or its load, whichever is greater;
means to restore a damaged or worn vehicle, its structure, systems, components or equipment; and includes the replacement of damaged or worn structures, systems, components and equipment with equivalent undamaged or new structures, systems, components and equipment.
means a vehicle with motive power, driver’s position and steering system, that does not have any pivot points to allow any part of the chassis of the vehicle to move or rotate in relation to any other part of the chassis of the vehicle; but includes a pivot steer vehicle.
(e) all bridges, culverts, ferries, and fords forming part of a road or street or motorway, or a place referred to in (d); and
(f) all sites at which vehicles may be weighed for the purposes of the Land Transport Act 1998 or any other enactment.
in relation to a road, means the authority, body or person having control of the road; and includes a person acting under and within the terms of a delegation or authorisation given by the controlling authority.
Roadworks zone
means a road or part of a road approved by a road controlling authority as a site for carrying out road works, and that is protected by temporary warning signs as specified in Part 1 of Schedule 4 of the Traffic Regulations 1976.
(b) if the towing vehicle is a rigid vehicle and has more than one axle in its rear axle set, is no more than 300 mm rearward of the rear axis of the towing vehicle.
means a vehicle lamp of lower power than the head lamps used for the purpose of indicating the presence of the vehicle when seen from a distance and also of indicating the approximate width of the vehicle; and includes:
(c) a sideways-facing side lamp, being a lamp mounted between the front and rear extremities on the side to indicate primarily the side of the vehicle.
means a single-tyred axle that is not a single standard-tyred axle.
means a single-tyred axle fitted with tyres smaller than:
(a) a manufacturer’s designated tyre section width of 330 mm and a rim diameter of 24 inches at the bead seat; or
(b) a manufacturer’s designated tyre section width of 355 mm and a rim diameter of 19.5 inches at the bead seat.
means a load that will fit on a motor vehicle within the dimension and mass limits in section 4.
Standard motor vehicle
means a motor vehicle whose dimension and mass limits comply with section 4.
means two axles having their centres spaced not less than 1 m and not exceeding 2 m apart and are load sharing.
means a motor vehicle (not being a traction engine) designed exclusively for traction at speeds not exceeding 50 km/h.
means a device used on a road for the purpose of traffic control; and includes any:
(c) marking or road surface.
means the authority known as Transit New Zealand established under the Transit New Zealand Act 1989.
means three axles, where:
(a) the centres of the first and third axles are spaced not less than 2 m and not exceeding 3 m apart; and
(b) all axles contain an equal number of tyres of the same size, and none of the axles is a single standard-tyred axle; and
(c) the axles are a load-sharing set.
means any axle, not being an oscillating axle, that has a wheel track of 1.3 m or more and is equipped with four or more tyres.
means a contrivance equipped with wheels, tracks, or revolving runners on which it moves or is moved; and includes a hovercraft, a skateboard, in-line skates, and roller skates; but does not include:
Vehicle axle index (VAI)
means a system for indicating the extent to which the axles of a motor vehicle are loaded, so that the effect of the axle weights on roads and bridges can be determined, and that is established by a road controlling authority when the vehicle is issued with an overweight permit under section 5.
means a vehicle used in a vehicle recovery service for towing or transporting on a road any motor vehicle; but does not include a vehicle that is not designed or adapted for the purpose of towing or carrying motor vehicles.
means visible under normal atmospheric conditions to a driver of normal vision.
LC (Motor cycle)
Schedule 1 SRT calculations [Ref. 3.4(c)]
Simplified analytical solution for SRT
Figure 1 Vehicle Roll Notation
Mu Unsprung Mass
kr Composite suspension roll stiffness
kaux Auxiliary roll stiffness
ha Axle Cg height from ground
hb Roll centre height from ground
hc Sprung Mass Cg height from ground
T Wheel track width
Axle roll angle
Body roll angle relative to the axle
Static Roll Threshold as a proportion of Mass
Defining new variables M and H as follows
In the general case the suspension has some lash. At some value of the body roll angle, , the load on the right hand spring (based on the figure) becomes zero. As the vehicle body rolls through a further angle , which is less than or equal to the lash divided by the spring spacing, no additional roll restoring force from the springs is generated. However, if the suspension has an anti-roll device this will still apply resisting moment. Once the full extent of the lash has been taken up further increments of are possible. At any stage the total body roll angle is + .
Using the graphical approach presented in Winkler et al (2000), consider the rotation of the total mass about R. Assuming small angles, after rotation the co-ordinates of the Cg of sprung mass relative to a roll centre at R are (- hc - (hc-hb)( + ), hc) and the co-ordinates of the Cg of the unsprung mass relative to the same roll centre R are (-ha , ha).
Thus the co-ordinates of the overall Cg are (-H – Ms(hc-hb)( + )/M, H)
and the rotation of the whole mass about R is
T = + Ms(hc – hb)( + )/MH (1)
Consider the sprung mass as a free body and take moments about the roll centre B
kr + kaux = Msg(hc – hb) + Msg(hc – hb) + Msg(hc – hb)( + ) (2)
Similarly consider the unsprung mass as a free body and take moments about B
kr + kaux = –F2(T/2 + hb ) + F1(T/2 – hb ) + Mug(hb – ha) + Mug(hb – ha) – Mghb (3)
but F1 + F2 = Mg and F1 – F2 = ktT . Therefore substituting in (3) gives
kr + kaux = kt T2/2 – (Mshb + Muha)g – (Mshb + Muha)g (4)
Equations (2) and (4) can be used to eliminate
ktMH + kauxMH – Msg(hc – hb) (Mshb + Muha)( + ) = kt T2/2 Ms (hc – hb) (5)
The moment balance equation Winkler et al (2000) use in their graph is
Moment due to lateral acceleration = Restoring moment from ground – Moment from the offset due to compliance. All moments taken about R.
Rollover occurs when the right hand side of this equation reaches its maximum. From Winkler et al (2000) the Static Roll Threshold (SRT) is given by
SRT = T/2H - T (6)
Thus all we need to do is determine T at the maximum roll resistance.
Restoring moment from the ground = ktT2 /2 up to a maximum of MgT/2 when the wheel lifts off.
The offset moment = MgH T.
Consider now various cases.
Basic case – suspension has no lash, i.e. = 0. The maximum moment occurs when Mg = ktT ,
i.e. = Mg/ktT. Substituting this in equation (5) gives
Substituting into equation (1) we can evaluate T thus from equation (6)
Figure 2 Suspension track width
Suspension has lash. There are two points where the resisting moment versus roll angle curve reduces slope and either of these could be the rollover point depending on which generates the highest resisting moment. The first is when the lash comes into play, i.e. when the right hand side spring (using the convention in the figure) becomes unloaded. This condition is that Msg = kst , i.e. = Msg/kst where ks is the spring stiffness and t is the suspension track width as shown in Figure 2. At this point = 0.
Substituting in equation (5) gives
and then substituting all the angle values into equation (1) and then (6) gives
Alternatively the unsprung mass may still be sufficient to resist rollover once the lash has occurred and thus the vehicle can withstand a higher lateral acceleration before rollover. In this case the full extent of the lash is applied, i.e. = l/t and wheel lift off occurs i.e. = Mg/ktT. Substituting these values in equation (5) gives
As before substituting all the angle values into (1) and then (6) gives
If the auxiliary roll stiffness is relatively high compared to the spring stiffness it is possible that rollover will occur after the onset of lash but before the lash is fully completed. In this case = Msg/kst and = Mg/ktT but is unknown. Substituting these values in equation (5) gives
The correct SRT value is the one that generates the greater resisting moment to rollover, although, in practice, dynamic effects will tend to favour the value given by equation (8) even if it is slightly lower.
The resisting moment less the overturning moment due to the offset is given by
For each of the three conditions above and T are known and so we can substitute in equation (11). The standard sequence of events is that as T increases, first there is the onset of lash, the full extent of the lash occurs and finally there is wheel lift off. In this case the two potentially critical events are the onset of lash and wheel lift off and the one with the larger moment determines which situation is critical and gives the SRT value. With a relatively higher auxiliary roll stiffness it is possible for wheel lift off to occur before the onset of lash or alternatively after the onset of lash but before full lash. In the first instance wheel lift off is the critical condition while in the second case the event which generates the maximum moment is critical.
If the relative roll stiffnesses of the different axles of the vehicle are significantly different an axle may lift off without vehicle rollover or a suspension may take up its lash without rollover. For the purposes of this analysis we consider only the SRT of a single vehicle with a maximum of two axle groups. Winkler et al (2000) consider a tractor-semi trailer as a combination but for the Vehicle Dimensions and Mass Rule each vehicle unit must be assessed in a stand alone mode. For a vehicle unit that is normally part of a roll-coupled combination some assumptions need to be made regarding the characteristics of typical other unit(s) that could be coupled to the vehicle.
The vehicle sprung mass is considered a rigid body. Thus the angle of the sprung mass from the roll centre is the same all the way along the body. The roll centre height is not necessarily a constant along the vehicle.
front + front + front = rear + rear + rear = general + general (12)
Note there is no general term in this equation because this angle in included within the general term. The concept of lash relates to the suspension and has no real meaning in the general position.
Consider the position of the Cg of the sprung mass along the vehicle and using the subscript s to denote this point. At this location hbs = (Ms_fronthb_front + Ms_rearhb_rear)/Ms, and s = (Ms_fronthr_front front + Ms_rearhr_rear rear)/Mshbs.
These two equations are derived from the rigid body assumption which requires that the roll centre lie along a straight line.
Consider now a moment balance for the sprung mass about the roll centre.
kr_rear rear + kaux_rear rear + kr_front front + kaux_front front = Msg(hc - hb) + Msg(hc - hb)( + ) (13)
and moment balances for the unsprung masses about centreline on ground
Define new coefficients as follows
(15) + (14) – (13) gives
Using (16) with (14) and (16) with (15) we can eliminate to give a pair of simultaneous equations
Note that the restoring moments from the tyres, and the corresponding term for the rear suspension reaches a maximum at wheel lift-off i.e. when = Mg/ktT and then stay at this value for all greater than this critical. This maximum moment is MgT/2. Equation (17) can be rewritten as follows to take this into account.
At each of the critical points on the solution path, three of the variables can be specified. Using equations (18) and (12) it is then possible to solve for the three remaining variables. In this way all the possible vertices on the solution path can be found. However, it is necessary to check each solution point for validity. At each valid solution point the SRT value can be determined using equation (16). The maximum SRT value calculated in this way is the SRT for the vehicle.
Vehicle parameters required
The equations derived above require the following vehicle parameters:
· Unsprung mass by axle group
· Sprung mass by axle group
· Centre of gravity (Cg) heights of the unsprung masses
· Cg height of the sprung mass
· Wheel track width for each axle group
· Roll centre height for each axle group
· Suspension track width for each axle group
· Tyre stiffnesses
· Suspension spring stiffness for each axle group
· Composite/Auxiliary roll stiffness for each axle group
· Suspension lash for each suspension
Some of these parameters are readily obtained while others require specialised testing, which has probably already been done by the manufacturer. In this latter case manufacturer-supplied data can be used. The approach used in the SRT calculator software is to require a minimal set of user-supplied data which can be readily obtained and to include a conservative set of default values for the data that is more difficult to obtain. Where the parameters for which default values are supplied can vary substantially and have a significant impact on the resulting SRT value, an option for user input of manufacturer-supplied data is offered. A description of the data input process and the default values used follows.
The user inputs the vehicle type, the number of axles, the tyre configuration and size and the tare and laden mass for each axle group. The unsprung mass is calculated using default values for the axle and wheel masses. Currently the mass values used are as shown in Table 1 and column 2 of Table 2.
Table 1 Default axle masses without wheels
Truck/Tractor steer axle 350
Truck/Tractor drive axle 700
Trailer axle 400
Table 2 Parameter variations for different tyre size and configuration
Tyre stiffness†
17.5 single 50 0.36 0.275 0.26 700508
single 70 0.36 0.365 980711
19.5 single 75 0.40 0.275 0.28 700508
single 105 0.40 0.365 980711
22.5 single 100 0.49 0.275 0.30 700508
single 140 0.49 0.365 980711
* For a dual tyre configuration the mass is double the single tyre mass.
† For a dual tyre configuration the tyre stiffness is double the single tyre stiffness
The unsprung mass is equal to the sum of the axle masses and the wheel masses for the group while the sprung mass is equal to the laden mass minus these axle and wheel masses.
The Cg heights for the unsprung masses are default values based on the tyre radius. The values used are shown in Table 2. Actual variations are relatively small and have only a minor impact because the sprung mass is generally much greater than the unsprung mass.
The Cg height of the sprung mass is calculated from the Cg height of the sprung mass component of the tare and the Cg height of the payload. Default values are used for the Cg height of sprung mass component of the tare. Currently this value is 0.56m above the unsprung mass Cg for tractors and trucks and 1.25m above the unsprung mass Cg for all trailers. While this value probably varies significantly from vehicle to vehicle, the mass involved is generally relatively small so the impact on the overall Cg is small. The payload Cg height is calculated from the load bed height, the load height and the type of load. At present all load types except general freight and containers are assumed to be uniformly distributed vertically and thus the payload Cg height is midway between the load bed and the maximum load height. For general freight and containers it is assumed that the load is not uniformly distributed and can be regarded as being equivalent to two uniformly distributed layers with the lower layer containing 70% of the mass and the upper layer 30%.
For the wheel track width, default values are used based on the tyre size and configuration. It is assumed that for all large trucks under consideration the overall width is 2.5m and hence the width to the outer edges of the tyres is approximately 2.4m. For single tyres the track width is then set to 2.4m minus the tyre width (see Table 2), while for dual tyres the track width is set to 2.4m minus the tyre width minus the dual spacing. Because of geometric effects the centre for the reaction force on a dual tyre set is not at the midpoint of the tyre contact width but further outboard. The correction factor is (1 + (dual spacing/track width)2).
The roll centre height and suspension track width are functions of the suspension and will be covered in the next section.
Standardised tyre stiffness values are used and these are shown in Table 2. These values are typical and it is unlikely that a certifier can obtain better data. Furthermore the tyre characteristics will change over time as the tyres wear and there is no requirement for vehicles to be fitted with the same tyres when they are replaced. Thus there is a good case for using standardised realistic values.
The input of correct suspension characteristics is the most difficult aspect of using the SRT calculation algorithm. Details of the performance characteristics of the suspensions do have a significant impact on the resulting SRT value but data on these performance characteristics are not always readily available. The approach used is to incorporate default generic air and steel suspension characteristics into the calculator that are typical of the lower end of the scale so that for most vehicles using the default suspension will predict an SRT at or below its actual SRT. The certifier has the option of not using the default suspensions but instead inputting manufacturer-supplied data for the actual suspensions fitted to the vehicle.
The suspension spring stiffness, the auxiliary roll stiffness and the composite roll stiffness are related and, in theory, any two can be used to calculate the third. Typically, the manufacturer will supply the suspension spring stiffness (for each spring) and either the composite or the auxiliary roll stiffness. The inputs to the SRT calculator software are the suspension spring stiffness and the composite roll stiffness.
Referring back to Figure 1, the sprung mass has rolled through an angle, , about the roll centre B. The suspension will generate a resisting moment to this roll, M. The composite roll stiffness is the M/ = kr. The value to be input to the software is per axle and units used are Nm/radian. If the values provided by the manufacturer are in any other units a conversion is required.
Part of this roll stiffness is generated by the vertical compression of the suspension. The spring stiffness value, ks, required for input to the software is the value for one side of the axle (i.e. per spring) and is in N/m. Any other units require conversion. If the suspension track width is t, then the restoring moment generated by vertical compression of the suspension is kst2 /2 and hence the roll stiffness associated with vertical compression of the suspension is kst2 /2. All other roll stiffness generated by the suspension through anti-roll bars and other mechanisms is called the auxiliary roll stiffness, kaux. Thus,
Given the spring stiffness, suspension track and auxiliary roll stiffness we can calculate the composite roll stiffness.
The suspension track width is measured in metres and is the centre-to-centre distance between the connections of the suspension to the axle.
Steel suspensions typically have some "lash" in the suspension where, when the spring load changes from compression to tension, the axle moves through a small deflection with minimal resisting force. For the input to the software this lash is the distance moved by the axle measured in millimetres, which, often, will be smaller than the lash at the spring slipper. Figure 3 illustrates a steel leaf spring configuration with suspension lash at both ends of the spring. Other designs have one end of the spring attached with a pin joint and only have lash at the other end. To determine the lash it will usually be simpler to measure the free play of the spring at the slipper mount(s) and then to calculate the lash at the axle from the geometry of the suspension. For example, if the axle is mounted halfway between the spring hanger and the slipper, the lash at the axle will be the average of the suspension lash at the two ends of the spring. If one end of the spring has no lash the axle lash will be half the suspension lash. For an air suspension the suspension generates very little restoring force in tension and so the system can be regarded as having a large lash value. Air suspensions always have substantial auxiliary roll stiffness so this does not mean that there is no additional resistance to roll once the suspension becomes unloaded.
Figure 3 Illustration of suspension and axle lash
The other suspension parameter needed for the calculator is the roll centre height. For the purposes of the calculator this is measured in metres upwards from the axle centre. Thus if the roll centre is below the axle the value will be negative. Note that in the derivation of the equations the roll centre height was measured from the ground.
Generic steel and generic air suspensions with suitable parameters are included in the calculator. The values of those parameters are shown in Table 3.
Table 3 Suspension parameters used by SRT calculator
steer axle 185000 0.8 130000 15 -0.02
steel 1000000 0.97 520000 30 0.2
Generic air 350000 0.97 780000 300 0.2
*Not needed if composite roll stiffness is known
To use a user-specified suspension, values for each of the parameter columns in Table 3 except auxiliary roll stiffness need to be provided by the manufacturer. If auxiliary stiffness is given instead of composite roll stiffness, equation (19) can be used to calculate the composite roll stiffness.
[Ref. 4.5]
(a) in a twin-steer axle set, or in a tandem axle set with a twin- or single large-tyred axle 5400
(b) in any other axle set 6000
(a) in a twin-steer axle set 5400
(b) in a quad-axle set 5500
(c) in a tandem axle set with two single large-tyred axles or in a tandem axle set with a single standard-tyred axle or in a tri-axle set 6600
(d) in any other axle set 7200
(a) in a quad-axle set 5500
(b) in a tri-axle set 6600
(c) in any other axle set 8200
4 Oscillating axle, in any axle set 9500
(a) spaced less than 1.3 m from the first axle to the last axle 14,500
(b) spaced 1.3 m or more but less than 1.8 m from the first
axle to the last axle 15,000
(c) spaced 1.8 m or more from the first axle to the last axle 15,500
6 Single standard-tyred axle with a single large-tyred axle or a twin-tyred axle
7 Two oscillating axles 15,000
Three oscillating axles, three twin-tyred axles, or three large-tyred axles:
(a) spaced 2.5 m or more from the first axle to the last axle 18,000
(b) spaced 2.4 m or more and less than 2.5 m from the first axle to the last axle 17,500
(c) spaced 2 m or more and less than 2.4 m from the first axle to the last axle 15,500
Four twin-tyred axles, or four single large-tyred axles 20,000
Table 5 Maximum sum of mass on any two or more axles that together do not constitute a single tandem axle set, single tri-axle set or single quad-axle set, where the distance from the centre of the first axle to the centre of the last axle is 1 m or more but less than 1.8 m (including maximum gross mass)
Table 6 Maximum sum of mass on any two or more axles that together do not constitute a single tandem axle set, single tri-axle set or single quad-axle set, where the distance from the centre of the first axle to the centre of the last axle is 1.8 m or more (including maximum gross mass)
14.8 m but less than 15.2 m 41,000
15.2 m but less than 15.6 m 42,000
15.6 m but less than 16.0 m 43,000
16.0 m or more 44,000
[Ref. 5.1(4)]
PERMIT TO EXCEED MASS LIMITS
Permit No. …………….
UNDER Land Transport Rule: Vehicle Dimensions and Mass 2002.....................
.................... is hereby authorised to use [Vehicle description].......................
registered No. ................ for .............. trip(s) on/between [Dates]:................
............................to transport [Description of load]: .....................................
from........................to.........................over the following route, subject to the
conditions, restrictions and maximum mass limits in this permit.
ROUTE AND SPECIAL INSTRUCTIONS:.............................................
1(a) The gross mass of the vehicle with the load must not exceed....kilograms
1(b) The total mass on any set of axles must not exceed the sum of the mass limits shown for those axles in the table above.
2 This permit is void and of no effect if any of its conditions are breached or if the permit is altered or mutilated without authority.
3 This permit must be carried on the vehicle and must be surrendered for inspection or on the demand of any enforcement officer, or an authorised agent of Transit New Zealand or a road controlling authority.
4 [Any other conditions]..............................................................
Authorised Issuing Officer.................................................[Name]
...........................................................[Designation]
.................[Controlling Authority......].........[Location]
* S = Single standard-tyred axle
SL = Single large-tyred axle
T = Twin-tyred axle
(4) = 4-tyred oscillating axle
(8) = 8-tyred oscillating axle
[Ref. 5.1(7)(a)]
NOTICE OF INTENTION TO ISSUE OVERWEIGHT PERMIT
UNDER Land Transport Rule: Vehicle Dimensions and Mass 2002, operators of heavy motor vehicles are notified that overweight permits will be issued on application for the transportation described below, under the authority of an appropriate heavy traffic licence, namely:
1. Type of vehicle [‘All heavy motor vehicles’ or set out type of heavy motor vehicle — eg, ‘two-axled heavy motor vehicles’.]
2. Commodity [Set out description of commodity.]
3. Period [Set out period permits will cover.]
4. Conditions [Set out the maximum mass limits, eg, ‘Class I weight limits must not be exceeded’, and any other special conditions.]
5. Road [List roads or describe area permits will cover.]
[Designation of authorised officer]
Date issued..........................................
[Refs. 7.3(9), 7.3(12)]
Table 1 Wording, size and colour specifications for warning signs
width (all
DOWN’ 200 mm/
21 mm 1100 mm
600 mm Fluorescent
retro-reflective Matt
AHEAD’ 150 mm/
520 mm Fluorescent
retroreflective Matt
VEHICLE’1
signs 150 mm/
mm Matt black White
If used at
retro-reflective White
1 Refer to Figure 4 in this schedule.
Table 2 Order of display of pilot signs for various size loads
First pilot ‘WIDE
FOLLOWS’ ‘DANGER SLOW DOWN’ ‘LONG LOAD
pilot (if
required) ‘WIDE
FOLLOWS’ ‘WIDE LOAD
‘HOUSE FOLLOWS’
AS APPROPRIATE ‘LONG LOAD
(if required) ‘WIDE
AHEAD’ ‘WIDE LOAD
‘HOUSE AHEAD’
Figure 1 Minimum dimensions of hazard warning panel [Refs. 2.1(4)(b), 6.10(1)(c) and (d)]
Figure 2 Orientation of hazard warning panels [Ref. 6.10(1)(a)(i)]
Figure 3 Dimensions of ‘OVERSIZE’ sign for overdimension vehicles [Ref. 6.11(2)(a)]
Figure 4 Warning sign for pilot vehicle [Refs. 7.3(9), 7.3(12)]
[Refs. 6.12(7), 6.12(8)]
1 Prohibited travel (X) during weekday
(1) Loads up to and including 5 m wide
(Nationwide1)
(2) Loads greater than 5 m wide
2 Prohibited travel (X) during weekend
1 The travel-period prohibitions for loads up to, and including, 5 m wide between 0630 and 0900 hours and 1600 and 1800 hours apply only to city areas as defined in 6.12(1).
[Ref. 6.12(1)]
Zone 1 Northland, Auckland, Bay of Plenty and Waikato Kamo and south of Kamo
Maungatapere and East of Maungatapere
Mungaturoto and East of Mungaturoto
North of the intersection of SH 2 and SH 33 Paengaroa
North of the intersection of SH 5 and SH 1 Tirau
North of the intersection of SH 3 and SH 31 Otorohanga
Wellington North to McKay’s Crossing
East to Te Marua including Te Marua
Christchurch South from Waimakariri River
North of Templeton
East of Dawsons Road Yaldhurst
Zone 2 Northland North of Kamo
West of Mungaturoto
Southern Waikato and Eastern Bay of Plenty The intersection of SH 2 and SH 33 Paengaroa and south of the intersection of SH 2 and SH 33 Paengaroa
The intersection of SH 5 and SH 1 Tirau and south of the intersection of SH 5 and SH 1 Tirau
The intersection of SH 3 and SH 31 Otorohanga and south of the intersection of SH 3 and SH 31 Otorohanga
Opotiki and north of Opotiki
Te Whaiti and north of Te Whaiti
Rangitaiki and north of Rangitaiki
North of Motuoapa
North of the intersection of SH 32 and SH 41 at Kurutau, but excluding SH 41 and SH 32 (Kurutau to Tokoroa)
North of the intersection of SH 43 and SH 4 Taumaranui
North of Awakino
Zone 3 Southern North Island (excluding Wellington as defined in Zone 1) South of Opotiki
East of Opotiki
South of Te Waiti
South of Rangitaiki
Motuoapa and south of Motuoapa
The intersection of SH 32 and SH 41 Kurutau including SH 41 and south of the intersection of SH 32 and SH 41
SH 32 Kurutau to Tokoroa
The intersection of SH 43 and SH 4 Taumaranui and south of the intersection of SH 43 and SH 4 Taumaranui
Awakino and south of Awakino
McKay’s Crossing and north of McKay’s Crossing
North of Te Marua
South Island and Stewart Island (excluding Christchurch as defined in Zone 1) North from Waimakariri River
Templeton and south of Templeton
Dawsons Road Yaldhurst and west of Dawsons Road Yaldhurst
[Ref. 6.6(1)(b)]
Auckland Harbour Bridge: Height 4.8 m, width exceeding 3.1 m contact Police Communications Centre. (Any load exceeding 3.1 m in width travelling over the Auckland Harbour Bridge must be accompanied by a Bridge Control Officer as authorised by Police Communications Centre.)
Auckland Motorway: No travel on Auckland Motorway (includes Northern, North Western, and Southern Motorways) if the width exceeds 3.1 m or the height exceeds 4.25 m. However, loads that exceed 4.7 m in height are permitted to travel from Ramarama Interchange to the end of the Auckland Southern Motorway.
Wellington Motorway: Maximum height 4.8 m, maximum width 3.7 m. However, an overdimension motor vehicle exceeding these dimensions may travel on the Wellington Motorway provided it complies with the road controlling authority’s conditions.
McKay’s Level Crossing North Island Main Trunk Line/SH 1 Paekakariki: Loads or vehicles exceeding 4.6 m in height require permission to cross under the wires from the rail operator.
Lyttelton Tunnel: Maximum height 4.27 m, maximum width 2.6 m, towing vehicle and semi-trailer maximum length 21 m, 2 m maximum for load overhanging front or rear of the vehicle. However, overdimension vehicles exceeding the above maximums may travel provided that the following conditions are met:
(a) the operator of the overdimension vehicle must obtain permission from the road controlling authority’s agent (Tunnel Control);
(b) the operator of the overdimension vehicle must comply with any piloting or travel time restrictions required by the road controlling authority’s agent (Tunnel Control).
Schedule 8 Swept path performance measures for maximum-sized standard vehicle
[Ref 7.1(5)]
Low-speed Offtracking (LSO)
This manoeuvre is a right-angle turn, similar to an urban intersection turn and illustrated in Figure 1 below. The vehicle travels at 8 km/h and the centre point of the first axle tracks a path describing a 90-degree arc of 9.8 m radius. This corresponds to an outside front wheel radius of approximately 11 m. LSO is the maximum lateral offset between the paths tracked by the rear axis of the rearmost trailer and the path tracked by the steer axle.
Figure 1 Low-speed Offtracking
Low-speed tracking measures
1. The vehicle must be able to turn through 360 degrees while staying within a circle of 25 m diameter (wall to wall) for both left and right turns. Alternatively, if the vehicle is an overdimension vehicle it must be able to turn through 90 degrees to the left or right within an outside radius of 15 m and without any part of the vehicle, except for collapsible mirrors, encroaching within a concentric internal radius of 9.5 m.
2. Outswing of the front corners of the trailer must not be more than 350 mm beyond the path of the front of the towing vehicle when driven through a 180-degree turn of 12.5 m radius (scribed by the outside front of the vehicle) for both left and right turns. (See Figure 2)
3. Tailswing measured from the centre of the rear axis to the centre of the rear of the vehicle, for each vehicle in a combination, must not exceed 500 mm through a 90-degree turn of 12.5 m radius (scribed by the outside front of the vehicle) for both left and right turns. (See Figure 3)
4. The inter-vehicle spacing must not fall below 400 mm through a 270-degree turn of 12.5 m radius for both left and right turns. The 400-mm spacing may be reduced to 300 mm in the case of a conventional log truck and log full trailer.
Figure 2 Outswing of front semi-trailer of B-train combination in 12.5 m radius turn
Figure 3 Tailswing of vehicle during 12.5 m radius turn
[Ref. 7.1(7)]
The ‘maximum swept path’ for a Category 1 level overdimension vehicle has been derived from the following combination:
Tractor: 4.35 m wheelbase, 5.5 m forward distance
Semi-trailer: tri-axle: 2.5 m, 11.4 m forward distance and travelling in steady state through a 90-degree turn inside a 50 m radius wall. The inside of the path is measured at the rear axis of the semi-trailer. The maximum width of this path must not exceed 4.7 m.
Figure 1 Swept path 50 m radius
Land Transport Rule - Vehicle Dimensions and Mass 2002 - Rule 41001