Axle weight flexibility

On this page

• What are the axle weight flexibility options?
• Before you apply
• Effect of axle weight flexibility
• No flexibility
• Class 1 axle weight flexibility
• HPMV axle weight flexibility
• User-defined axle weight flexibility
• Further information

Axle weight flexibility options for high productivity motor vehicles (HPMV's) give more choice to operators while still ensuring the safety of road structures. There is a trade off between the gross weight that can be achieved, and axle weight flexibility limits that are necessary to protect road structures from the possible increase in axle set weights. In other words, increasing axle weight flexibility (AWF) may result in reduced maximum gross weight.

Compliance is required with the specified individual axle mass limits; the specified axle set mass limits; the specified axle group mass limits; and the gross mass limit to ensure damage to road structures does not occur. Vehicles must also meet all required safety standards (eg brakes, static roll threshold and towing connection requirements).

What are the axle weight flexibility options?

The three axle weight flexibility options are:

• Class 1 axle weight flexibility
  This option should be selected where all of the axles, axle sets, and pairs of axle sets are loaded below the Class 1 limits, and flexibility is only required up to these limits. See further details below.
• HPMV axle weight flexibility
  This option should be selected where some of the axles, axle sets, or pairs of axle sets are loaded above the Class 1 limits, or where a greater level of flexibility is required. See further details below.
• User-defined axle weight flexibility
  This option may be selected where the applicant is not satisfied with Class 1 or HPMV AWF, and wants to specify their own axle mass limits.See further details below.

Before you apply

Before you apply, you will need to check the maximum mass limits of your vehicle, because your permit will not be able to exceed these limits.The final permitted mass may be reduced further by road structure limitations on your nominated route.
At the very least, you will need to check the following limits for your vehicle before applying:

• Maximum mass limit based on the first to last axle spacing (see Factsheet 13g)
• Maximum mass limits on other critical axle spacings depending on the type of vehicle you have (eg axles 1-4, 5-8, 3-6, 3-8 and 1-8 for R22T22) (see Factsheet 13g)
• GVM & GCM from your Certificate of Loading
• Brake capacity
• Static Roll Threshold (SRT) for the mass you want to apply for
• Tow connection ratings.

Effect of axle weight flexibility (AWF)

The effects of AWF can be seen by looking at the example of a truck and full trailer, shown below (type R22T22 vehicle):

The maximum gross mass limit of the HPMV above is 54,000kg over the 18.29m wheelbase (see Factsheet 13g for details). This is the maximum mass that the HPMV is able to achieve on an unrestricted route. However, the gross mass applied for may be less than the maximum HPMV limit due to critical structures on a route, vehicle carrying capacity limiting its gross mass, or other economic reasons. Through applying for permits, and discussions with NZTA Permit Issuing Officers (PIOs), the maximum achievable gross mass for a particular vehicle on a particular route can be determined (see our guidance maps which indicate the capacity of critical structures).

By requesting AWF, the load effects caused by a particular vehicle may increase. This may result in the maximum achievable gross mass for a particular vehicle being reduced, compared with the “No Flexibility” case. HPMV applicants need to first determine whether they require AWF, and secondly what level of AWF is required. The higher the level of flexibility (eg. HPMV AWF instead of Class 1 AWF), the higher the potential reduction in gross mass.

The following sections show examples of each AWF option, for the vehicle R22T22, truck and full trailer detailed above. The total mass applied for is shown to reduce with increased levels of flexibility requested. This is to highlight the reduction in the gross mass achievable if there are critical structures on a route. However, it should be noted that if a route is unrestrictive, requesting AWF may not result in any reduction in gross mass.

By requesting AWF, the load effects caused by a particular vehicle may increase. This may result in the maximum achievable gross mass for a particular vehicle being reduced, compared with the “No Flexibility” case. HPMV applicants need to first determine whether they require AWF, and secondly what level of AWF is required. The higher the level of flexibility (eg. HPMV AWF instead of Class 1 AWF), the higher the potential reduction in gross mass.

The following sections show examples of each AWF option, for the vehicle R22T22, truck and full trailer detailed above. The total mass applied for is shown to reduce with increased levels of flexibility requested. This is to highlight the reduction in the gross mass achievable if there are critical structures on a route. However, it should be noted that if a route is unrestrictive, requesting AWF may not result in any reduction in gross mass.

No flexibility

This option should be selected where the distribution of load to the HPMV’s axles is able to be reliably achieved.

• The vehicle axle mass limits are chosen by the applicant, up to the mass limits for individual axle(s) or axle sets, as per Tables 1 to 5 of Schedule 2 Part B (Mass limits for High Productivity Motor Vehicles) of the Vehicle Dimensions and Mass (VDM) Rule 2002. See Factsheet 13g High-Productivity Motor Vehicles for more information.
• The vehicle gross mass limit and the axle group mass limits shall not exceed the limits in Table 6 of Schedule 2 Part B (HPMV). See Factsheet 13g High-Productivity Motor Vehicles for more information.

The sum of the individual axle mass limits across the vehicle is equal to the gross mass limit of the vehicle.

Example of 'No flexibility' permit application

Example of table on 'No flexibility' permit

'No flexibility' example (The gross mass of the vehicle with the load must not exceed 54,000 kilograms)
Axle number	1	2	3	4	5	6	7	8
Axle type	S	S	T	T	T	T	T	T
Axle Mass (kg)	5,000	5,000	8,000	8,000	7,000	7,000	7,000	7,000
Spacing from previous axle (m)	0.00	1.90	3.57	1.32	4.90	1.25	4.10	1.25
Tyre size	Standard	Standard	Standard	Standard	Standard	Standard	Standard	Standard

• The permit does not allow for any Axle Weight Flexibility (i.e. a vehicle is non-compliant if any of its axles exceed the axle mass limits on the permit).
• The advantage of selecting no AWF is that the load effects of the vehicle will be less than that of a similar vehicle with Class 1 or HPMV AWF. As such, the vehicle will be able to safely carry a higher gross mass across critical road structures than if Class 1 or HPMV AWF was selected.

Class 1 flexibility

This option should be selected where all of the axles, axle sets, and pairs of axle sets are loaded below the Class 1 limits, and flexibility is only required up to these limits.

• The vehicle axle mass limits shall comply with the individual axle, axle set and pairs of axle set limits in Tables 1 to 5 of Schedule 2 Part A (General Mass Limits) of the VDM Rule 2002. See Factsheet 13 Vehicle dimensions and mass: guide to the factsheet 13 series for more information.
• The vehicle gross mass is provided by the applicant. The gross mass and the axle group mass shall not exceed the limits in Table 6 of Schedule 2 Part B (Mass Limits for HPMV). See Factsheet 13g High-Productivity Motor Vehicles for more information.

The sum of the individual axle mass limits across the vehicle can be greater than the gross mass limit of the vehicle.

Example of 'Class 1 flexibility' permit application

Example of table on 'Class 1 flexibility' permit

'Class 1 flexibility' example (The gross mass of the vehicle with the load must not exceed 52,000 kilograms)
Axle Number	1	2	3	4	5	6	7	8
Axle Type	S	T	T	T	T	T	T	T
Individual Axle Mass Limit (kg)	5,400 (Class 1 limit)	5,400 (Class 1 limit)	8,200 (Class 1 limit)	8,200 (Class 1 limit)	8,200 (Class 1 limit)	8,200 (Class 1 limit)	8,200 (Class 1 limit)	8,200 (Class 1 limit)
Axle Set Mass Limit (kg)	10,800 (Class 1 limit)		15,000 (Class 1 limit)		14,500 (Class 1 limit)		14,500 (Class 1 limit)
Axle Group Mass Limit (kg)	28,000 over axles 1 – 4 (truck) (Class 1 limit)				28,000 over axles 5 - 8 (trailer) (Class 1 limit)
Axle Group Mass Limit (kg)			29,000 over axles 3 – 6 (Class 1 limit)
Axle Group Mass Limit (kg)			42,000 over axles 3 – 8 (sum of mass on application form for axles 3-8 and within HPMV limit)
Spacing from previous axle (m)	0.00	1.90	3.57	1.32	4.90	1.25	4.10	1.25
Tyre Size	Standard	Standard	Standard	Standard	Standard	Standard	Standard	Standard

• The mass of axles, axle sets and pairs of axle sets can vary up to the Class 1 limits (shown in the table). Groups of three or more axle sets (i.e. axles 3-8 or 1-8) are limited to the sum of the mass applied for. Therefore, Axle Weight Flexibility has been provided to the applicant.
• Class 1 AWF can increase the load effects of a vehicle by up to 7%. Hence, this may result in a reduction in the allowable gross mass if there are restrictive bridges on a route.

HPMV flexibility

This option should be selected where some of the axles, axle sets, or pairs of axle sets are loaded above the Class 1 limits, or where a greater level of flexibility is required.

• The vehicle axle mass limits shall comply with the individual axle, axle set and pairs of axle set limits in Tables 1 to 5 of Schedule 2 Part B (Mass Limits for HPMV). See Factsheet 13g High-Productivity Motor Vehicles for more information.
• The vehicle gross mass limit is provided by the applicant. The gross mass and the axle group mass shall not exceed the limits in Table 6 of Schedule 2 Part B (Mass Limits for HPMV). See Factsheet 13g High-Productivity Motor Vehicles for more information.

The sum of the individual axle mass limits across the vehicle is greater than the gross mass limit of the vehicle.

Example of 'HPMV flexibility' permit application

Example of table on 'HPMV flexibility' permit

'HPMV flexibility' example (The gross mass of the vehicle with the load must not exceed 50,000 kilograms)
Axle Number	1	2	3	4	5	6	7	8
Axle Type	S	T	T	T	T	T	T	T
Individual Axle Mass Limit (kg)	5,400 (HPMV limit)	5,400 (HPMV limit)	8,800 (HPMV limit)	8,800 (HPMV limit)	8,800 (HPMV limit)	8,800 (HPMV limit)	8,800 (HPMV limit)	8,800 (HPMV limit)
Axle Set Mass Limit (kg)	10,800 (HPMV limit)		16,000 (HPMV limit)		15,000 (HPMV limit)		15,000 (HPMV limit)
Axle Group Mass Limit (kg)	29,500 over axles 1 – 4 (truck) (HPMV limit)				29,500 over axles 5 - 8 (trailer) (HPMV limit)
Axle Group Mass Limit (kg)			31,000 over axles 3 – 6 (HPMV limit)
Axle Group Mass Limit (kg)			40,000 over axles 3 – 8 (sum of mass on application form for axles 3-8 and within HPMV limit)
Spacing from previous axle (m)	0.00	1.90	3.57	1.32	4.90	1.25	4.10	1.25
Tyre Size	Standard	Standard	Standard	Standard	Standard	Standard	Standard	Standard

• The mass of axles, axle sets and pairs of axle sets can vary up to the HPMV limits (shown in the table). Groups of three or more axle sets (i.e. axles 3-8 or 1-8) are limited to the sum of the mass applied for. Therefore, Axle Weight Flexibility has been provided to the applicant.
• HPMV AWF can increase the load effects of a vehicle by up to 12%. Hence, this may result in a considerable reduction in the allowable gross mass if there are restrictive bridges on a route

User-defined flexibility

This option may be selected where the applicant is not satisfied with Class 1 or HPMV AWF, and wants to specify their own axle mass limits. There may be benefit in this option, where the level of flexibility requested on each axle is relatively small (i.e. less than a 7% increase in axle weight).

• The vehicle axle mass limits are chosen by the applicant and shall comply with the axle and axle set limits in Tables 1 to 5 of Schedule 2 Part B (Mass Limits for HPMV). See Factsheet 13g High-Productivity Motor Vehicles for more information.
• The vehicle gross mass limit is chosen by the applicant. The gross mass limit and the axle group mass limits shall not exceed the limits in Table 6 of Schedule 2 Part B (Mass Limits for HPMV). See Factsheet 13g High-Productivity Motor Vehicles for more information.

The sum of the individual axle mass limits across the vehicle is greater than the gross mass limit of the vehicle.

Example of 'User-defined' permit application

Example of table on 'User-defined' permit application

'User defined flexibility' example (The gross mass of the vehicle with the load must not exceed 50,000 kilograms)
Axle number	1	2	3	4	5	6	7	8
Axle type	S	S	T	T	T	T	T	T
Axle Mass (kg)	5,000	5,000	8,000	8,000	7,000	7,000	7,000	7,000
Spacing from previous axle (m)	0.00	1.90	3.57	1.32	4.90	1.25	4.10	1.25
Tyre size	Standard	Standard	Standard	Standard	Standard	Standard	Standard	Standard

• The mass of axles can vary up to the User Defined limits applied for (shown in the table). Therefore, Axle Weight Flexibility has been provided to the applicant.
• The mass on any axle, axle set, or combination of axle sets must not exceed the mass limits set out in Tables 1-6 of Part B of Schedule 2 of the Vehicle Dimensions and Mass Amendment 2010.
• User defined AWF can increase the load effects of a vehicle by 20% or more. Hence, this may result in a substantial reduction in the allowable gross mass if there are restrictive bridges on the desired route.

Further information

Depending on factors like bridge capacity, bridge length and vehicle axle spacings, the maximum permitted gross mass may be reduced for the AWF options compared to the 'No flexibility' option. This is a complex interaction and it will be important to work with the Permit Issuing Officer to get the best solution for your operation.

You may find when compared to the 'No flexibility' option, the 'Class 1 flexibility' and 'HPMV flexibility' applications may not be approved due to potential for increased loading of critical bridges. This will need to be kept in mind when completing the application form. Whichever option is chosen, the permit issuing officer will advise you of the outcome.