May 31 2002

New Zealand is set to become the first country in the world requiring trucks to meet minimum standards for stability, Acting Transport Minister Judith Tizard announced today.

Ms Tizard said the new Vehicle Dimensions and Mass Rule, to come into effect on July 1, includes specific new requirements for heavy vehicle stability, to reduce the number of crashes where trucks roll over.

"New Zealand has a high rate of heavy vehicle rollover crashes compared to many other countries. These crashes are potentially very dangerous, which is why the measures we're introducing today are so important."

Trucks rolled over in 29 percent of heavy vehicle crashes attended by the police Commercial Vehicle Inspection Unit from July 1996 to November 1999. This compared to just over three percent in the United States.

"With our winding and difficult network of roads the potential is high for trucks to get into trouble. Truck drivers need to keep their speeds down, especially around corners, but it's also important that the vehicles themselves are as safe and as stable as we can make them. Obviously a stable truck is less likely to flip over than an unstable one."

The Rule also simplifies the mass and dimensions limits of different types of heavy vehicles. It does not include any increase to the maximum weight (44 tonnes) or length (20 metres) of New Zealand's largest vehicle combinations.

Under the Rule heavy vehicles will be required to undergo stability testing before they can be issued with a Certificate of Fitness. Vehicles that do not meet the minimum stability requirement will need to be modified or reduce the height or weight of the loads they carry.

The stability checks will be carried out using a "static roll threshold" calculator developed in New Zealand, which indicates how much force a vehicle can withstand in a steady curve without flipping over.

"These stability calculations provide a clear, measurable indication of what amount of stability is acceptable. Operators will know exactly how high and heavy their vehicles can safely be loaded, and they'll be much less likely to roll over."

Ms Tizard today also announced a separate change that will allow log trucks to operate with longer and lower loads, following successful on-road trials. Under this change, the logging trucks themselves will not be any longer, but they will be allowed to carry loads up to two metres longer than is currently permitted. (See separate statement).

Ms Tizard said neither of these changes were related to the Transit NZ proposals to increase the maximum weights and dimensions of vehicles.

“Work on those proposals is continuing as a separate project. The Ministry of Transport is looking at issues raised in submissions on the proposals.

“The government is aware of the argument that such changes could increase cost-effectiveness. Equally, we recognize that New Zealand roads are some of the most difficult in the world and that many people oppose the idea of bigger trucks. No changes will be made to the rule without extensive public consultation.”

Ends
Vehicle Dimensions and Mass Rule - Questions and answers

What are the proposed changes?
The Rule, scheduled to come into force on 1 July 2002, rationalises and simplifies the mass and dimension limits of different types of heavy vehicles.

This Rule does not increase the maximum weight (44 tonnes) or length (20 metres) of our largest vehicle combinations. However, more vehicles will have access to those upper limits. This will promote the use of safer and more stable vehicles like semi-trailers by allowing them to operate at their optimum capacity.

The Rule also introduces specific new requirements for heavy vehicle stability, aimed at reducing the number of rollover crashes on New Zealand roads. New Zealand is the first country in the world to introduce this stability test as a regulatory requirement.

Who will the Rule affect?
All heavy vehicle truck and trailer operators and drivers.

What are the benefits of the new Rule?
Heavy vehicles will be safer and more stable. The Rule also clarifies the law, rationalises it, and reduces compliance costs for those have vehicles who previously had to seek exemptions from regulation dimension limits to operate efficiently.

What was the process of consultation on the Rule?
The Rule has undergone two rounds of consultation: the first round involved consultation with industry groups and other interested parties and the second round involved public consultation. Thirty-nine submissions were received from the first round of consultation and 134 from the second round.

Why are you introducing stability requirements?
New Zealand has a high rate of heavy vehicle rollover crashes compared to many other countries. Rollover occurred in 29 percent of heavy vehicle crashes attended by the Police Commercial Vehicle Inspection Unit from July 1996 to November 1999.

How is vehicle stability measured?
Vehicle stability is measured in terms of "static roll threshold", or SRT, which indicates how much force a vehicle can withstand in a steady curve without flipping over.

SRT is measured in g's, with one g being equal to the natural pull of gravity - 9.8m/s². The greater a truck's SRT, the more force it can withstand without rolling over and the more stable it is. The Rule requires heavy trucks and heavy trailers to have a "static roll threshold" greater than 0.35g.

How is SRT calculated?
Transport Engineering Research New Zealand has developed a simple calculator for determining the SRT. The calculator is available on the LTSA website. The calculator uses a set of mathematical equations to determine a vehicle's likelihood of rolling over.

How many trucks will it affect?
All heavy trucks and trailers will need to meet the minimum “on-road” stability requirements but only heavy trailers will need to be tested (because trailers are typically less stable and are the ones causing stability problems). Around 14,000 trailers will need to be tested and certified, and the LTSA predicts that around 20 percent might not meet the 0.35g SRT requirement.

How many rollover crashes could be prevented?
We estimate the new requirements could prevent around 30 heavy vehicle loss of control and rollover crashes where no other vehicle was involved.

Are there stability requirements in other countries?
Stability standards are not required in other countries, although Canada, Australia and the United States are still considering this.

Why has New Zealand created its own stability standards?
Because of our difficult terrain, New Zealand vehicles are exposed to higher risk of rollover, and the performance levels have been developed to combat the safety issues arising from this.

How will the new stability requirements be enforced?
Trailers over 10 tonnes gross weight will have to be tested and given a stability certificate. Vehicles registered before 1 July 2002 must be tested before their first Certificate of Fitness check on or after 1 July 2003. Vehicles registered after 1 July 2002 must be tested before their first Certificate of Fitness check occurring after 1 January 2003. After their initial test, an SRT rating will be shown on the vehicle’s Certificate of Loading and will be checked when Certificate of Fitness inspections are made.

What will happen to vehicles that fail the stability tests?
Vehicles which do not meet the minimum stability requirement will have three options:
1. modify the trailer (eg, using smaller tyres or adjusting suspension)
2. carry lower loads (this restriction will be stated on their loading certificate).
3. carry lighter loads (this restriction will be stated on their loading certificate)

What are the major changes proposed to rationalise the mass and dimension limits?
The Rule does not increase to the maximum weight (44 tonnes) or length (20 metres) of our largest vehicle combinations. However, more vehicles will have access to those upper limits due to a rationalisation of the existing requirements. Checks have been carried out to ensure that safety will be maintained with the rationalisation.

The Rule proposes common rear overhang and overall length requirements for all heavy vehicles towing trailers and for all heavy vehicles that do not tow trailers. (Rear overhang is the distance measured behind the rear axle of a vehicle including its load.) This would result in an increase in rear overhang and length for rigid vehicles (including mobile homes and mobile homes converted from buses) that are not towing trailers.

How do the dimensions and mass limits in the Rule compare to those in other countries?
Many of the new limits bring requirements in New Zealand in line with international standards. However, Australia and other overseas countries have very different roading networks than New Zealand, and consequently their maximum dimension and mass limits are different from those here - for example, much larger vehicles are allowed on some Australian roads.

© Scoop Media