Bigger, heavier trucks and buses could soon be approved to use New Zealand roads despite an admission from officials it could lead to more serious accidents.

Announced at the start of December, the changes to the Land Transport Rule: Vehicle Dimensions and Mass 2002 (the VDAM Rule) would allow trucks up to be up to 5cm wider and higher and one tonne heavier.

The Ministry of Transport projects the economic benefit of the changes will be $93 million over the next 30 years.

But in a discussion document, the ministry said heavy vehicles posed a challenge to road safety because the crash rate for trucks was three times higher than for light vehicles.


The document said one of the key risks was that bigger vehicles could increase the consequences of some crashes.

However, the risks were "expected to be mitigated" by there being fewer trucks on the roads because they could carry more in a load and would likely hasten the uptake of new safety technologies such as autonomous emergency braking, blind spot warning systems, electronic stability control, and lane departure warning systems.

A Campaign for Better Transport committee member, Jon Reeves, said the Government should halt the proposal because the changes would mean more head-on, overtaking and roll-over crashes on New Zealand's hilly, windy and narrow roads.

According to the Accident Compensation Corporation, the average social cost of a road fatality is $3,981,700.

Mr Reeves said if 23 deaths over 30 years were caused by the larger vehicles, the economic benefits would be wiped out.

Mr Reeves, who has written a submission on the proposal, said he wanted the Ministry of Transport to:

• Give full details on how they calculated their productivity gains,

• Reveal how many people would be killed or seriously injured from the larger trucks and buses, and

• Estimate the costs of raising bridges, widening roads and other infrastructure changes.

The Hamilton City Council has also made a submission and councillor Dave Macpherson said the changes should not be backed unless there was a guarantee safety issues and the costs of damage to city infrastructure would be covered by the trucking industry or the Government.

Transport Minister Craig Foss said the changes were still a proposal and he welcomed submissions from the public.

Mr Foss didn't know how many submissions had been received but said about 50 people attended two events which detailed the new rules.

The main concern was the added safety risk.

"Any fatality and accident is obviously one too many."

But the changes would mean companies could import vehicles with new, more advanced safety technology.

Submissions close on Wednesday.

The numbers


heavy vehicles were on NZ roads in 2014.

17.5 years - average age of the fleet.

34 per cent are used imports, mainly from the 1990s.

18 per cent of road fatalities (2010-14) involved heavy vehicles with drivers responsible for 35 per cent of these.

21.5 per cent Heavy vehicles emitted 21.5 per cent of CO2 in 2014.