The Maritime Union has taken a swipe at a proposal to allow heavier trucks on the roads as submissions on the issue draw to a close.
The Land Transport Rule -- Vehicle Dimensions and Mass Amendment could be signed off by the end of 2009 with application for permits starting in 2010.
The amendment would create a permit system allowing some trucks to carry up to 50 tonnes on specified routes. The statutory limit is currently 44.
Submissions on the issue close this week, with division over whether productivity gains from allowing trucks to carry greater loads outweighs environmental and safety effects.
Maritime Union general secretary Trevor Hanson said heavier trucks would lead to greater danger on the roads and more damage to them.
Rising fuel costs and environmental pressures such as greenhouse emissions also meant the move was a negative one.
Mr Hanson said promotion of coastal shipping and rail was needed to move the transport industry forward.
But a trial with heavier loads run from last year showed productivity increased between 10 and 20 percent, trip numbers reduced by 16 percent and fuel use dropped 20 percent.
Transport Minister Stephen Joyce last month said emissions, noise and vibration effects of heavier vehicles were also tested and results showed no measurable increase in any of them.
Mr Joyce maintained the move would reduce freight costs and help exporters and New Zealand "grow faster out of the current global recession". It would also lead to fewer trucks being on the road.
The proposal has also been opposed by the Green Party, with MP Sue Kedgley saying heavier trucks would present major hazards to other motorists, and that many of New Zealand's roads were not suitable for very heavy vehicles.
