Allowing electric cars in bus and high-occupancy vehicle lanes is being suggested to encourage more drivers to take advantage of renewable power generation.
The idea has been put to Auckland Council by electric vehicle charging-point supplier Mark Yates, in a submission on the city's energy resilience and low-carbon action plan.
Mr Yates says bus and transit lanes should be open to plug-in hybrids, as well as pure electric cars, to reward drivers for cutting carbon emissions and help to compensative them for higher purchase prices.
He says they could be given special green or blue number plates, to help traffic enforcement officers and to raise the public profile of electric vehicles.
But he told the Herald the exemption should be lifted once the electric car fleet gained enough numbers, as it should not be allowed to clog bus lanes.
"There will be an attraction to buy the vehicles because consumers will pay an extra amount to be able to travel in a bus lane when other people can't, and it will give them a higher profile," said Mr Yates, of the electric charging equipment supply company JuicePoint.
Neither did he think the concession should be available to the thousands of unplugged hybrid cars already on the roads, as their electric motors are powered by petrol or diesel engines.
Motor Industry Association chief executive David Crawford said allowing electric cars into bus lanes was an example of a "soft" incentive which could warrant investigation, although his organisation was opposed to financial subsidies which tended to skew markets.
The only general government incentive for plug-in electric cars is an exemption from road-user charges until 2020, although subsidies are common overseas.
Although about 250 electric cars are on New Zealand roads, the number may soon be boosted by second-hand imports from Japan, selling for as little as $25,000 on Trade Me.
Mr Yates' submission to the low-carbon plan also calls for free public parking and more charging points for electric vehicles, ideas which are supported by Auckland Council environment, climate change and natural heritage committee chairman Wayne Walker.
But he said allowing electric cars in bus lanes would be "tricky" because of plans to increase bus services. An Auckland Transport spokesman said bus and high-occupancy transit lanes were "about reducing congestion on our roads".