Fuel taxes are due to be replaced in coming years, with all vehicles coming into the scheme.
Transport Minister Chris Bishop announced this week petrol, diesel, electric and hybrid vehicles will pay for the road network based on distance travelled and the weight of vehicles.
That would mean the end of the petrol tax of about 70c per litre being paid at the pump.
AA principal policy adviser Terry Collins said basing road upkeep on vehicle weight in the nation’s light fleet was flawed because heavy vehicles were the major contributor.
There was "negligible" difference between a 1200kg car and a 2000kg car in relation to the damage they did to roads, he said.
"It kind of irritates me when I hear about this weight thing on vehicles. The light fleet is not the vehicle that’s causing the damage to the road, it’s the trucks. You have to be about eight tonnes and then depending on your axle configuration that’s when you are really starting to do damage to your roads. The light fleet subsidises the heavy industry [who] are the ones smashing up our roads and the potholes."
A fair system would need to look at who was causing road damage and who should pay the repair bills.
The government did not want to fully do this because they did not want to drive the cost of freight up as 94% of goods were delivered by truck, he said.
AA members are also seeking assurances about private companies expected to gather charges and the privacy of data being collected.
Mr Collins said car drivers wanted to know who would collect valuable data tracked electronically and how it would be used after the scheme was first introduced.
He questioned if driver movements would be used for police enforcement or road safety by the Ministry of Transport.
"Or will it be sold for somebody who wants to know how far you are travelling so they can sell you a car?"
The administration costs of private firms would include a profit margin and they could be expected to "clip the ticket", he said.
A cost breakdown for the road user charge had yet to be set, but was expected to be more than already being paid.
Yet to be announced was whether plans to raise the fuel excise duty by 22c per litre over three years from 2027 would transfer to road user charges.
Mr Collins said the government would take a hit on GST no longer being paid from 7c of tax removed for each litre of petrol bought at the pump.
Overall, the AA supports the changes in principle because of their potential to unlock other benefits.
Distance travelled was considered a better indicator of road risk than the amount of fuel being used as a basis for ACC contributions.
Car drivers pay about 6c per litre for petrol towards ACC payments.
Mr Collins said changes should also be made to motorbike registrations as motorcyclists often owned several bikes, but could only ride one at a time yet made multiple ACC contributions when not on the road.
"By going to distance based it will be a much fairer way for them to make their contribution. So, we think that would be a really good outcome. We also think warrant of fitness should be based on the distance a car travels because distance travel is a better indicator of wear and tear than the age of the vehicle."
Modern vehicles with a three year warrant could have completed 100,000km, yet a collector’s car such as a 1955 Chevrolet had to be tested every year even though it might have only done 5000km a year.
Combining all the systems based on distance would be better for motorists, he said.
The AA will also watch with interest the scheme’s impact on the uptake of more energy efficient vehicles.
Road users on a distance-based charge who are paying $1.60 per litre for fuel after the tax is removed may be tempted to drive larger vehicles than a Suzuki Swift because they would not cost as much to run.
