The size of the country's car fleet is heading the wrong way in the race to reduce emissions - vehicles are getting heavier, which means they burn more fuel.
Photo:
The safety ratings which favour bigger cars are not helping.
But what if they were changed?
The government's new emissions reduction plan aims to bankroll low and middle income families into cleaner cars using half a billion dollars in subsidies.
But the tide is running the other way in the safety scores laid out on the government's RightCar website.
Lighter cars burn less fuel and can also have a 5-star safety when compared to others of similar size, but if it's a choice between the safest small vehicle and safest big one, buyers increasingly go for large, with SUVs and utes regularly dominating sales.
The trend has been studied by public health professor Alistair Woodward, and he was worried about the mixed messages buyers faced.
"It's very confusing," he said.
"You know, it's entirely understandable how people might feel that a three-tonne or two-tonne light truck is a great vehicle for carrying the family around them.
"But the problem is, there's a trade-off ... the environmental damage and the increased risk to other road users."
All around the world, cars are getting heavier, on average edging up above a tonne and a half or more.
Nowhere around the world is vehicle mass with all its pros and cons - such as bigger cars doing more damage - factored in to safety ratings directly and fully, though they do give a nod to it.
Now Vehicle Importers' Association (VIA) chief executive David Vinsen has begun asking, what if it was?
"What we're suggesting is that maybe mass needs to be taken into account as well, when we look at the overall safety of the fleet, not just the individual vehicle," Vinsen said.
"If every vehicle was lighter, the overall safety of the network and the fleet would increase.
"And when we posed that idea, officials have found it interesting, we understand there's been some internal discussion and debate."
The Ministry of Transport is looking at VIA's analysis.
That showed the trend over time made lighter cars less and less safe, since they had increasingly more chance of crashing into a ute or SUV.
Since actual crashes are factored into the used car safety ratings, this will tend to knock safety stars off the lighter cars over time.
Also, money is now directly attached to safety ratings for the first time, under the clean car scheme, since any car rated two stars or less cannot get any rebate at all.
Pedestrians and cyclists suffer too, as they come off much worse if hit by a heavier vehicle.
Auckland Transport is waking up to this and prioritising "vulnerable" transport users.
Vinsen said it was very early days and New Zealand would not be able to go it alone in trying to change the international safety rating systems.
"For there to be any changes it would be quite radical and would take a long time, for the government to change its whole premise of safety ratings for passenger vehicles."
There was work going on into this in other countries, he said.
The Ministry of Transport today said driving a heavier vehicle "does not always mean you will be safer".
"There are currently no plans for the government to advocate for direct consideration of mass in vehicle safety ratings," manager of mobility and safety Matthew Skinner said in a statement to RNZ.
"However, we will continue to work with the sector on vehicle safety across a wide range of safety issues so we can get more people into safer cars."
Woodward backed VIA's suggestion.
"That's a good idea because we know that there is a relationship with mass, and it wouldn't be too difficult, I don't think, to factor in to the algorithms that produce the safety ratings."
Advances in design have made some SUVs and utes safer for other motorists and pedestrians, such as by reducing their propensity to roll over smaller cars.
But not everyone wanted safety ratings played with.
Hayden Johnston, a mass importer of electric vehicles and hybrids at GVI, said the government's increasing attempts to influence the car market were curtailing customer choice.
"I look at our stock, what we're purchasing now versus what we were purchasing five years ago, and it's severely limited as far as model variety goes," Johnston said.
"Right across the board."
Other previous safety initiatives, such as making electronic stability control mandatory, had wiped out a whole segment of commercial vans, he said.
Conversely, the wider the range of late model or new cars there was a market for, the more the fleet would be upgraded over time, Johnston argued.
He was forecasting the opposite will happen - that when a second emissions fee kicks in under the Clean Car Standard in January next year, the range of vehicles that will be competitive to import will shrink further.
The AA said VIA's suggestions about mass was worth considering, however, it was complex and what was really needed was a national strategy for what the fleet should look like in coming years.
