New figures show that in more and more fatal road crashes, something is found to be wrong with the vehicle.
The Motor Trade Association (MTA) obtained data from the Ministry of Transport that shows the percentage of fatal crashes involving some sort of vehicle factor - often bad tyres or lights - had tripled from 5 percent to 15 percent since 2013.
The rate climbed at the same time as Warrant of Fitness fail rates increased.
The MTA, which represents thousands of garages, said the government's new 10-year Road to Zero plan did not appear designed to adequately tackle the problem of unsafe vehicles on roads, as opposed to its aim of lifting standards to improve the safety of used cars being imported.
The trend in the crash data was unmissable and undeniable, said MTA spokesperson Greig Epps.
"In 2013 vehicle factors contributed to 12 fatal crashes. By 2018 the number was 51, a fourfold increase."
Vehicle factors played a part in four percent of serious and minor injury crashes.
The WOF failure rate (for when a vehicle was first presented for a warrant) rose from 35 percent nationwide in 2013 to more than 40 percent, and was higher in some regions, including Waikato.
The MTA told the ministry in late 2018 that its lack of focus on vehicle roadworthiness was summed up by its poor oversight of the Transport Agency and in turn the agency's poor oversight of WOF inspections.
The information fed back from garages about WOF fails to NZTA remained far too vague to pinpoint common failings, the MTA said.
Of the 51 fatal crashes involving vehicle defects in 2018, 23 involved worn tyres.
"We're deeply concerned New Zealanders are losing the know-how and habit of maintaining their vehicles in a safe condition," Epps said.
Even getting the crash data itself was difficult and he had had to chase officials for it, he said.
The ministry said more than a year ago it was trying to fit the data into a new, more interactive format, but in late 2019 it was still saying the same thing.
The concern was that inadequate data collection and analysis was being fed in to policymaking such as Road to Zero, Epps said.