Motorists should be checking their cars regularly for safety problems, but many wouldn't even know what to look for, he said.
"Aunt Polly, at 75 years of age, would never even look at her car," he said.
A spate of fatal accidents involving non-warranted cars has sparked calls for drivers to take more responsibility for the roadworthiness of their vehicles.
The Motor Trade Association warns the onus is on motorists to ensure their cars are fit for the road now that WoF checks are set to be less frequent.
As of July, about 1.2 million cars made after 2000 that were once subject to six-monthly inspections will now be checked annually.
"Some of these vehicles are already 14 years old, and have clocked up several hundreds of thousands of kilometres' travel - they're not new cars," association spokesman Hamish Stuart said. "Risks will increase if owners aren't vigilant."
Dunedin siblings Danielle Ngametua Kiriau, 17, and Shannon James Kiriau, 22, were both killed when their green-stickered Honda Integra crashed last month. The car was not up to warrant of fitness standard.
Another fatal crash near Kopaki in Waikato last month - in which an unrestrained baby travelling on its mother's lap later died - is thought to have been partly caused by two bald tyres.
AA general manager of motoring affairs Mike Noon said the most important thing for drivers to check was tyre tread and air pressure.
A simple check with a 20 cent coin could reveal whether tyres were fit for the road.
"You push the coin into the tyre, with the 20 at the bottom, and if you can see the base of the 2 then that means you've only got 2mm of tread and you should be considering changing your tyres."