The onus is on Western Bay drivers to check their cars' roadworthiness following a spate of fatal accidents involving non-warranted vehicles.
The Motor Trade Association (MTA) warns motorists should be taking responsibility to ensure their cars are fit for the road now warrants of fitness checks are set to be less frequent.
Several crashes in recent months involved cars that should not have been on the road, with some having gone years without safety checks, MTA said.
As of July this year, about 1.2 million cars made from 2000 that were once subject to six-monthly warrant of fitness 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 are not new cars," MTA spokesman Hamish Stuart said.
"Risks will increase if owners are not vigilant."
Western Bay of Plenty road policing manager Senior Sergeant Ian Campion said there were a "raft" of car faults that could cause accidents on local roads. These ranged from problems with brakes and bald tyres, through to people driving too quickly on a "space saver" spare tyre.
People should not have to be reminded to do regular checks on their own cars, he said.
"Checking things like the oil ... that your windscreen doesn't have big cracks in it, that your brake lights are working.
"When I got my first car I was taken around the vehicle by my father and [shown] what I was to check on a weekly basis."
Parents could pass this information on to their children, Mr Campion said.
"There are some vehicles that we see out there on the road that simply should be scrapped."
Dunedin siblings Danielle Ngametua Kiriau, 17, and Shannon James Kiriau, 22, were both killed when their green-stickered Honda Integra, which should not have been on the road, crashed last weekend. The car was not up to warrant of fitness standard.
Another fatal crash near Kopaki in Waikato on Monday - in which an unrestrained baby travelling on its mother's lap later died - is thought to have been caused partly by the condition of two bald tyres.
AA general manager of motoring affairs Mike Noon said the most important thing to check was tyre tread and air pressure.
"A lot of people have relied completely on their warrant of fitness but there are things that, as an owner of a vehicle, you should be doing on a regular basis."
A simple check with a 20c 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."
The right air pressure for tyres could usually be found on the inside of the driver's door, Mr Noon said. A third to half of all vehicles had the wrong tyre pressures, which could be dangerous.
Other things to look out for included "squealing" of the brakes - which meant the brake pads were wearing out - and making sure indicators and lights were working.