The onus is on owners to keep their vehicles safe, despite many now only needing a warrant once a year.

Legislation that began to be phased in in October 2013 means Vehicle Testing New Zealand is starting to see cars come in that haven't been tested for a warrant for 12 months, instead of six.

VTNZ spokesperson Melissa Cheals says while it's a bit too soon to see the effect of the new rules, motorists do need to pay more attention to things like tyres.

"Customers need to really keep an eye on their cars between checks. Problems can get expensive to fix, and I think with the longer period between warrants it's only going to get more important."