Police will this summer enforce the 4km/h speed ticket threshold for 62 days in a row - a move that could spell the end of the 10km/h speed tolerance.
For two months from December 1, police will be aggressively targeting drivers travelling at more than 4km/h over the speed limit.
If the extended trial was a success, the the 4km/h speed threshold could become a permanent fixture on our roads, Assistant Commissioner of road policing Dave Cliff said.
"I wouldn't rule it out. We've got to look at what we can achieve over this two-month period and then look at what comes next."
It would take a few months to analyse summer crash data.
"We could end up having a really noticeable reduction in road trauma. And that's what we're trying to do."
A reduced speed tolerance was first introduced on New Zealand roads over Queen's Birthday weekend 2010 and has been used during public holiday periods since.
"Our research shows that when police combined high visibility tactics with a reduced speed threshold during Queen's Birthday weekends in 2010 and 2011, the total number of fatality/injury crashes reduced by 25 per cent, compared with the previous two years. That's an average of 30 people whose lives were saved."
Last summer in the December-January period there were 346 crashes, leading to 359 serious injuries and 57 fatalities - much higher than the rest of the year, Mr Cliff said.
AA New Zealand said reducing the speed threshold was a positive move, but merely issuing tickets would not be the answer.
AA spokesman Dylan Thomsen said police needed to target high-risk areas, rather than just motorways or near passing lanes.
Bright cars to push safety message
Police announced yesterday red and orange patrol cars would be rolled out as a trial across the country - but they may not be the safest colour to convey the message.
Assistant commissioner of road policing Dave Cliff said he hoped the colourful cars would become a talking point.
"They're very much a conversation starter," he said. "It's all around them being quite distinctive patrol cars. We need to get the public thinking and talking about road safety."
Twenty-eight of the Holden VF Commodore SV6 patrol cars would be spread around the country over the next year, as older cars came up for replacement.
But red cars were not necessarily the safest colour on the road, some evidence suggests.
In a 2004 research white paper into the safest coloured cars on the roads, the AAA Foundation for Traffic Safety in the United States said there was evidence that cars of certain colours were less safe than others.
The AAA Foundation determined that silver, white and yellow cars the colours of most police cars and ambulances - were the least likely to be involved in crashes.
Brown, black and green cars were the most likely - almost twice as likely as white cars - to be involved in serious injury crashes, it said.
Red was one of the least visible car colours.
Police said a red patrol car previously trialled in Waikato, in June last year, had drawn "a hugely positive public response".