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The speed tolerance is normally 10km/h above the limit, but since Queen's Birthday weekend 2010 has been lowered to 4km/h for holiday weekends when traffic volumes are higher.
Figures released under the Official Information Act show there were almost 115,000 speeding offences recorded on public holidays and over long weekends in the past two years and about half were the result of drivers travelling between 5km/h and 10km/h over the speed limit.
The lower tolerance would have generated a significant amount in fines - police issued a total of 92,503 infringement notices for speeding offences between Labour Day 2012 and last Queens Birthday weekend worth a total of $5.7 million.
The lower threshold is currently being trialled outside holiday weekends for the first time. The assessment period began on December 1 and will end on January 31 when police will decide whether it could become permanent.
National Road Policing Manager Superintendent Cary Griffiths said there was no magic bullet when it came to improving road safety, but there was a significant drop in road deaths over the time of the trial.
A full evaluation would be made. "We've certainly seen the results from this - the questions will be, would we see the same results if it was done permanently or is the fact there is a change and a whole lot of advertising around it?
"We have to look at a whole range of factors."
Between December 1 and yesterday afternoon there had been 36 deaths on the roads, compared with 51 in the same period in 2012.
"That's 15 more Kiwis who are walking around who wouldn't be last year. The whole aim of the summer programme is exactly that, to pull down the deaths and injuries which we know can be done."
Mr Griffiths said feedback from road policing staff indicated motorists had seen the advertising, admitted slipping up and had accepted the $30 fine (for being between 4km/h and 10km/h over the limit) with good grace.
Last month there were 23 deaths which was the lowest December since monthly records began in 1965.
The previous January had 18 deaths.
"That was extraordinarily low and the first time under 20 since monthly records began. This month is tracking virtually the same, the same number of fatal crashes (12) but one more fatality - so 13 deaths versus 12 at the same time last year. So we are on track at present for the second lowest or lowest January on record."
The Automobile Association surveyed 10,000 members just before Christmas and found 57 per cent backed the lower tolerance, with 82 per cent wanting police to retain the 10km/h limit for passing lanes and motorways.
• 114,536 speeding offences recorded on public holidays and long weekends in 2012 and 2013.
• 92,503 resulted in infringement notices worth $5.7 million.
• About half of speeding offences were the result of drivers travelling between 5km/h and 10km/h over the limit.
• An extended trial reducing the speed tolerance from 10km/h to 4km/h began on December 1 and ends on January 31.