Police are putting the brakes on speeding this summer but some motorists fear the new 4kmh enforcement tolerance may penalise drivers with faulty speedometers.
As part of a national summer road safety campaign starting this week, police have set a tolerance of 4kmh, as opposed to the typical 10kmh, above the official speed limit.
Tasman district road policing manager Inspector Jennifer Richardson said the campaign would be accompanied by a continued focus on drink-driving, restraints and other unsafe behaviour.
During the two-month period last year there were 416 serious injuries on New Zealand roads, including 57 deaths.
The lower tolerance campaign, which has been trialled over long weekends in the past, will run until January 31, she said.
"I do not think people should be too worried, they should simply stay within the speed limit."
Crash rates dropped by 25 per cent during the Queen's Birthday weekends of 2010 and 2011 compared with the previous two years.
Nelson artist Shawnee Young said the lower 4kmh tolerance raised issues for motorists.
"That is not very much leg room, how do you know your speedometer is reliable?"
Roadside speed monitors were always "way higher" than what was displayed in her car, she said.
"I never believe them. How could I possibly prove I was travelling at 49 and not 55 without paying a mechanic an arm and a leg?"
She feared this could be a growing problem, especially with the influx of summer holidaymakers.
Some speedometers in cars read in 10kmh brackets, and a 4kmh could prove difficult to establish, she said.
Liam Beale said on the Nelson Mail Facebook page that he got pulled over at Easter for doing 8kmh over the limit.
"The car I had at the time read 5kmh low, so in essence I thought I was doing 103kmh. Got let off though."
Julie Gibbs said her speedometer was definitely out by a few kilometres per hour, which was confirmed by her GPS system.
"I use that now for monitoring speed," she said.
A Tasman police spokeswoman said if somebody thought they had a faulty speedometer, they should get it fixed.
They should not think they might be allowed to speed and avoid getting ticketed, she said.
The possibility of appealing a ticket if a member of the public was ignorant of a faulty speedometer should be taken up with the police infringement bureau in Wellington, she said. The reduced speed initiative was not a new campaign and the public seemed to respond well to it over the year.
The results from the weekends when it had been used had shown a significant reduction in serious injury crashes and fatalities.
AA principal adviser Mark Stockdale said all New Zealand cars were built to international standards that required speedometers to overstate the true speed.
Throughout Europe, for example, there was a 14kmh threshold so a car travelling at an actual speed of 100kmh might read up to 114kmh.
"In all likelihood, for you to be ticketed by the police you would have to be travelling well above the speed limit."
This would be an unlikely defence, he said.
However a speedometer might be negatively affected if there was incorrect tyre pressure or the vehicle wheels were the wrong size. The onus would again be on vehicle users to ensure these were correct, he said.
The AA recommended that vehicle users should check their tyres once a month to ensure optimum safety.
Vehicle Testing NZ operational excellence manager Brian Sara said the only way to accurately test the accuracy of the speedometer was by using a dynometer which was an expensive piece of equipment.
"Therefore it would be highly impractical for the Government to introduce testing the speedo within the warrant of fitness test."
NZ Transport Agency road safety director Ernst Zollner said the holiday safety campaign would be welcomed by most New Zealanders.
A clear majority of Kiwis supported police enforcement of speed limits to prevent crashes, he said.
In the past year more than 250 people had lost their lives on roads, and many more had suffered debilitating injuries, he said. "That's a situation no-one should accept, and New Zealanders are looking for decisive action to reduce this needless suffering."
"The Transport Agency will be supporting the campaign with targeted advertising urging drivers to slow down and keep themselves, their families and others safe."
- The Nelson Mail