It's a great Kiwi tradition - but a Taupo man who flashed his headlights to warn another driver of a speed camera was pulled over by police.
As police yesterday announced a big increase in speeding tickets last year, Paul Gamble was driving to work on State Highway 1 between Taupo and Tokoroa when he passed a mobile speed-camera van.
"It was hidden behind a bush on a downhill stretch of road so they're clearly after someone who is just going down the hill and speeding up a bit."
Mr Gamble, 39, said he carried on for half a kilometre and saw a vehicle coming in the opposite direction.
"I thought, 'He's travelling a little bit', and did the friendly thing and gave him a flash."
A police vehicle was behind the car and its driver pulled Mr Gamble over.
"I can't remember the exact words; it was either inappropriate or excessive use of headlights," he said.
It is against the law - with a penalty of $150 - to flash dazzling, confusing or distracting vehicle lights, although police say the law is used sparingly.
Mr Gamble wasn't given a ticket for that but for having only one working headlight. But he says he was still stopped on the "premise of excessive headlight use".
He said he flashed his lights only once and did so to slow people down - which in theory was what the speed camera was set up to do.
"I could have said I saw a dog on the side of the road but I didn't say anything ... [The officer] clearly knew there was a speed camera set up there."
Bay of Plenty police acting road policing manager Senior Sergeant Stu Nightingale said the Taupo area was high-risk, which was why there was a focus on enforcing the road rules.
"This is due to the high number of fatalities that have occurred in recent years," he said.
"State Highway 1 in particular has had a number of serious and fatal crashes, many due to speed."
Mr Nightingale said a critical factor in cutting the road toll was having the support of the travelling public.
"Rather than alerting speeding drivers to enforcement, we would ask drivers to get behind what police are trying to achieve and encourage them to alert police to speeding or dangerous driving so we can take action and try to prevent serious harm to other innocent road users."
The number of speeding tickets issued last year soared to almost double the total for 2009.
In 2009, the figure was 329,838; last year, it was 627,000.
Police minister Judith Collins put the increase down to the new cameras - which National condemned as a revenue-raising exercise when it was in Opposition.
She rejected a suggestion that warning signs be installed near speed cameras, saying drivers would slow down in that area then speed up again.
She said the new digital cameras did not break down as often as the old "wet film" cameras, and took clearer images of cars.
The minister said police did not get the money from speeding fines. "They are, however, responsible for bringing down the road toll and I think that's a good thing.
"People should understand that if you speed, you may well get a ticket and you're going to have to pay for it."
In 2003, then Opposition police spokesman Tony Ryall questioned the merit of hidden cameras and lowering the speed tolerance level from 10km/h to 5km/h over the limit,
Yesterday he said his 2003 criticisms were about the way the cameras were being used. Asked if it was a case of saying one thing in opposition and another in government, he said "no, certainly not."
- Additional reporting: APNZ