Government measures to stop boy-racers from cruising neighbourhoods and doing burnouts brought an 18 per cent drop in street-racing offences last year compared with the year before.

But Police Minister Judith Collins has mixed feelings about the results.

She is itching to see the first car crushed under the Government's boy-racer legislation that has been in effect since December 2009.

"I have been to a demolition yard in Onehunga, Auckland, where they asked me to push a button. And it was awfully good fun," Mrs Collins told the Herald.

"What we said when we brought in the legislation is that, ideally, no cars would be crushed ... But it would be quite nice if we could get one crushed. I would quite happily do that.

"I think I would auction off the rights on Trade Me and give the proceeds to child-cancer research."

She may soon get her wish as one person in Christchurch has two out of three strikes to his name already.

Under the law, a driver commits an offence if they show "unnecessary exhibition of speed or acceleration", do burnouts without reasonable excuse, or pour oil/petrol/any substance on the road for "loss of traction".

After three offences within four years, a court can order the vehicle to be crushed, as long as it will not result in "extreme hardship" to the offender.

The number of recorded street-racing offences dropped 18 per cent in the year to October, compared with the previous year. Forty-nine notices to impound vehicles have also been issued for a range of offences.

Police report not only a fall in the number of boy-racer offences, but boy-racers have been congregating on the streets far less than they did a year ago.

The number of calls to police about boy-racers peaked at 1023 for February last year, but has since nearly halved to 519 in October.

"We are getting the results that we wanted," Ms Collins said.

"What we've seen is a huge drop in illegal street-racing offences."

The Government's crackdown was triggered by an attack by boy-racers on Christchurch police Sergeant Nigel Armstrong in January 2009, who was shot at and attacked when confronted by about 300 people.

"In addition to that, we've brought in digital radios for police in Canterbury, Auckland and Wellington, which means illegal street racers can no longer use scanners to listen in to police activity," Ms Collins said.

She said there were 60,000 scanners around the country "with criminals listening in on police, but there's also a lot of people who are bored who want to listen in".

Meanwhile, the minister said the Crown was considering appealing a recent court decision that found boy-racer activity did not, in itself, cause a fear of violence.

She was referring to three people who had charges of unlawful assembly against them dismissed. They were part of a group of 28 boy-racers who were arrested in one swoop in June in Christchurch.

Recorded offences for illegal street racing:
* January 1, 2009-October 31, 2009: 2341

* January 1, 2010-October 31, 2010: 1926

* Percentage drop: 18 per cent

Number of calls to police about boy-racers:
* February 2010: 1023

* October 2010: 519