Police in Christchurch say they've prosecuted nearly 100 drivers in the past six months for anti-social road behaviour.
They say they've taken a hard line on boy-racers, impounding 80 vehicles and making 95 prosecutions.
The prosecutions are either for driving offences or for failing to supply information.
Senior Sergeant Glenn Nalder says they've been specifically targeting cars doing burnouts and donuts and have focused on directly responding to complaints from the public.
Mr Nalder says they've worked at making best use of the tools available to them, including the bylaw introduced in July, under which drivers who cruise on multi-lane roads or some suburban streets can be fined up to $1000.
Since the bylaw's introduction, Mr Nalder says, complaints have fallen significantly throughout the city.
Christchurch mayor Bob Parker says the message appears to finally be getting through to boy-racers, and the by-law has clearly been very effective.
