More than 700 cars have been impounded since the "boy racer" bill was introduced in May.
In the five months to the end of last month, police impounded 721 cars.
The police districts where the most vehicles were impounded were North Shore, Counties-Manukau and Bay of Plenty, all with a count of102 vehicles.
Waikato had 62 impoundments, Auckland 29 and Wellington 52.
The Street and Illegal Drag Racing Bill covers activities ranging from intentionally pouring liquid on roads, to street racing.
Figures showing how many people have been fined under the law were unavailable.
But Inspector John Kelly, of the police commissioner's office in Wellington, said it seemed that the drivers were getting better.
"It's early days but from just looking in the papers you can see the complaints about boy racer behaviour have gone away," he said.
"It seems the bravado they were showing in the early days is getting less and less."
Dangerous driving was decreasing, despite police consistently impounding 100 cars a month.
"We just wanted to curb their behaviour a bit and I think we've done that," he said.
Cars can be impounded for 28 days if involved in unauthorised street racing and anyone found to have poured liquid on roads for skidding can be issued with a $600 ticket or fined $3000.
Those skidding or speeding risk charges of reckless driving and fines of up to $4500. If someone is hurt the driver may face a maximum five years' jail, a fine up to $20,000 and disqualification from driving for a year or more.
Mr Kelly said the law was not keeping police overly busy.
"I think initially police would have been a bit busier.
"But I think their intervention at the start has prevented further problems downstream."
Waikato road policing manager Inspector Leo Tooman said that the problem would never go away but the law was making boy racers think twice about what they were doing.
"They hate having their cars impounded, they really do," he said.
"You might as well chop their legs off ... It really hurts them and I think as a result of that they are thinking a bit more about what they are doing.
"But they will always be there, these kids in their cars."
