The mayor of Christchurch has warned boy racers not to challenge police because of a new anti-cruising bylaw.
Police arrested 30 people in Christchurch on Friday night after dozens of cars were used to block a motorway on-ramp.
Police say about 140 people gathered in the area, with about 40 cars driving in different directions and endangering other motorists.
But Canterbury Road Policing Manager, Al Stewart, says there had been similar problems on that on-ramp in the past, and they don't believe Friday night's gathering was a protest against the new rules.
However, Mayor Bob Parker says the bylaw, which bans cruising on multi-lane roads and certain other streets, may result in the boy racers moving from the inner city to other areas.
He says the city council won't be giving up on the problem.
In a separate incident, a 26-year-old man was killed and five others injured in a car crash following a police chase in the central city.
It was the ninth death associated with a police chase in recent months. Two people were also critically injured when the car hit a power pole while fleeing police.