The speed limit on a section of State Highway 10 near Kerikeri will be dropped from 100km/h to 80km/h in a bid to reduce serious crashes.
The limit on either side of the Kerikeri roundabout is already 80km/h but that will now be extended north by about 2km, to a point 500m north of Waimate North Rd.
The New Zealand Transport Agency, which is responsible for the country's state highways, said increased development in the area had brought more traffic and a corresponding increase in crashes.
Highway manager Brett Gliddon said lowering the speed limit was part of NZTA's commitment to reducing the number of deaths and serious injuries on the roads.
"It recognises that people make mistakes and are vulnerable in a crash, and aims to reduce the price paid for a mistake so crashes don't result in death or serious injuries. This includes building safer roads, and encouraging people to drive their vehicles at safe speeds."
The new limit changes will come into effect on June 25. New signs and markings along the highway will highlight the new lower speed limit and encourage drivers to slow down.
Recent serious crashes on SH10 north of the Kerikeri roundabout include a head-on smash on August 15 last year which left a woman and two young children seriously injured. Fatigue was thought to be a factor.
The woman was charged, as was a motorcyclist who drove through the accident scene and collided with a police officer.
On September 28, 2013, two young women were badly injured when the modified car they were passengers in rammed a car which had stopped at the scene of an earlier accident. A crash investigator put the car's minimum speed at 157-168km/h.
The women had to be cut from the wreckage and were flown to Whangarei Hospital. Both suffered broken legs and one a broken back. The driver was sentenced to eight months' home detention and disqualified from driving for two years.