The speed limit for SH58 will be lowered to 80kph from tomorrow, adding 1 minute to the journey.
The stretch of road connects the Hutt Valley to Porirua, and has been a well known high risk crash area.
In the past 10 years, 4 people have died, and 68 have been injured.
The new speed limit hopes to increase safety and reduce the number of future incidents on the road.
Along SH58 there are many rural residential roads which can be hazardous to turn into, and are often connected to several crashes as people turn into a road, and get hit by an oncoming car. Several roundabouts are planned to help combat this issue.
As transmission gulley nears completion in 2020, SH58 is set to become a much busier road so addressing road safety now is crucial.
New speed limit signs will be installed.