State Highway 58 between Hutt Valley and Porirua will be closed all weekend from 8 tonight so contractors can make the road safer.
Waka Kotahi said new median and side safety barriers will be installed between Moonshine and Mt Cecil Roads.
It said this means more vehicles will be using State Highways 1 and 2, so drivers should expect congestion and delays.
The road will be reopened at 4am on Monday.