A section of State Highway 2 in Upper Hutt was blocked for most of this morning following a serious crash.
The incident happened around 6.45am on Sunday in the suburb of Timberlea, near Topaz St, and involved one vehicle.
One person was taken to hospital in a critical condition where they are now stable, while a second person received serious injuries.
The highway was closed between Upper Hutt and Remutaka Hill, specifically between Topaz St and Beechwood Lane for several hours, but reopened around 11am.
The police's Serious Crash Unit was investigating.