Trucks backed up on State Highway 1 following the crash. Photo: Nick Brook
The highway was closed following the 12.45am single-vehicle crash with traffic detouring via Lakeside Rd.
The detour itself became blocked when a heavy vehicle got stuck on Clarks Rd and trucks were backed up for about a kilometre mid-morning.
Light traffic was allowed to detour the detour via Station and Remote roads in order to rejoin SH1, south of Milton.
Waka Kotahi said the state highway reopened at 10.20am.
Police said the second person from the car who sustained serious injuries had been transported to hospital.
Enquiries into the circumstances of the crash are under way, police said in a statement.
