The crash occurred on the north lane at Pukerua Bay.
The driver is in intensive care after a crash that has closed state road 1 north of Wellington.
One vehicle crash occurred just north of Pukerua Bay about 2.30 on Sunday.
The highway was blocked in both directions until 6 hours while emergency services were in place.
The vehicle ended up on the roof in the north lane.
The driver flew to a hospital in Wellington in a serious but unstable condition.
A hospital spokesman said the patient was in a severe state of intensive care on Sunday morning.