Traffic was being diverted around the coastal Mangawhai Heads route. It was expected to add at least half an hour to the journey.
The busy Northland highway was earlier under stop go signs between Waipu and Brynderwyn . It was expected to take up to three hours before the highway was able to flow normally again.
Police said no one was injured in the crash.
A second serious accident briefly closed State Highway 6 in the Rai Valley in Marlborough briefly this morning.
Police said a helicopter was needed to fly an injured person to hospital and the highway between Opouri and Kokorua Roads was closed for landing.