One lane of SH1 at Brynderwyn is now open to traffic after a truck rolled about 4am this morning.
The crash happened between Baldrock Rd and SH12.
Stop and Go signs for north and southbound traffic on SH1 are being used on the northbound passing lane.
Motorists should expect to queue and will experience delays.
Drivers can also use an alternative route along Kaiwaka-Mangawhai Rd, Mori St, Molesworth Drive, Mangawhai Heads Rd, Cove Rd, The Braigh, before rejoining SH1.
It is not yet known when SH1 will be fully reopened.
A crane has to be brought in to right the truck and trailer.
The male driver suffered moderate injuries following the crash between Baldrock Rd and SH12.