The Transport Agency warns there will be traffic delays north of Dargaville for several weeks while contractors repair a major slip.
SH12 at Rotu has been down to one lane since mid-August, when it slumped after heavy rain.
NZ Transport Agency said the repair job should be finished by mid October, and the one lane would stay open throughout.
It said better drainage and a new retaining wall would make State Highway 12 more resilient in future storms.
