Motorists will be shifted to the new road on the Brynderwyn Hills early next month as work to improve safety cranks into top gear.
The $18 million New Zealand Transport Agency project started in December 2014 and is on target for completion before the end of this year.
NZTA's Northland highway manager Brett Gliddon said motorists would notice changes on that stretch of state highway from the beginning of May.
After the summit and bottom sections of the new road alignment were finished, due by the beginning of May, he said traffic would be moved down from the existing road to the new road.
"Southbound traffic will be moved first, followed by northbound traffic. This is expected to take about a week and there will be speed restrictions to keep motorists and those working in the area safe.