State Highway One between Whangarei and Marsden Pt is to get a $400 million-plus upgrade to four lanes, with work due to start in 2019.
Transport Minister Simon Bridges says 22km of state highway will be upgraded. The section between Oakleigh and Port Marsden Highway should be finished within 3 to 5 years and the upgrade between Whangarei and Oakleigh in 5 to 7 years.
Getting consents and buying property may affect the timeframe.
"The Government and the NZ Transport Agency recognise the importance of securing the safety and resilience of this key road corridor for the future prosperity of the Northland," Bridges says.
"Upgrading this section of highway to four lanes and separating traffic will significantly reduce the high number of fatal and serious injury crashes in the area, many of which involve drivers crossing the centre line and colliding with oncoming traffic. It will also provide a more reliable and resilient connection to the port.