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.

"More than 3 million tonnes of freight is exported from Northport each year and improving the region's freight connections to key export markets will be a game changer for the wider Northland economy," Bridges says.

The improvements will also help support growth south of Whangarei where there are significant opportunities for industrial development and housing.

The work is expected to cost $400 million to $500 million and is part of the corridor between Auckland and Whangarei.

"Ultimately we're planning a significant upgrade of the highway all the way from Whangarei to Auckland, which will include the completion of the Puhoi to Wellsford Road of National Significance which will make journeys along this entire corridor safer and more efficient," Bridges said.

NZTA will work with iwi, local communities and key stakeholders as the project moves through the planning and construction phase.