A Board of Inquiry has granted consent for the Puhoi to Warkworth motorway north of Auckland, known as the "holiday highway".
The New Zealand Transport Agency acting highway manager Steve Mutton said the draft decision from the Board of Inquiry was welcomed by NZTA.
"The draft decision is great news and an exciting and important step towards improving transport connections between Auckland and Northland and the rest of the upper North Island," Mr Mutton said.
The first stage of the project involves constructing a 18.5km four-lane motorway from the Johnstone's Hill tunnels on State Highway 1 north of Auckland to a roundabout north of Warkworth.
Ramps to and from Auckland are planned near Puhoi.
NZTA will provide feedback to the Environmental Protection Authority (EPA) within 20-working days.
Construction could start between 2016 and 2019, subject to the Board's final decision in September, Mr Mutton said.
It is estimated the motorway will take five years to build.
"While it's important to remember that the final decision is yet to be made, we are encouraged by the draft decision, which has followed an extremely rigorous fact-finding process," Mr Mutton said.
"Whangarei to Auckland is one of New Zealand's key transport routes, and investigations on how to continue improving and securing this corridor are ongoing, including for the Wellsford to Warkworth section."
The $760 million extension is the first half of the Ara Tuhono Puhoi to Wellsford Road of National Significance.
The Government had flagged the motorway as a vital freight and tourism link with Northland.
Motorway won't help Northland - Greens
Green Party transport spokeswoman Julie Anne Genter said the motorway extension was a waste of money.
"The project is actually in the Auckland Region and will only encourage more long distance commuting by car, worsening congestion."
Other road projects would make more of a difference to Northland, such as maintenance and safety upgrades to SH1 north of Puhoi, she said.