The new Hobsonville motorway in Auckland has been opened six months ahead of schedule.
The 9km road, built at a cost of $220 million, forms part of the 48km western ring route, which the Government has designated a road of national significance.
The road - an alternative to State Highway 1 - runs between Manukau and Albany via highways 20, 16 and 18.
Transport Minister Steven Joyce says the Hobsonville section will reduce congestion in northwest Auckland and improve journey times from the west to the North Shore.
Following the opening by Prime Minister John Key on Saturday morning, the public were able to walk and cycle the road during the afternoon and it will open to traffic on Sunday.
