Parts of State Highway One in Auckland have been reopened to traffic after being was closed for major works to be completed.
The northbound lanes of the Southern Motorway were closed from the Newmarket off-ramp 24 hours ago and were not due to be reopened until Monday morning.
But the Transport Agency says work to switch the motorway traffic lanes to the new viaduct finished before 3pm on Sunday, and the motorway has been reopened.
The section that was closed is one of the busiest in Auckland, with about 65,000 vehicles using the road on a Sunday.
The acting state highways manager for Auckland, Steve Mutton, says a team of 150 people worked overnight to replace the older viaduct with wider and seismically stronger lanes.
He says people took heed of advice and avoided travelling on the motorway during the closures.
Mr Mutton says the works are part of a $215 million project to clear congestion on the motorway.