The intersection of Ōtaki Gorge Road and State Highway 1 will be closed for three months from Sunday while work on the Peka Peka to Ōtaki Expressway is completed.
The intersection is a vital connection for the road.
A detour, using Hautere Cross Road, School Road and the new Te Horo Beach Road overbridge, is in place.
Traffic heading north will use the existing State Highway 1 intersection with Te Horo Beach Road and traffic heading south will use the existing intersection with School Road level crossing.
Right turns in and out of these intersections have also been closed, so that no traffic is turning across State Highway 1.
Speed restrictions do apply.
A Transport Agency spokesperson said the closure was made following engagement and communications with the community to ensure regular users were aware of the detour.
It is expected to be in place for 11 weeks, after which the next stage will begin by reopening Ōtaki Gorge Road and closing the School Road level crossing.
"The Peka Peka to Ōtaki Expressway will provide motorists with safer, more reliable journeys, increase the efficiency of freight and movements to and from Wellington, help ease local congestion and assist in facilitating economic development in the area," the spokesperson said.
"Waka Kotahi thanks motorists for their patience and understanding while these important works take place."