A slip has closed all three southbound lanes of State Highway 1 into Wellington city.
The slip fell just south of the Newlands on-ramp at the top of Ngauranga Gorge at about midday on Tuesday, New Zealand Transport Agency says.
Northbound lanes were also closed.
Police urged drivers to avoid the area as there would be long delays.
Alternative routes are possible via Johnsonville or SH58, then on to SH2.