The Rimutaka Hill road has reopened after being closed in both directions by a large slip this afternoon.
The New Zealand Transport Agency says motorists should expect delays while the backlog of traffic clears.
The slip came down about one kilometre north of Kaitoke, on the Upper Hutt side of the hill but has now been cleared.
NZTA said contractors on site estimated that about 50 to 60 tonnes of material had fallen from the hill, completely blocking one lane and partially blocking the other.
Motorists were advised to delay travel or use an alternative route.
Rimutaka Hill Road