The Transport Agency is warning drivers the seaside cliffs and banks south of Kaikoura are still very unstable.

The section of State Highway One between Peketa and Goose Bay has re-opened after a week of rockfalls caused by wet and windy weather, while more than 200 workers are scrabbling to clear the rest of the route.

Drivers have had to use the Inland Route 70 via Waiau instead, lengthening trips between Christchurch and Kaikoura by up to an hour.

NZTA's Pete Connors says drivers should expect more closures as winter approaches, because contractors haven't yet secured all slopes.

"Basically until we get the permanent repairs done there's still material to come down," he said. "Obviously when it rains that's when its going to happen."