After a massive slip last year the Haast Pass is set to re-open completely next week - ready to withstand a boulder the size of small car.

State Highway 6 has been closed at night for over a year through the Haast Pass - when a September slip at the Diana Falls site brought more than 40,000 cubic metres of rock onto the road.

New Zealand Transport Agency regional performance manager Pete Connors says they're installing the most complex rock-fall protection system in Australasia to have the road ready next Wednesday.

He says more than 30-tonnes of steel mesh and three separate fences will be able to stop a boulder weighing up to 16-tonnes travelling at over 90-kilometres an hour.