A business owner has described plans to partially reopen the road through the Manawatu Gorge as a "lifesaver".
The road will be open to one lane of westbound traffic during the day and in both directions at night by the end of May.
Margaret Rose of Rose Coachlines said the road's closure nine months ago had taken a huge toll on her Dannevirke-based business.
"Even if it's just one way, well ... we'll take it.
"We've had more maintenance and have had to find money for extra fuel and wages and of course, the school children we've had to transport to Palmerston North have suffered too.
"Sometimes they're late getting to class because of the hold-ups and accidents on the Saddle Rd."
The road was closed on August 18 last year because of a slip. It reopened for three days before another, massive slip closed it again.
Transport Agency state highways manager David McGonigal said the road would be closed again if there were any stability or safety concerns.
He said the bridges along the affected stretch were severely damaged and would have to be rebuilt.
"Full two-way unrestricted operation is still likely to be around four months away," Mr McGonigal said.
"Building a new bridge across this distance in this challenging location would normally take up to 12 months, but we're not prepared to keep motorists waiting that long, so we'll be working 24/7 where possible and aiming to get them rebuilt within four months."
He said workers had done a "phenomenal" job removing "the largest pile of dirt we've ever seen on our highway network". Although there was still plenty of work to go, the partial reopening was a "tremendous milestone".
"This has been probably the biggest disruption that this region has suffered in decades, but despite the enormous stress this has put the community under, people have taken it in their stride and remained positive."