Manawatu Gorge work crews aim to have a single lane of the roadway reopened by the end of next week.
David McGonigal, Palmerston North state highways manager for the New Zealand Transport Agency, said the crews had set themselves a new target of getting the road open by the close of winter, weather permitting.
"We're now getting closer by the day, rather than by the week or month and, if Mother Nature comes to the party, we're confident we'll be waving vehicles through earlier than we expected," Mr McGonigal said.
"While work will continue on-site for a while, our top focus right now is getting ready to have one lane available for the public to use within two weeks. We'll then finish the job over September and, hopefully, have the road fully reopened to two lanes around late September."
He said work teams had made significant progress on retaining walls and a bridge, and had also been busy on "rock anchoring" - inserting steel rods into the rock slope. Work had continued on laying down the new driving surface.
Crews had been carrying out maintenance work on other parts of the gorge in anticipation of the reopening. Work had been completed on alternative routes as well, he said, repairing "damage caused by weeks of lousy weather".
"Constant rain is a headache for everyone because we have to wait for the weather to ease before we can carry out repairs."
The gorge reopened at the end of May after being closed on August 18 last year after heavy rain caused a major slip. The gorge reopened two days later before another massive slip closed the roadway again. About 370,000 cubic metres of material were moved before the road reopened, "enough to fill a bathtub in every New Zealand household", Mr McGonigal said.