The Arthur’s Pass/Otira Gorge alpine route (State Highway 73) linking Canterbury and the West Coast will be closed each weekday from 10am to 6pm for the essential resurfacing work.
"The forecast at this stage is looking reasonably good for four days of full daytime closures this week from Tuesday," said Mark Pinner, system manager in the central South Island.
Contingency days are built into the planned closure, so the overall timeframe to complete the work by December 15 may still be manageable, he said.
"We know this closure will be unwelcome for many regular road users, businesses along the route and visitors to the West Coast, but this fortnight before the Christmas holidays has the least impact overall, compared to later options, and follows extensive engagement with travel, hospitality and freight operators."
The alternative route linking Canterbury and the West Coast will be via Lewis Pass/Reefton (SH7), which adds about an hour from Greymouth.
Pinner said on closure days people travelling from the West Coast will need to be at Otira by 10am if they are heading east on SH73 and back at Arthur’s Pass after 6pm to get home.
The route will be open the weekend of December 9 and 10.
Emergency services would be escorted through SH73 as required. The road will reopen fully each day outside the 10am to 6pm closure.
"Our aim is to ensure that the highway remains safe and fit for purpose for many years to come," Pinner said.
"We want to reduce the potential for more frequent short-term delays in the future due to failures in the road surface. It is now starting to crumble in places.
"This road is constantly under significant stresses from its grade (16%) and the alpine environment with seasonal weather extremes."