Takaka Hill has reopened to allow a steady flow of traffic to get on the move using a single lane.
The hillside had collapsed during ex-Cyclone Gita, leaving one section of SH60 in desperate need of a complete rebuild.
The New Zealand Transport Agency (NZTA) had issued statements saying they were prioritising essential travel this morning but as queues for the single-lane access route began to clear they had started to allow non-essential travel.
Vehicle restrictions for pedestrians, cyclists, vehicles towing caravans, boats or trailers, truck and trailer units or over-dimension units remained in place.
Transport Agency System Manager Frank Porter said motorists using the single-lane would be under escort in guided convoys, with strict safety controls in place from 9 am to 5 pm.
The road had been "severely damaged" and while crews had made great progress clearing debris from more than a dozen large slips this week, the hillside had completely collapsed at a site approximately 1.5km west of Riwaka, taking most of the road with it.
Mr Porter said priority would be given today to essential vehicles and those most urgently needing to get in and out of the region.
"We're urging people who don't absolutely need to travel immediately to allow us to give priority to those who do," he said.
"The most pressing need is getting fuel, feed for stock and essential freight into Golden Bay, and getting milk and other freight, tourists and people who need to attend medical appointments to the Nelson side of the hill."
Mr Porter said a regular schedule of full road closures would be necessary in order to allow construction crews access to rebuild the road.
"This is a narrow and confined site, and much of the work needed to rebuild the road won't be able to be carried out while traffic is flowing through.
"We'll need to balance the need to keep the road open as much as possible with the need to fully rebuild it as quickly as possible.
"It's too early to say exactly what work will be required, but it's a big job which is likely to take several months to complete."
There were several roads in Canterbury, including alpine and mountain passes, that remained closed at midday.
• SH79 Geraldine to Fairlie – Use SH1 and SH8 as an alternate route.
• SH1, north of Kaikoura, Mangamaunu to Clarence – The next update is expected by Monday at 5pm.
• SH1, south of Kaikoura, between Peketa and Goose Bay - The next update is expected by Monday at 5pm.
• SH1 Goose Bay to Ferniehurst – The next update is expected by Monday at 5pm.