UPDATED 6.32PM As the first cars rolled south from Kaikoura on State Highway one today, drivers rolled down their window to return a "Merry Christmas" from a red nose-wearing road worker.

Transport Minister Simon Bridges had helicoptered in from Wellington to turn a Stop Go sign, wrapped in tinsel, at the Kahutara Bridge and officially reopen the road south.

About 50 road workers and contractors watched him do it, some with Rudolph ears and Santa hats attached to their hard hats.

Access to Kaikoura has been very limited since the 7.8 earthquake on November 14 caused major landslides on SH1 along the coastline.

This week the inland road opened, and today's opening of SH1 south provides another route and the most direct from Christchurch.

Bridges said it became apparent a couple of weeks ago that the road might reopen before Christmas, and the teams working on it had gone above and beyond, many working seven days a week.

"I've asked a lot of them how long they have been working. In many cases they have effectively said, 'we don't want to tell you because we're not sure we are allowed to work that hard'. But they have done it, and hats off to them."

The Transport Minister said many people who had been working to get SH1 reopen were not roading contractors.

"A bunch of girls and guys from the whale watch, who obviously can't do that - they have been turning the signs and doing a lot of the monitoring."

SH1 south from Kaikoura will be open only between 6am to 8pm until all of the slip faces have been stabilised and traffic signals installed along a section of the route that is still only single-lane.

Bridges also announced today that an "alliance" had been formed to work on SH1 and the rail route both north and south of the town, including the NZ Transport Agency, KiwiRail, Fulton Hogan, Downer, Higgins and HEB Construction.

Eve Parkin, owner of the nearby Kaikoura Peketa Beach Holiday Park, said things had been "desperate" since the earthquake, and the road reopening was a boost.

"We are extremely excited, today. I think [people will start coming back] - just look around, isn't it beautiful?"

Derrick Millton, a Kaikoura District Councillor, was at the bridge to see the road officially open.

Millton's Clarence farm is off SH1 north of Kaikoura, and it was his cows that were marooned on a patch of grass after the quake - with television images of the animals' plight going around the world.

He said today's road opening was "seriously good news" for Kaikoura residents.

"They have been through all sorts of pressure - they have run out of food, they have had serious things going wrong. They have got through all of that now, and good on them."

To the north of Kaikoura, Millton said it was difficult to get equipment and supplies for the farm, but they were getting used to it.

"We have just learnt that it's going to be like that, and we've just got to put up with it."

The Government has committed to rebuilding SH1 and the rail route both north and south of Kaikoura, estimating that could cost up to $2 billion. Today, Bridges said he still through opening SH1 to the north could be about a year away.