A video released as part of the Christchurch Dilemmas series shows the massive scale of repairs to quake-damaged State Highway 1, north of Kaikoura.
Nine slips were caused by the magnitude 7.8 earthquake in November, which blocked what was the main route from Picton to Christchurch.
The six minute video from the creators of When a City Falls interviews workers on the northbound part of the highway, which is due to open on December 15.
"It would have to be the biggest job in New Zealand," site supervisor Peter Thompson said.
"Pictures and paper clippings don't do justice, until you can see it first hand."
The $1.3 billion project will rebuild road and rail links between Picton and Christchurch.
Abseilers removed rocks and they now monitor slip movement.
"They get to see up close what is happening, what's loose," said site earthworks manager Rob Walker.
"It's pretty high risk for them and for us, but without them we can't continue on.
"All credit to them, you wouldn't see me up there."
Funded by NZ On Air, the interactive documentary's producer said the series aimed to "energise residents to participate in their own recovery".
A young man involved in the highway repair said: "In 20 or 30 years' time, it's still standing, [I can say] I was a part of this, I built this. It feels good."