A huge slip just south of Kaikoura last Thursday night nearly buried a digger, and the NZTA are still trying to figure out how to remove it.

The slip happened overnight while the 20 tonne excavator was empty, and no one was working.

Steve Mutton, a programme manager for the NZTA, said the incident happened "while it was parked up there".

He said it would not have been an issue for his staff if the slip had occurred during the day.

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"Our experienced operators would have been able to move away from the slip into a safe zone."

Mutton said they were trained in "fragile environments" and the excavators they use have protection from rockfall and rollover.

The NZTA also has geotechnical engineers check the risk of slips in helicopters every morning.

Digger operators also know what to look for when a slip is about to occur, Mutton said.

"It tends to break away from the edges before the main slip happens."

Mutton said he did not know what the driver's reaction was to discovering his partially buried digger in the morning.