Impatient motorists have been ignoring overnight road closures at the Haast Pass, some forcing the gates open to travel through the damaged highway.
Overnight closures have been in place on State Highway 6 between Haast village and Makarora since a slip was brought down at the Diana Falls, near the Gates of Haast bridge, last September.
The slip has often seen rock - some as big as houses - and debris spill across the road overnight during heavy rain.
As recently as last Tuesday, at least 150 cubic metres of rock and material closed the road for an entire day while contractors worked to clear the debris.
Senior Sergeant Allan Grindell, of Wanaka police, said one motorist, a 22-year-old Queenstown resident, had smashed through the locked gates on Sunday night, causing serious damage to their van in the process.
Police pursued the motorist from Albert Town, just outside Wanaka, to Cromwell, before he was arrested and put into psychiatric care.
Mr Grindell condemned the actions of the driver.
"This incident speaks for itself. These gates are there for a reason - safety."
He said the driver had put himself at risk, as well as others.
"We all know the perils of the Haast Pass with rockfalls."
Two Canadian tourists were killed when the slip first came down during a fierce storm last September.