Up to 50 serious crashes have been avoided because of road safety barriers on the new Waikato Expressway, the transport agency says.
The Cambridge section of the expressway was opened in December last year, and its flexible road safety barriers, on the road's side and median, have been hit 48 times since.
New Zealand Transport Agency chief safety adviser Colin Brodie said as far as he was aware no fatalities had occurred along the expressway in the past year, meaning the barriers had stopped crashes causing serious injury and death.
"They will not stop all crashes, but they sort of safely capture the vehicle slowly, take the energy out of the collision and direct it back into its own lane.
"[In] the vast majority of those collisions, the vehicles travel on their way and we never get to find out who they were."
Mr Brodie said the use of such barriers was becoming more common.
The 16km Cambridge section of the expressway, which runs from Tamahere to just south of Cambridge, cost $250 million.