An out-of-control car took out median barrier posts on the Brynderwyns but the driver walked away unscathed.
The accident happened about 1.45pm on Saturday.
A New Zealand Transport Agency spokesman said the driver lost control on the north side of the Brynderwyns, hit the barrier and took out 10-15 median barrier posts and wire.
The driver was, however, pushed back into the left lane.
"This is exactly how the central median barrier is designed to work. The car was prevented from crossing into the path of oncoming traffic and potentially hitting other vehicles," the spokesman said.