He said the car remained in the left lane and came to a stop.
Road workers have put road cones along the damaged section of the median barrier and the posts and wire will be replaced as soon as the work can be scheduled.
NZTA has urged motorists to take extra care during wet weather and to drive to the conditions, keep to the speed limit and maintain a safe stopping distance from other vehicles.
The government agency spent $16 million on safety improvement in the Brynderwyns by widening the road and installing a median wire rope barrier to separate north and south bound traffic. Work was completed mid last year.