A 33-year-old man is in a serious but stable condition in hospital after a car rolled off the road near Nelson.
Police were notified of the incident just before midnight.
The driver was ejected from the vehicle, which had landed in a paddock along State Highway 60, near Appleby.
Police and members of the public located the injured man, who was taken to Nelson Hospital before being transferred by helicopter to Wellington Hospital's intensive care unit.
A search of the area where the vehicle came to a halt was conducted with the assistance of firefighters who used thermal imaging equipment to ensure no-one else had been ejected from the car.
Senior Sergeant Clare Robertson said police did not believe there was anyone else in the car.
The Serious Crash Unit attended the scene of the crash overnight and its investigation.