Another driver found the man's car off the side of the Mitchell Highway about 10 kilometres north of Orange at about 6.50am on Saturday and called emergency services, who responded to find the man trapped in his vehicle.

MAP: The area where the crash occurred ...

NSW Fire and Rescue freed the man, who was then transported to hospital in Sydney via helicopter.

He was the only occupant of the vehicle, and was believed to be travelling towards Orange at the time.

Central West Police District Acting Inspector Susan Mackenzie said police had been unable to speak to the driver since the collision and were unsure how the car had left the road.

The Mitchell Highway was closed in both directions for several hours, with diversions via The Escort Way, Peabody Road, Wellington Street, Edward Street and Hill Street.