Police are appealing for witnesses to an incident which occurred in Upper Chute this morning.
A man, aged in his 70s, parked his car near to his home address and then got out of the vehicle.
It is believed the vehicle then rolled backwards and collided with the man, which left him trapped under a wheel.
A nearby farmer was able to use his own tractor to lift the vehicle from the man prior to the arrival of the emergency services.
Sergeant Andy Moreton said: “The victim sustained serious injuries as a result of this incident and was flown to Southampton General Hospital by air ambulance where he remains in a critical condition. “The road was closed for four-and-a-half hours to allow specialist officers to carry out a full investigation.
“We would like to appeal to anyone who may have witnessed the incident to call police on 101 immediately.”