I WAS PARKED IN OUR LEVEL DRIVEWAY, WHILE THE CAR WAS RUNNING, AND GOT OUT OF THE CAR AFTER MAKING SURE IT WAS IN PARK. SHUT THE DOOR, AND THE CAR ROLLED DOWN THE DRIVEWAY OVER A SMALL HILL AND HIT THE RAILROAD TRACKS IN FRONT OF OUT HOUSE. NO ONE WAS INJURED.THE PARKING MECHANISM ON THIS VEHICLE DID NOT OPERATE EFFECTIVELY, THE SHIFTER SAID IT WAS IN PARK,AND THE CAR JUMPED INTO GEAR.