I DROVE MY CAR OUT THE GARAGE INTO THE COMMON ALLEY IN REVERSE, ONCE OUT THE GARAGE. WHEN I WAS OUT OF GARAGE ATTEMPTED TO CLOSE THE GARAGE DOOR WITH THE GENIE , AND THE GARAGE DOOR WOULDN'T CLOSE . I DROVE THE CAR FURTHER AWAY FROM THE GARAGE/BUILDING IN REVERSE TO DETERMINE , WHETHER THE GENIE WOULD OPERATE FROM ANOTHER POSITION , NEXT THING I KNEW THE CAR WAS ACCELERATING UNCONTROLLABLY, BETWEEN 20 - 25 MILES PER HOUR IN REVERSE NEXT TO OUR BUILDING'S GARAGES . MY CAR ONLY STOPPED BECAUSE I SLAMMED INTO MY NEIGHBOR'S GARAGE , WHICH WAS 4 DOORS DOWN FROM MY OWN GARAGE . MY ACCELERATOR WAS ESSENTIALLY, FROZEN...A RUNAWAY ACCELERATOR. SIMILIAR INSTANCES WHILE I WAS IN THE DRIVE MODE , BUT JUST FOR QUITE , SHORT, TIMES.