MY VEHICLE WAS PARKED IN A DRIVEWAY. PRIOR TO PARKING, I HAD FOLLOWED THE MANUFACTURER'S INSTRUCTIONS ON HOW TO HAVE MY CAR MEMORIZE THE LAST 100 FEET DRIVEN IN ORDER TO USE THE BACKUP ASSIST FEATURE. WHEN I STARTED MY VEHICLE, I ACTIVATED THE BACKUP ASSIST FEATURE FOLLOWING THE MANUFACTURERS INSTRUCTIONS. MY VEHICLE RESPONDED ACCORDINGLY AND THE BACKUP ASSIST FUNCTIONED NORMALLY FOR THE FIRST FEW SECONDS. THE BACKUP ASSIST THEN DISENGAGED AND MY CAR ACCELERATED BACKWARDS, WENT OFF ITS TRACK AND BACKED FORCEFULLY INTO A BRICK WALL BEFORE I COULD APPLY THE BRAKES. DAMAGE TO THE REAR OF THE CAR WAS EXTENSIVE. I DID HAVE THE CAR EVALUATED BY BMW ENGINEERS FOR POTENTIAL DEFECTS IN SOFTWARE OR SENSORS, BUT I WAS TOLD THAT THE SYSTEM FUNCTIONED AS INTENDED. MY RESPONSE IS THAT THE SYSTEM IS INHERENTLY UNSAFE IF IT CAN DISENGAGE AND ACCELERATE IN REVERSE WITHOUT DRIVER INPUT. IN ADDITION, MY VEHICLE IS STILL IN THE REPAIR SHOP AWAITING CERTAIN PARTS FROM GERMANY.