I WAS PULLING UP TO PARK BEHIND A TOYOTA PRIUS ON A ROAD THAT WAS PARTIALLY COVERED WITH SNOW & ICE. THE WHEELS ON THE RIGHT SIDE OF THE VEHICLE WERE ON SNOW & ICE AND THE WHEELS ON THE DRIVER'S SIDE OF THE CAR WERE ON DRY ROADWAY. I WAS DRIVING SLOWLY TO PARK WHEN THE CAR SUDDENLY ACCELERATED INTO THE REAR BUMPER OF THE TOYOTA PRIUS. THE ENGINE WAS RACING WILDLY AND MY ATTEMPT TO BRAKE WERE INEFFECTIVE. THERE WAS DAMAGE TO THE REAR TRUNK & BUMPER OF THE PRIUS AND DAMAGE TO THE FRONT OF THE SUBARU. I SUSPECT THAT THE SUBARU TRACTION/SPEED/STABILITY/ELECTRONIC THROTTLE CONTROLS HAD MALFUNCTIONED. *TR