I WAS BACKING OUT OF MY GARAGE AND I HAVE AN L SHAPED DRIVEWAY. I WAS GOING APPROX. 2MPH AND THEN I TOOK MY FOOT OFF THE GAS AND WAS "COVERING" THE BRAKE AND SUDDENLY THE CAR BEGAN TO ACCELERATE AND I TRIED TO BRAKE, BUT THE CAR SLAMMED INTO A PARKED CAR AND STILL DID NOT STOP. IT CONTINUED TO ACCELERATE UNTIL I ENDED UP IN THE STREET. I WAS TRYING TO BRAKE THE ENTIRE TIME, BUT THE CAR DID NOT STOP AND CONTINUED TO ACCELERATE. MY FOOT WAS NOT ON THE GAS. WE LIVE ON A RESIDENTIAL STREET IN THE SUBURBS AND LUCKILY NO ONE WAS HURT. THE SIENNA AND THE PARKED CAR BOTH HAVE EXTENSIVE BODY DAMAGE.