WHILE TOWING A TRAILER DOWNHILL AT 55 MPH WITH CRUISECONTROL SET, ACCELERATOR PEDAL WENT TO THE FLOOR, CONSUMER HIT CANCEL CRUISE BUTTON 3 TIMES, BUT VEHICLE INCREASED SPEED, RPMS WENT TO 4500. CONSUMER THEN APPLIED BRAKES, BUT THAT DID NOT SLOW VEHICLE DOWN. TRAILER BEGAN TO FISHTAIL, VEHICLE FLIPPED, RPMS WERE STILL OVER 4000. CONSUMER SHUT OFF ENGINE, VEHICLE THEN CAUGHT ON FIRE UNDER THE HOOD. NO INJURIES, VEHICLE AND TRAILER WERE TOTALLED. *AK