CAR HAD UNSOLICITED ACCELERATION WHEN BACKING UP. CAR WENT FLYING BACK IN FULL ACCELERATION. HIT RAILING/STAIRS.I PUT CAR IN PARK. THOUGHT I MUST HAVE HIT ACCELERATION BY MISTAKE SO I WENT TO PUT CAR IN DRIVE TO PULL INTO PARKING SPACE, WHEN I TOOK FOR OF BRAKE THE CAR CAREENED OUT OF CONTROL FULL ACCELERATION. I TRIED BRAKE FOOT PRESSING PEDAL DOWN CAR WOULDN'T STOP. I STEERED INTO LOW CEMENT PARKING SPACE BUMPER AND BUSHES TO STOP CAR. - 1024.00 TO REPLACE THROTTLE BODY THAT HYUNDAI CHECKED OUT AND SAID IT WAS STICKING. HYUNDAI CHARGED ME FOR THE THROTTLE BODY REPLACEMENT - I AM WAITING ON ESTIMATE OF PROPERTY DAMAGE I DID WHEN I ATTEMPTED TO BACK OUT OF PARKING SPACE AT MY DOCTOR'S OFFICE.