I PARKED MY CAR AT THE TOP OF MY FRIEND'S VERY STEEP DRIVEWAY. I NEVER PARK DOWN IT BECAUSE WITH THE ELECTRONIC ACCELERATOR, I ALMOST GOT STUCK ONCE NOT BEING ABLE TO GIVE THE VEHICLE A SUFFICIENT AMOUNT OF GAS TO ACCELERATE UP THE STEEP GRADE. I NORMALLY PARK OFF THE ROAD AT THE TOP, BUT DECIDED TO PARK FACING OUT FROM THE DRIVEWAY. EVEN AT THE TOP, THERE IS A GRADE, BUT IT IS NOT RIDICULOUS. I PARKED IN 1ST GEAR (MANUAL) AND PUT THE E-BRAKE ON. MY FRIEND AND I WERE IN HER WALK-OUT BASEMENT FOR ABOUT 10 MINUTES WHEN WE HEARD WHAT SOUNDED LIKE A DOOR SLAMMING SHUT. WE WENT TO THE DOOR AND SAW MY CAR HAD ROLLED DOWN THE 200' DRIVEWAY AND IN TO HER DECK. THE BASEMENT DOOR IS UNDER THE DECK. THE CAR WAS HOLDING THE DECK UP AND THE DECK WAS KEEPING THE CAR FROM CONTINUING OVER A RETAINING WALL AND DOWN A 30' DROP. WE CALLED 911 BECAUSE OF THE STRUCTURAL DAMAGE, THE CAR AND DECK STILL MAKING NOISE, NOT KNOWING HOW LONG IT WOULD HOLD, AS WELL AS US BEING TRAPPED IN THE BASEMENT UNTIL IT WAS SECURED. ONCE THE FIRE DEPARTMENT HAD THE WHEELS CHOCKED THEY OPENED THE DRIVER SIDE DOOR TO MAKE SURE THE E-BRAKE WAS ON. THEY VERIFIED THAT IT WAS, IN FACT, ENGAGED. THIS WAS ALL PUT IN THE POLICE REPORT. THERE IS OVER $7K DAMAGE TO THE CAR AND $4K TO THE DECK. KIA INSPECTED TODAY AND DIDN'T FIND ANY DEFICIENCY IN THE E-BRAKE. I HAD THE SINKING SUSPICION THAT NOTHING WOULD BE FOUND. IT MAY HAVE BEEN A MIXTURE OF EVENTS THAT CAUSED THE FAILURE, BUT IT STILL HAPPENED AND WAS STILL A MECHANICAL