WE WERE TRAVELING ALONG A FAMILIAR COUNTRY ROAD ON A WARM SUNNY DAY. WHEN WE ARRIVED AT A RURAL STORE THERE WAS ONLY ONE OTHER CUSTOMER THERE. I SLOWLY EASED INTO THE DESIGNATED PARKING AREA WHICH WAS SITUATED ABOUT 17 INCHES ABOVE THE LAWN BELOW. I WAS PROBABLY TRAVELING LESS THAN ONE MILE AN HOUR. WHEN I BRAKED, THE CAR ACCELERATED AND PROPELLED ITSELF OVER THE BLOCKS AND RAILROAD TIES THAT ARE FOUND IN FRONT OF PARKING SPACES, AND WE LITERALLY FLEW ABOUT 7 FEET OUT AND DOWN ONTO THE GRASS STOPPING JUST A FEW FEET FROM A TREE AND A FENCE. WHILE IN THE AIR, ALL I HAD TIME TO DO WAS PUT MY FOOT DOWN HARD ON THE BRAKE BECAUSE THERE WAS NOT ENOUGH TIME TO TURN OFF THE ENGINE DURING THE 5 SECONDS THIS WAS HAPPENING. OUR FIRST REACTION WAS THAT I MIGHT HAVE HIT THE ACCELERATOR INSTEAD OF THE BRAKE, AND THOUGH I FOUND THIS INCONCEIVABLE BECAUSE I HAD NEVER DONE ANYTHING LIKE THAT BEFORE AND BECAUSE THE TWO PEDALS ARE SO DIFFERENT, I COULD NOT CONSIDER ANOTHER EXPLANATION. HOWEVER, AS TIME PASSED, WE CAME TO THE REALIZATION THAT THIS COULD NOT BEEN THE CASE BECAUSE EVEN IF I HAD PRESSED THE ACCELERATOR BY MISTAKE I WOULD HAVE HAD TO HAVE "FLOORED" IT TO GET THAT KIND OF ACCELERATION IN SUCH A SHORT DISTANCE, AND EVEN MISTAKING IT FOR THE BRAKE I WOULDN'T HAVE "FLOORED" THE BRAKE BECAUSE I WAS ONLY ABOUT 18 INCHES FROM WHERE I WAS TO STOP. EVEN UNDER NORMAL CIRCUMSTANCES, THE PRIUS JUST DOES NOT HAVE THIS IMMEDIATE KIND OF ACCELERATION WE EXPERIENCED. I CANNOT HELP BUT THI