IN A PULL FORWARD PARK SPOT, SHIFTED TO REVERSE TO BACK OUT. CAR LURCHED BACKWARD VERY FAST. CROSSED THE ROAD, STOPPED BY A 4' X 6' POST SET IN THE GROUND. THE COLLISION BROKE THE POST AND CRACKED MY CAR'S REAR BUMPER. I PUT MY FOOT ON THE BRAKE, BUT IT COULD NOT CONTROL THE SPEED. THANKFULLY, NO PEOPLE WERE IN THE ROAD. NO INJURIES. THIS WAS PIN A COMMERCIAL FARM, WHERE PEOPLE CAN HARVEST THE FRUITS AND VEGETABLES. THE ROAD IS BLACKTOP. MY CAR LEFT SKID MARKS ACROSS THE WIDTH OF THE ROAD. IT WAS A FRIGHTENING EVENT FOR ME AND MY FRIEND. I CALLED MY CAR DEALER LATER TO ASK IF THERE HAD BEEN ANY INCIDENTS LIKE THIS...SHIFTING INTO REVERSE AND THE CAR ZIPPED OFF- OUT OF CONTROL. TECH SAID ' NO'.