PARKED CAR ON DRIVEWAY FACING HOME. DRIVEWAY IS UPHILL FROM STREET TO HOUSE. PUT CAR IN "PARK" AND UPON GETTING OUT THE CAR IT STARTED ROLLING BACKWARDS. I WAS UNABLE TO STOP CAR AND IT ROLLED DOWN THE DRIVE & PART OF THE YARD, KNOCKING DOWN A TELEPHONE POLE GUIDE WIRE, CROSSED THE STREET & STOPPED WITH HALF OVER THE OPPOSITE CURB & DAMAGING A MAIL BOX.