THIS REPORT IS BEING FILED BY AN ACCIDENT RECONSTRUCTIONIST AT THE REQUEST OF THE VEHICLE'S INSURANCE CARRIER. VEHICLE WAS PROCEEDING IN THE LEFT LANE OF A 4-LANE (2 LANES IN EACH DIRECTION, DIVIDED BY A DOUBLE-YELLOW CENTER-LINE) STATE HIGHWAY WHEN OPERATOR'S AIRBAG DEPLOYED FOR NO APPARENT REASON, CAUSING LOSS OF CONTROL. THE VEHICLE THEN DRIFTED LEFTWARD ACROSS CENTER-LINE AND BOTH ONCOMING LANES, AND CAME TO REST AFTER MOUNTING THE CURB AND COLLIDING WITH A FIRE HYDRANT. EVENT WAS WITNESSED BY TWO, SEPARATE, INDEPENDENT AND INVOLVED MOTORISTS. VEHICLE'S OWNER WAS THE ONLY OCCUPANT AND WAS INJURED. OWNER PURCHASED USED VEHICLE IN JANUARY, 2012 REPORTED PREVIOUS TROUBLE WITH CLUTCH, TRANSMISSION, AND THAT MILEAGE AT THE TIME OF INCIDENT IS ON KNOWN DUE TO THE FOR REPLACEMENT OF THE OPERATOR'S CONSOLE, AND WAS THEREFORE ESTIMATED. ITS SPEED AT THE TIME IS ALSO ESTIMATED AT 40 MPH, THE POSTED SPEED LIMIT. *TR