I WAS STOPPED TO TURN LEFT AND WAS HIT FROM BEHIND. THE OTHER VEHICLE WAS TRAVELING AT A SPEED ESTIMATED AT 45-50MPH. WHEN MY VEHICLE WAS STRUCK FROM BEHIND, THE DRIVER'S SEAT BACK COLLAPSED COMPLETELY. THE SEAT BACK FOLDED BACKWARDS UNTIL HITTING THE BOTTOM OF THE REAR SEAT. MY VEHICLE WAS THEN PROJECTED ACROSS ONCOMING TRAFFIC, WHILE MY SEAT WAS RECLINED. FORTUNATELY, I DID NOT STRIKE THE ONCOMING VEHICLES AND THERE WAS NO PASSENGER OR CAR SEAT IN THE REAR SEAT.*AK