DRIVING 35MPH WHEN VEHICLE WAS REARENDED & SLAMMED INTO VEHICLE IN FRONT. DRIVER'S SEAT COLLAPSED BACKWARDS FROM EITHER BEING REARENDED OR REARENDING OTHER VEHICLE. OWNER DOES NOT REMEMBER DUE TO BEING UNCONSCIENCE AT THE TIME. AIR BAG DID DEPLOY & SEAT BELT HELD. ENGINE STILL RUNNING & FUEL CUT OFF SWITCH FAILED. DRIVER AWOKE & CUT IGNITION OFF. *AK *SLC