I WAS THE SOLE OCCUPANT OF THE CAR, STOPPED AT A MAJOR INTERSECTION, WAITING FOR THE LIGHT TO CHANGE. DRIVER OF A PICK-UP TRUCK, TRAVELING AT 40-45 MPH FAILED TO BRAKE ADEQUATELY AND SLAMMED SQUARELY INTO THE REAR OF MY 2005 MAZDA SEDAN. NO INJURIES WERE SUSTAINED LUCKILY AS THE CAR WAS NOT FORCED INTO THE VEHICLE AHEAD. HOWEVER THE SEATBACK OF THE DRIVER'S SEAT SNAPPED VIOLENTLY BACKWARDS JUST AFTER MY HEAD STRUCK THE RESTRAINT BOLSTER. I AM CERTAIN THAT THE SEAT BACK WAS PROPERLY LATCHED BEFORE THE CRASH AND SHOULD NOT HAVE FAILED TO HOLD IT UPRIGHT. AFTER THE CAR WAS REPAIRED THE SEATBACK LATCHING MECHANISM SEEMS TO BE WORKING, BUT NO REPAIR WORK WAS DONE TO THE SEAT. THERE IS NO ASSURANCE TO ME THAT THIS DRIVER'S SEAT ASSEMBLY WOULD WITHSTAND ANOTHER CRASH OF ANY SORT. *AK