CONSUMER'S VEHICLE WAS SITTING STILL IN TRAFFIC WHEN A SUV SLAMMED IN REAR SIDE OF VEHICLE. CONSUMER HAD A SEAT BELT TENSIONER THAT DIDN'T LOCK. CONSUMER PUSHED THE SEAT BACK TRYING TO PREPARE FOR AIR BAGA WHICH THE DIDN'T DEPLOY. VEHICLE WAS TOTALED. MERCEDES BENZ DEALER STATED AIR BAGS ACTED AS DESIGNED.*AK