I WAS STOPPED AT A TRAFFIC SIGNAL BEHIND ANOTHER VEHICLE. I WAS REAR ENDED BY ANOTHER VEHICLE AT APPROXIMATELY 40 MPH. I WAS WEARING MY SEAT BELT. *NM THE BACK OF THE DRIVERS SEAT FAILED, CAUSING ME TO FALL BACKWARD AND HIT MY KNEES ON THE PLASTIC PANELS ON THE UNDERSIDE OF THE STEERING COLUMN. WHEN I HIT THE VEHICLE IN FRONT OF ME, SINCE THE SEAT BELT WAS NOW SLACK, THE INERTIA LOCKS WERE RENDERED INEFFECTIVE AND I HIT THE STEERING WHEEL, CAUSING INJURIES TO MY CHEST AND FOREARMS. I SUPPOSE I SHOULD BE HAPPY THAT I WAS NOT SERIOUSLY INJURED OR KILLED, BUT THE FAILURE OF THE SEAT BACK CAUSED UNNECESSARY INJURIES. I HAVE PICTURES IF YOU ARE INTERESTED.