A seat-belted firefighter was seated in the right front captain’s seat of a fire truck when responding to an emergency call. As the vehicle proceeded through an intersection, it was struck near its right front wheel by a passenger car. The fire truck lost control and proceeded in a northern direction where it impacted multiple vehicles that were stopped in the westbound lanes of traffic. During the impact, the seat-belted firefighter was ejected out of the right front passenger door, which had opened during the crash. The firefighter sustained serious injuries as a result of the failure of the seat belt in this fire truck accident. ARCCA engineers were asked to examine the seat belt mechanism to determine why it opened up and also to study the biomechanics of the injuries involved.