When analyzing injury cases, it is important to determine if utilized safety equipment acted and reacted correctly. In motor vehicle accidents, this is an important element in accident investigation and analysis.

Restraint systems (seat belts)

The seat belt is designed to hold the occupant in the seat and therefore, couple the occupant to the vehicle allowing them to accelerate (or decelerate) together. The use of a seat belt reduces the overall acceleration of the occupant and the probability of the occupant’s body striking structures within the vehicle, also known as secondary collisions. The seat belt accomplishes this by distributing restraining loads over bony portions of the body such as the pelvis, shoulders, and chest. The use or non-use of a safety restraint is an important parameter to consider while reconstructing motor vehicle accidents and occupant kinematics. Whether or not a seat belt is used has a direct impact on the motions and forces felt by a vehicle occupant.

Air bags

In vehicular accidents, air bags are meant to prevent catastrophic injury. Air bags are designed to rapidly inflate in the opposite direction of a vehicle occupant’s initial movement during a severe collision, and then quickly deflate. The air bag provides the occupant with a cushion and restraint during a severe accident to reduce the chances of secondary collisions with the interior of the vehicle. If the occupant is not restrained by the seat belt and/or air bags do not deploy as per their intended design and function, an occupant’s body can contact other structures inside the vehicle. These secondary collisions typically provide the mechanisms for an injury. Air bag deployment is an important factor in determining the severity of a motor vehicle accident.

Helmets

In recreational vehicle accidents, it is important to understand if a subject helmet has served its intended function. The proper fit of a helmet must always be analyzed. It is recommended that the involved helmet is inspected to determine the severity of an incident and if the safety device has been compromised beyond its designed and intended purpose.