OCCUPANT KINEMATICS

The first step in any successful automotive product liability case is a careful evaluation of the facts.  First, of course, there must be a determination that the vehicle was defective and unreasonably dangerous.  But a careful attorney has to take it one step further.  It must be proved that the defect was the cause of some injury or harm to the client.  In order to do this there must be some analysis of the movement of the bodies of the occupants within the car during the crash sequence, or the movement of a body that was ejected up until the final point of rest.  This is where the field of occupant kinematics comes in to play.

Kinematics is simply an analysis of the motion of objects.  Occupant kinematics is an analysis of how the occupants’ bodies moved relative to the movement of the vehicle and a determination of why those bodies moved in the way that they did.  Occupant kinematics is based upon Newton’s Laws of Motion.  His first law is that a body in motion will stay in motion and that a body at rest will stay at rest unless acted on by some external force.  A corollary to this is that motion is always in a straight line unless there is the action of an external force.  In a collision the motor vehicle may decelerate rapidly, accelerate rapidly or make an abrupt lateral movement, depending on how the collision occurred.  If the bodies of the occupants tend to stay in motion in a straight line, they will come into contact with some part of the occupant compartment unless the restraint system prevents them from doing so.

The restraint system in a motor vehicle is designed to allow the occupants to ride down the forces in a crash without being seriously injured or killed.  Seat belts and air bags, when properly designed and manufactured, can be very effective in avoiding injury or death.  Once it has been determined that there is a defect in the restraint system, an analysis of the occupant kinematics must be done to establish whether that defect was the cause of injury or death to the occupant.  In order to do this, there are a number of other concepts that come in to play.  The difference in velocity, referred to as delta v, must be determined.  In a very oversimplified example, if two vehicles are in a frontal collision, each going 50 mph, the delta v would be the difference in velocity from 50 mph to whatever speed was achieved by the vehicle immediately following the crash.  If the vehicles crashed and then recoiled by 5 mph the delta v would be (50 + 5 = 55) 55.  Another concept that is used to evaluate occupant kinematics is barrier equivalent speed.  This is the speed at which a vehicle hitting an immovable barrier would demonstrate crush identical to the subject vehicle.  This is not the same as delta v.  Another factor that must be determined is the principal direction of force.  Once these various factors are determined then an analysis can be done of the occupant kinematics.

This explanation of occupant kinematics is very simplified.  It requires the assistance of a qualified expert to do this analysis.  These experts have a number of tools today to assist them.  For example, motor vehicles today come equipped with a Crash Data Recorder that can yield important information about speed, airbag deployment, the function of the seatbelt, braking and so on.

The lawyers at Jinks, Crow and Dickson have years of experience in evaluating and prosecuting automotive product liability cases.  We have the knowledge and resources to employ experts who are proficient in doing the type of analysis required in these challenging cases.  We will continue to use our knowledge and resources to give our clients the best representation possible when these tragic crashes occur.

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