Pitfalls for Low Speed Injury Defense

TASA ID: 399

Imagine, for a moment, a rear-end collision takes place, where the plaintiff sitting in the driver's seat of his struck vehicle reports to have injuries similar to shoulder, neck and back strains.  With no apparent damage to either vehicle, a collision reconstructionist estimates a collision speed of below 5 MPH.

Using a speed of 5 MPH, a biomechanical expert then estimates the acceleration g-forces (movement force of the person inside the vehicle) to be at or below 1.  After reviewing various reference texts, the expert then states that the forces are well within the human tolerances and typically within the range of normal, daily activities.  Therefore, the injuries reported by the plaintiff were not associated with this collision and could be caused simply through his/her daily living. 

Is this direct correlation between acceleration forces and injuries an accurate way to determine the cause of the injury within a reasonable degree of scientific/engineering certainty?  The simple answer is no.  Certain pitfalls, generalizations and misuse of research data by biomechanical experts lead to erroneous conclusions. 

The first pitfall is the basic methodology of correlating forces to the cause of injuries among the general population.  The leading researcher in trauma injury causation, for at least the past 25 years, has been the National Highway Traffic Safety Administration (NHTSA), a research branch of the Federal Department of Transportation.  Never has NHTSA, or any of its associated sub-contractors, been able to find a direct correlation between collision forces and injuries using data collected by their programs.

The second pitfall is the inability to quantify human variability into a general force-injury analysis.  Do all individuals respond the same to collision forces?  For instance, a vehicle with four restrained occupants strikes a wall.  Will all the occupants exhibit the same injury patterns or be injured at all?  Real life trauma research with multiple occupants in vehicles has demonstrated no ability to quantify human variability. 

The third pitfall is the translation and direct correlation of a collision force into a usable g-force.   It is true that a Delta-V (MPH or ft/sec) is the most commonly used indicator of collision force.  However, a collision force applied during maximum engagement of a real time collision between two striking vehicles is measured in milliseconds.   In comparison, a g-force (ft/sec2) not only factors in a collision force but also incorporates the time sequence in which this force was applied. 

In actual collision events, the applied time frame is always an unknown variable.  Only in a staged collision, where some type of an accelerometer is placed in the tested vehicle, can the applied time frame be calculated.  Bio-mechanical experts in real time collision events cannot accurately quantify the time frames, which renders any calculated g-forces as a mere educated guess and does meet the standard of reasonable degree of scientific/engineering certainty. 

The fourth pitfall is the research on which the biomechanical experts rely and base their opinions.  Can staged collision testing of human subjects be the same as real-time collision events?   In a staged collision, the human volunteer has an expectancy of an impending collision force.  In comparison, a driver in a real time collision event is usually totally unaware of the impending collision.  Can this difference be accurately quantified?  Again, the simple direct answer is no. 

In addition, many staged tests designed to prove that an individual cannot be injured in a low speed collision do not accurately represent the general population.  In some instances, the testing takes place with less than 10 test subjects.  Typically, the human subject is a healthy person absent of any pre-existing injuries and of average age and weight.  The testing does not includepeople outside the norm for height, weight, and age and certainty does not expose individuals to collision forces if it is apparent that they have a pre-existing condition.

So, if a real-time collision event involves a person outside the norm, can a correlation between force and injuries be used based on testing procedure and information?  Again, the simple direct answer is no. 

Biomechanical experts couch their conclusions with terms such as "based on my experience, research and testing" in determining that no causal link is evident between the collision force and the plaintiff's reported injuries.  In fact, experience, research and testing show just the opposite.  There is no prior conclusive evidence or research to show a direct correlation exists between collision forces and injury causation. 

This article discusses issues of general interest and does not give any specific legal or business advice pertaining to any specific circumstances.  Before acting upon any of its information, you should obtain appropriate advice from a lawyer or other qualified professional.

This article may not be duplicated, altered, distributed, saved, incorporated into another document or website, or otherwise modified without the permission of TASA.

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