Analyzing Injuries Sustained In Low-Speed Accidents

Common Terms Defined

Biomechanics – "The study of the mechanics of a living body, especially of the forces exerted by muscles and gravity on the skeletal structure."

By education, a mechanical engineer (usually) with advanced degree(s) in human anatomy, physiology, tolerance of biological tissue, neuroscience, kinematics and dynamics to name a few.

Low-speed impact (LSI) – Generally considered less than 5 to 8 miles per hour.

Employing the laws of physics and human tolerance, biomechanical engineers analyze the forces of the impact and whether a mechanism of injury existed during the impact. (It is important to keep in mind that biomechanics may not necessarily question the presence of the injury.)

However, these experts will evaluate whether there were forces and an "injury mechanism" present in the specified collision would have been sufficient to produce the alleged injury.

A biomechanical analysis can often reveal many claimed injuries to be quite unlikely given the forces involved in the subject incident. Some low-speed claims may involve claimants with real back, shoulder, wrist, and knee injuries; however, the vehicle contact forces in the specified incident did not approach the level required to 1.) produce an injury mechanism consistent with the claimed injuries and 2.) generate forces high enough to receive any injury at all. In other words, we may not dispute that the claimant has the injuries, but may very well question whether they could have been received during this event.

Using a biomechanical-oriented accident reconstruction and injury mechanism analysis can often produce a strong defense against these claimed injuries. Examining accident reports, medical files, damage appraisals, photos, and so on, a biomechanical expert will formulate an opinion/report as to whether there were forces sufficient to produce an injury mechanism that could cause the alleged injuries.

Elements of a LSI Analysis

Photographs: Ideally, all vehicles, showing the areas of contact-digital and paper photos. If possible, be sure to "walk the clock," meaning that while circling the vehicle, take photographs from all sides, not just the impact area. Photograph the bumper shock isolators, if so equipped. Photograph the interior, airbags, the dashboard, and the steering wheel. Several years later at trial there may be claims that secondary impacts "pushed into vehicle ahead" and so on. Photo documentation now can help refute such future claims.

Medical reports: Obtain the claimant's (and other occupants if possible).

Damage/repair appraisals: For each vehicle involved.

Depositions: Make sure the right questions are included.

Police reports: If any

Witness accounts: If any

Other occupants? Injuries?  Seating Location(s)?

Supplemental restraint (airbag) diagnostic module data (Black Box): If available.

When equipped with this information, we can hope to achieve an accurate determination of the range of speed at impact.  Calculate the "g" or acceleration forces on the subject vehicle and occupants. Compare the alleged injuries to the force (based on the laws of physics) present in this collision. Then scientifically determine whether there was sufficient force to create the "injury mechanism" necessary to cause the alleged injuries.

When presented with a description of the incident, the biomechanical engineer will analyze certain information. Typical reports to be reviewed are as follows:

• Police Accident Report
• Insurers Investigation Report
• Medical records
• Deposition transcripts
• Plaintiff's Answers to Defendant's Interrogatories
• Color photographs of incident scene, including both vehicles
• Auto body shop repair estimates
• Auto repair report
• Insurance invoices

To see a list of typical injuries claimed in low-speed auto accidents, click on "Next."

In addition, a biomechanics firm may take into account other information and materials based on company-specific protocols. This may include, for example, reports from the Insurance Institute for Highway Safety (IIHS) about low-speed crash tests at 5 mile per hour.  

Vehicle Damage and Crash Severity

The vehicle photographs are relevant in the consideration and analysis of the physical forces in the subject incident. Let's suppose that a review of the photographs of the plaintiff's vehicle often reveals only minor cosmetic damage and no structural damage. Inspection of the bumper shock isolators can then reveal impact forces.

Kinematic Analysis

Using the claimant's age, height, weight, seat belt usage, and the laws of physics, the biomechanical engineer calculates relative motion of the claimant and the vehicle at the time of impact. According to the laws of physics, when a vehicle is contacted in the rear, it will move forward, if there is enough energy. If there was forward motion of the vehicle, then the process would result in a rearward motion of all occupants' bodies relative to the interior of the vehicle. This would then cause all occupants' bodies to load into the seat and seat back structure, thus coupling their motion to the accelerating vehicle. The low accelerations resulting from these collisions would cause little or no rebound of occupants' bodies away from the seat back. Certainly, any minimal rebound energy is well within the range of protection of the available seat belt.

With those facts in hand, the biomechanical engineer would review the claimed injuries one by one addressing whether there were sufficient forces present in this event to have produced injury mechanisms for each of the alleged injuries.

The final opinions are based upon an objective scientific analysis of the subject incident. Accepted scientific principles are used to determine the crash severity and occupant kinematics, thereby enabling an evaluation of injury mechanisms, if any. Subjective findings, such as verbal medical history, may be useful in injury diagnosis, but they can not be solely relied upon in causally relating a reported injury to a specific event. This is the job for a biomechanical engineer enlisted by the insurer.

Each case and injury will be different. However, the laws of physics are constant and apply identically to every collision. With a sufficient amount of the information outlined above an accident reconstruction can be completed and an objective biomechanical analysis can determine whether there was an injury mechanism present to cause the claimed injuries and to support those findings in a court of law.

ARCCA, Inc. is a nationwide forensic engineering firm specializing in accident reconstruction, injury causation/biomechanical engineering and product failure/subrogation analysis. www.ARCCA.com