Low Speed Rear End Impacts: Vehicle and Occupant Response


Low Speed Rear End Impacts: Vehicle and Occupant Response

Davis CG

Background:   There is a controversy regarding likelihood of injuries sustained when one car strikes another at a relatively low speed with little or no vehicle damage. Plaintiffs often claim injuries while defendants counterclaim that injuries could not have occurred with such a relatively minor impact.

Objective: To review the dynamics of low speed rear-end collisions resulting in little or no visible damage and to see if occupant injury can occur; also, to discuss diagnostic and treatment that may be helpful to the clinical practitioner.

Data Selection:   A medline search of low speed rear-end was conducted. Other articles and studies were reviewed that discuss low speed rear-end collisions and factors impacting the neuromusculoskeletal system relevant to clinical practitioners. Articles included were: human low speed rear-end tests, lab tests on cadavers, automotive engineering papers, and peer reviewed journal articles on whiplash. A few live animal and simulation studies were considered for the background of possible injury mechanism and vehicular deformation. Excluded were non rear-end collision and single case reports.

Data synthesis:   The data was studied to find a relationship between the resultant vehicle dynamics with occupant movement, biologic mechanisms of injury and the neurological mechanisms causing complaints. Data was also studied to investigate objective findings supporting subjective complaints.

Conclusion:   In low impact collisions, there are usually no skid marks, minor or no visible damage to the vehicle. There is a lack of relationship between occupant injury vehicle speed and/or damage. There does not appear to be an absolute speed or damage to a vehicle for a person to experience injury. Crash tests indicate a change of vehicle velocity of 4km/h (2.5 mph) may produce occupant symptoms. Vehicle damage may not occur until 14-15km/h (8.7 mph). Occupant soft tissue and joint injuries resulting from low speed vehicle collisions respond positively to afferent stimulation of mechanoreceptors. The diagnosis of the occupant injuries is reliant upon standard orthopedic neurological testing, the autonomic concomitant signs and qualitative sensory testing.

Key Indexing Terms: Cervical Spine; Whiplash Injury; Low Speed Collisions