Is Acceleration a Valid Proxy for Injury Risk in Minimal Damage Traffic Crashes? A Comparative Review of Volunteer, ADL and Real-World Studies.

Paul S Nolet,Arthur C Croft,Vicki L Kristman,Michael D Freeman,Larry Nordhoff,Maurice P Zeegers

doi:10.3390/ijerph18062901

Abstract

Injury claims associated with minimal damage rear impact traffic crashes are often defended using a “biomechanical approach,” in which the occupant forces of the crash are compared to the forces of activities of daily living (ADLs), resulting in the conclusion that the risk of injury from the crash is the same as for ADLs. The purpose of the present investigation is to evaluate the scientific validity of the central operating premise of the biomechanical approach to injury causation; that occupant acceleration is a scientifically valid proxy for injury risk. Data were abstracted, pooled, and compared from three categories of published literature: (1) volunteer rear impact crash testing studies, (2) ADL studies, and (3) observational studies of real-world rear impacts. We compared the occupant accelerations of minimal or no damage (i.e., 3 to 11 kph speed change or “delta V”) rear impact crash tests to the accelerations described in 6 of the most commonly reported ADLs in the reviewed studies. As a final step, the injury risk observed in real world crashes was compared to the results of the pooled crash test and ADL analyses, controlling for delta V. The results of the analyses indicated that average peak linear and angular acceleration forces observed at the head during rear impact crash tests were typically at least several times greater than average forces observed during ADLs. In contrast, the injury risk of real-world minimal damage rear impact crashes was estimated to be at least 2000 times greater than for any ADL. The results of our analysis indicate that the principle underlying the biomechanical injury causation approach, that occupant acceleration is a proxy for injury risk, is scientifically invalid. The biomechanical approach to injury causation in minimal damage crashes invariably results in the vast underestimation of the actual risk of such crashes, and should be discontinued as it is a scientifically invalid practice.

Highlights

PubMed and Google Scholar were searched for additional papers that described either rear impact crash testing of live human volunteers or reviews of such studies, and the reference lists from the papers were examined for studies that were not discovered in the initial search
Proceedings of international car crash conferences were searched for papers that were overlooked by the first 3 strategies, including the International Research Council on Biomechanics of Injury (IRCOBI), Society of Automotive
Our analysis demonstrates that the theoretical basis for the biomechanical injury causation approach is scientifically invalid

Summary

Introduction

Traffic injury claims after minimal damage crashes make up a substantial portion of civil litigation. A major point of contention in such litigation is injury causation, with claimants most commonly relying on the opinion of a treating clinician to establish the crash as the cause of persisting injury [1]. Insurer defendants often rely on an engineering or “biomechanical approach” as a basis for denying the causal nexus between the crash and the claimed injuries [2,3]. The approach most commonly utilizes a sequential multi-step process [4]: first, the collision is reconstructed for severity, quantified by the speed change or “delta V” (∆V) of the crash. The reconstructed delta V is compared to experimental

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