Thoracic deformation response of pedestrians resulting from vehicle impact

Abstract

Postmortem human surrogates were positioned in a mid-gait pedestrian stance and struck laterally by a vehicle buck traveling at a speed of 40 km/h. Three tests were performed with a midsize passenger car buck, and two tests were performed with a sport utility vehicle buck. Each subject was equipped with two chest bands positioned at the level of the 4th and 8th ribs to measure changes in cross- sectional shape of the upper and lower chest. Absolute and normalized deflection, deflection velocity, and the viscous criterion were calculated for frontal and lateral dimensions. Deformation-time histories were generated for the midsagittal and midcoronal chords passing through the chest centroid as well as for off-centroidal chords. Despite being positioned initially perpendicular to the impacting vehicle, the subjects exhibited maximal loading of the anterolateral thorax. Therefore, a polar coordinate system was centered at the initial chest centroid position and radial changes of chest deformation were recorded. Though similar in application to the standard frontal and lateral impact analyses, this radial technique appears better suited to the pedestrian environment in that it identifies a single position of maximum deformation rather than tracking only preselected locations. Maximum deformation levels and rates of deformation indicated that peak values were in the range of those resulting from traditional frontal and lateral sled tests as well as frontal and side dummy certification tests. Provided that consideration is given to the oblique nature of the loading, the results indicate that conventional injury criteria and biofidelity requirements used for occupant dummies could be reasonably applied to the pedestrian environment.