Citation

Wood DP, Walsh DG. Int. J. Crashworthiness 2002; 7(3): 285-305.

Copyright

(Copyright © 2002, Informa - Taylor and Francis Group)

DOI

unavailable

PMID

unavailable

Abstract

Pedestrian Forward Projection occurs in collisions between children and the fronts of cars and between adults and the fronts of SUV's, LTV's and trucks. Real life collision data shows that the projection distances are longer in Forward Projection impacts than in other types of pedestrian collision. When a Forward Projection impact occurs the pedestrian initially after impact has a substantially upright attitude. The pedestrian topples to the ground and slides, bounces, and rolls before coming to rest. Previous analyses have modelled the pedestrian post impact behaviour as consisting of 3 stages: free flight, ground impacts; slide to rest. This paper models the first phase of the pedestrian post-impact movement as forward motion of an initially vertical rigid-body with the base (feet) in contact with the ground, this ground contact generating an overturning, toppling, moment. Analysis shows that the time to ground impact is typically 1.25 times greater than the "free fall" case. The projection distance to ground impact is correspondingly increased. The vertical velocity of the C.G. on ground impact is typically 96.5% of the "free fall" case. As a consequence, the retardation of the pedestrian movement due to the ground impact is less than for the "free fall" case. The longer time interval to ground impact and the lower vertical velocity on ground impact contribute to an increased total projection distance for the pedestrian compared with the "free fall" analysis. In short, by modelling the first phase as the forward motion of a rigid body whose base remains in contact with the ground an increased projection distance is obtained as has been found to occur in Real Life. Application of the overall model, which includes impact phase time duration and restitution effects data, to child and to adult impacts show a high degree of agreement with the Real Life data. Upper and lower limit equations are derived for impact speed estimates from projection distance for child and adult Forward Projection collisions.

Language: en