EXPERIMENTAL AND FIELD ACCIDENT ANALYSIS STUDY OF FACTORS EFFECTING REAR SEATED CHILD OCCUPANT INJURY RISK AND SAFETY IN REAR IMPACTS

摘要

Understanding of parameters influencing injury risk levels of rear seated children in rear impacts are needed to improve designs and reliability of child restraint protection. In this study, a series of "multi-variable" rear-impact crash tests were conducted to examine several key variables, such as front seat inertial resistance and yield, which affect rear child injury risks. Field accident rear child injury cases involving fatal and/or severe injury to the child were also studied for comparison with experimental results. In some cases it was noted that front seat components, such as seat adjusters, could "fail" and allow a sudden lack of inertial resistance to the front occupant, resulting in a dangerous violation of the rear child space. A quasi-static (QS) seat test concept was used for measures of front seat strength/yield performance and reliability of minimizing rear child occupant space intrusion. Four age groups of rear-seated child surrogates seated behind both the stronger "belt-integrated-seat" (BIS) systems and the more yielding "non-belt-integrated" (NBI) seats were experimentally evaluated for child injury risk based on a wide range of variables. Earlier studies reviewed "multi-variable" child injury risk findings for the 3 and 6 year-old H-III surrogates in various child restraints. This study focuses mainly on "multi-variable" testing related to rear impact injury risk of the 12-month CRABI, seated in "forward facing child seats", and the 6-month CRABI seated in "rear facing child seats". Variables studied included: differences between the stronger BIS designs and the less strong NBI type front seats; Effects of front occupant size differences; Effects of impact severity levels; Differences of child restraint systems; and other factors such as Rear cargo intrusion. The results show that, among other things, increased "front seat yield" is a key factor that relates to increases in the injury risks of the rear-seated child in rear impacts. In addition, the study shows that stronger seat designs, like the BIS types, tend to provide a safer environment for the rear child in rear impacts than the NBI seats. Also, the study showed that needed optimum levels of front seat strength and rearward "yield" resistance, can be compromised and render the seat as an "unreliable" safety device if seat components "fail" in a sudden and unpredictable manner. Suggestions are made to more realistically test for the seat component failure issue. Finally, the dynamic crash test "multi-variable" child "injury" measures, and test results, are presented for the 4 child groups and are compared to actual cases studied.