Thoracic Responses of Rear-Seated Midsized Male Surrogates during Frontal Sled Tests

The purpose of this study was to evaluate the thoracic responses of the 50th-percenitle male Hybrid III, THOR, and post mortem human surrogates (PMHS) in the rear seat during frontal sled tests using conventional and advanced restraints in multiple vehicle environments. Twenty-one sled tests were conducted using the Hybrid III and THOR in seven vehicle bucks, and 12 PMHS sled tests were performed using four vehicle bucks. Trends in chest deflections between vehicles and restraint conditions were compared between surrogates. The Hybrid III and THOR thoracic injury risk predictions were compared to the thoracic skeletal damage observed during the PMHS tests. The Hybrid III chest deflections were statistically significantly greater for vehicles equipped with conventional restraints compared to those equipped with advanced restraints. The THOR chest deflections generally followed this trend, but the differences between restraint types were not statistically significant. Hence, the THOR thoracic response and injury predictions might be less sensitive to the presence of advanced restraints. The PMHS sustained lower chest deflections and less damage, on average for the vehicles equipped with advanced restraints. However, this outcome was confounded by PMHS variability, the effect of submarining on thoracic response, and other design differences between vehicles, leading to no statistically significant difference in chest deflection between vehicles with and without advanced restraints. All PMHS sustained at least nine rib fractures regardless of restraint condition, so it was difficult to assess the accuracy of the THOR and Hybrid III injury risk predictions. However, both ATDs accurately predicted a high injury risk for the vehicle that resulted in the most severe PMHS damage. These results support previous studies that suggest the implementation of advanced restraints may reduce injury risk in the rear seat. However, the results also suggest that other vehicle characteristics, apart from restraint type, influence thoracic injury outcomes in the rear seat.