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Objective: The goal of the study was to develop experimental chest loading conditions that would cause up to Abbreviated Injury Scale (AIS) 2 chest injuries in elderly occupants in moderate-speed frontal crashes. The new set of experimental data was also intended to be used in the benchmark of existing thoracic injury criteria in lower-speed collision conditions.Methods: Six male elderly (age >63) postmortem human subjects (PMHS) were exposed to a 35 km/h (nominal) frontal sled impact. The test fixture consisted of a rigid seat, rigid footrest, and cable seat back. Two restraint conditions (A and B) were compared. Occupants were restrained by a force-limited (2.5 kN [A] and 2 kN [B]) seat belt and a preinflated (16 kPa [A] and 11 kPa [B]; airbag). Condition B also incorporated increased seat friction. Matching sled tests were carried out with the THOR-M dummy. Infra-red telescoping rod for the assessment of chest compression (IRTRACC) readings were used to compute chest injury risk. PMHSs were exposed to a posttest injury assessment. Tests were carried out in 2 stages, using the outcome of the first one combined with a parametric study using the THUMS model to adjust the test conditions in the second. All procedures were approved by the relevant ethics board.Results: Restraint condition A resulted in an unexpected high number of rib fractures (fx; 10, 14, 15 fx). Under condition B, the adjustment of the relative airbag/occupant position combined with a lower airbag pressure and lower seat belt load limit resulted in a reduced pelvic excursion (85 vs. 110 mm), increased torso pitch and a substantially lower number of rib fractures (1, 0, 4 fx) as intended.Conclusions: The predicted risk of rib fractures provided by the THOR dummy using the Cmax and PC Score injury criteria were lower than the actual injuries observed in the PMHS tests (especially in restraint condition A). However, the THOR dummy was capable of discriminating between the 2 restraint scenarios. Similar results were obtained in the parametric study with the THUMS model. [ABSTRACT FROM AUTHOR]

• NASS CDS data have been augmented with information on each vehicle's pre-tensioner and force limiter seat belt systems. • Multivariate logistic regression models were developed to assess the real-world effectiveness of advanced seat belt systems. • The presence of load-limiting devices was significantly associated with preventing fatal injuries. • The use of low-force load-limiting devices (<4.5 kN) was associated with reducing the risk of whole-body AIS3+ injuries. • Slight deviations from the pure frontal direction in the collision resulted in an increased risk of AIS2+ and AIS3+ injuries. Contemporary research has pointed out that while newer cars are contributing to the decrease of AIS2+ and AIS3+ injuries in several body regions, this effect is not shown for thoracic injuries like rib or sternal fractures. The objective of this study is to assess the effectiveness of advanced seat belt systems incorporating pre-tensioners and load limiters in the prevention of fatal, AIS2+ and AIS3+ injuries overall and then focus only on the head-face-neck and thoracic areas. Data from the NASS CDS database between 2000 and 2015 was augmented with specific vehicle information taken from NHTSA's NCAP tests to identify the characteristics of the seat belt of each vehicle involved in a collision. Multivariate logistic regressions were developed to assess the likelihood of injuries for belted front seat occupants in frontal impacts. The presence of pre-tensioners and load limiters with a low load limiter (<4.5 kN) was significantly associated with a decreased risk of fatal and AIS3+ in the whole body (OR = 0.31 (p < 0.05) and OR = 0.70 (p < 0.1)), while high load limiters were significant in the prevention of fatal injuries (OR = 0.42). These effects should be considered always in combination with the delta-v of the collision, as the interaction term between delta-v and advanced seat belt features was significant. In the crashes considered, the model predicted a higher risk of injury for women compared to men, controlling for other occupant and crash factors. Impacts with a slightly oblique component increased the risk of injury compared to pure frontal impacts. After controlling for the presence of pre-tensioners and load limiters, the vehicle model year variable was found to be insignificant in any of the regression models. This study shows that the real-world effectiveness of advanced seat belts still requires further analysis. Other effects like age or impact direction might be more influential in the injury outcome than these seat belt features. [ABSTRACT FROM AUTHOR]