Rear seat restraint system optimization for older children in frontal crashes.

OBJECTIVE Analyses of crash injury data have shown that injury risk increases when children transition from belt-positioning boosters to the vehicle seat belt alone. The objective of this study is to investigate how to improve the restraint environment for these children. METHODS A parametric analysis was conducted to investigate the effects of body size, seat belt anchorage locations, and rear seat design parameters on the injury risks in frontal crashes of children aged 6 to 12 years old using a newly developed parametric child anthropomorphic test dummy (ATD) model. Restraint design optimizations were also conducted to obtain ranges of optimal restraint system configurations that provide best protections for 6-, 9-, and 12-year-old children. RESULTS Simulation results showed that child body size was the dominant factor affecting outcome measures. In general, lower and more rearward D-rings (upper belt anchorages), higher and more forward lap belt anchorages, and shorter, stiffer, and thinner seat cushions were associated with improved restraint performance. In these simulations, children with smaller body sizes require more-forward D-rings, inboard anchors, and outboard anchor locations to avoid submarining. However, these anchorage locations increase head excursions relative to more-rearward anchorages. CONCLUSIONS The balance of reducing head and knee excursions and preventing submarining indicates that an optimization approach is necessary to improve protection for 6- to 12-year-old child occupants. The findings of this study provided design guidelines for future rear seat restraint system.