Optimizing the Rear Seat Environment for Older Children, Adults, and Infants

Abstract

Objective: Our recent rear seat safety research found that more-forward and higher lap belt anchorage locations and much shorter and stiffer seat cushions can improve the protection of older children from 6 to 12 years old who are using the vehicle belt without a booster. The objective of this study was to investigate whether the optimal rear seat restraint systems for adults and infants are consistent with those for older children.Methods: We conducted sensitivity analyses and design optimizations for adults and for infants in a rear-facing child restraint system (CRS) using a set of MADYMO models, an automated simulation framework, and occupant belt-fit and posture prediction models from our previous studies. A series of 12 sled tests was also used to validate the computational models.Results: The optimal belt anchorage locations and the seat cushion length for older children, adults, and rear-facing CRS-seated infants conflict with each other. In particular, more-forward lap belt anchorage locations that prevent submarining for older children would reduce the protection to both adults and CRS-seated infants, although the protection is still acceptable based on regulated injury criteria. A shorter seat cushion could provide optimal protection to older children and adults but would significantly increase the CRS rotation.Conclusions: The findings of this study suggested that adaptive/adjustable restraint systems are necessary to simultaneously improve the rear seat occupant protection for all age groups.

Does unbelted safety requirement affect protection for belted occupants?

“…To enable the large-scale sensitivity analyses and design optimizations, an automated computer program was developed using a combination of LS-DYNA, Mode-FRONTIER, and other in-house programs to vary the restraint configurations and conduct injury risk evaluations. Similar work has been done previously in optimizing restraint system for occupants with various sizes (Hu et al 2013a(Hu et al , 2013b.…”

“…In recent years, computational ATD models have been routinely used for optimizing occupant compartments and restraint systems in vehicle safety designs (Forsberg and Nilsson 2006;Gu et al 2013;Hu et al 2013aHu et al , 2013bKim and Jeong 2010). More in-depth investigations on optimization methods and their efficacy in optimizing occupant restraints have also been performed (Deb et al 2002;Yang et al 2005).…”

Optimizing Seat Belt and Airbag Designs for Rear Seat Occupant Protection in Frontal Crashes

“…Without a booster, the initial slouching posture of the 6 YO ATD would likely induce submarining even with the advanced restraints. Previous computational studies (Hu et al, 2013a;Hu et al, 2013b) have shown that reducing the length of the seat cushion may be a possible solution to reduce the submarining risk for the 6 YO without boosters. However, a short seat cushion may compromise the protection to adult occupants and infants in child seats (Hu et al, 2013a).…”

“…Previous computational studies (Hu et al, 2013a;Hu et al, 2013b) have shown that reducing the length of the seat cushion may be a possible solution to reduce the submarining risk for the 6 YO without boosters. However, a short seat cushion may compromise the protection to adult occupants and infants in child seats (Hu et al, 2013a). Further investigations are necessary to determine the best ways to reduce submarining risks for children smaller than adults who sit on the vehicle seat without a booster.…”

“…Tests using postmortem-human-subjects (PMHS) have also been conducted by the same group (Forman et al, 2009), and the results suggested that 3-point seat belts with progressive load-limiters and pre-tensioners can improve the kinematics (increase forward torso rotation) of rear seat occupants with reduced belt load and chest acceleration. Hu et al (2012b;2013a;2013b) conducted several series of frontal sled tests and computational simulations focusing on optimizing the rear seat and belt geometries for 6-12 year-old (YO) children, mid-size adults, and infants in rear-facing child restraints. It was found that the optimal belt anchorage locations and seat cushion length and stiffness were significantly different for occupants with different sizes, suggesting that adaptive/adjustable restraint systems may be necessary to simultaneously improve the rear seat occupant field performance for all age groups.…”