A Simulation Study on the Efficacy of Advanced Belt Restraints to Mitigate the Effects of Obesity for Rear-Seat Occupant Protection in Frontal Crashes

Abstract

Objective: Recent field data analyses have shown that the safety advantages of rear seats relative to the front seats have decreased in newer vehicles. Separately, the risks of certain injuries have been found to be higher for obese occupants. The objective of this study is to investigate the effects of advanced belt features on the protection of rear-seat occupants with a range of body mass index (BMI) in frontal crashes.Methods: Whole-body finite element human models with 4 BMI levels (25, 30, 35, and 40 kg/m 2 ) developed previously were used in this study. A total of 52 frontal crash simulations were conducted, including 4 simulations with a standard rear-seat, 3-point belt and 48 simulations with advanced belt features. The parameters varied in the simulations included BMI, load limit, anchor pretensioner, and lap belt routing relative to the pelvis. The injury measurements analyzed in this study included head and hip excursions, normalized chest deflection, and torso angle (defined as the angle between the hip-shoulder line and the vertical direction). Analyses of covariance were used to test the significance (P < .05) of the results.Results: Higher BMI was associated with greater head and hip excursions and larger normalized chest deflection. Higher belt routing increased the hip excursion and torso angle, which indicates a higher submarining risk, whereas the anchor pretensioner reduced hip excursion and torso angle. Lower load limits decreased the normalized chest deflection but increased the head excursion. Normalized chest deflection had a positive correlation with maximum torso angle. Occupants with higher BMI have to use higher load limits to reach head excursions similar to those in lower BMI occupants.Discussion and Conclusion: The simulation results suggest that optimizing load limiter and adding pretensioner(s) can reduce injury risks associated with obesity, but conflicting effects on head and chest injuries were observed. This study demonstrated the feasibility and importance of using human models to investigate protection for occupants with various BMI levels. A seat belt system capable of adapting to occupant size and body shape will improve protection for obese occupants in rear seats.

A parametric ribcage geometry model accounting for variations among the adult population

“…Details about the RBF-TPS have been previous described by (Donato and Belongie, 2002). Similar methods have been used to build parametric FE models previously (Klein et al, 2015;Ma et al, 2011;Wang et al, 2015).…”

Optimizing Occupant Restraint Systems for Tactical Vehicles in Frontal Crashes

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Impact Response Comparison Between Parametric Human Models and Postmortem Human Subjects with a Wide Range of Obesity Levels

“…An advanced seat belt system with shoulder or lap pretensioner can effectively reduce the body excursions, and a seat belt load limiter can reduce the chest deflection at the cost of increasing the head excursion in severe frontal crashes. Therefore, load limits that can adapt to occupants with different obesity levels are needed to protect the head and chest at the same time .…”