Small Occupant Neck Injury Biomechanics in Frontal Crash: A Study to Address the Variation in Restraint Performance with a Conventional 3-Point Single Loop Belt System

The seatbelt is the primary restraint device that increases the level of occupant protection in a frontal crash. The belt performance is enhanced by the supplemental restraint provided by the airbag; seat and knee bolster working in combination with this primary restraining device. Small occupants are vulnerable to upper neck injuries when seated very close to the steering wheel. A lot of research and data availability for this situation ultimately led to the development of countermeasures capable of reducing upper neck loading. However, no data or research is available on the lower neck dynamic response of a small occupant primarily a 5th percentile female seated away from the steering wheel.

MADYMO (Mathematical Dynamic Modeling), a biodynamic code is employed to validate a standard NHTSA (National Highway Traffic Safety Administration) frontal impact rigid barrier test with a 5th percentile ATD (Anthropomorphic Test Device) in the driver position. This validated model is utilized to understand the effect of the chest to steering wheel distance on the lower neck flexion values. This study demonstrates that with the conventional seatbelt system the occupant protection performance changes with a change in the chest to steering distance. Sensitivity analysis is employed to identify the most significant factor dictating the small occupant’s lower neck biomechanics.

The study shows that with an increase in distance between the chest to steering wheel, the lower neck flexion moment increase for a 5th percentile female when restrained by a conventional single loop seatbelt system. Analytical method in conjunction with computational simulations is used to explain the data trend.