Historically, the observed seat belt usage rate for occupants has varied across a number of factors (e.g., primary or secondary use law, seat location, etc.). Of these factors, the age of the driver or occupant has been consistently noted as an important characteristic that is linked to the use of the seat belt. For example, the seat belt use rate for drivers and front seat passengers in the U.S. in 2002 was estimated to be over 70% for adults [1] but over 10% less for pre-teens [2] and teenagers [3], which are generally less than 60%. This discrepancy between younger age groups and adults has been reported in several states across the country [2-5]. Eby et al. [4] reported that individuals 4-15 years old, seated in the second and third rows, wore seat belts about 50% of the time in the left and right positions. In a separate four-state observational study of teenage and older occupants by Womack et al. [6], teen seat belt use in the back seats was only 10.9%. Together, these studies indicate pre-teen and teenagers wear seat belts less frequently than comparable adult cohorts, and that they will be even less likely to wear a seat belt when they are located in the back seat positions. Given the differences in anatomy, maturation, and behavioral patterns between adults and younger age groups, the handling and latching actions used by the different age groups could be factors that account for the differences in belt use rates. Previous research has shown that occupants handle the seat belt in various ways (e.g., grasping the seat belt webbing with their dominant limb, rotating the upper body during the fastening process) [7]. Some differences are a function of the vehicle design (location of seat belt retractor), and other differences are determined by the preference of the occupant. While these studies have documented how people grasp and transport the belts, there has been little quantitative analysis on the insertion of the latch plate (often called the tongue) into the buckle. Since younger individuals are less likely to use available seat belts, we were interested in determining whether younger individuals attempted to latch seat belts differently (e.g., using less force). In this study, we examined the human response capabilities of teens and adults (younger and older) during the fastening process. Specifically, this study examines the kinetics used by occupants involved in the fastening process of the seat belt-buckle. Based on well-known differences in the maturation and force control between children and adults [8], we hypothesized that teens would produce less overall force and have more variability in their response patterns.
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