Safety Belt Fit, Comfort, and Contact Pressure based on Upper Anchorage Location and Seat Back Angle 2003-01-0954

A seat belt usability study was conducted to investigate factors associated with seat belt comfort and convenience related to shoulder belt contact pressure, shoulder belt fit, and seat belt upper anchorage location.

Two major objectives were addressed in this study: (1) Determine the shift in the contact pressure while changing the seat back angle and seat belt attachment points / B-pillar location by utilizing a body pressure measurement system; (2) Identify how seat belt contact pressure and fit affect users' subjective feeling of comfort.

Results from the statistical analysis shows that the seat belt contact pressure increases when the D-ring moves away from the driver in the fore-aft direction (X-axis) whereas height adjustment of the D-ring (Z-axis) is not statistically significant in terms of pressure distribution. Seat back angle, fore-aft (X-axis) and lateral (Y-axis) positions of the D-ring, and seat belt sub-segments are found to be statistically significant in the analysis of subjective comfort rating for contact pressure, which comply with the results obtained from the statistical analysis of mean contact pressure and distribution. In the analysis of subjective comfort rating on seat belt fit/routing, height adjustment of the D-ring is statistically significant. This indicates that the height adjustment for seat belt upper anchorage point is essential to achieve a better seat belt fit, help reduce the risk of seat belt rubbing the neck or slipping off the occupant's shoulder, given that it cannot improve the contact comfort by reducing the contact pressure.