Repositioning an Off-Shoulder Seatbelt Using Seatbelt Pretensioners

Paper i proceeding, 2025

Front-seat passengers have been reported to occasionally wear the seatbelt off-shoulder. Whether pretensioners can restore the belt’s correct position (and optimize its protective ability in a crash) has not yet been studied; nor has its effect on the occupant’s head kinematics. This study sought to address these gaps. Volunteer tests examined seatbelt repositioning possibilities and the influence of seatbelt-to-seat geometry and body shape. ATD sled tests compared electrical pre-pretensioners and pyrotechnical pretensioners and assessed the effect of a crash pulse on seatbelt repositioning. Mathematical simulations analysed in-crash occupant kinematics with a fully and partially repositioned shoulder belt. The results show that, while the seatbelt could be fully repositioned in most situations tested, the electrical pre-pretensioner achieved full repositioning more often than the pyrotechnical pretensioner. In a sled test with a full-frontal crash pulse of 40 km/h, the repositioning ability was not affected, and the occupant kinematics with a fully repositioned belt were comparable to those with a belt that was correctly positioned originally (reference test). This study concludes that the seatbelt-to-seat geometry is the most important factor for seatbelt repositioning and that a fully repositioned seatbelt maintains occupant head kinematics similar to those observed with a nominal seatbelt fit.