Seat Belt Retractor Performance Evaluation in Rollover Crashes 2005-01-1702

For more than 20 years, field research and laboratory testing has consistently demonstrated that wearing a seat belt dramatically reduces the risk of occupant death or serious injury in motor vehicle crashes. Emergency-locking retractors (ELRs) are critical components of a seat belt assembly that engage and then lock, preventing additional webbing from leaving the retractor spool. Recent studies have raised concerns about the effectiveness of retractor locking mechanisms in multi-planar collisions, including rollovers. The chaotic and unrepeatable nature of real-world rollover crashes challenge simulated rollover testing. To date, there are no generally accepted and repeatable laboratory testing methods or test devices to assess seat belt retractor performance in the presence of multiple, simultaneous acceleration impulses.

This study examines a new effectiveness test, and related test device, to measure retractor performance in rollover type crashes. The tests simulate multiple, simultaneous accelerations in a repeatable manner with a free body mass loading the belt. The evaluation matrix includes multiple impact speeds, impact orientations and rotational speeds. This study describes the test device design, methodology, and results for a ball-in-cup emergency locking retractor sensing mechanism. This retractor performance evaluation provides a practical and repeatable diagnostic tool for controlled testing of emergency locking retractors in simulated rollover impacts. Tests results showed that, when subjected to simulated rollover conditions with ground impacts, the retractor remained locked.