Seat Belt Latch Plate Design and Pretensioner Deployment Strategies Have Limited Effect on In- and Out-of-Position Occupants in High-Severity Rear-End Collisions

In rear-end collisions, the seatback provides primary occupant restraint during initial rearward motion of the occupant relative to the vehicle interior as the vehicle is accelerated forward by collision forces. When properly used, seat belts contribute to limiting occupant excursion and loading by working in concert with the seatback, as well as managing forward excursion on rebound after rear-end impacts. A lack of data evaluating the role of seat belt restraint component technology in limiting occupant motion and loading during high-severity rear-end impacts has been identified. This knowledge gap is particularly apparent for occupants who are not seated normally, in position, at the time of impact. Previous static pretensioner deployment tests suggest that different combinations of latch plate design and pretensioner deployment strategies might have different effects on occupant restraint. In this study, dynamic sled tests (40 km/h) were conducted to assess how various combinations of latch plate designs and pretensioner deployment strategies affect anthropomorphic test device (ATD) motion and loading in high-severity rear-end impacts. The results of these tests demonstrate that gross occupant motion is affected by pre-impact occupant position. Pretensioner deployment and latch plate design did not affect the loading or rearward excursion of out-of-position occupants during high-severity rear-end impacts. Latch plate design also did not influence rearward or forward head excursion of these occupants in the absence of pretensioner deployment. Maximum forward head excursion during rebound was modestly reduced with some pretensioner deployment strategies. The results of these tests demonstrate that differences in occupant loading were driven by the pre-impact ATD position and resulting seat interactions, rather than by pretensioner or latch plate contributions.