Overview of Seat Design Changes and Performance

NHTSA published an ANPRM to update FMVSS 207. This study was conducted to provide a historical background on seat designs and test performance based on literature review and updated prior work. Seat designs have continuously evolved, including changes in seat and head restraint geometry. Most seats today have a conventional design, with D-ring on the B-pillar. Seatbacks have become taller; most are now designed with an open perimeter frame allowing the occupant to pocket while offering load-limiting features. Head restraint have become bulkier cushioning the head early during ride-down. Various methods are used to evaluate seats including quasi-static pull tests, and dynamic sled tests. The pull-tests were conducted with a body block simulating upper torso loading; the results showed a continuous increase in rearward loading strength. Seat strength averaged 10,902 in-lbs in seats with model year (MY) 1989 and older and 28,716 in-lb in MY 2010+, decreasing dynamic seatback rotation. Despite these change, occupant biomechanical responses obtained from 40 km/h rear sled tests were similar and well below injury thresholds. Chest 3ms averaged 14.6  4.6g with 1990-1999 MY- and 15.7  2.4g in 2010+ MY seats; these peaks occurred prior to maximum seatback deflection. Head restraint properties have also changed, resulting in better scoring performance in the IIHS 16 km/h rear sled tests. This study underlined needs to use various methods to evaluate seats, including quasi-static pull tests to assess ultimate strength, low speed sled tests to assess whiplash protection and high-speed sled tests to assess serious injury potentials.