The Influence of a Seat Track Load Limiter on Lumbar Spine Compression Forces in Relaxed, Reclined, and Upright Seating Positions: A Sled Test Study using THOR-50M

Automated vehicles come with the expectation of new, comfortable seating positions, in particular with seats moved rearward to increase legroom, and with reclined seatbacks and tilted seat pans for relaxing and sleeping. However, in a frontal crash the increased seat back angle can induce more severe compression forces in the lumbar spine. This research evaluates the influence of active and passive seat track load limiting on lumbar spine compression forces in frontal impacts for three seating positions using THOR-50M. The objective was to reduce the lumbar spine compression force for reclined occupants to a level similar to that of upright occupants, yet without increasing the levels of any variables measured in the European New Car Assessment Programme (Euro NCAP) assessments of adult occupant safety. The lumbar compression forces sustained in the reclined seat back positions were reduced effectively by the active seat track load limiter from 6 kN to the 4 kN levels observed for upright occupants. All other injury measures except for chest compression measured as Rmax were likewise reduced. Despite the limitations of a simplified set-up and the use of THOR-50M outside its validation regime, the active seat track load limiter appears to be an implementable and efficient engineering solution to a pressing real-world issue.