Effects of Recline on Passenger Posture and Belt Fit

Abstract

Highly reclined postures may be common among passengers in future automated vehicles. Detailed data on posture and seat belt fit in such postures is needed to design appropriate seats and restraints but is not currently available. A laboratory study was conducted in which 24 men and women with a wide range of body size were measured in a typical front vehicle seat at seat back angles of 23, 33, 43, and 53 degrees. Data were gathered with and without a sitter-adjusted headrest. Posture was characterized by the locations of skeletal joint centers estimated from digitized surface landmarks. Regression analysis demonstrated that lumbar spine flexion decreased with increasing recline, and the differences between supported and unsupported head and neck postures were greater at larger recline angles. The lap portion of the three-point belt was more rearward relative to the pelvis in more-reclined postures, and the torso portion crossed the clavicle closer to the midline of the body. The regression models developed in this study will be useful for the design and assessment of seats and restraints for future vehicles.