RELATIONSHIPS BETWEEN OCCUPANT MOTION AND SEAT CHARACTERISTICS IN LOW-SPEED REAR IMPACTS

Sled tests were conducted with some seats that had different characteristics to understand the relationships between occupant motion and seat characteristics in low-speed rear impacts. The position of the head restraint and the stiffness distribution of the seatback were selected as parameters expressing seat characteristics. Volunteers' cervical vertebral motions were photographed with an x-ray cineradiographic system at a speed of 90 frames/sec as well as the visible motions of the dummies and volunteers. The results indicated that the head restraint position and upper seatback stiffness influenced occupant motions. Correlations between visible motions, such as ramping-up, retraction, and extension were also analyzed, and some correlations were found.