The posture, pressure and subjective responses of forty subjects (20 male, 20 female) were measured during two highway drives. Four video cameras were used to measure targets on each subject in addition to measuring EMG and pressure in the seat cushion and the seat back using pressure mats. Subjective questions were asked at specific time intervals or if the subject adjusted the seat or indicated they were feeling uncomfortable. The goal of this research was to compare the objective measurements to the subjective comfort responses of the subjects. In this report we describe the posture of the subjects during two different highway drive tests. During the fixed back drive, the seatback angle was controlled at a 15o or 30o back angle, in random order, with subjects able to control all adjustments on the 12-way power seats except back angle. During the free comfort drive, subjects had full control over all of the 12 adjustments (6-way power seat, 4-way lumbar support, 2-way back angle). We found that compared to the SAE seat design template, Oscar, all subjects sat with their hip joints significantly forward of the H-point and that the point of maximum deflection (D-point) for the subjects was further forward and with less penetration than that of the design template. Both males and females sat with similar torso-thigh angles as that of the design template, but males sat with a more reclined posture than females and with larger elbow angles. Compared to the design knee angle, both males and females were significantly less than that of Oscar, with males having an even smaller angle than females. Most males had the seat at the full rear-ward position, which was probably a factor in their knee angle. The reclined (30o) seatback angle resulted in the most upright posture, but we strongly suspect that this was maintained with significant muscle activity in order to position the back and head to operate the vehicle.
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