The Seated Soldier Study: Posture and Body Shape in Vehicle Seats

Abstract

Designing vehicles for the safety and comfort of occupants requires detailed information on posture, position, and body shape. This report presents the methods and results of a study of soldiers as drivers and passengers in vehicle seats. A total of 257 male and 53 female soldiers were measured at three Army posts while minimally clad, wearing the Advanced Combat Uniform (ACU), with the addition of personal protective equipment (PPE), composed of the Improved Outer Tactical Vest (IOTV) and Advanced Combat Helmet (ACH), and with encumbrance (ENC) simulating the gear of either a rifleman or SAW-gunner. Standard anthropometric data, such as stature and body weight, were recorded. Participants were measured as either drivers or crew. Five driver workstation configurations (packages) were produced in a vehicle mockup by varying the steering wheel position relative to the pedals. The participants adjusted the seat to obtain a comfortable driving posture. The three-dimensional locations of body landmarks were measured using a FARO Arm coordinate digitizer. In the crew conditions, the experimenters varied the seat height and back angle and conditions included a simulated protective footrest. A whole-body laser scanner was used to record body shape at each garb level. A statistical analysis of the body landmark data was conducted to obtain models to predict soldier posture as a function of vehicle factors, such as seat height, and soldier attributes, such as stature, and garb level (ACU, PPE, or ENC). Driver posture was strongly affected by steering wheel position and crew posture by seat back angle. Adding PPE and ENC resulted in more-upright postures, but the effects on spine posture were small. Statistical models of both seated and standing body shape were developed from the scan data, including the effects of PPE and ENC on space claim. The effects of ENC on space claim were largely independent of body size. The results of this study have broad applicability for the design and assessment of military vehicles.