Abstract
A forward‑leaning occupant posture reduces the distance to nearby structures (e.g., dashboard, steering wheel, or seat ahead), leading to non-optimal utilization of the available ride-down distance in the case of a frontal crash. This study examined whether forward‑leaning occupants can be repositioned using reversible belt‑tensioning during constant‑speed travel at 70 km/h and controlled braking, and whether responses differ by belt system or sex. Sixteen volunteers experienced both conditions in upright (25°) and forward‑leaning (−15°) postures using Belt‑in‑Seat (BIS) and B‑post belt geometries. Reversible pre‑tensioning (250 N or 500 N), triggered during constant speed or at braking onset, was used to reposition forward‑leaning occupants, with upper‑body kinematics and muscle activity recorded.
Reversible pre‑tensioning (250 N or 500 N), triggered during constant speed or at braking onset , was used to reposition forward‑leaning occupants, with upper‑body kinematics and muscle activity recorded. Low‑level pre‑tensioning returned most volunteers to their preferred upright posture during constant‑speed travel, though elevated muscle tension limited or delayed repositioning in some individuals. During braking, tested tension levels did not fully reposition the average volunteer.
Forward‑leaning volunteers began with the upper torso positioned ~300 mm forward of upright. During constant‑speed repositioning with the B‑post belt, the upper torso returned to ~50 mm forward of preferred seating within 500 ms. The BIS geometry achieved near‑complete repositioning, whereas simultaneous braking slowed the response and left the upper torso ~90 mm forward. No significant sex‑based differences were observed. Flexor muscles were more active than extensors during repositioning, indicating resistance to the imposed movement.
This work provides a dataset on volunteer repositioning from forward‑leaning postures at 70 km/h, including scenarios involving controlled braking, suitable for Human Body Model evaluation.