In this study, we focused on two ride comfort phenomena relating to low-frequency motion. One is human body instability, which means the leaning of the pelvis and torso during cornering. The other is lateral human body shaking, which means the phenomenon of the occupant body shaken by the low-frequency roll vibrations of the vehicle body, and lateral and roll motion in antiphase are generated to head and thorax, and there is a trade-off between them.

For the reduction of lateral human body shaking, we optimised backrest bolster height and separation to minimise the transmission of excitation force from the seat to occupant upper body. For reducing driver body instability, we optimised cushion bolster shape/rigidity to enable thigh to exert greater muscular force as drivers maintain their postures by active muscular responses during cornering. For passengers, we increased cushion pad rigidity/damping capable of moderating the roll motion of pelvis passively and providing greater support to thorax for the reduction of passenger body instability.

The results of the laboratory and field studies showed that the prototype seat we developed achieved a significant reduction of the two phenomena simultaneously for both drivers and passengers