Motion sickness with combined fore-aft and pitch oscillation: effect of phase and the visual scene.

BACKGROUND

The view ahead influences the motion sickness of car passengers but has been found to have little influence on the sickness caused by low frequency fore-and-aft oscillation. Acceleration and deceleration of vehicles is accompanied by pitch motions that may influence sickness.

HYPOTHESES

It was hypothesized that: (1) a visual scene would influence sickness caused by combined fore-and-aft and pitch oscillation; and (2) sickness would be dependent on the phase between the fore-and-aft oscillation and the pitch oscillation.

METHOD

While viewing one of three visual scenes (internal view, blindfold, or external view), 6 groups of 20 subjects were exposed for 30 min to 1 of 2 motions (in-phase or out-of-phase combinations of 0.1 Hz fore-and-aft and pitch oscillation). The 0.1-Hz fore-and-aft oscillation at +/- 1.26 ms(-2) rms (displacement of +/- 3.18 m) was combined with +/- 3.69 degrees pitch oscillation either in phase (so the pitch increased acceleration in the plane of the seat to +/- 1.89 ms(-2)) or out of phase (to reduce acceleration to +/- 0.63 ms(-2)).

RESULTS

With both types of motion (in-phase and out-of-phase oscillation) there was significantly less sickness with an external view than with an internal view or a blindfold. There was evidence of an interaction between the effects of viewing condition and the effect of the phase between the fore-and-aft and the pitch oscillation consistent with blindfolded subjects experiencing less sickness when they experienced greater forces.

CONCLUSIONS

Motion sickness caused by combined fore-and-aft and pitch oscillation depends on both the visual scene and the phase between the fore-and-aft and pitch motions. The minimization of sickness arising from such motions should involve the optimization of both the visual environment and the phase.