Visual field effects on motion sickness in cars

Background. It is commonly assumed that car passengers who suffer from motion sickness will benefit from being able to see the road ahead. Hypothesis: it was hypothesized that variations in the external view (including restrictions to forward view and the provision of an artificial real-time video view) would affect the development of sickness during a 30-min suburban car journey. Method: Motion sickness was investigated in 4 experiments using 15 different conditions, with 20 subjects in each condition. The conditions involved artificial restrictions to view, restrictions arising from different seating positions, and the provision of a video view of the road ahead. Subjects provided ratings of motion sickness at 1-min intervals during the 30-min journey. The motion sickness susceptibility of subjects was matched between groups of subjects and the car motions were measured in three axes to determine whether the motion conditions were similar across conditions within each experiment. Results: Absence of a visual field (blindfolded) resulted in similar sickness to that with no external forward view (with or without a side view). A wide or narrow forward view (with or without a side view) reduced sickness. For the conditions of these experiments, seating position did not significantly affect sickness. The provision of a real-time video view of the road ahead did not reduce motion sickness. There was circumstantial evidence that horizontal acceleration at frequencies below 0.1 Hz contributed to sickness. Conclusions: It is concluded that sickness in cars is dependent on the visual scene. The minimization of sickness by the provision of visual information requires improved understanding of those factors that combine to cause and suppress sickness.