Application of the subjective vertical–horizontal-conflict physiological motion sickness model to the field trials of contemporary vessels

Subjective-vertical conflict theory (Bles et al., 1998) postulates that all motion sickness provoking situations are characterized by a condition in which the vertical (gravity) sensed by the visual, vestibular and non-vestibular proprioceptors are at variance with the subjective (expected) vertical. SV-conflict models have successfully been used by Bos and Bles (2000), Verveniotis and Turan (2002b), Bos et al. (2002a) and Dallinga et al. (2002), to predict motion sickness of passenger ferries. However, considering the prevalence of significantly high level of horizontal acceleration aboard contemporary vessels, Khalid et al. (in press) proposed a further elaboration of a physiological (subjective-vertical–horizontal, SVH-conflict) model that explicitly incorporates the effects of horizontal accelerations. They hypothesized that the explanation of motion sickness variability may improve, by considering the combined effects of subjective vertical as well as subjective horizontal conflicts (difference between the sensed and 'expected' horizontal accelerations). This paper briefly presents the SVH-conflict model and demonstrates its application to 68 field trials of 10 different vessels. Percentages of seasick passengers, observed during the field trials, are statistically compared with physiological and descriptive (O’Hanlon and McCauley, 1974; ISO 2631-1, 1997) motion sickness models. In general, SVH-conflict is statistically outperforming the descriptive models and displaying improvement over the SV-conflict model.