Motion sickness occurence in public road transport

The purpose of the research conducted in this thesis was to increase understanding concerning the aetiology of motion sickness in public road transport. The research examines the occurrence of motion sickness amongst vehicle passengers to determine its dependence on the characteristics of vehicle motion. Other factors in the immediate environment which may influence the development of sickness and the behaviour and disposition of passengers were also investigated.A questionnaire survey of 3,256 coach travellers was conducted over 56 private hire coach journeys. Information on passenger characteristics, travel regularity, activity during travel, use of anti-motion sickness drugs and self-reported motion sickness susceptibility was collected. Measurements of vehicle motion were made on all journeys yielding over 110 hours of coach motion data from 17 drivers. Details of the travel environment (visibility, temperature and seating) were also recorded.Overall, 28.4% of passengers reported feeling ill, 12.8% reported nausea and 1.7% reported vomiting during coach travel. Passenger motion sickness increased with increased exposure to low frequency (below 0.5 Hz) lateral and, to a lesser extent, fore-and-aft coach motion. Such motions mainly result from the driving behaviour of individual drivers who, as a consequence, are implicated in coach motion sickness occurrence. Motion in other axes correlated less well with sickness although there was some inter-correlation between axes. Sickness levels were greater for drivers who averaged higher magnitudes of lateral and fore-and-aft vehicle motion. Nausea occurrence was greater on routes classified as being predominantly cross-country where magnitudes of lateral vehicle motion were significantly higher. Lateral motion and consequent sickness increased from the front to the rear of each vehicle. No significant differences in sickness were found between the nine different vehicles used in the study. Travel sickness decreased with increasing passenger age and greater travel experience. Females were more likely to feel ill during coach travel than males by a ratio of four to three. Poor forward visibility was associated with increased sickness. Passenger illness occurrence was approximately three times higher for passengers with no view of the road ahead than for passengers with good forward visibility, although vehicle motion was found to be more influential than visual information in determining sickness. Illness ratings differed as a function of travel activity. No clear relationships were found between the occurrence of travel sickness and temperature, food consumption or time of travel.Findings were broadly consistent with extant theories of motion sickness, although no one theory provided a complete and satisfactory explanation of the data. The pattern of sickness responses suggested: (i) habituation through greater travel regularity may occur independently of reductions in travel sickness occurring with age; (ii) habituation through greater travel regularity may be related to the use of visual information by experienced passengers in addition to familiarity with the motion experienced; (iii) the incidence of travel sickness could be significantly reduced, although not eliminated by improving the external forward visibility afforded to passengers, (iv) Whilst motion exposure and vision are important factors in the aetiology of motion sickness, the most reliable predictors of sickness were found to be previous susceptibility, travel experience and age.