Trains are generally thought to be relatively safe for those prone to motion sickness, though tilting-type cars are sometimes said to cause such nausea. However, the actual conditions of motion sickness occurrence and the vibration characteristics affecting it have not been satisfactorily clarified. A survey of about 4,000 passengers was therefore conducted on special express trains running throughout Japan. To collect data under a variety of running conditions, the survey was conducted on a total of 52 trains on eight sections and 14 vehicle types (including eight types of tilting car). At the same time, the vibration characteristics of these trains were measured.
The survey showed that the ratio of passengers experiencing motion sickness was higher in tilting-type cars, with an average ratio of about 1.3% compared to 0.3% in non-tilting cars. To investigate the vibration characteristics affecting motion sickness, a large number of prototype filters (i.e. band-pass filters) were made to analyze the relationship between low-frequency vibration and passenger sickness (Fig. 1). The analysis showed that, of longitudinal, lateral, and vertical vibration, lateral vibration causes sickness most, with the peak of the correlation at around 0.25 to 0.32 Hz. That is, trains with vibration elements in this range experience a higher rate of passenger nausea. Using the above findings, a filter (frequency weighting curve) to evaluate the influence of train-sickness was developed by considering the correlation coefficient in the figure as the weighting for each frequency (Fig. 2). By correcting the lateral vibration data of each train with this filter to determine the cumulative value over a certain time period, it becomes possible to forecast the ratio of passengers who will experience motion sickness.