Ride comfort and motion sickness in tilting trains

Sammanfattning: This thesis presents a systematic study of human responses to different motions and strategies of car body tilt control regarding ride comfort, working/reading ability and motion sickness on high-speed tilting trains. Experiments with test subjects were performed in a tilting train on curved track as well as in a moving vehicle simulator. The study is multi-disciplinary, combining knowledge and methods from the fields of railway technology, human factors and vestibular science.The main experiment in a tilting train was performed with about 75 seated test subjects, mainly students from Linköping University, making three test runs. In total, these subjects participated in about 210 individual test rides, each with a duration of about 3 hours. Additional tests on comfort disturbances with pushbutton technique have been reported in the project. The simulator experiments used a total of about 75 subjects, making some 320 test rides each of about 30 minutes duration. Test motions consisted of combinations of horizontal (lateral) acceleration and roll acceleration, together with either roll or horizontal acceleration. Rate of change of horizontal acceleration (jerk) and roll velocity were of the same order of magnitude as in a tilting train environment, but horizontal acceleration alone was about half the magnitude. Horizontal and vertical vibrations from a tilting train were added to the test motions, and train seats and interior train noise were also introduced to create a "train feeling".Test designs and methodology have been developed during the course of the experiments. The test subjects answered questionnaires, four times per test run in the train experiment and each 5 minute in the simulator experiment. The investigated variables were: estimated average ride comfort, estimated ability to work or read, and occurrence of symptoms of motion sickness (dizziness, nausea and not feeling well). Lateral and vertical accelerations together with roll motions were monitored and recorded for later evaluation.Results from the train experiments show that the estimated average ride comfort was about 4 on a 5-degree scale, which indicates “good”. Results also show that a reduced tilt compensation of the lateral acceleration while curving together with a reduced tilt velocity of the car body reduce the provocation of motion sickness. However, a reduction in tilt compensation may produce an increased number of comfort disturbances due to lateral acceleration in the car body. Regression analysis shows that motion doses from roll acceleration may be used to predict the incidence of motion sickness.The simulator experiments show that the primary sources of provocation of nausea and motion sickness are the motion doses from roll and lateral acceleration in the horizontal plane. The study proposes a hypothesis and a model of provocation of motion sickness. It is shown that motion sickness has a time decay, or leakage. A model for this leakage is proposed.The determinative types of motion for provocation of nausea and motion sickness in tilting trains are identified and future tilting train and/or simulator experiments are proposed in order to further investigate their influence.