One of the leading causes of traffic accidents is the reduction of driver's arousal level. Only a driver with an appropriate arousal level can drive an automobile properly. The purpose of this research is to find the possibility of quantifying the reduction of this arousal level.
Two methods are used to quantify the reduction in arousal level: one is related to the driver's behavior, and the other is related to his physiological status. The characteristics of controlling the steering wheel are used as indicators of the driver's behavior, which represents the status of information processing in the brain. The variation of heart rate is used as an indicator of physiological status, which could directly represent arousal level related to drowsiness.
Eight male and two female drivers participate both in on-the-road tests for the characteristics of controlling the steering wheel and in a test with a driving simulator for the heart rate variation. The results indicate that the characteristics of steering wheel control has a component directly related to driver's visual information processing, which is especially dubbed “visual control component”. The higher the visual control component, the better the driver's performance, which is measured as lanekeeping performance. Moreover, the visual control component is subject to be influenced by an arousal level of a driver. The heart rate typically varies during the entire process from entering a simulator to hypnosis at the wheel. The typical variation could imply the possibility of quantifying a driver's arousal level.