Abstract
This study discussed driver's sensitivity and adaptability to variation of horizontal vehicle dynamics characteristics. In order to seize characteristic of driver adaptation to variation of the yaw-rate or sideslip angle gain, we conducted some experiments using real small vehicle. The subjects had in common that it is difficult to distinguish lateral motion from yaw motion, when the vehicle dynamics characteristics changes. However, due to the difference of the attributes of the driver, there was a difference in the trend of the adaptive operation.