A railway is organized by a variety of individual technologies, and functions safely and properly as a system, therefore it is necessary for the system safety to study each potential unsafe case caused by earthquakes. Recent reports imply that railway vehicles could be derailed by earthquake ground motions without fatal damages of vehicles or tracks. Thus, we should further study the derailment mechanism to pursue to minimize the risk of railway system safety against large earthquakes. Particularly, for more comprehensive understanding on the derailment mechanism of high speed railway vehicle, the derailment process should be experimentally studied. Therefore, in this study, we arrange an experimental setup with 1/10 scale vehicle and roller rig providing both conditions of high speed wheel/rail rolling contact and large amplitude excitations. Through the experiment, we obtained the outcomes. (1) Two types of vehicle derailment motions are observed ; one is rocking derailment and the other is sliding derailment. Derailment motions are similar regardless of vehicle speed. ( 2 ) By contrast, the excitation amplitudes for derailment decrease according to the increase of vehicle speed particularly by low frequency excitations. ( 3 ) The excitation amplitudes for wheel lift of flange height are relatively independent of vehicle speed. (4) Based on the similarly of fundamental vehicle dynamics between the 1/10 scale vehicle and full scale vehicle, those observed mechanisms should be applicable to full scale vehicle.%日本ぼ世界有数の地震多発地域にあり，各分野で巨rn大地震の災害から社会を守るための研究や対策が継続rn的になされてきた．鉄道におぃては，構造物の強化やrn早期に地震動を感知して列車を停止させる警報システrnムの導入等がなされてぃる，鉄道は巨大なシステムでrnあり，致命的な災害に対するリスクを最小化するためrnには起こりうる事象につぃて個々に検討しておく必要rnがあると考える．
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