Oscillatory wheel load fluctuations of considerable amplitudes are observed on high speed railway vehicles such as those of Shinkansen. It is thought that the fluctuations are generated through very small irregularities with short wave lengths on the rail surface, and the frequency of fluctuation is estimated to be approximately 50 to 60 Hz. A computer simulation was carried out using a single wheelset model to investigate the influence of vehicle/track parameters and oscillatory wheel load fluctuations on derailment, and the dynamic behavior of wheelsets running on wavy rails at high speed was analyzed. From the results of this calculation, it is found that the external forces to cause derailment are little affected by the existence of such high-frequency wheel load fluctuations, and that the duration where the derailment quotient continuously exceeds the limit value relates to the height of wheel flange climbing and jumping. This paper proposed a method of safety assessment which is applicable to such conditions.

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