It is very important to understand the mechanism of track deterioration and predict the track settlement or track irregularity growth rate for reducing track maintenance costs and designing new track structures. The authors established a track settlement prediction model which consists of a vehicle/track dynamic model and applies a track settlement law. The adequacy of the prediction model was roughly validated by comparing with track site measurements carried out for five years. The track settlement law adopted for the prediction model is divided into ballast settlement and subgrade settlement. The ballast settlement law was established based on settlement experiments in which applied loads were simple but practical loading conditions were not. In this paper, the influence of wheelbase of a bogie on the interaction of response, rail seat force and sleeper displacement between the leading axle and the trailing axle of a bogie is studied with the focus placed on vehicle speed, unsprung mass, the stiffness of track structures and rail type.

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