ABSTRACT
In 1950's, studies on track deterioration due to ballast settlement were initiated in Japan. These included those not only on the settlement of ballast, but also on the ballast acceleration which caused the ballast settlement and proposed the coefficient of track deterioration. The design of the track of the Tokaido Shinkansen depended on it. The narrow gauge lines in Japan bear heavy traffic. A theory for track deterioration was considered necessary and developed depending on the experimental results in early age. In particular the track of the Tokaido Shinkansen, which was a challenge to the unknown high speed, was designed using this theory. This chapter suggests the repeated growth of track irregularities and rectification converges toward a certain value of track irregularities. As the growth of track irregularity aggravates the performance of track that the track forms smooth running ways for wheels, it has been called "Track Deterioration".
