Improvements in High-Speed Ballasted Track Design: Benefits of Bituminous Subballast Layers

Track design plays an important role in high-speed rail performance. Increases in high-speed traffic demand and maximum rail speeds will necessitate the development of new, low-maintenance structural solutions for high-speed ballasted tracks. This paper shows that use of tracks with optimum resiliency can reduce railway system operational costs. Use of an alternative to the conventional granular subballast is discussed. The results with Japanese and Italian high-speed lines showing the effectiveness of bituminous subballasts formed the basis for a study focusing on the viability of this option. With Spain used as an example, a theoretical analysis of the characteristics of the bituminous track design is presented. The results of this analysis showed that structural performance was good when a 12-cm to 14-cm conventional bituminous subballast layer was used in lieu of the usual granular layers. Also discussed are ways that a bituminous subballast can reduce track maintenance needs