How Railway Systems Work

Centrifugal force causes strong friction between wheels and railheads, which shortens their life span and can result in derailment. In order mitigate centrifugal force acting on a train running at a curve and improve passenger comfort, track should have cant. (page 37) Conicity decreases the friction between wheels and rails at curves; high conicity is therefore advantageous for steering around a steep curvature. As operation speed increases, the radius of a track at curves should increase due to the fact that the short radius there hinders train speed. Thus, higher speed trains generally have wheels with a lower conicity. (page 51) Due to use of crushed stones, ballast tracks require much maintenance to clean fouled stones in order to increase drainage capability. More recently, concrete slabs have been widely adopted in order to reduce maintenance costs. Concrete slab is used at the areas that are typically difficult to maintain, such as long tunnels and the areas that require high air quality, such as metro. (page 72)