Switch angle design: Formulation, inferences, and uses

Abstract

Jerk, lateral acceleration, and unbalanced superelevation are induced at the point of switch due to the combined effect of the switch angle and speed. Two sets of formula are derived to compute the values of jerk, lateral acceleration, and unbalanced superelevation due to the switch angle and speed separately. A sudden change in the direction of motion by the switch induces jerk which affects passenger comfort. The jerk due to the sudden change in the direction of motion is formulated in this paper by using the cubic spiral formula. It is demonstrated that the jerk at the point of switch has a positive (direct) relation with the speed and switch angle, but has a negative (inverse) relation with the pivot pitch. It is demonstrated that the switch angle should be optimized to reduce the lateral jerk. To capture the effect of the speed, the effective radius at the point of switch is formulated first and then formulas are derived for the jerk, lateral acceleration, and unbalanced superelevation at the point of switch due to speed. Finally, the aforementioned formulas are added to obtain the total values at the point of switch. The formulas are applied on American Railway Engineering and Maintenance-of-Way Association (AREMA) turnouts and validated by computer simulation using Vampire. These formulas would be helpful for the practicing designers and engineers.