Optimization of alignment considering ride comfort for superimposition of vertical and horizontal curves

Abstract

Superimposition of horizontal and vertical curves may hamper train ride comfort and running stability and inflate maintenance costs. However, designing a track plan without superimposed curves is difficult owing to fixed points that have to be either avoided because of geographical conditions or traversed so that existing structures are utilized. This article presents a method to optimize the alignment of horizontal curves to enhance train ride comfort and running stability when horizontal and vertical curves are superimposed in the case of railway construction/renovation. An algorithm was developed to determine the combined range of radius–transition curve lengths ( R− Lt) for feasible horizontal curves that pass fixed points; it was verified through a comparison with Kufver's iterative method using Inrail software. To determine the horizontal curves for optimal ride comfort when horizontal and vertical (convex) curves are superimposed under feasible R− Lt boundary conditions, a solution algorithm was developed using the object function of ride comfort ( PCT). Finally, the simplified analysis method using PCT was verified via vehicle/track interaction analysis.