A Graphical Method for Designing the Horizontal Alignment and the Cant in High-Speed Railway Lines Aimed at Mixed-Speed Traffic

To realize the design of mixed-traffic railway lines, the choice of radius must ensure a comfortable ride for passenger vehicles, safe freight transport, and acceptable maintenance costs of vehicle wheels and railway infrastructure. This is not a straightforward task, and what is worse, there is a worldwide lack of clear criteria to limit the design parameters involved in the geometric definition of high-speed railway lines. The proof of this is the great number of technical standards (or recommendations) that are applied depending on the period of time, the administrations involved, or the technicians in charge. If the line is going to be aimed at mixed-speed traffic, this indetermination is even more severe, as the different type of trains that are forecasted to use the tracks (with different loads, speeds, etc.) should affect the limits of the design parameters. To begin to solve this problem, this paper aimed (1) to analyze the design parameters and limitation defined in several technical standards that are used to design high-speed railway lines, (2) to propose a graphical method for designing the horizontal alignment (the cant, the radius, and the clothoid), and (3) to apply the method to a real example to compare our proposed design with the original project for a case study in Spain.