Automatic Design of the Horizontal Alignment of a Road Interchange: The Case of a Trumpet-Type

Abstract

This paper investigated the automatic design of road interchanges in the framework of mathematical optimization. To introduce the approach, we focused on a trumpet-type interchange, and specifically on S-type and loop ramps. By analyzing all geometric elements, we propose a geometrical model that provides, from an appropriate decision vector, a complete parametrization of the ramps. We established safety and spatial constraints (including restrictions on passage through forbidden areas) and formulated a nonlinear optimization problem, the numerical solution of which gives the design of the interchange ramps. The goodness of the model and the accuracy of the method proposed for its numerical resolution was checked using an academic problem designed so that its solution can be analyzed easily. Finally, the practical usefulness of this methodology was shown in a real case study, redesigning an existing interchange on a Spanish highway.