Road design is carried out by highway planning authorities and engineering offices and is still separated into three elements: the horizontal and vertical alignment plans and the cross section. The three-dimensional (3D) picture of the road, which enables road users to adapt their driving style, is not obtained until these 3 design elements are superimposed on each other. In order to avoid any possible geometric design errors caused by separate processing and the subsequent superimposition of the plans, basic mathematical and design factors have been developed to allow a 3D geometrical design methodology. The 3D axis consists of a sequence of 3D elements (fixed elements, dialogue elements and coupling elements). Fixed elements should always be selected if it is unnecessary to introduce any variation to the course of the axis based on the design conditions. However, if the idea is to adjust the design of the road to match existing geometrical constraints to an even better degree at individual points, dialogue elements must be used. In contrast to the fixed elements, a dialogue element allows the course of the axis to be varied at individual points by altering the parameters without introducing any change to the constellation of fixed points. Coupling elements serve to link fixed and dialogue elements. Calculating the axis using 3D geometrical design elements opens up new opportunities for further developing a design methodology for roads.
Abstract