Methodology for Checking Shortcomings in Three-Dimensional Alignment

Road design by highway planning authorities and planning offices is performed at three separate levels: the horizontal and the vertical projections and the cross section. Experiments have shown that shortcomings in the three-dimensional (3-D) alignment may still occur when these three levels are processed separately and then superimposed. It makes sense to calculate virtual perspective views and special control parameters with the use of visualization tools and then to check the 3-D alignment with those tools. Shortcomings of this kind can cause accidents, particularly on two-lane rural roads. Unified model assumptions that match the driver's vision must be set to ensure the comparability of the central perspective views. Drivers absorb images from a central perspective when driving along a road. A driver's inability to recognize a section of the road in the driving area ahead gives rise to blind sections. Designers need to use standard 3-D elements as much possible. These shortcomings are of two major types: those that are safety related and those that are merely aesthetic. A methodology has been developed to check the 3-D alignment for shortcomings in the three basic stages (checking for standard 3-D elements, safety-related shortcomings, and aesthetic shortcomings). By using the visualization tool VISS ALL 3D, the design engineer can calculate the virtual perspective views with the safety-related shortcomings and illustrate them in the blind-section graph. Shortcomings in the 3-D alignment must be eliminated at the end of the redesign process.