Three-dimensional approach for roadway alignment design incorporating driver perception

In alignment design, appropriate dimensions of the different road elements are selected to provide optimum mobility and safety without adversely affecting the environment and within specific cost constraints. Current design practices are based mainly on a two-dimensional (2D) analysis that does not guarantee a satisfactory design. An alternative design practice should account for the three-dimensional (3D) nature of the roadway alignment. Several research efforts have been expended in the 3D highway analysis including sight distance, vehicle dynamics, and driver behaviour and perception. Based on this research, alignment design is a closedloop procedure that depends on driver behaviour in terms of expected operating speed, which depends on the driver perception of the alignment, which in turn depends on the alignment combination. The end result is that it may be too complex for designers and practitioners to implement the findings of these research efforts. Therefore, the objective of this paper is to compile the previous research on 3D alignment design and driver perception in order to devise step-by-step procedure to incorporate these research findings in the design practice. More emphasis is put on quantitative models for easily implementation of the devised procedure.