Unified Design of Horizontal Circular Curves

Abstract

A unified method for designing complex horizontal curves and all traditional categories of horizontal curves is presented. The unified method is applicable to complex curve geometry involving any number, combination, and configuration of circular arcs. Traditionally, complex curves have to be solved on an individual basis because they do not exhibit a consistent pattern suitable for mathematical analysis. This difficulty is overcome in the unified method by the use of (0, 1, −1) variables to designate the types and configuration of arcs of the horizontal curve. The solutions of traditional curves are special cases of the unified solution. By setting the proper values of these variables, the known solutions of the simple, compound, and reverse curves are obtained. Application of the method is illustrated using practical examples involving street widening, median design for a Y‐intersection, a cul‐de‐sac, and a three‐centered asymmetric compound curve. The method should be of interest to highway professionals who are concerned with achieving computational efficiency in designing highway horizontal curves.