Unit Curve for Design of Highway Transitions

Abstract

Calculations required for the design of a transition (spiral) curve are often facilitated by the use of tables that give the elements of the curve for selected values of length and minimum radius of the transition. The use of such tables can be dispensed with and the design done more simply by the use of a master curve called the unit curve. The elements of the unit curve are developed and listed in this paper. Every element (linear dimension) of a field highway transition, including the tangent distance, is obtained from the corresponding element of the unit curve as a multiple of the characteristic constant of the field curve. This characteristic constant is