Development of transitioned vertical curve II Sight distance

The mathematical properties of a new vertical curve that consists of a transition curve (cubic polynomial), a parabolic curve, and another transition curve have been presented in a companion paper. The present paper addresses the sight distance characteristics of this new curve, called transitioned vertical curve. The minimum sight distance and the required curve length are analytically derived for both crest and sag curves, considering various cases related to the minimum sight distance and the lengths of transition and parabolic curves. Using the developed analytical models, example design graphs are established for the length requirements of the transitioned vertical curve based on the upper range of stopping sight distance presented by the American Association of State Highway and Transportation Officials. The transitioned vertical curve, which resembles the spiraled horizontal curve commonly used in practice, represents an alternative to the simple vertical curve especially for sharp vertical alignments.