Development of transitioned vertical curve II Sight distance

The mathematical properties of a new vertical curve that consists of a tran sition 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 ar e analytically derived for both crest and sag curves, considering various c ases related to the minimum sight distance and the lengths of transition an d parabolic curves. Using the developed analytical models, example design g raphs are established for the length requirements of the transitioned verti cal 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 vertica l curve especially for sharp vertical alignments. (C) 2000 Elsevier Science Ltd. All rights reserved.