AASHTO’s guideline for geometric
design of highways and similar guidelines require that roadside areas on the
inside of horizontal curves be cleared of high objects to provide stopping
sight distance. The guidelines have analytical models for determining the
extent of clearance, known as the horizontal sightline offset or clearance
offset, for simple curves. Researchers in the past have developed analytical
models for clearance offsets for spiraled and reverse curves. Very few
researchers developed analytical models for available sight distances for
compound curves. Still missing are models for horizontal sightline offsets and
locations of the offsets for compound curves. The objective of this paper is to
present development of analytical models and charts for determining horizontal
sightline offsets and their locations for compound curves. The paper considers
curves whose component arcs are individually shorter than stopping sight
distance. The resulting models and the charts have been verified with accurate
values determined using graphical methods. The models and the charts will find
application in geometric design of highway compound curves.
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