Module 3: Geometric design of highways

Lecture 16 Horizontal alignment III

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Setback Distance

Setback distance $m$ or the clearance distance is the distance required from the centerline of a horizontal curve to an obstruction on the inner side of the curve to provide adequate sight distance at a horizontal curve. The setback distance depends on:

1. sight distance (OSD, ISD and OSD),
2. radius of the curve, and
3. length of the curve.