The Geometric design of a highway consist of horizontal alignment, vertical alignment and cross-sectional elements.
Horizontal alignment of a highway defines its location and orientation in plan view. Vertical alignment of a highway deals with its shape in profile.

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Highway curves are designed so that safety and comfort of the driver is maintained. There is a gradual change from a tangent to the start of a circular curve.
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Parabolic curves find there usage when we have to connect sections of highways or railroads of differing gradient. The use of a parabolic curve provides a gradual change in direction along the curve. Continue Reading »

The most common type of horizontal curve used to connect intersecting tangent (or straight) sections of highways or railroads are Circular curves. In most countries, two methods of defining circular curves are in use: the first, in general use in railroad work, defines the degree of curve as the central angle subtended by a chord of 100 ft (30.48 m) in length; the second, used in highway work, defines the degree of curve as the central angle subtended by an arc of 100 ft (30.48 m) in length. Continue Reading »