Road curve
Road curves are regular bends in roads to bring a gradual change of direction. Similar curves are on railways and canals.
Curves provided in the horizontal plane are known as horizontal curves and are circular or parabolic.
Four types of circular curves are on roads:
- Simple curve
- Compound curve
- Reverse or serpentine curve
- Deviation curve
Simple curve
A simple curve has the same radius throughout and is a single arc of circle, with two tangents meeting at the intersection (B in this diagram).
Compound curve
A compound curve has two or more simple curves with different radii that bend the same way and are on the same side of a common tangent. In this diagram, MN is the common tangent.
Reverse curve
Also called a serpentine curve, it is the reverse of a compound curve, and two simple curves bent in opposite directions are on opposite sides of the common tangent.
Deviation curve
A deviation curve is simply a combination of two reverse curves. It is used when it is necessary to deviate from given straight path to avoid intervening obstructions such as a building, and place of worship, or river.