Horizontal Curves : meaning and their types

Definition of Horizontal curves

A horizontal curve provides a transition between two tangent strips of roadway, allowing a vehicle to negotiate a turn at a gradual rate rather than a sharp cut.

Types of horizontal curve

Horizontal Curve

Simple Horizontal Curve

The simple curve is an arc of a circle. It is the most commonly used. The radius of the circle determines the “sharpness” or “flatness” of the curve. The larger the radius, the “flatter” the curve.

Compound Horizontal Curve

Surveyors often have to use a compound curve because of the terrain. This curve normally consists of two simple curves curving in the same direction and joined together.

 Reverse Horizontal Curve

A reverse curve consists of two simple curves joined together but curving in opposite directions. For safety reasons, the surveyor should not use this curve unless absolutely necessary.

 Spiral Horizontal Curve

The spiral is a curve with varying radius used on railroads and some modern highways. It provides a transition from the tangent to a simple curve or between simple curves in a compound curve.