Curves and its types (Horizontal and Vertical curve)

Curves and its types (Horizontal and Vertical curve)

Types of horizontal curves

1) Simple curve
2) Compound curve
3) Reverse curve
4) Transaction curve

 Simple curve

 It is a circular curve which consists of a single arc of uniform radius. This curve is expressed in terms of degree of the curve, which is the angle subtended at the centre by a chord of 30 metre length. This type of curve is suitable for large radius and for slow moving traffic.

 Compound curve

 This is a circular curve which is comprised of a series of two or more simple curve of different radii which turn in the same direction. This type of curve is used to avoid cutting through hard ŕocks, heavy cutting of filling etc.

 Reverse curve

 This is a circular curve consisting of two simple curve of same or different radii which turn in the opposite direction. These curves are suitable for highway lying in hilly regions.

 Transition curve

  It is the curve having a radius which decreases from infinity at the tangent point to a designed radius of the circular curve. This type of curve in generally introduced on highway between a straight and circular curve to provide ease and gradual change in direction of a road alignment.

Types of vertical curves 

1) Summit curves
2) Valley curves

Summit curves 

 Summit curves are the vertical curves having their convexity upward. The centrifugal force will act upward against gravity when a fast moving vehicle travels along a summit curve and there will be no problem of discomfort to the passengers.

Valley curves

 Valley curves are the vertical curves having their convexity downwards. At the valley curves centrifugal force acts downwards adding to the pressure on the suspensions in addition to the self weight of a vehicle moving on the curve.