Horizontal Curve

It is the curve in plan to provide change in direction to the centerline of the road.

It may be design in terms of

1. Radius of curve (R)(M)
2. Degree of curve (D)(o)

NOTE:- Degree of the curve is the centered angle subtended by an arc of length 30 m.

When a vehicle travels on horizontal curve the centrifugal force acts horizontally outwards through the center of vehicle

The centrifugal force depends upon speed of vehicle on a radius of horizontal curve

It will be concentrated by lateral/transverse friction developed between the tyre & pavement, which helps the vehicle to change direction along the curve.

Pc=mv2/R =Wv2/gR

Pc/w=v2/gR

Is termed as “Impact Facture” or “certification ratio”

The force acting on vehicle has the tendency to either overturn the vehicle outward about wheels & to shift the vehicle literally outwards

For stability of vehicle with the conditions are to be checked as follows

1. Overturning effect

For overturning of vehicles 

         MR >= Mo

        wb/2>=Pc.h