Extra Widening Of Pavement On Curve Road

When a vehicle takes a turn to negotiate a horizontal curve, the rear wheels do not follow the same path as that of the front wheels. Normally the rear wheels follow the inner path on the curve as compared with front wheels.

The vehicle occupies more width than it occupies on the straight portion of the road. To compensate this, the carriageway width increased on the entire curved portion of the road, which is called extra widening of pavement on curve.

The formula of Extra widening

The total extra widening (We) required on a horizontal curve is given by the following equation:

We (in m) = Mechanical widening(Wm) + Psychological widening(Wps) = nl²/2R + V/9.5√R

Where ‘n‘ is the number of the traffic lane, l is the length of the wheelbase of the longer vehicle in m (generally taken as 6 m), V is the design speed of the vehicle in Km/h and R is the radius of the horizontal curve in m.