The necessity of providing extra widening on horizontal curves:

1) When a vehicle travels on horizontal curves, it occupies more width than that it occupies on straight road. This reduces the capacity of the road in respect of accommodating number of vehicles on horizontal curve. To compensate for this effect the width of the road on horizontal curve is increased.

2) This also increases the visibility on the curves.

3) On curves, the vehicles occupy a greater width because the rear wheels follow the inner path as compared to the front wheel.

4) On curves, drivers have difficulty in steering their vehicle to keep to the center line of the road.

5) Drivers have psychological fear to drive close to the edge of the pavements on curves.