Disadvantages of heavy camber

Camber is the cross slope given to the carriageway so that rainwater drains to the sides. A heavy (too steep) camber is one steeper than the value recommended for the surface type (about 2.0 to 2.5% for bituminous surfaces in IRC/NRS 2070). Its disadvantages are:

1. Traffic concentrates at the crown. Drivers avoid the steep sides, so vehicles use the centre of the road. This causes uneven wear, early rutting and cracking along the centre, and makes passing and overtaking difficult.
2. Discomfort and unsafe driving. Vehicles tilt towards the edge, steering becomes tiring, and slow vehicles and two-wheelers feel unstable. Tall or heavily loaded trucks risk overturning or sliding towards the edge, especially on wet surfaces.
3. Fast, scouring flow at the edges. Water runs quickly across the steep surface and erodes the shoulder and the pavement edge.
4. Higher cost. More material is needed at the crown, the surface area is bigger, and more construction effort is needed to make a steep cross-section.
5. Difficulty at curves and junctions. A heavy camber is hard to blend with superelevation on curves and with side roads at junctions, and needs a longer run-off.
6. Harder maintenance. Steep side slopes make resurfacing and shoulder maintenance more difficult and raise the risk of edge breaking.

Hence camber is kept just enough to drain the surface. IRC recommends about 1.7 to 2.0% for cement concrete and high-type bituminous surfaces, 2.0 to 2.5% for thin bituminous surfaces, 2.5 to 3.0% for WBM and gravel roads, and 3.0 to 4.0% for earth roads.