Why are curved roads banked

So that vehicles do not topple or skid off the road.

Explanation:

As a vehicle is negotiating a curve, two equal and opposite forces act on the vehicle; centripetal force which keeps it moving and centrifugal force which tends to throw it out of the path.

In order to avoid skidding off the road curved roads are banked. Banking a curved surface provides the centripetal force that points towards the center of the road hence the vehicle or car does not skid off or topple.

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