State the necessity of cross drainage works for roads. - Transportation Engineering

State the necessity of cross drainage works for roads.

Necessity : 

            The stability of road pavements can only be maintained if their surface and

foundation bed remain in dry condition. The entrance of water in the sub grade or any other

layers of the road pavement, even for short intervals, is undesirable and dangerous because

it is considered as one of the major causes of the road failure. Hence it is necessary to

provide proper cross drainage works for roads.