Causes of failure in flexible pavement: The following are the causes of failure in flexible pavement:

1) Ineffective road surface drainage system such as, (i) inadequate cross slope of the pavement surface or shoulders and (ii) inadequate longitudinal slope of the road side drains, which result in the stagnation of water on the shoulders or on the pavement surface on some road stretches.

2) Blockage or silting up of longitudinal and cross drains resulting in stagnation of water on the road.

3) Inadequate sub-surface drainage system or improper functioning of the drainage/ GSB layer, leading to stagnation of water on the subgrade or within any of the pavement layers and resultant damages to the pavement layers.

4) Environmental factors including heavy rainfall, soil erosion, high water table, snow fall, frost action, etc.

5) Inadequate compaction of embankment, subgrade or any of the pavement layers or settlement of embankment foundation itself, which could result in settlement of the supporting layers of the pavement resulting in damage to the roadway.

6) Defects in construction method and quality control during construction.

7) Defects in the quality of materials used in any of the pavement layers.

8) Increase in the magnitude of wheel loads and the number of load repetitions or passage of excessively overloaded commercial vehicles, exceeding the design values.

Causes of failure in Rigid pavement: The following are the causes of failure in rigid pavement:

1) Defective drainage system may lead to failures in rigid pavements such as mud pumping, unless preventive measures are taken up at the design and construction stages.

2) Use of nondurable materials which start deteriorating during weathering cycles.

3) Improper alignment of dowel bars may lead to stress concentration and cracking near the joints.

4) Structural inadequacy of the pavement structure consisting of the cement concrete (CC) pavement slab, sub-base and subgrade, with respect the actual loading conditions to which the pavement is being subjected to.

5) Inadequate compaction of embankment or subgrade or settlement of embankment foundation itself, which could result in settlement of the supporting layers of the rigid pavement; these may lead to opening up of the joints or even non-uniform settlement of the pavement slabs resulting in deterioration in riding quality.