The drainage system of highway should fulfill the following requirements:
1. The surface water from the carriage way and shoulders should be drained off effectively and as soon as possible without allowing it to percolate to the sub-grade.
2. The surface water from the adjoining land should not be allowed to enter the roadway.
3. The side drains should have sufficient capacity and longitudinal slope to discharge maximum surface water collected in the region.
4. The flow of surface water along the slopes or across the road should not be allowed to erode them or form ruts.
5. The seeping water or seepage and other sources of under ground water such as capillary rise water etc., should be drained off at the earliest by sub surface drainage system otherwise it will reduce the bearing power of the sub-grade