Moisture control: surface and subsurface drainage

Probably the most important factor in good pavement design is drainage, because without good drainage the road construction can deteriorate very rapidly. Excess water, whether it results from precipitation or groundwater, will have a detrimental effect on road foundations and pavements and on traffic movement and safety. Consequently, good drainage design is fundamental to economic road design.

Good road drainage has three functions:

Good drainage design begins with good route location. Roads that avoid poorly drained areas, unstable and/or weak soils, frequently flooded sites and unnecessary stream crossings greatly reduce the costs and dangers associated with the need for road drainage.