There are two aspects, which must be addressed in answering the question: “Why is road drainage so important?”. They are:
• A road’s infrastructure is an engineering work, aimed at the establishment of a platform on which vehicle circulation is possible under safe conditions, with proper traffic flow, utility, and economy, independent of the region’s climate conditions; and
• Water, along with heavy traffic, is one of the greatest causes of road deterioration. As previous chapters have shown, even relatively small increases in water content can often result in significant reductions in the mechanical properties of the aggregate and soil layers in and under the road, thereby speeding up pavement failure.
The overall objective is, therefore, to keep the pavement and the subsoil dry enough to avoid any potentially harmful effects of the water and to control the environmental effects of that drainage water. This is done by decreasing the infiltration through the pavement platform’s surface by adopting integrated solutions. These should simultaneously
• permit the re-establishment of natural groundwater patterns,
• avoid the access of runoff water from nearby land areas to the road platform,
• reduce the risk of erosion due to surface and subsurface flow on/in the nearby slopes, and
• provide preventive measures against soil and/or the aquifer’s contamination either as a consequence of an accident or due to regular traffic and the construction.
