What component sits on top in the typical flexible pavement layer sequence?

In a typical flexible pavement layer sequence, the surface course is positioned on top. This layer is critical because it is the part of the pavement that directly interacts with vehicles and serves as the first line of defense against traffic loads and environmental factors. The surface course is designed to withstand the wear and tear from traffic while providing skid resistance and a smooth riding surface.

It is also engineered to protect the underlying layers from moisture infiltration and to distribute loads effectively. The materials used in the surface course can include bituminous mixtures that are chosen based on performance needs, which might include durability, flexibility, and resistance to deformation. Proper design and construction of the surface course are essential to ensure the longevity and functionality of the pavement structure.