A. The surface course, also referred to as the wearing course, is the upper layer in a roadway and is composed of asphalt concrete.

B. The binder course is a layer of asphalt concrete that holds the materials above and below it together.

C. Base course provides additional support, allows for drainage and provides resistance to freezing.

D. Subbase course is often made from crushed stone or other filling.

E. Compacted subgrade is compacted soil or dirt, and provides the foundation of the pavement structure. It can become harder and more stable over time.