Here are the layers of asphalt pavement. The bottom layer is polypropylene which is mostly the existing soil. Then, it needs a wide granular base course which is usually stabilized with asphalt, cement or fly ash.
The binder course is also called the base lift, which is the bottom layer of the asphalt pavement. Meanwhile, the wearing coat is the top layer and is responsible for the smooth ride and skid resistance. The wearing coat may be made of multiple layers, depending upon the structural needs.