Deposits occur in pits or lakes as residue from crude petroleum that has seeped up through cracks in the earth. The use of asphalt for street paving in the United States began in 1870. Course A road's top layer, which directly supports moving vehicles, is called the wearing course. It is made of a solid layer of pavement and is designed to be smooth and to withstand erosion from traffic and weather. Two main types of pavements are used bituminous, or flexible, pavement and concrete, or rigid, pavement.
Bituminous pavement is cheaper and easier to construct, but it requires more maintenance.
Concrete pavement lasts for a very long time with minimal upkeep but is much more expensive and time-consuming to build. Bituminous Pavement Bituminous pavements are made with by-products of petroleum, such as asphalt. Weather and seasonal changes can cause roadways and the earth below them to rise or fall slightly. As these natural shifts occur, bituminous pavements allow the road surface to bend or flex slightly without breaking. Bituminous material softens when heated and can be prepared and applied in a wide range of concentrations.