Road covering is a term used to describe the surface of a road. It can be made up of a variety of materials, including TAR, TARMAC, and MACADAM. TAR is a dark, viscous material made from the distillation of coal, wood, or petroleum. TARMAC is a mixture of TAR and aggregate, such as gravel, which is used to form a hard wearing surface for roads. MACADAM is a type of road construction in which layers of small stones are compacted together with a binding material, such as TAR or asphalt. All three of these materials are commonly used to cover roads and provide a durable surface for vehicles to travel on.