Roads are seal-coated to prevent the road from further deterioration or as part of a reconstruction of that road. Seal-coating (also known as ‘tar & chip’) involves the spraying of a liquid petroleum emulsion (tar) onto the road surface, followed by the spreading of fine gravel onto the top of the emulsion. This process is like putting a new “roof” on the road surface. The emulsion is applied hot, fills in most cracks, and when cool provides a water-resistant seal. The gravel is applied to make the road drivable by providing traction and also to delay the wearing off of the emulsion. Old roads that are in extremely bad condition are not usually seal-coated, but have their asphalt ground up and a new gravel base is applied. These roads are left to settle a year before being seal-coated the following year.