The process is referred to as sealcoating which most road agencies in Michigan use as a relatively low cost method of preserving existing pavements. The tar is actually an emulsion of water and liquid asphalt which penetrates and seals small cracks in the existing pavement. Sealing these cracks on a regular basis prevents water from seeping into and softening the base of the road and over time causing potholes to form. The porous stone that we use to cover the asphalt emulsion sticks and, after rolling and sweeping, provides a slightly roughened skid resistant surface to improve safety. Although sealcoating can preserve and extend the life of the pavement, it is only a surface treatment and does not fill any existing bumps, holes, or irregularities and thus does not improve the ride quality. For this reason it is important to apply sealcoat to a road BEFORE this deterioration occurs, which leads us to sealcoat roads that are in generally good condition rather than waiting for them to deteriorate to the point that extensive patching is necessary.