The plows are designed to ride on "guides" (shoes) that raise the blade approximately 1/2 inch from the surface of the roadway. This is done to prevent damage to both the vehicle and infrastructure from raised manholes, catch basins or water valves. When plowing, our goal is to make residential streets passable; not to clear them to the bare pavement. Once the street has been plowed and salted, the interaction of the salt and vehicular traffic is required to melt the remaining snow cover. Streets with low traffic volumes will therefore remain snow covered longer.