This is not always a problem, but can be a significant problem if certain conditions prevail. Sometimes conditions at the road surface promote snow packing, a situation where a hardened layer of frozen precipitation adheres firmly to the asphalt. Such conditions include transition from freezing rain to sleet to snow. This layer may also develop if the temperature drops rapidly during or right after the snow fall, and the residual salt is inadequate to prevent freeze-up. When this hard-packed layer exists, even the Townships’ heaviest scraper plows tend to ride up onto it, rather than scrape it off. In such cases, several days of sunshine or above freezing temperatures may be needed to loosen up and disperse this layer. Department personnel may have to return to retreat the areas in the interim, even several days after the event.