Editing Snow removal (section)

==De-icing and anti-icing==
[[File:Winter road treatment using salt brine.jpg|thumb|Salt [[brine]] sprayed and dried on a road surface for anti-icing before a snow storm]]
{{Main|De-icing}}
De-icing is defined as removal of existing snow, ice or frost from a roadway, airport runway, roof, or other surface. It includes both mechanical means, such as plowing, vacuuming or scraping, and chemical means, such as application of salt or other ice-melting chemicals. Anti-icing is treatment with ice-melting chemicals before or during the onset of a storm in order to prevent or delay the formation and adhesion of ice and snow to the surface. [[Brine]], or wetted salt, is usually applied shortly before the beginning of a snowstorm. When properly performed, anti-icing can significantly reduce the amount of salt required and allow easier removal by mechanical methods, including plowing.<ref>Cornell Local Roads Program, ''Snow and Ice Control Operations for Local Highway Officials''</ref>

The de-icing of roads has historically been accomplished by [[snowplow]]s or specially designed [[dump truck]]s that spread [[salt]], often mixed with [[sand]] and [[gravel]], onto slick roads. [[Rock salt]] is normally used because it is inexpensive and readily available in large quantities. However, [[brine]] freezes at −18&nbsp;°C (0&nbsp;°F), and so it is ineffective at these low temperatures. It also has a strong tendency to cause corrosion, [[rust]]ing the [[steel]] used in most vehicles and the [[rebar]] in concrete bridges. More recent snowmelters use other salts, such as [[calcium chloride]] and [[magnesium chloride]], which not only decrease the freezing point of water to a much lower temperature<ref>{{Cite web|url=https://www.fhwa.dot.gov/publications/research/safety/95202/005.cfm|title=Recommended Anti-Icing Practices - Manual of Practice for An Effective Anti-Icing Program , June 1996 - FHWA-RD-95-202|website=[[Federal Highway Administration|Federal Highway Administration (FHWA)]]|access-date=2019-02-23}}</ref> but also produce an [[exothermic reaction]], whose dissipated heat further aids in melting. In addition, they are somewhat safer for [[concrete]] [[sidewalk]]s, but excess should still be removed.{{Disputed inline|Deicer safety|date=December 2015}}

Recently, organic compounds have been developed that reduce the environmental impact associated with salts and that have longer residual effects when spread on roadways, usually in conjunction with salt brines or solids. These compounds are generated as byproducts of agricultural operations, such as [[sugar beet]] refining or [[ethanol]] [[distillation]].<ref>[http://www.betterroads.com/articles/brjul01a.htm Better Roads- dead link pending resolution with Better Roads magazine<!-- Bot generated title -->] {{webarchive|url=https://web.archive.org/web/20060624191744/http://betterroads.com/articles/brjul01a.htm |date=2006-06-24 }}</ref> A mixture of some selection of these organic compounds with a combination of salts results in a substance that is both more easily spread and more effective at lower temperatures (−34&nbsp;°C or −30&nbsp;°F).<ref>{{cite web |url=http://www.magicsalt.info/Magic%20Salt.htm |title=About Magic Salt - the most highly effective ice melting product |access-date=2011-01-04 |url-status=dead |archive-url=https://web.archive.org/web/20090605032512/http://www.magicsalt.info/Magic%20Salt.htm |archive-date=2009-06-05 }}</ref>

Since the 1990s, use of liquid chemical melters has been increasing, [[sprayer|sprayed]] on roads by nozzles instead of a spinning spreader used with salts. Liquid melters are more effective at preventing the ice from bonding to the surface than melting through existing ice.

Several proprietary products incorporate anti-icing chemicals into the pavement. Verglimit incorporates calcium chloride granules into asphalt pavement. The granules are continually exposed by traffic wear, and release calcium chloride onto the surface. This prevents snow and ice from sticking to the pavement <ref>Verglimit SA, Capabilities of Verglimit, http://www.verglimit.eu/en_capabilities.php, Sep 20, 2010, retrieved 12/14/2010</ref>
Cargill SafeLane is a proprietary pavement surface treatment that absorbs anti-icing brines, to be released during a storm or other icing event. It also provides a high-friction surface, increasing traction.<ref>Cargill, Inc., SafeLane Surface Overlay, http://www.cargillsafelane.com/, retrieved 12/14/2010</ref>

[[File:road sprinkler tsurugi.JPG|thumb|A Japanese road sprinkler system. This system combines the mechanical action of the water to remove the snow and the > zero temperature of the water to melt the snow. This system can only be used where ground temperatures do not regularly drop below zero, otherwise sheet ice formation could result (although a continuous water flow would act as an impediment to this).]]

In Niigata, Japan, relatively inexpensive hot water bubbles up through holes in the pavement to melt snow, though this solution is only practical within a [[city]] or [[town]]. Some individual buildings may melt snow and ice with [[electric power|electric]] [[heating element]]s buried in the pavement, or even on a [[roof]] to prevent [[Ice dam (roof)|ice dams]] on the [[Roof shingle|shingles]], or to keep massive chunks of snow and dangerous [[icicle]]s from collapsing on anyone below. Small areas of pavement can be kept ice-free by circulating heated liquids in embedded piping systems.