It provides safety and mobility for motorists, commercial vehicles and emergency vehicles. Salt is used as the principal deicer because it is the most available and cost-effective deicer. Rock salt is preferred because it is cheap and effective. It costs 20 dollars a ton where as an alternative like calcium magnesium cost around 700 dollars a ton. Some 10 million tons of deicing salt is used each year in the U.S. and about 3 million in Canada.
Salt is used to keep snow and ice from bonding to the pavement and to allow snowplows to remove.
When salt is applied to ice and snow it creates a brine that has a lower freezing temperature than the surrounding ice or snow. Water, which includes the effects on ground water, surface water and aquatic life and land. Most of the salt applied to the roadways eventually ends up in the ground water. Salt effect two areas of ground water, chloride concentration and sodium concentration. Chlorides may be present in the form of sodium chloride crystals or as a ion in a solution.