Background Because of its effectiveness, availability and low cost, salt is the highway deicer in common use today. By removing ice and snow from a slick roadway surface, salt promotes winter driving safety and continued mobility, even under adverse snow and ice conditions. Rock salt and solar salt are used on highways. Fortunately, most snowstorms occur when the temperature is near freezing, where salt is very effective.
Salt is used as a deicer because it lowers the freezing point of water.
The melting action of salt forms a brine, or a strong saline solution, that can penetrate below the surface of ice and packed snow. Brine prevents water from freezing and bonding to the pavement. When ice melts due to the presence of salt, heat is absorbed. This is called an endothermic reaction. That is how salt reduces the freezing point.