Salt lowers water’s freezing point, the temperature at which it changes from a liquid to a solid and vice versa.

Melting water already frozen is called deicing. Preventing water from freezing in the first place is called anti-icing. Both methods give tires more traction with the pavement, keeping roads open and safe while protecting lives and commerce.

Any substance that dissolves in water lowers its freezing point, but each substance will have varying outcomes. For example, sugar can lower water’s freezing temperature, but salt’s lower molecular weight makes it six times more effective.

How quickly salt melts frozen water is dependent upon a number of variables, including temperature, time, and the rate of application. Fortunately, it is usually not necessary to melt all the snow and ice on a road. Merely destroying or preventing the bond between pavement and frozen water is a more efficient, economical and environmentally sensitive approach.


Federal Highway Administration data and index on snow and ice