When snow and ice blanket roadways, road crews plowing and treating roads becomes a common sight.
Ohio has used salt since the 1930's as the primary weapon to battle ice and snow on roadways. Even now it remains the most efficient, cost-effective means to keep highways safe and passable, according to the Ohio Department of Transportation (ODOT). State road crews spread an average of 650,000 tons of salt each winter season.
But how does road salt work? In simplest terms, it lowers the freezing point of a solution of which it is a component and breaks the bond between ice and snow and the road surface.
Water freezes at 32 degrees. But adding salt to water lowers the freezing point below 32 degrees.
When salt is spread on ice, salt molecules combine with ice molecules. Since the freezing point is lowered, the ice melts into water.
Crews sometimes pre-treat roads with brine, a solution with a high salt concentration. Doing prevents formation of a bond between the snow/ice and the road surface.
The use of salt or brine becomes ineffective below 14 degrees, however.
Salt is not the only substance that can be spread on roads to help melt ice and snow. Sugar and alcohol would also work, for example. But salt, despite rises in costs the past few years, remains cost effective.
But does the use of salt result in safer roadways? A recent study indicated half of all crashes are weather related. Another study determined that snowstorms increased the accident rate on Iowa roadways by 1,300 percent.
A team at Marquette University determined that in the first four hours after salt is applied to roadways, crash rates dropped 85 percent and injury crashes 88.3 percent.