This winter has been unusually severe across much of the United States, requiring transportation agencies to put down large amounts of salt to melt snow and ice on roadways.

Last year, U.S. officials applied about 17 million tons of salt to roads, says Lori Roman, the president of the Virginia-based Salt Institute, an industry group. Roman says the totals are on track to be higher this year.

Ron Wright, who manages snow and ice removal for the state of Idaho and co-founded the industry group Pacific Northwest Snowfighters, says this winter has left transportation departments scrambling for salt, especially in the East and Midwest. However, Chicago Mayor Rahm Emanuel insists that the Windy City will have enough road