Weather forecasts are key in deciding when to do anti-icing. Salt brine is effective down to temperatures of 20-25 degrees, according Mark Pfeiffer, director of public affairs for the state Transportation Cabinet. Apply it when it's too warm and rain will wash it off. Use it when temperatures dip below 20 and there's a risk ice will bond to the road anyway.
At temperatures colder than that, KDOT will mix liquid calcium chloride - a blend of salt brine and lime - with road salt in a process called "pre-wetting." That solution is used after snow falls. The reason: At 62 cents a gallon, it's expensive.
Currently, KDOT's District 7 in Lexington provides anti-icing on roads only in Anderson, Scott and Fayette counties, according to Bobby Sturgeon, the district's acting chief engineer. Boyle, Mercer and Garrard counties will get anti-icing next year if requested equipment arrives, he said.
"We've got the equipment ordered," he said, "but it seems like we always run one season behind."
Highway engineers use a kind of outside-in approach when anti-icing. Rural roads are done first, then secondary streets, then major highways and bypasses.
"We start with (rural roads) first because we know when it starts snowing, those are going to be the last ones we get to, " Sturgeon said.