While the temperature outside is an important factor in driving conditions on the state’s roadways — it’s not the most important measurement for keeping the roads clear. Dennis Burkheimer, winter operations administrator for the Iowa Department of Transportation, says the temperature at ground level and below plays a bigger role.He says it tells them exactly what the precipitation will do once it hits the pavement, and he says it tells them how to treat the road, such as what type of chemical to use and how much. Burkheimer says the state has a network of 53 weather stations statewide that feed the air and pavement temperatures on a nearly real-time basis. He says they also have subsurface probes that tell them what the temperature is 17 inches under the ground. He says in the fall the soil temperature is often warmer and that helps keep the pavement warmer. Burkheimer says temperatures just above freezing — or 32 degrees — are the signal to get things going.He says typically 35 degrees is where they start looking at applying salt or chemicals to the roadway. He says if it’s going to get colder than that, then they don’t apply anything. He says once the temprature drops well below freezing — salt loses its effectiveness. He says it takes five times as much salt at 20 degrees as it takes at 30 degrees to melt the same amount of ice and snow, and so if it drops below 20 degrees, he says they have to use things other than salt to treat the roadways. You can find out more about treating the roadways by visiting the D-O-T’s weather website at: www.dotweatherview.com.
