Located 50 miles northwest of Chicago, McHenry County is one of the the fastest growing counties in Illinois. If it continues to double population every six years, half a million people will inhabit the county's 611 square miles by 2020.

Changing from a rural to an urban community constantly challenges the McHenry County DOT to look for new ways of providing the safest traveling environment possible, especially during the winter. Using 19 plows that are occasionally supplemented with smaller trucks, crews battle an average of 40 inches of snow, ice, and freezing rain on 550 lane-miles of road every year.

The department's policy is to achieve bare pavement as soon as possible using the least amount of material. To that end, it began experimenting with anti-icing — applying chemicals to roads before a weather event to prevent black ice — during the 2000-2001 season. Because fully effective anti-icing initiatives require easily accessible and up-to-date pavement and weather data, the department is developing a road weather information system (RWIS) that will eventually consist of five monitoring sites: one in each corner of the county and one directly west of its office.

Road weather information systems comprise a variety of technologies that take much of the guesswork out of determining which maintenance actions to perform and when. Sensors imbedded in pavement collect pavement temperature and traffic count data that's transferred both wirelessly and via a hardwired cable to a software program that can be formulated into reports on everything from surface temperature history and moisture total history to traffic speeds and types of vehicles. The system allows agencies to track the progress of pavement-clearing efforts in real time before, during, and after storms.

“It took years of planning and budgeting work, but we now have a system in place that will allow us to provide even greater service to the county,” says Maintenance Superintendent Mark DeVries. “This helps the weather service help us.”

Placement of sensors and receivers is key.

“Bridge data is extremely valuable for frost scenarios,” DeVries says. “So to get true wind speeds, we placed sensors on a bridge and its approach that are directly west of a maintenance facility in an open area.”

A second monitoring station/site is near an overpass leading to a state tollway so the data it collects can be shared between McVries' operation and the Illinois State Toll Highway Authority. McHenry County is part of Clarus, an initiative the U.S. DOT and National Oceanic and Atmospheric Administration launched in 2004 to build a nationwide weather observing and forecasting system that provides road surface temperatures from other jurisdictions.

“We're part of a regional group made up of the city of Chicago, the Illinois DOT, the Illinois Toll Authority, and McHenry County all sharing data,” DeVries says, adding that he expects seven other counties to join by the end of the year. In addition to the tollway, the department shares data with the Illinois DOT and the Chicago DOT.

Data sharing has helped the county's winter operations by allowing DeVries access to greater regional weather data. “Using information from the Illinois DOT, we have been able to see data from the west of us to predict weather systems that may be approaching,” he says.