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Detection of Road and Bridge Surface Conditions Using Time Domain Reflectometry and Dielectric Relaxation Spectroscopy

John Evans, Professor, Department of Chemistry and Biochemistry, University of Minnesota Duluth

October 13, 2011

To improve public safety on potentially hazardous winter roadways, researchers from the University of Minnesota Duluth have developed a system to detect snow and ice on road and bridge surfaces.

At an October 13 seminar, chemistry and biochemistry professor John Evans outlined the development of the system, which was designed to be inexpensive, versatile, and easily deployable in almost any location. Ultimately, Evans said, the real-time information collected by the system could be used to warn motorists about unsafe conditions or trigger deicing operations by maintenance crews.

Evans’s system consists of an array of passive, puck-shaped sensors installed directly in the road or bridge surface. All sensors in a given area, such as on a single bridge deck, are connected to a common local data acquisition system that wirelessly transmits data back to a central processing system. The sensors and acquisition system can be powered by solar panels, making the system ideal for deployment in remote locations.

The detection system uses time domain reflectometry to acquire dielectric relaxation spectroscopy data, a technology that has traditionally been used to determine moisture content in soil, optimize water delivery to agricultural fields, and identify faults in high-speed electronic circuits.

Each individual sensor sends out an electric pulse and collects data on how the material surrounding the sensor reflects that pulse. Evans explained that a material’s response to the electric field changes depending on its temperature and state, so ice, water, and air all react differently. The processing system is able to determine whether the roadway surface contains ice, water, deicing chemicals, or nothing at all by comparing the collected data to baseline measurements for a variety of materials.

“We ultimately use this very complex information to determine a simple response: Is the roadway safe or unsafe?” Evans said.

When the system detects ice or other dangerous roadway conditions, it could be used to trigger electronic signs that alert drivers to potentially hazardous conditions. It could also send information to maintenance crews or individual plow operators pinpointing the location where deicing is needed.

The system was scheduled to be deployed at a test site in Cloquet, Minnesota, in the fall of 2011 in partnership with the Minnesota Department of Transportation (MnDOT). Sensors were slated to be installed in a former weigh station that MnDOT continues to plow and salt.

“It should be a good test station to evaluate the technology,” Evans said.