Michigan Finds a Solution for Icy Bridges
Pavement and weather sensors keep tabs on bridge conditions in the Lower Peninsula.
The Challenge
Bridge decks often freeze before the adjacent roadway does when winter storms hit Michigan's Lower Peninsula. This can cause hazardous travel conditions, as drivers move from clear pavement to an icy bridge deck. To keep bridge decks clear, highway agencies apply salt and other materials—commonly known as deicing chemicals—that either prevent ice from forming or break the bond between ice and the pavement. Checking the conditions of bridge decks to determine which need to be treated with deicing chemicals can be a time-consuming process.
Looking for a more efficient approach, the Michigan Department of Transportation (DOT) decided to implement a road weather information system (RWIS), a technology evaluated under the Strategic Highway Research Program (SHRP). The system allows highway maintenance managers to retrieve up-to-the-minute data on pavement and weather conditions at bridges and other trouble spots.
Putting the Technology to the Test
Michigan DOT has installed 11 RWIS stations on bridges that experience high accident rates during the winter or that are far from maintenance garages. Each site includes pavement sensors, which measure the temperature of the road surface, determine whether the pavement is wet or dry, and measure the amount of deicing chemical on the road. An atmospheric sensor determines air temperature, precipitation, and relative humidity.
Data from these sites are sent to a central computer that maintenance crew chiefs can access to get information on bridge conditions, which is critical for deciding when and where to send the plows or to apply deicing chemicals.
The RWIS stations have helped maintenance crews do a better job of scheduling winter maintenance operations. The timely, site-specific information means crews no longer have to guess when bridge decks require attention-saving the State money on equipment, personnel, and materials. Says Michigan DOT's Leo DeFrain, "If the systems tell us that there is high humidity or an approaching storm and that temperatures are around freezing, then we send out a truck. If the temperature is above freezing, we save the cost of sending out the truck and crew."
Even more important than the cost savings are the safety improvements. The accurate and timely information on bridge conditions helps the DOT keep bridge decks clear of ice and snow.
Michigan DOT's winter maintenance crews are clearly pleased with the RWIS, DeFrain says. "There are winter maintenance managers who say they'd like to have an RWIS station in their area, and when systems go down managers ask us to fix them. That's a pretty good indication that the systems are working well."
The Benefits
By giving Michigan DOT a jump on preventing icing on bridge decks, the RWIS
- Improves safety for motorists.
- Cuts costs for crew time and deicing chemical use.
- Reduces wear on equipment and bridge decks.
