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      Why do bridges ice before roads?

      "In the winter like this, it's a little tougher; when it starts snowing, everything's slippery," said Mike Harrington, Operations Director with Marquette County Road Commission.

      Harrington knows the toll that cold weather can take on roadways.

      "We have forces available around the clock," Harrington said.

      Doing the best they can to keep up with Mother Nature, the Marquette County Road Commission clears the highways of snow and other frozen precipitation; a process, he describes, as a vicious cycle all winter long.

      "If it's snowing so hard that we can't keep up with keeping the roads clear, then we'll switch over to a sand," Harrington explained. "And you'll see the road surface go to a matted snow/ice. We have to wait then until the snow lets up and the temperature is right. And then we'll salt it and get it back to a bare road."

      Roads are slower to develop ice than bridges because the ground acts as an insulator, radiating heat onto the road surfaces above it. Bridges, however, are completely surrounded by air. And as the air temperature drops, the pavement on the bridge deck cools quickly, allowing any moisture to form as ice.

      Overpasses on US-41 are treacherous for slippery conditions. Many auto accidents have taken place there, thanks to vehicles skidding out of control, 32 to be exact (each red marker on the map in the video represents an actual auto accident on a bridge in 2011).

      So remember, the next time you see the sign that says 'Bridge ices before road,' "...assume the bridge is slippery if it's the colder weather months" Harrington advises. "And kind of be aware; slow up like we recommend all the time when there's slippery roads. And if you do feel the car kind of wiggle, don't slam on the brakes or steer hard and try to steer out of it."