PAULDING - Red means stop, green means go, and for motorists using two bridges in Paulding County, blue means watch out for ice.
Hoping to prevent crashes on frozen bridges, the county has bought and installed 34 reflective signs to warn motorists when ice is likely to form on the County Road 73 and County Road 105 spans that cross the Maumee River.
The circular signs, which are 6 inches in diameter, include five triangular panels that come together in a point. When the temperature drops to 36 degrees or below, the panels begin turning from white to blue, indicating that ice may have formed on the bridge deck.
“In the cold weather they will change from a silverish white to a blue,” said county Engineer Mark Stockman. “It's almost like a star, but a blue star is hidden behind the white one, and when it's cold, the blue one rotates so you can see it.
“We want to give the drivers another clue that it might be icy on the bridge,” he said.
Mr. Stockman said the signs begin about one-fifth of a mile from the bridge in each direction as motorists approach. The first sign drivers see “says blue indicates freezing temperatures,” he said.
The reflectors are mounted on guideposts and don't require electricity or other power.
“They work by themselves,” Mr. Stockman said. “So no matter what time day or night, they'll change color and the public will be warned.”
Ice on bridges and highway overpasses is a particular concern for winter drivers because such spans typically freeze even when surface roads haven't, surprising motorists.
Rod Nuveman, a Lima-based transportation engineer for the Ohio Department of Transportation, said bridges freeze at higher temperatures than surface roads because their undersides are exposed to cold air.
“The ground actually acts as a little bit of an insulator, and it keeps that road surface a bit warmer,” Mr. Nuveman said.
He added: “There is no science to that at all. We'll have some bridge decks freeze at one area and not at another.”
The transportation department is not employing the warning signs, but Mr. Nuveman said they're worth trying. “Anything to slow people down across icy bridges is a good thing,” he said.
Joe Rutherford, a spokesman for the agency's District 2 office in Bowling Green, said the state may consider using the reflectors, depending on Paulding County's experience.
“Obviously, we're interested in how that test turns out,” Mr. Rutherford said. “I don't think that's out of the question.”
Paulding County is one of the first jurisdictions in Ohio to use the signs, made by Bluestar Specialty Products, Inc., of Salem, Ore.
Larry Schader, director of sales for the company, said the city of Fairfield, O., bought reflectors to outfit five bridges this fall.
Mr. Stockman said a crash last winter on the County Road 73 span, commonly known as the Forder-Bethel bridge, persuaded him that a warning system was needed.
“Five minutes before we got the [salt] trucks there, someone had an accident on the bridge,” he said. “That's why I wanted the signs, because we can't be everywhere at once.”
The reflectors went up last week, just in time for the cold snap that has driven temperatures into the 20s and 30s in northwest Ohio. Mr. Stockman said he has ordered reflectors for a third bridge and hopes to install them on about 50 of the 200 county-maintained bridges “right off the bat.”
“My thinking is, if a bridge is long enough that you can skid and get into trouble, I'll go to the expense and cover it with signs,” Mr. Stockman said.
Paulding County paid $83 apiece for the signs, with a total cost of just over $2,800 to outfit the two bridges done so far, he said.