The clear, wire-reinforced plastic has been erected along both sides of the bridge over Upton Avenue and partly over Central Avenue. More are to be put up.
An Ohio Department of Transportation spokesman said last week that clear panels have been chosen for the bridges because they weigh less and are easier to mount than the regular noise-wall panels used elsewhere along the freeways.
"They also create a more comfortable driving environment" because the panels mounted on bridges are closer to the driving lanes than is the norm for noise walls, said Melissa Ayers, a spokesman at ODOT headquarters in Columbus.
The clear panels cost about twice as much as the opaque ones — about $50 a square foot instead of $25 — but on bridges they reduce the need for special engineering to handle the extra weight.
On several projects, Ms. Ayers said, the department also has agreed to use the panels where normal walls would hide a prominent public landmark, such as a church. If businesses want the walls so they can be seen from the freeway, she said, they have to pay the cost difference.
There are no official data comparing the two noise-wall types’ effectiveness, “but we think that the same result is accomplished with both,” Ms. Ayers said.
Among the plastic walls’ earliest uses was the Woodrow Wilson Bridge in metropolitan Washington, where the transparent material installed nearly a decade ago served a dual purpose: to preserve motorists’ view of the Old Town in Alexandria, Va., and to keep the wall from casting shadows on that historic district.
The Ohio Department of Transportation first used transparent noise walls in 2005, at an I-71 widening project in Franklin County, and the Columbus area is where most of the 10 such walls in the state have been built, Ms. Ayers said. They have also been put up along I-75 in Dayton and along State Rt. 2 in Lake County, just east of Cleveland.
With Ohio’s oldest plastic walls being less than 10 years old, their exact lifespan is unknown, the department spokesman said, but they “are not affected by dirt or smoke and do not need to be manually washed to maintain their clarity. Every wall is performing very well, and there are no signs of needing to be replaced.”
Along with putting up the transparent walls over Upton and Central avenues, contractors for the department have built noise walls along the eastbound lanes between Sherbrooke and Douglas roads, along with replacing some walls elsewhere in the work area.
The department expects to shift westbound I-475 traffic, now using the left lanes, onto the rebuilt and widened right lanes this month but has not announced a date. Eastbound traffic was shifted to the right lanes in late August. The $64 million I-475 reconstruction and widening between Douglas and I-75 is scheduled for completion next year.
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