Michigan has ended a six-year moratorium on the construction of expressway sound walls. The State Transportation Commission recently adopted a new policy.
But officials say that doesn't mean new barriers will be popping up between busy highways and neighborhoods.
Communities must submit an application to the Michigan Department of Transportation and pay 10 percent of the costs. They must also have land use restrictions controlling development near existing freeways.
The moratorium began due to the lack of funding, but now there may be some money available. A spokesperson for the state transportation department says the sound walls would cost between $1 million and $1.5 million.
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- Noise barriers are solid obstructions built between the highway and the homes along a highway.
- Barriers do not completely block all noise they only reduce overall noise levels, but effective noise barriers typically reduce noise levels by 5 to 10 decibels, cutting the loudness of traffic noise by as much as one half.
- Barriers can be formed from earth mounds or "berms" along the road. Earth berms have a very natural appearance and are usually attractive. However, earth berms can require a lot of land to construct, especially if they are very tall.
- Barriers can also be formed from high, vertical walls. Walls require less space, but they are usually limited to 25 feet in height for structural and aesthetic reasons.
Traffic Noise Barriers:
- Reduce the loudness of traffic noise by as much as half.
- Do not completely block all traffic noise.
- Can be effective, regardless of the material used.
- Must be tall and long with no openings.
- Are most effective within 200 feet of a highway.
- Must be designed to preserve aesthetic values and scenic vistas.
- Do not increase noise levels perceptibly on the opposite side of a highway.
- Substantially reduce noise levels for people living next to highways.
Source: http://www.fhwa.dot.gov/environment/keepdown.htm (U.S. Department of Transportation, Federal Highway Administration)