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Noise Reduction Measures
Buffer Zones are open and undeveloped lands that border a highway. The land is usually purchased by highway agencies so that future dwellings and development cannot be built close to the highway, which would otherwise be impacted by excessive traffic noise. Buffer zones often improve the roadside appearance of highways. However, due to the often-high cost and amount of land that must be purchased, creating buffer zones are often not reasonable.

Noise Barriers are solid obstructions constructed between a highway and noise-sensitive receptors adjacent to the highway. Noise barriers can be very effective, often reducing highway traffic noise levels by as much as 10 decibels. Noise barriers can be formed from mounds of earth (earth berms) constructed along the highway, or from freestanding walls (noise walls), or from a combination of both. Earth berms have a natural appearance and are usually attractive, but can require a lot of space especially if they are high. Noise walls can be constructed using wood, metal, concrete, brick and other materials. They are usually limited to less than 25 feet (8 meters) in height due to structural reasons. There are limitations to noise barriers. They must be long enough and high enough to block the view of a highway. Openings in a noise barrier for entrances, driveways or intersections defeat the effectiveness of the barrier. In certain instances, when homes are widely spaced apart, noise barriers cannot be constructed due to unreasonable costs.

Vegetation can sometimes be used to reduce highway traffic noise. In order for vegetation, such as trees, to be effective in decreasing traffic noise levels, it must be high enough, wide enough and dense enough that it cannot be seen through. A 10 dB noise reduction can be achieved with a 200 foot width of dense vegetation. If dense vegetation exists along a proposed highway alignment, it can often be incorporated as a noise reduction measure. On the other hand, it is usually impossible to plant enough vegetation along side a highway to achieve a meaningful noise reduction and the FHWA does not consider the planting of vegetation to be a noise abatement measure.
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