An additional benefit of buffer zones is that they often improve the roadside appearance. However, because of the tremendous amount of land that must be purchased and because in many cases dwellings already border existing roads, creating buffer zones is often not possible. Open space can be left as a buffer zone between residences and a highway. Noise barriers are solid obstructions built between the highway and the homes along the highway. Effective noise barriers can reduce noise levels by 10 to 15 decibels, cutting the loudness of traffic noise in half.
Earth berms have a natural appearance and are usually attractive.
However, an earth berm can require quite a lot of land if it is very high. Walls take less space. They are usually limited to 25 feet in height for structural and aesthetic reasons. Noise walls can be built of wood, stucco, concrete, masonry, metal, and other materials. Many attempts are being made to construct noise barriers that are visually pleasing and that blend in with their surroundings.