Highway noise barrier location for maximum benefit/cost

A benefit/cost analysis of noise barrier location was conducted, which suggests that (a) for flat terrain, or terrain in which the roadway and receivers are equally elevated but separated by a ditch or other depression, the best barrier location is near the receiver, (b) for roadways raised above the right-of-way by 4 ft (1·2 m) or more, the best barrier location is probably near the highway, but this should be verified by detail design, (c) for a depressed roadway, the best barrier location is near the receiver, and (d) for terrain in which the roadway and receivers are separated by more elevated terrain, barrier location must be studied in detail—for elevations of the intermediate terrain that exceed the grade elevation by 2 ft (0·6 m) or so, the best barrier location may be the raised intermediate point.