I am attempting to make a plan for the re-development of a residential and commercial area, in a medium sized city. One of the major issues in this redesign is traffic.... there is simply way too much of it. It is not possible to reduce the traffic load, due to the fact that an interstate highway, intersects here, with a major state highway, and which both intersect (closely) with 5 other local avenues. One way I have come up with to reduce traffic in the area in to make one of those major avenues essentially a bridge, which bypasses the whole area to be developed. But in an area where space is at a premium, it is not practical to simply make the avenue a non-intersecting thruway. This is where my question comes in. Is it practicable to place a 5 lane road, on top of special structures, which would double as both supports for the raised roadway, and as commercial shops? I believe the roadway would be about 15' above the surrounding ground. My main concerns are integrity and noise. Would there be enough room underneath this roadway for shops? Second, if the shops were placed under the roadway, how much noise would there be in the shops? Would it be like a non-stop freight train running above your head? Or would it be more like white noise? Any thoughts?