In terms of barriers, (elevated) railroad lines are suddenly not interesting...
Railroads emit MUCH more noise than freeways. For example a railroad with regular trains can easily emit around 75 - 80 dB, even at low speeds, while a freeway at 55 mph barely get above 60 - 65 dB at close range (within 100 feet). Since the decibel scale is logarithmic, this is a huge difference. Very quiet railroad infrastructure + trains may be limited to 65 - 70 dB at close range.
No, if they really care about the local residents and noise emissions, fighting railroads is much more effective.
Also, noise emissions of freeways can be mitigated much better, for example quiet pavement. Porous asphalt can reduce as much as 6 - 8 dB compared to concrete slabs. It's also slightly easier to install noise barriers next to a freeway than around an (elevated) railroad, which often runs through dense urban areas where 10 feet high noise barriers are not considered acceptable. (A Berlin wall, if you will).
“We’re rolling back the freeway system,” said John Norquist, president and chief executive of the Congress for a New Urbanism, a group based in Chicago that promotes walkable cities.
So people should walk 20 miles to work? I suggest this guy visits Africa to see how his ideas really work... We're not talking about downtown or midtown, but the Bronx. Nothing would get more "walkable" than it already is by removing expressways. Are these guys really that naive that removing freeways shrinks cities to 4 square miles with sky-high housing prices?