Railways are unique because they go right through the densest part of towns and cities. For them to be most effective, they should be within biking or ideally e

Railways are unique because they go right through the densest part of towns and cities. For them to be most effective, they should be within biking or ideally even walking distance of a significant number of homes and offices. If you place a railway on the outskirts of a city, nobody is going to use it. This means you're going to have to use very significant noise reduction to keep the area livable. Highways care a lot less about location. Place them a one-minute car ride outside the city, and its noise becomes basically irrelevant. The city grows and swallows the highway? Just place an industrial area or mall between the highway and any homes. When homes aren't an arms-length away you can get away with far more primitive noise reduction.