Though plans in many cities have a long way to go before becoming reality, a point in favor of reuse is that it can be cheaper to renovate old rail structures than to tear them down. The Reading Viaduct, an old elevated railway line in Philadelphia, would cost $50 million to demolish versus $36 million to retrofit, according to the Center City District, a business improvement group.

Cities See Another Side to Old Tracks – NYTimes.com.