One of the reasons rail trails are fairly popular is because it preserves the railroad right-of-way for potential future use. Even if the rails are removed and pavement put down, it's far cheaper to pull the pavement up and re-lay rails if you need the line in future (like for light-rail or commuter service) rather than to have to re-acquire the right of way again or build an entirely new line. The term is "railbanking." [0]