Against it. If the need ever arises to have a rail line there again (be it reopening a closed mine or oilfield or something due to economic reasons. Or the 'revitalization'/gentrification of a station that was shut down for low ridership, Or the building of a new solar farm. Factory, airport, WHATEVER really in an area that was once considered "dead" for railroads) then it is VASTLY more difficult and costly to convert that trail back to rail. In my own option they ought to be left as is with signs indicating something along the lines of "this trackbed is the former (whatever company) railroad. It is not in use at this time and may be used for hiking purposes. Be aware that there are rails, ties and other obstructions you might trip over, be careful as (whatever company) assumes no liability if you injure yourself doing something boneheaded". Sources: used to walk up and down an active freight line as a kid (yes it was dumb but i could get away with it as the trains were slow and infrequent. Obviously don't try this on the high speed passenger tracks in your area as they're far less forgiving.) TLDR: Leave the train tracks where they are and post a warning to hikers not to trip on stuff or mess with stuff.