This organisation [url= http://www.railstotrails.org/index.html ]Rails to Trails[/url] is proposing that bike tracks get built alongside existing rail corridors.
I am aware of efforts here to convert disused lines into bike trails, but not alongside existing ones. A gravel path would be good enough for me - what a boon to for long distance rides.
Ok if you live in the US..
The US's rail safety record means the likelihood of getting mown down by a derailing train would be enough to put me off riding alongside their railways!
It's an interesting theory, there's often not much room though!
In Oz, out west we used to ride alongside the rail lines and sometimes on them (during the Wet).
Much nicer gradients than most roads 🙂
Close to me there is a cycle path laid on a trackbed that they now want to re-open. the funding for the rail line is paying to have the cycletrack relaid alongside.
