We have biked the Cotton Valley rail trail many times.
https://cottonvalleyrailtrail.org/
The multi-use includes private rail cars as well as biking, walking, running, cross country skiing and snowmobiling.
Biking is between the rails on some sections and along side in others. Between the rails is filled with hard packed gravel.
On one trip there we were happy to see a private rail car meet with a dozen or so small rail cars on the track.
Alan