If I'm on a track that's being used by trains, I am going to want to have permission and know the schedule. Abandoned tracks don't exist . . . at least not for long.
All of the abondon tracks I know of in my neck of the woods have been taken up. There was one track that had a tunnel through Pigion Mt. that would have been neat to travel, but as soon as they stopped using it, the tracks came up. The tunnel is still there, but the last pictures I saw of it, I'm not sure I would want to venture through it now anyway.
Have you been in Lowes or Home Depot and seen fence post that have the same basic profile as a rail? That's because they take these old rails and heat 'em and stretch 'em out and make fence post out of them. One section of rail will make a whole lot of fence post. The owner of the rail isn't going to let that kind of money lay on the ground for very long.
For what a GOOD golf cart and a set of wheels would cost, you can probalby buy a decent speeder anyway. I'm still looking.
