We have a converted rail road track that's now a bike path near where I live. It's nearly completely straight and so pretty boring. Plus, because it's not a loop you have to ride back every time, which feels like drudgery. Practically it's a good idea because there are not a lot of uses for an old rail track, but you won't get kids to do it repeatedly and us adults get sick of it pretty quickly too.
I live near one as well. It’s straight and boring but it’s 50 miles long, which gets it from just outside DC all the way to the edge of the suburbs. So, I can ride out (I live near the mid point), loop on country roads, and ride back. It’s not exciting but it beats driving 25 miles to start my ride.
Before I had a car, the W&OD trail was how I got places. Maybe I was just a weird kid, but the freedom of getting places on my own, trumped any monotony of the ride, and I doubt my parents would have let me bike in car traffic.
