I don't use trains that often but when I do I can't help but scour the embankment and trackside for bmx bikes, frames etc.
I know the chances of finding anything are slim but that great thread a few years back proves finds are possible.
I've even come up with a little visual mapping thing in my head so if something did turn up I would have a decent chance of finding the location on Google earth
Daft I know but I'm on a train now and it makes the journey a hell of alot easier