Track bed
Base portion of a railway-supporting structure / From Wikipedia, the free encyclopedia
The track bed or trackbed is the groundwork onto which a railway track is laid. Trackbeds of disused railways are sometimes used for recreational paths or new light rail links.
![Thumb image](http://upload.wikimedia.org/wikipedia/commons/thumb/a/a5/Section_through_railway_track_and_foundation.png/640px-Section_through_railway_track_and_foundation.png)