Railway/Track bed

Track bed is the material on which track is laid. A number of different types are used on model railways, including:
 * Formed foam underlay which gives a ballasted effect (e.g. Peco, Hornby)
 * Cork or art board which is then ballasted
 * Dense foam track bed strips which are then ballasted (e.g. Woodland Scenics)

Functions of the track bed include:
 * Levelling out minor imperfections and grade changes on baseboard
 * Raising the track above the baseboard, as with the prototype
 * Noise absorption

On a real railway the track bed is made up of layers of ballast and stone which runs over engineered parts of the route, which may be bridges or cuttings or graded earth. The track bed supports the track and spreads the weight of the trains.

On a model railway the defining feature visually is ballasting. For this to work, the track has to be raised above the baseboard by at least 2-3mm. Foam underlay mimics the ballast effect, fitting between and coming up to the level of the top of the sleepers. Other forms of track bed need to be ballasted by the modeller, and this is one of the most time-consuming parts of building a model railway. Done well, it looks great - done badly, not so.