There seems to be a lot of interest in using HDPE plastic to create ground level and raised track beds. The latest G Rail magazine has an article about this and this link [style="color: #3366ff;"]
http://www.btcomm.com/trains/primer/roadbed/ladder1.htm < Link To http://www.btcomm.com/tra...er/roadbed/ladder1.htm [style="color: #000000;"]has an article on how to do it.
[style="color: #3366ff;"][style="color: #000000;"]If you go to the supplier website (www.filcris.co.uk) they have a section on garden railway products and, if I recall correctly, further links to other stories on how people have used the material.
I haven't used it so can't comment on the claims as to how easy it is to lay or how durable it is in service. However, it's on my list of options for my planned extension.