I've seen this in an article about the all-japan dirt trials in Sport compact car magazine.
They run these competitions in racing facilities consisting of a very large terrain on which several small gravel sections are linked together like a web. By blocking some of these roads, they create a closed layout on which they race!
A track like this in LFS would be really cool since people could create their own tracks and making one facility so versatile would eliminate the need to design a rallycross layout to existing tracks.
BTW if you didn't understand what I tried to explain, I'm quite sorry but I didn't find any picture of such facilities. Just say it and i'll draw one to illustrate my point.