Creating hard-passable roads

[Narzew]

Hi all, I have already learnt how to built various types of asphalt and classic dirt roads (default asset), but I want to do something more.
I thought about creating muddy track (like road to Yakutsk), something similiar to road shown in picture.
http://www.ssqq.com/archive/images/sibe ... %20357.jpg
Some roads in Iceland (near Akureyri) was very hardly passable (I must switch to manual gear to pass it).
Can anyone explain me how to create mud/icy/grassy paths ? Or how I can create other surface that is quite hard to pass or slow down the truck ?