In Iceland, off-roading is strictly prohibited. Unfortunately, it still happens and one can find tracks of off-roading all over the central highlands. On the other hand, in the landscape, some roads that are mapped on Atlaskort do not look like much more than some tracks in the landscape either, and may have neither an F-number nor a sign where they depart from larger roads.
Under these circumstances, how would I tell a road from a place where several cars have illegally off-roaded before? Must a road have an F-number to be permissible for driving? If I have a (possibly old) map that shows a road somewhere, and I subsequently see that road in the landscape, does that mean driving there is fine, or is there some more official source stating what exactly are the roads that are officially recognised?