New map generated with proximity constraints, i.e. the probability of a road being generated gets lower the more roads are already nearby. Probabilities can also be boosted with this method.
All this talk about "scrollbars are necessary when [input method]", and it misses the fact that scrollbars are useful regardless of that. They show your position in the scroll area and how much area there is. The illusion of completeness problem? Not nearly as much of a problem if there's a fucking scrollbar.