@orlet Idea of ignoring roads was to try and tweak everything
I disliked how they jigsawed around trying to be on the road more, especially when I specifically designed most of them to have same number of legs as other bodyparts. Idea with plainCost == 1 is more logical step, yes.
As for documentation, well, it is not even a side effect, just a long train of thoughts. Solved I guess 8).