Burton, all good points. Other questions are: solar orientation is far less than ideal, because of shadows from trees, vehicles, dirt, etc. and sloped roads in the "wrong" direction.
Snow plows, and sanders.
Structural supports - this is essentially a grade level building.
Cabling underground, and interactions with water, and freezing, etc.
Scuffing and lowered efficiency.
All of these would be address simply by building long conventional PV installations along limited access highways; in the median strip and/or along the edges. Like this:
