You would have to go only two miles north or south to find an overpass. It would depend on the locale and the needs of the farmers.
One question that comes up has to do with farmers' access. It's the same thing on the Trans-Canada Highway west of Banff, where they have these two huge culverts above the road to allow wildlife to cross the highway. You can easily do the same thing or even put a concrete one up. I saw this in a picture at the conference today.