Just think of the potential productivity of the highway median strips.Irrigated by runoff from the bitumen.Very accessible - just watch out for the B-Doubles.

Heavy metals. Mmm, tasty.

In all seriousness, what, if any, metals, pollutants, etc and so forth, issues would you have growing food next to or within highways? I assume there would be some potential for problems, but how serious would it be?

Given living within 500 ft. of a heavily trafficked road increases lung damage, etc., significantly, I'd not dismiss the problem.

Cheers