Ah, yes, a field where any single square foot may be run over by a tire about 2 dozen times per year obviously has the same rubber exposure as a road.

Quit with the dumb, snarky retort. It doesn't make you look smart, it does the opposite.

Proximity to roads not only exposes a garden to tire dust, but also the asphalt can leech into the soil and be absorbed by the plants. Plus there's the volatiles in car exhausts.

It's common gardening advice to keep gardens at least 30ft from roads to prevent these problems. It's far better to grow vegetable in the bacl yard instead.