I would imagine that the biggest obstacle would be pollution affecting the crops but with how much land is being effectively unused it would be worth the engineering effort to attempt.
Assuming interstate ⇒ USA, I don’t think the USA has a shortage of land.<p>Also, if you want to use vehicles on that land, how do you get them there? “Via the interstate” is the obvious answer, but the vehicles may be too slow for that (minimum speed on interstates typically is ≥ 40 mph), and barriers in the middle of the road may limit you to movement in one direction.