Let me think. Ah: We could actually solve two problems at once, microplastics and rolling resistance, by using steel wheels on steel streets. Make a street lane two beams of steel, that saves on material, and the wheels conical so that they follow those beams automatically, replacing the car's differential. In case we need more grip we can spray sand, though as the street is now steel we can also use magnets for breaking. I should patent that!