A smart road could be like a train track, completely automated, then you would enter in a cart, input a destination and the centralized system will compute yo2u

A smart road could be like a train track, completely automated, then you would enter in a cart, input a destination and the centralized system will compute yo2ur route and speeds, this needs a lot more infrastructure but theoretically you could have huge speeds and no stops at intersections, just some small slowdowns to allow carts pass near each other at intersections.