This was supposed to be a key aspect of the original idea for EPCOT, too: streets would be tri-level, cars on the lowest level, delivery trucks on the next leve

This was supposed to be a key aspect of the original idea for EPCOT, too: streets would be tri-level, cars on the lowest level, delivery trucks on the next level, and above-ground restricted to pedestrians. You can see https://en.wikipedia.org/wiki/EPCOT_(concept) https://en.wikipedia.org/wiki/EPCOT_(concept) for more information.