side note: I think it'll be cool/crazy to see some kind of city-level planning that models like cars moving on the ground in real time, and things (drones) flying in the air, 3D buildings/space they take up... that would be a cool system to setup. I thought Airbus was doing something like that for their Vahana since it isn't piloted.
For traffic simulation there is https://github.com/a-b-street/abstreet which is very impressive project.