Because of the aerial street grid that can be viewed on the vehicle's computer or a helmet's shield using AR? Basically replicate a street 30 feet above ground with enough clearance to avoid large vehicles. It doesn't need to be some massive flying vehicle. It can start with the little Jetson One vehicle. Stop signs and traffic lights in the AR grid can be used too. However, a flying vehicle would need to be able to hover in order to yield to another vehicle.