Real pilot here.
Here are the air traffic management rules for what I shall call "Class V Airspace" :
- Class V airspace generally only exists in the most congested urban areas of the United States, where normal air traffic procedures cannot sustain the high volume of VTOL traffic. Class V airspace generally consists of the region between 1000 and 3000 feet AGL. In more congested urban areas, Class V can exist between 1000 and 5000 feel AGL, with higher limits for airspeed in the region between 3000 and 5000 feet. Air Traffic above Class V airspace shall adhere to VFR or IFR flight rules, whatever that airspace is classified as, whether it be Class B, C, D or E.
- Air Traffic inside of Class V airspace must travel between 100 and 150 knots, with altitude mapped to aircraft magnetic track such that at odd levels of 1000 feet (For example: at 1000, 3000, and 5000 feet) the aircraft must be traveling North (0 degrees). As the aircraft climbs (or descends), it must adjust its magnetic ground track heading to map to the altitude it is at, so that as it makes an ascending right-hand turn (or descending left-hand turn), its altitude is an even multiple of 1000 feet at the instant it is heading South (180 degrees). This allows the aircraft to make a standard 3-degree-per-second climbing turn at 1000 feet-per-minute while only conflicting with other aircraft either directly in-front or behind it. Aircraft must yield to conflicting aircraft in-front by passing on the right.
- Air Traffic below 1000 feet and above 700 feet shall not exceed 100 knots, and shall yield right-of-way to any other aircraft on its right.
- Air Traffic above 400 feet and below 700 feet AGL shall not exceed 50 knots.
- Air Traffic below 400 feet shall not exceed 25 knots.
- Landing aircraft have right-of-way over landed aircraft at vertipads.
- In Class V airspace, separation is maintained using visual see-and-avoid techniques and ADS-B telemetry. Conflicts are handled using standard aeronautical right-of-way procedures.
And there you go!
It would probably take the rest of my night to provide the calculus of why this works and requires nothing more. In short, having access to the volume of air above even a large city far exceeds the traffic density that would have to exist to require a more complex management solution. Traffic congestion with automobiles is a result of their 1.5 dimensional nature: In a car, you can only move forward and possibly switch lanes. We like this as drivers because it make all the possible collision vectors collapse to only a few possible directions. Modern aircraft traffic rules somewhat also do the same thing. (See this link and this link).
By mapping altitude to heading, we collapse the possible collision vectors to only ahead and behind. This method would work great for the average urban area. In areas where traffic density is much higher, it would make sense to have "climb" zones and "descent" zones where the mapping is still followed, but in addition only standard climbing or descending turns are allowed. Otherwise, aircraft are free to fly straight lines between points; getting to your desired heading only requires that you make a climbing/descending circle until your pointing where you want to go.
The altitude mapping method works great for vehicles trying to get around, but how do we handle take-off and landing? This requires that we remove the mapping requirement for the regions where take-off and landing operations happen. To resolve the collision hazard, we restrict the cruising speed considerably. By restricting flying speed in the lower layer near the ground, any conflicts that could result in a collision will happen slow enough that either one or both pilots can react with ample room. The worst-case approach speed is 50 knots for a head-on situation below 400 feet, and 100 knots for the 400 to 700 foot region.
Transitioning to the more busy and fast layer from the lower layers requires starting on a north heading as your aircraft passes through 1000 feet AGL. Aircraft climbing to this level will tend to align to north as they approach 1000 feet, at which point they must be traveling at least 100 knots and at most 150 knots. Thus, any conflicts are happening at 50 knots in-front or behind.
In the case of aircraft transitioning to the slow layer from 1000 to 400 feet, the aircraft will deviate from North to various random headings. The possible conflict vectors expand to a field of regard of 360 degrees (a conflict can come from any direction), but by the time these aircraft have descended to 400 feet, they should only be traveling 25 knots, which again yields conflict velocities of only 50 knots.
The most important feature of this approach is that the occupant(s) of the vehicle are in control, and have full proficiency and ability to make decisions based on what their instruments and eyes tell them. I've always been severely bothered by the various inventors and futurists that think that flying ought to be only handled by automated systems, with the occupants at their mercy. Flying is a talent and a freedom that the average person can master and should be able enjoy.