First these are ground effect vehicles, not true aircraft. While Star Trek, Star Wars, Blade Runner, The Jetsons, and every scifi I can think of has "magically hovering" private transportation, I am trying to design a more reality-based highway system for the flying cars in my near future. Click here for a video of the cars I designed during a typical flight. This is not urban traffic, it's a highway system which simply expands the suburban area around a business center, like the American Interstate system. Even with the average car boasting 800 BHP the LH2 economy lacks the energy density to give everyone their own personal aircraft, so I can't use the vertical lane separation which may otherwise be ideal, however canals, open water, and grassy fairways replace paved roads and the great efficiency gains of ground effect flight bring more remote areas closer to population centers.
Basically your route is continuous and cars never really need to stop before their exit. The speed limit is 160 kph / 100 mph.
In the way that we occasionally punch the accelerator and inefficiently launch into the oncoming lane to pass a slower vehicle, My vehicles enter free space at intersections for brief periods.
Now, there is a complete civil engineering task to fully design traffic flow in this scenario but I'm focusing now on lane separation given only real-world aerodynamic forces are maneuvering the vehicles. Here is the jist of the how highway system works:
Roads are not rigidly constructed, they are augmented reality overlays in the driver's field of view. Except for basic emergency markers, all traffic signals, lane indicators, signs, and even billboards are augmented reality overlays.
Drivers will never need to compensate for wind gusts. "Smart Roads" provide active air movement data to vehicles, Cars anticipate and auto-correct for most gusts up to 45 mph cross-winds. Obviously the effectiveness diminishes at low speeds, assume traffic travels at the speed limit.
Drivers never “swerve.” Smart roads dynamically adjust their own lanes based on road conditions, such as an accident vehicle or passing ship. If your path will be obstructed for any reason such as an accident or passing ship, your display will see a "hill" ahead and your car simply jumps over the obstruction. Proximity sensors prevent tailgating, so cars can never be surprised.
The car fully controls yaw to place the car on the smart road, ascending or descending as needed. Drivers work in two dimensions only. The feel of driving the vehicle is much like a car, with a slight addition of pitch and roll in turbulent air. The road determines their correct altitude until they go "off roading".
Exiting the highway is done by pulling out of the main lane of traffic, decelerating, and banking away onto another road or off-road area.
Cars are smart, but not fully automated. They have proximity-based cruise control, predictive gust correction, and lane-drift correction. Mostly however, the driver determines the lane and speed.
There is no commercial freight on this highway but it will cross marine freight lanes and other obstacles occasionally. This is handled by hopping the road over the obstacle in a virtual bridge. Again, cars automatically follow the road and there are no surprises.
Turns are no less than 250m inside radius and speed limits reduce to 80mph. (This is a correction - originally wrote “diameter”)
There is no anti-gravity anything. They rely on Power-Augmented RAM for lift.
They use air cushion hovering.
(These pictures are concept art for reference, not a final design)
I do expect the vehicles to still be "road legal", meaning they are no more than 8 feet wide on ground, 10 feet max with extensible wings. They have very basic wheels which can brake and provide neighborhood propulsion.
While this mode eliminates hazards of poor traction from ice, snow, sand, or rain, it adds wind hazards.
Today US road lanes are officially exactly 11 feet wide, for a maximum legal vehicle width of 8 feet. If I were to visualize traffic in this type of highway, what would be the normal lane separation? How close are we to oncoming traffic, and passing traffic?
Vehicle performance will be much like the vehicle in this patent, however thrust and yaw can be used to decelerate the car at 0.6g on the road, but not at all in free flight where obstacles need to be handled as a plane would.
Items outside the scope of the question
I am only looking at lane separation for this specific road. As I describe driving on this highway in the story, what does it look like? The following other related engineering problems will be handled elsewhere:
Traffic queuing for entering and exiting vehicles
Vehicle technical specifications not already included
Urban (low speed) travel
Smart road fundamentals of operation
Weather other than winds (precipitation, temperature, etc.)