An autopilot just keeps an aeroplane flying on course at a set altitude, and speed, it does not look out for collisions, in turbulent conditions the pilot usually takes over
If one aircraft is within 1000 ft (altitude) of another this is treated as highly dangerous.
If one aircraft can see another this too is considered as highly dangerous
In crowded spaces aircraft are under the direction of the local air traffic control.
The most uncontrolled time is take-off and landing, autopilots could do these but pilots normally do because pilots can deal with grey areas (maybes) while automated systems can only deal with black or white (yes or no).
But above all, the passengers don't know when the pilot is in control or the automatic system.
As a control problem, having all cars automated would be relatively easy, if all the vehicles are to follow the rules but if this were the case journey times would increase more than I think users would tolerate.
We may not think of it in this way but all of us gamble to a greater or lessor degree to make progress, without this city traffic would grind to a halt.
Take turning out of a junction from a minor road into a busy major road, do we wait until the road is clear or do we we try and predict where the main road traffic is going to be while we make an entry?
Or a cross road with four cars one in each road, waiting to move, some will be indicating, some not, some correctly positioned on the road some not.
The road signs and road markings should help but in heavy traffic we often pass the signs without noticing because we were busy watching the traffic.
Road markings should help but do the other drivers know the difference between stop and give way?
What about the vehicle positioned to turn right but signalling left or vice versa or no signal, are they going straight ahead or just forgot their indicator?
Is the indicator from the last turn they made?
We are aware of vehicles waiting behind us so we make a judgment, a calculated guess, or we gamble.
Why?
Very few if any will be thinking, I am in the right, I will move and if you hit me it will be your fault.
Most, will draw on past experience, I did this last time and it worked so...
Wrong decisions are likely where software is involved, from badly written, bugs or simply unforeseen circumstances.
This risk can be reduced to almost zero by having three control systems, each independent (different, hardware, and software) and only acting on the majority verdict.
I think we are likely to go ahead with automated cars simply because it's sexy but in that case we ought to decide how many dead and injured can we accept.
Note, we never made that decision when cars were introduced.
