We are not going to talk about self-driving cars, but rather about what happens in our heads during a ride.
Once upon a time, I was hauling some oversized cargo in a trailer, approaching our house via a sidewalk and thinking about nothing in particular. There's an old lady pushing an old man in a wheelchair in a distance in front of me. I ding my bell in advance to prevent surprising them when I get closer. The lady looks around, swerves a little, goes closer to a kerb and speeds up as if running away from someone. That's strange, I'm not chasing her, but there is no one else behind, so it means she got scared after all. I'm slowly closing the gap and starting to hear what they are talking about. Well, not really talking - they are passionately cursing about *ing cyclists. Oh no, that's a misunderstanding, I didn't mean it that way. I'm slowing down to their leisurely walking pace and begin: "Good afternoon, don't get disturbed, I'm just going to check if I fit besides you." Because the cargo of mine is really wide and also fragile, going over grass is not an option. "Oh, I see I don't fit. But that's no problem because I'm going to..." There's no time to finish that I'm going to turn right here into this door on the left and so I'm not going to try to overtake them anymore, because the couple starts telling me angrily what they think about me and what I should do. So I apologize, dismount, turn and think something about *ing elderly people.
And then it dawned on me: why the heck was I trying to overtake them when I was going to turn right here into this door? I didn't have to ring, I could dismount and quietly walk the bike to the door without the two even noticing I was there, and it would have cost me nothing at all! This is exactly the same situation I see on the roads almost every day, which never stops irritating me: a car hastily overtakes me just to slam on the brakes right in front of me and then turn somewhere. WHY?
So, let's make a reconstruction: what was I thinking about at the moment? I don't remember, but certainly not about driving the bike. There was no need for that, the sidewalk was straight, no danger in sight, the controls were operated subconsciously. Upon spotting the slowly moving couple, the subconscious mind automatically sent a signal "they are considerably slower than you => overtake them" and immediatelly called the standard overtaking subroutine: check the situation ahead (free => OK), ding (OK), move to the left (OK), check width (insufficient => abort maneuver, slow down, return to the right, end). And it probably looks the same from behind a steering wheel. Conscious mind plans the overall strategy (I'm going to turn over there), the subconscious reacts to external inputs and resolves traffic situations by automated routines (yield to this, pass that, stop here, overtake this etc.). For the conscious mind to fully take over and, instead of automated reactions, keep coming up with solutions optimized for every particular situation, it takes certain amount of concentration. Unfortunately, that's not always the case.
What is the takeaway from this? That driving any vehicle, motorized or not, requires constant attention. Nothing new, but worth repeating.
P.S.: Yes, I know riding a bike on sidewalks is illegal here. If I get caught and fined, I will not protest.