The way this game produces 'activity' in your vicinity is that it requires your presence basically.
The way I can word it is that the game "stuff" around you (the Pedestrians, the cars being driven around on roads, etc) exists because YOU are there; rather than because "IT" is there. Meaning that the game systems, scripts, etc... it's dependent on YOU being there, in order for the 'radius' of activity of things to exist within to even be there in the first place. So essentially, the player character is the 'center of scrips generation' and movement around (for Pedestrians, Cars, and anything else in the radius of activity that moves around).
SO...
The reason why I say this is because the irony of observation of A.I. routines like staying on the roof of a car to see how far it would go means that you can ONLY observe such behavior in the first place because YOU are there. In other words, that car you stand on would CEASE TO EXIST once it 'passes outside the radius' that you probably don't see yourself as a player because it's far enough into the distance (and because Night City is filled enough with infrastructure as to block view in general of the 'horizon' point; where you'd see things pop out of existence).
But if you physically stay on a car, then the car itself CAN exist for as long as you can stay on it, because... well because you're there, you're the center of 'existence' and for things to pop into view. However, even doing that has its limitations because the developers didn't obviously program a full 24/7 Life Simulation into every spawnable cars and Pedestrians into the game. So even if A.I. scripts for Pedestrians and Cars can "pop" into existence from the edge of your player radius, it doesn't mean that they were coded to do 'something' for more than 10 minutes.
It's not a system like... for example like in Skyrim, where you have literal A.I. 24/7 Packages that gives 'life' and 'purpose' (although very basis and rudimentary, but it's there) to specific Named and 'fixed' NPCs that 'belong' to specific Towns that would enter their own designated house where they actually live at night when the sun goes down to go sleep on their actual bed; then wake up at the same hour every morning to leave their house and go to the local Town market until midday, to then leave Town and walk out to a nearby Inn and sit on a random bench and stay there until 6 in the afternoon. THAT sort of "life simulation" simply does not exist in this game, because it wasn't ever worked on ever, at all, at any point, during development.
All the cars and Pedestrians just move about in random directions without goal nor purpose in this game, it's just there for appearance within the player's radius of activity; and outside of that radius there is merely nothing being generated, and only the general city infrastructure exists in a permanent fashion. So what I'm trying to say in the end here that trying to observe any sort of semi-intelligent or logical A.I. routine or behavior in this game is an exercise in futility.