I mean that a human is ready to jump in at any point an "exception" happens.

Example: During parking, which I witness daily in my building, it happens all the time.

1. Car gets stuck trying to park, blocking either the garage or a whole SF street 2. A human intervenes, either in person (most often) or seemingly remotely, to get the car unstuck.

I'm not in the US and have never seen a self-driving car.

Can you explain how a human intervenes in person?

Do you mean these cars have a human driver on board? Or the passenger drives? Or another car drops off a driver? Or your car park is such an annoying edge case that a driver hangs around there all the time just to help park the cars?