Edit: ellaboration. Stopping in traffic and calling the cops because of this is going to be a non-starter. If you're the cause of the blockage how are they going to get there? The GP is right, there are many situations where it's not going to well, and I can see lots of pranks by highschoolers that will completely mess with self driving cars.
Heck an accidental release of confetti would be an interesting experiment.
The cops would only be called if the car is blocked for several minutes or the passenger decides to do so. Nobody cares if the car has to brake for a few seconds and then continues driving as usual. We spend far more time at traffic lights anway.
Heck an accidental release of confetti would be an interesting experiment.