No doubt we'll see people doing this, however. Because change is scary.
Just turn around? So the cars will be near spherical in design and with 4 wheel steering? Cool.
There are so many unresolved issues around self-driving cars, and the answer always seems to be "just do this", without any real solution to the problem as described. Self-driving vehicles may well be a good thing, but let's not stick our heads in the clouds and assume "it'll be okay".
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.
They can do that now unless you are suggesting running them over as a solution.