Earlier quoted context omitted.
Rolling a ball on the street is probably enough to stop human drivers as well. Is carjacking that much of a problem where you live? I've never heard of anybody being carjacked here. I guess you could equip your car with one of these devices if you're concerned: https://www.youtube.com/watch?v=aLhWzMOccTg
A human driver has a good chance to recognize the situation for what it is and just hit the beachball. (Or heck, the hoodlum himself.)
Given that autonomous vehicles are supposed to lower the amount of traffic accidents, they should be programmed to exclude the lethal traffic accidents which are justified (basic on split-second information, live a little). At least beach balls will be relatively easy to recognize with computer vision. Problem is those pesky hoodlums will start dressing up as beach balls, throwing inflatable dolls in front of cars. And if you think that's a crazy idea, just wait and see what the actual future comes up with.
Honestly, the 21st century is basically clickbait: You won't believe what happens next!