According to Autoblog, university researchers “have figured out how to hack self-driving cars by putting stickers on street signs.”

Alarmingly, one sentence in the full article states: “After figuring out how to confuse the system, though, they only need a photo of the target sign, a color printer, some sticky paper, and the will to live with the consequences of causing someone to blow through a stop sign at 45 miles per hour.”
This is a variation on destroying, altering, defacing, or removing a traffic sign. I guess, as an academic exercise it is worth knowing that this is possible. Making it general knowledge will have unintended consequences.
I share your concern, John, however I think one must hope that making it public knowledge will make the software people do a better job of encoding the signs (if encoding is the correct word) so that they will become dramatically more challenging to “hack.” It might also raise awareness among highways personnel and, say, law enforcement officers, to get them to pay attention to road signs and check that there is nothing unusual about them. Thanks, as ever, for your comment.