I said this in my comment: "...with the human sign as a fall back or as a second point of reference."

You wouldn't remove human sign identification from the algorithm, you just supplement it with the small QR code under the sign.

Not that I think QR codes are a good idea, but why does this property matter?

People can be dicks to each other in myriad ways, I don't find these arguments that you could trick self-driving cars super compelling.