I wonder if there are magic QR codes (other barcode types available) that the car can read and follow, e.g. if they drive into Waymo's cavern and the Internet connection isn't solid.

GoPro's "Labs" has a special firmware for their cameras, and the configuration doesn't happen by selecting items on the tiny screen, but on a webpage that generates a QR code that can then be entered into the GoPro by pointing it to the generated QR code.

It seemed reasonably clear from the article--and from the sign--that the sign is for passing humans to read. The traffic cone is for the AI driver. Waymos don't drive over traffic cones. I suspect this is essentially 100% effective.

There were some attacks based on modifying road signs: https://arxiv.org/abs/2307.08278 . At the very least Cars can be tricked into going over local speed limit. I wonder if fake one way street signs would have priority over build in maps.