This is a brick, you can get them cheaply from any construction store. If you drop it from a bridge, or throw it properly from a road side, you can crash a human driven car’s windows based visual system and cause accidents.

And provably none of them are as good as robots.

Yes, because you can. You can’t design safety critical tech with the assumption that you don’t need to worry about adversarial inputs. People are assholes. I suppose if you really want a profit oriented motivation, you could force people to stop so you can rob them, without being so conspicuous as setting a road…

I mean... you’re right. But if we had self driving cars the signs they currently use would be good enough since the cars would actually pay attention to them.