[xypage]

Yeah but an optical illusion to confuse a human would have to cover most of the sign I think, and I know this isn't a random sticker but if this is possible there's no way that people don't make some and put them on signs just to mess with the cars because they can. In fact, I'm sure they'd do the same with stickers that would confuse people, it's just that there aren't any (that we know of, but considering self driving is a lot newer than people driving I'd say finding one for cars already but not people is telling on it's own) small enough that they wouldn't get immediately removed.

[WithinReason]

Why not just remove the sign if you want to mess with people?

[xypage]

If you remove a sign it gets replaced right away, if you put a sticker that barely covers it like this then it probably doesn't get taken off for weeks, if at all.