[cynix]

If a stop sign was removed, I probably would've driven straight through without stopping too. How would I know there used to be a stop sign?

[dostick]

Yes, i mean what happens more often- if sign is not fully removed, but bent by collision or turned sideways by hooligans or something. Human would recognize that. Car will not.

[AtheistOfFail]

Most algorithms can handle slightly turned signs. However signs that are gone could be dangerous.

[daenz]

Sounds like the cars should share a centralized database of critical sign locations, and cross reference their GPS location with the database. When they approach a location that the database says should have a sign, and one is not detected, it should behave as if there was a sign, and report the incident to somebody.