Turn a temporary road sign for 30 speed-limit into a 80 speed-limit with some black-tape (I have already seen it done when people were angry to be fined by spee

Turn a temporary road sign for 30 speed-limit into a 80 speed-limit with some black-tape (I have already seen it done when people were angry to be fined by speed-detector for a few excess km/h, (or just for the lulz) ). It probably won't fool humans, but it's an edge case that a self-driving car may ignore.