In the UK, we have "New Layout Ahead" signs everywhere. Once erected, they seem to stay in place forever and increase noise. Is there any evidence that these are beneficial?
Seriously, some places there are just so many signs that you couldn't possibly take in the information they provide in time. And the majority of the information they provide isn't useful.
One of the things I hate the most are the digital signs that are springing up everywhere. These things are expensive, and >99% of the time they are distracting me with pointless messages about watching my speed, not drinking and driving, not driving while tired etc. Such a waste, and surely causing more harm than good.