Some are there because they need to be, some aren't. In my country most of them aren't there to keep you safe but to have a revenue stream. I know a couple of

Some are there because they need to be, some aren't. In my country most of them aren't there to keep you safe but to have a revenue stream. I know a couple of signals that are there to just make people slow down, and they work even if a lot of us know that there's no radar there.