Sign Wednesday: Necessary?

Signs of necessity are normally put up to warn of previous accident or behavior. For example this sign:



The slippery when wet sign is infamous because of people falling but more importantly people suing a company because they didn't have a sign of warning.

Now this brings us to this sign:



If we take the same logic and say that this sign is here out of necessity then there must be a problem with previous accident or behavior. I only wonder how many times there were previous accidents or behaviors before it became necessary?


(Thanks to Sam Luce for the sign.)