Sometimes there are warning signs of potential danger. Here is one:
I believe the idea in the sign above is that beyond the fence is China. The warning is for those who may have no passport or other documentation, so it would be dangerous for them to try to enter China without papers. There is the subcontext, of course, that there is a cliff there and below that 9825 kilometers of open sea and THEN China. So, sure there may be danger. There are other countries and continents beyond the fence as well, and I imagine that the sign could be a reminder to those traveling anywhere “out there.”
Sometimes the signs are superfluous as is any encouragement to “be careful”, to “take care”, because presumably a reasonable person will take care.
But it is also nice to know that someone else is wishing it for you anyway . . .