Lost in Translation

Every once in a while there are messages that somehow don't seem to make sense across cultures, no matter how much one tries to understand them. Here is one I saw a couple of days ago. This sign is posted on a fence surrounding an area that seems to be under construction.

This translates to "Attention! Use a seatbelt." I'm a bit confused about what the words and picture together are trying to convey here (if it's any help, the sign is facing a street that is not accessible to drivers of private cars). Is it a message intended specifically for crane operators? If so, why is it facing the street full of pedestrians?