Browse this website collection of perplexing safety signs.
http://juliasmexicocity.typepad.com/safetygraphics/
Whoa!
Bad designs:
http://www.baddesigns.com/examples.html
one of my favorites http://www.baddesigns.com/USB.html (which way does the usb go in? I always seem to have to flip it)
Think about these when we are designing signs or safety programs in healthcare.
Simple test: have someone who has no knowledge of your project interpret your sign or try to follow your process without any instruction. You will identify many problems with usability this way. It is also enlightening to see what in your design contradicts human tendencies
Safety Dog's Blog 