Patterned street markings for the blind

Whoa! I had no idea that the gridded dot patterns guiding the blind had different patterns for different situations. Like the idiot that I am, I just assumed that the dotted patterns themselves were the indication to a blind person that they should be cautious while coming upon them. While yes, that is true, the dotted patterns are just one of many different patterns I now know to mean different things to somebody who can't see. Things like bike paths, or tram stops, or train stations, or crosswalks. So interesting! 

Look at all of these scientific optical illusions you can do with dot patterns

Here's a fun scientific experiment you can replicate easily. Using printed dot patterns on white paper and a photocopy of that same pattern on transparency, Tadashi Tokieda explains how simply rotating and moving the transparency layer can create lovely (and sometimes nauseating) moire patterns. It's an illusion and practical effect that I've seen used in books before, but having it explained in detail is neat.