Spiral street sign stickers

I wrote once before about mysterious stickers I saw on street signs in the area. Now that it's bike season and I have my bike at work, I decided to alter my usual route for this morning's ride to get pictures of a few of them.

This is the best example of one of these stickers, this one in blue.

This one, in red, has had its "tail" torn off.

This one seems to be new, and features three of them, in red, yellow, and green, all of them smaller than the other ones I've seen around.

All three of these pictures feature the tail pointing off to the lower right at about the same angle, but others I've seen have it pointing off to lower left.

Someone went to the trouble to make these and someone else put them up in various places. They must be trying to say something, but I have no idea what, nor any thoughts on what to search on to find out. Anyone know?