Some Theories

I can't really make a strong argument for any of these, but it's all I got.

• A street worker is leaving his "signature" when he is on the crew to repave a street, much like signing your name in wet sidewalk pavement.
• They are some kind of route marker for a route, where the directional-orientation and numbers tell you how many blocks to go and where to turn in order find the next set.
• Some kind of dorky geocaching thing.
• An advertisement for Domino's Pizza
• stupid conceptual artwork.