Esoteric Road Symbols

Curious markings on local Sullivan County roads: A pink triangle (Greek letter Delta, shown here inverted), emblem of the goddess Demeter; symbol for the red planet, the Roman god of war, and of masculinity? Somehow I don't think the Mars sign with "MH" in the middle means "Men's Mental Health", though it could. (The arrow, in this case, was pointing into a wooded area.) And what about that point in the center of the triangle?

Actually, the blue image probably means (at least according to the intent of the person who sprayed the paint) something like "Man Hole". I'm not sure about the Delta. Maybe "Drain"? That's a wild guess. Anyone have another answer?
During a six mile walk, I passed more than a dozen such signs painted on new pavement. I imagine the images were deliberately placed there by public employees (or contractors) with very specific intentions, probably related to the infrastructure of and around the roadbed.
But what I find genuinely interesting is that symbols themselves are everywhere, with such potentially different meanings embedded in the eye of each observer.
Click either image for further commentary.
I took these photos on Rockridge and Thompsonville roads in the Town of Thompson, near Monticello, in late November 2007.