What are These Utility Street Markings?

ANSI. I kick myself for not thinking of that. 100% on target. Thank you.

The green paint boys came through yesterday. They marked sewer lines.

I also walked around and saw "bore" (for "horizontal boring" rather than trench digging) in white paint.

And other informative (to them) messages:

These markings suggest that they will do a cross bore under the street and install a pull box.

I'm starting to think the 3" might be a 3" line containing multiple cables and the 1.25" might be 1.25" cross tubes going under the street. I don't know if you ever made it back into my hood, but our power poles are in the back yards. All of the "HH" markings line up with power poles, but the "HH" points to the pole and the "1.25" points to the street away from the pole.

With all of the "HH" markings lined up with poles it would seem like they might go to the poles. But, the tube markings don't go in the direction of the poles. And, if they were going to the poles, then why would they do all this extra underground horizontal boring? And, the markings suggest that they are not boring to the poles (that they are lining up with). Thus, the mystery continues.

The electrical lines coming from the poles might be laid down next.

Perhaps the box will have power for amplification equipment joining the communication lines.

As a slightly side note, I'm sure you, SE, know about "fusion splicing". But, for anyone else reading this, it is interesting to do a YouTube search on "Fusion Splicing Fiber Optic Cable". The utility workers in the little white fiber trailers can cut and join fibers in about a minute each. If the fiber is on the pole, then they will bring it down and work in a clean and comfortable environment inside the trailer.

When they are done making the splices they will put the splices in a black plastic "Coyote", hang the Coyote on the support wires on power poles and take up the slack with the loops shown in the picture below.

The municipalities have been doing a lot of upgrades in my area, and when I’m walking our dog(s), I read the little colored flags but of course I forget what they are,

thanks for the info.

These markings are probably associated with a set of plans that HH (company or name of principal) has submitted for permitting...waiting for inspection...

Looks like Chinese to me!