What are these things?

[Steve Grisetti]

Occasionally, I see these thing signs along the road or along median strips just outside the city.

I've had lots of people guess what they were (gas lines, sewer lines, airport navigation, etc.) -- but does anyone know definitively what they are?

I knew I could count on you guys.

[Ron]

Speed Limit - 128 MPH

No idea, I've seen them too. I think they're usually near electrical power lines, so maybe something to do with that? It also appears that it's made in such a way that aircraft can read them too.

My guess - Power Lines at 128 feet.

[Chuck Engels]

Steve, I didn't know they had runways right down the middle of the street in Milwaukee

[Todd08]

Steve, that is a marker for pipe line patrol planes

PIPE LINE MARKER.jpg

[Chuck Engels]

This is the best, and the smartest forum in the known universe

Steve, did you know you have a pipeline running under your house?

[Steve Grisetti]

Thank you, Todd!

I will sleep so much easier tonight.

[Todd08]

That’s all one pipe line, were I live they pump it back into the ground for storage, and then send it else were in the country and Canada. If you get a chance look at the map in the attachment, I live between Shelby 2 and Washington 10 fields. They only show the 20”, 24” 36” dia. Pipe lines.
http://www.dtegasstorage.com/pdfs/customerMeeting2007.pdf

[Steve Grisetti]

I also got this nice reply from Wisconsin Energies, confirming it:

Dear Mr. Grisetti,

Thank you for contacting We Energies. I had to research this a bit myself. The picture was very helpful.

This is a casing vent. The number on it allows for aerial patrols. There is a gas main (large diameter and/or high pressure) running under the street. The pipe is in another pipe called a casing. The casing provides extra protection from the effects of vehicle traffic above. Should there be a leak in the gas pipe, the vent pipe allows the gas to dissipate into the atmosphere rather than allow it to be trapped underground where it could migrate into a basement.

[Clayton]

Note to Steve....

"this is NOT a smoking pad"

"this is NOT a smoking pad"

[GerryB]

What a clever idea!
Please Mr Terrorist, why not place your IED here, or by any of the other numbered poles ....
Own goal, comes to mind!
Gerry