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Decoding Sidewalks

If you’re like us, you’ve been going on a lot of walks during the pandemic, which means more time staring at sidewalks. But you may not have noticed the complex network of construction markings under your feet. And why would you, they're fairly boring to look at. However, for some, decoding sidewalks is a bit of a hobby. You might assume the scribbles refer to past construction jobs or upcoming plumbing repairs, but once you learn how to decode them, it becomes a giant, city-wide puzzle! #geeks


First up: Colors. Decoding the color of the spray paint is a quick way to hone down your options. Here are some basics, courtesy of the 99pi.org website:


Red: Electric power lines, cables, conduit and lighting cables

Orange: Telecommunication, alarm or signal lines, cables or conduit

Yellow: Natural gas, oil, steam, petroleum or other flammables

Green: Sewers and drain lines

Blue: Drinking water

Purple: Reclaimed water, irrigation and slurry lines

Pink: Temporary survey markings, unknown/unidentified facilities

White: Proposed excavation limits or routes


Symbols and letters are painted in one or more of the above colors, and are luckily quite literal. For example:


D is fordepth

H/V is for high voltage

S/L is for street lights

H/P is for high pressure


The same goes for the symbols. Arrows tend to indicate the direction of flow or where the equipment terminates. Numbers accompanying the symbols indicate the length, breadth or depth of the work (typically in feet).


These markings weren't always around. It all started in 1976, when workers in Los Angeles by mistake cut through a petroleum pipe and blew up half the block. Ever since then, construction work has been recorded in national databases so people know where the pipes and wires are buried.


Next time you take a stroll, see if you can decipher the messages and map the world beneath your feet.


Learn more:

Colorful Language: Decoding Utility Markings Spray-Painted on City Streets

Decoding The City: The Road Graffiti Placed by Utility Workers

Secret Language On The Sidewalk: Decoding ‘Utility Graffiti’

Image by Kurt Kohlstedt at 99pi

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