Decoding Utility Markings Spray-Painted on City Streets | Hacker News Reader

Decoding Utility Markings Spray-Painted on City Streets

99percentinvisible.org

74 pointsdeadbunny22 comments

A coworker of mine shared this neat little book which contains, among other things, descriptions of a lot of the internet infrastructure markings one can find on the streets of NYC based mostly on the author's own observations:

https://www.amazon.com/dp/B018CH0MX2

Definitely something I had never really thought about until recently.

I see a lot that say "USA". Always curious what that means. Presumably not United States of America. (this is in California)

It indicates that the markings were made by Underground Service Alert, the entity that's on the other side of 811.

c.f. https://en.wikipedia.org/wiki/Underground_Service_Alert

Thanks!

Awesome. Thanks.

The European standards for pipes as formal plaques on the wall, and the UK one which uses a different notation and premade concrete stub-sign at ground level had me fascinated.

Here’s some examples of the UK signs:

https://www.plateandlocate.com/article/1/name/Buried-valves-...

Oh they're far more modern than I was used to.

http://metricviews.org.uk/wp-content/uploads/070-rc.jpg

was what I was expecting. Glad they've gone metric and modern.

I was putting in a gate once and had them come out to mark the utilities. There was a gas line running through the area, but it was marked at 3 feet off from where I was digging the post holes. When we pulled the auger out of the ground I noticed the gas pipe right on the very edge of the hole. I'm still not sure how the auger didn't cut through it. I'm also not sure how they managed to be so far off the mark.

UK anecdote here, but I remember reading that the paper maps that this stuff is recorded on, can be many decades old and were originally hand-drawn so not very accurate. In the UK at least, quite often roadworks cut through pipes and cables accidentally even though they should know where everything is.

That's fairly poor locating there - either they were using a paper map or using a radiodetection line locator and the operator wasn't very good or the line/tracer wire was electrically continuous with another nearby structure and it was throwing off the signal.

Anecdata, but I worked several years in infrastructure projects (and in the course of that cut numberless pipes, cables - both electricity and communications - and what not), the basic issue in my experience was the sloppyness with which the drawings of the utilities layouts were made or the use of "unreliable" references.

A typical one, is the indication (on the drawing) that a cable is 30 cm from the border of the sidewalk, but in the - say - 30 years since that cable was laid down the sidewalk has been enlarged by 40 cm AND a new cable has been laid down at 30 cm from the new sidewalk AND this other new cable has not been added to the drawing (or it has been added to another drawing by mistake).

So you go there, actually find "a" cable 30 cm from the sidewalk, believe in good faith that it is the one on the drawing, and next minute you cut the one now under the sidewalk.

It is only a few years that GPS positioning is used for cable and pipes layout (which should give better "absolute positioning") but the issues about mis-labeling and mis-reporting (given also the number of different companies, particularly telecommunications ones that may lay new cables) have not changed much AFAIK.

We once had a set of bored piles (Ø 1000 mm) for the foundation of a sustaining wall miss a high pressure large diameter (Ø600 mm) methane pipeline by millimeters (the drilling rig bit the steel pipe covering, making the actual metal of the pipe shiny).

The explanation was that the people making the drawing and maintaining the pipeline took as reference the milestones of the road (that were replaced because a curve was added some kms before and shifted by 100 m) and gave our project the green flag because we were almost 100 m away from the pipeline.

We were putting in an electrical line for the City, had the utilities marked out, all good. Apprentice cut through an 1-1/4" (32mm) gas main with the ditch witch. Suddenly saw sand puffing up; had the presence of mind to cut the engine before running. It wasn't our fault, though, because the gas utility marked it 5' (1.5m) off. It happens.

As UK'er my first thought was 'Are the UK colour codes the same?'

And yes, They are!

https://www.cornerstoneprojects.co.uk/index.php/blog/undergr...

I didn't undestand why they said that diggers are on their own in the UK, and then in the next paragraph went on to talk about the UK's colour codes. It seemed like a contradiction.

I have a client who does groundworks and they always know when there's supposed to be something down there. You use the detectors to double check not as your only source. There could be something down there that's old and not on the registry or that HV power cable could be a few feet to the left of where it's supposed to be.

When you're the man taking a circular saw to the pavement and your boss is the one paying for the repairs, you check!

For markings of such importance, you'd think they would have a standardized stencil. The video of the worker spray painting seems a little too nonchalant, potentially opening the door to misreading. And if standardized, there could even be a digital reader (like an OCR?) to tell others exactly what it means in the event of confusion or differing interpretation.

There’s not many options for what it could be, so it’s pretty easy to figure out. The color is most important, with some additional info like utility (which are few and welol known) and width.

I wonder how they factored in that red-green color blindness affects up to 8% of males. Should color really be the most important? Would be interesting to see what percentage of accidents are attributed to misreading a symbol vs a color vs anything else.

It's probably old enough that they didn't. Plus as said elsewhere, where NOT to dig. If looking to intersect it someone who can see the color correctly will have to identify the location.

Those markings are primarily useful for indicating where -not- to dig or trench; it often doesn't matter what the markings identify.

If digging needs to intersect any of those areas it generally means doing it by hand.

Really hard to read that chart. The font is like 4 pixels tall total with massive compression artifacts.

I clicked on it and got a bigger image that was easier to read.

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