Streams

Those Little Orange Discs on Top of Street Lights? They're Photo Cells

Monday, June 02, 2014 - 01:00 PM

Well, this one's a bit of a layup. For our new reporting project, I asked you to submit nominations for "city mysteries" -- things that have always bugged you about life in the New York area that we could try to get to the bottom of. City quirks that have an answer that lies just beyond the grasp of Google. Parking regulations, construction sites, bodega cat regulations, things like that...

The overwhelmingly popular request on Facebook -- if you're the type who is overwhelmed by six -- had to do with the little orange plastic things (LOPT) on top of street lights. You know the ones.

The LOPT debate quickly rose to the top of our thread, so in a brief detour into "let-me-Google-that-for-you-territory," here's the answer: they are photo cells that turn the the street light on and off, depending on how dark it is. Sometimes they are a small round disc, sometimes they are a little wand. But they are always mysterious (until now).

And guess what: a Department of Transportation spokesperson tells us that they are not always orange -- though we've yet to see another color.

But the mystery (or this blog post) does not end here, because several of you pointed out that there are other types of LOPT attached to some lamps. And you're right! What, then, are these bulb-like orange things you see on some light posts, often part way down the pole?

Turns out, they are vestiges of NYC's fire-box era (also known as pre-cell-phone era). The orange bulbs indicate that an emergency box -- which connects you directly to the FDNY -- is nearby. This tableau nicely captures the diverse ecology of street light appendages.

The city's 15,000 remaining fire boxes should still be functional, by the way, but according to recent FDNY data, only 2.6% percent of fire emergency calls originate from these boxes, and some 88% of those are false alarms.

One last note on the solar cells: Before individual sensors on lamps, each pole was connected to the next but equipped with isolation transformers or a circuit cutout that allowed the current to pass through the lamp even if that particular bulb was not working. The cells are more power-efficient, less susceptible to breakdown, and don't have to be manually turned on each evening and off in the morning. They are also independent from one another. The DOT tells us, by the way, that this is not the case for highway and parks lights -- those are group controlled by one large solar panel.

We were not able to receive confirmation or denial that this is possible:

If you want to recommend a mystery for us to investigate, post on the Facebook thread below. If you're not on FB, email blshow@wnyc.org with "City Mystery" in the subject line.

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Comments [8]

Helen from UES

WHAT IS THE DEAL with those liquid nitrogen tanks on the streets?!

Jun. 09 2014 10:45 AM
My Space from Brooklyn

Can we change the discussion to "Why are so many street lamps ON during the daylight"?
It is because these little $2 light sensors are broken. So the lamps stay lit 24hrs every day. If the lamp is 150 watts, and stays lit an extra 12hrs each day, that is 1.8 kwhrs each day. Or about $0.45 per day of ConEd electricity wasted. Or about $13.50 every month of wasted electricity. For a $2 sensor! Think about that the next time you see a street lamp lit in the daytime.

Jun. 06 2014 01:48 PM
AMHess from Harlem

@Bill from uws

Supposedly this design (also at 34 St A/C/E and Atlantic Av 2/3/4/5) was originally intended to avoid chaos at these busy stations by keeping people from transferring between local and express trains across a crowded platform.

Jun. 03 2014 11:04 AM
Bill from uws

Why are there 3 platforms at the 34th St. 1/2/3 station? Every other express station has 2.

Jun. 03 2014 07:46 AM
Frank Hall from Fair Lawn

@David Ranada, you're right; they're not "photovoltaic cells," (as in cells that are generating power) they're called "photocells," and they're really just a kind of switch. They're nothing new, either. They just open and close the electrical circuit, based upon whether or not they are exposed to light. Your description of them as "sensors that turn on the street lights when the sky darkens" is apt.

Jun. 02 2014 07:18 PM
Dave from Sunset Park

Interesting that they're for gamewells.

Jun. 02 2014 04:35 PM

@David - You're right, we've clarified - the sensors turn the light on and off, they don't power the light by themselves. Thanks for the information!

Jun. 02 2014 03:30 PM
David Ranada from Astoria

There must be some misunderstanding. The orange street light devices cannot be "photovoltaic cells that power the street light." They are most likely ambient-light sensors that turn on the street lights when the sky darkens enough. This explains a laser's ability to turn a lamp off when fired at the "photo sensor," as the video correctly states. Photovoltaic panels that power individual street lights are, on the other hand, 1. flat, 2. usually pointed south, toward the sun, 3. larger than the orange devices and 4. a very dark color. Even if they did contain photovoltaic circuitry, the orange devices don't have nearly enough surface area aimed in the right direction to generate enough electricity to power a street light. Google image searchs for "street light sensor" and "photovoltaic street light" will immediately reveal the differences.

Jun. 02 2014 03:19 PM

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