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

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The little orange photovoltaic cell on top of NYC street lamps.

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 with "City Mystery" in the subject line.