streetlights— high-pressure sodium (orange) versus mercury vapour (green) (Atlanta: house, price)

[bryantm3]

recently i've become interested in streetlights, and i wondered why all the streetlights here in the metro atlanta area are orange, when i remember as a little kid (early 90s) that they were green!

i then found out that the old streetlights, from around the late 1930s to the 1980s and early 1990s were lit by mercury vapour bulbs which cast a green glow. they've gradually been replaced by high pressure sodium lights which glow a yellow-orange colour at night.

however, i took a trip to greenville (SC) last night and i saw that most of the streetlights there were still mercury vapour powered, whereas i don't remember seeing any MV streetlights still remaining in the atlanta area.

here's the difference between the two:

mercury vapour:





new high pressure sodium lights:





honestly after driving through greenville i really miss the soft green glow of the old streetlights. it's strange that something so major has happened, that our entire world at night has changed and not many people have noticed.

does anyone know if there are areas of atlanta where the old ones haven't been replaced?

[chalvey]

Cool, I never knew that. I grew up several years after you mid to late 90's & always saw HP sodium lights. Sorry mate, I don't know of any places.

[cqholt]

The newest trend among streetlights are LED. They burn brighter, use 40% less energy, and last longer.

[PKCorey]

In Baltimore, mercury as well. Used to turn bright green/blueish then you knew it was time to head inside of the house!

[Mal93]

The HP sodium lights are also less impactful to insects and birds. While all artificial lighting causes confusion in creatures (including humans whose circadian rhythms are thrown off by LED bluish lights or night brightness), HP sodium seems to cause less issues...maybe because the orange color doesn't "travel" as far? Bugs aren't "attracted" to artificial light-- they are dazed by it, and bug mortality has increased as more outdoor lighting has increased since they are sitting ducks for predators or collapse in exhaustion. Birds falling dead out of the sky or having confused migratory paths is also blamed on light pollution.

There were always tons of fireflies in Atlanta (we still have a good many thanks to our many parks and streams), but the more streetlights you have, the less you will see them. They like other night bugs tend to prefer light that follows the strength of the moon. Obviously those prison-level blazing security lights on every corner of the house are a bit brighter to them. I know, some people will be "its a bug...if it dies that's less I have to spend on the pest control service" but these bugs eat mosquitos, pollinate (moths) and would probably prefer to go about their business than be sucked into the brightness next to back doors and sidewalks.

I am glad more cities are taking care to reduce the glare of outdoor lighting by ensuring the lights are covered and directed more like a spotlight than a floodlamp. Its actually safer-- "floodlights" create deep shadows and silhouettes, where you can actually see more with a directed light.
I always hated the buzzing noise the old streetlights made when they came on...

Anyone remember when ATL couldn't pay their electric bills and the connector had no lights at night? Conversely, I remember when the huge bridge downtown (by Grady) first got the interior lights installed and they turned ALL of them on. Talk about being blinded!!

[nrgpill]

Actually plasma technology is even more efficient than today's LED when it comes to lumens per watt, although price might sway in LED's favor right now. Something like LG PLS holds a lot of promise, even for indoor horticulture. As for LED's, I personally love the tech but only a few manufacturers at this juncture produce anything of quality (Cree & Osram, then you have a bunch of Chinese outfits).

Originally Posted by cqholt

The newest trend among streetlights are LED. They burn brighter, use 40% less energy, and last longer.

[ATLTJL]

In fish tanks, you can get blue LEDs that are supposed to be good for the fish because they mimic light from the moon.

What if we replaced everything with blue LEDs? It would look odd, but I wonder if the soft glow of moonlight would be better for the environment.

[nrgpill]

Perhaps if science can yield which nm spectrum actually mimics the moonlight, then it is plausible.

Going back to the topic at hand, LED would be a good way to go, but the spectrum blend has to be an ideal mix while the lens angle is wide enough for decent coverage. The lens angles are critical in the overall application because at wider angle you start to lose lumens. In horticulture application you typically see 60 degrees to 120 degree lens all blended before reaching the plant canopy.

Originally Posted by ATLTJL

In fish tanks, you can get blue LEDs that are supposed to be good for the fish because they mimic light from the moon.

What if we replaced everything with blue LEDs? It would look odd, but I wonder if the soft glow of moonlight would be better for the environment.

[rcsteiner]

Originally Posted by bryantm3

recently i've become interested in streetlights, and i wondered why all the streetlights here in the metro atlanta area are orange, when i remember as a little kid (early 90s) that they were green!

i then found out that the old streetlights, from around the late 1930s to the 1980s and early 1990s were lit by mercury vapour bulbs which cast a green glow. they've gradually been replaced by high pressure sodium lights which glow a yellow-orange colour at night.

however, i took a trip to greenville (SC) last night and i saw that most of the streetlights there were still mercury vapour powered, whereas i don't remember seeing any MV streetlights still remaining in the atlanta area.

If you fly over the Atlanta metro at night, it becomes obvious that there are two distinct types of lighting that are common in the metro: the orange sodium lights, and others which are much whiter in color. Everything is a patchwork, and I would guess that the mix is roughly half and half, but I suspect most of the non-sodium lights are in commercial parking lots and similar places while the sodium lights are lining residential streets.

[bryantm3]

Originally Posted by rcsteiner

If you fly over the Atlanta metro at night, it becomes obvious that there are two distinct types of lighting that are common in the metro: the orange sodium lights, and others which are much whiter in color. Everything is a patchwork, and I would guess that the mix is roughly half and half, but I suspect most of the non-sodium lights are in commercial parking lots and similar places while the sodium lights are lining residential streets.

yes, that's what i was thinking— but the whitish coloured ones are mostly the new metal halide lights. i've seen very few of the MV lights in atlanta, just one or two here and there that got looked over. anyone know when they replaced them all?