Better Streetlights for Tulsa

[patric]

Alright, so it looks like Las Vegas is basically following IES standards. Assuming the luminious efficacy is around 90 lumins/ a watt we should have a total light output of around 36,500 lumins.Using the inverse square law I got a luminious intensity of around 28 lux. It seems to fall in line with the IES standards for intersection lighting.a measure of the total "amount" of visible light emitted by a source.

Lumens is a measure of the total amount of visible light emitted by a source, and is usually printed on the packaging or right on the lamp.
What you measure on the ground is going to be either Footcandles (US) or Lux (Europe).

Typically, the average residential streetlight in Tulsa is going to be an open-bottomed prismatic ring NEMA luminaire, burning a 100-Watt High Pressure Sodium lamp, which outputs 9,500 Lumens and places about one footcandle of light on the street beneath the light.

IES standards (actually "Recommended Practices") take into account the street surface reflectivity, so a quiet residential street with asphalt pavement and few conflicts might range from 0.4 to 0.8 footcandles.  Keep in mind this is weighted for Sodium light, so bluer light sources (which the dark-adapted eye is much more sensitive to) should be less intense to achieve comparable visual acuity.

I found a picture if a warm white, in this case 2800 kelvin, streetlight. It's a metal halide, and it's optics are poor. It's still worth a look, I think.

They look like different fixtures, the one with the lens "dropped" is what you want to avoid.
As far as lamp type, here's the super secret streetlight label decoder chart:

[Cetary]

I was in San Jose the other week, and my visit there was an eye opener.One light source that I'd thought I would never see,low pressure sodium, I got to see firsthand lighting whole streets.I saw cobra head style LPS fixtures.Here are some of the lights.

http://goo.gl/maps/1y1LP

http://goo.gl/maps/4N51J

I really have to ask. Between reading about the advantages LPS and seeing it first hand, what's so bad about it? Also how would one of the pictured cobraheads compare to a metal halide, 5000 K blue rich,unsheilded acorn light?

[patric]

I really have to ask. Between reading about the advantages LPS and seeing it first hand, what's so bad about it? Also how would one of the pictured cobraheads compare to a metal halide, 5000 K blue rich,unsheilded acorn light?

Low Pressure Sodium (LPS) is monochromatic.  It renders only one color: yellow.
It has some uses, such as beachfronts, wildlife refuges, zoos, migration areas and astronomical observatories, but it's really not suitable for the urban center (such as you pictured) mainly because of the poor color rendition.  To hang a number on that, the Color Rendering Index, on a scale of 0 to 100, has incandescent light at 100 and LPS as 0.  Dont confuse color rendering with color temperature, though.

The Sodium lights Tulsa uses are High Pressure Sodium, which have spikes of other colors in the spectrum that allow the eye to see more than just the dominant reds and oranges.

LPS has a tubular form-factor like fluorescent lights, so the fixtures you are seeing are not really the "Cobra-head" we see with HID lights like HPS, Metal Halide or Mercury Vapor.  They are probably still in use there because they have a very long life, low maintenance, and are likely paid off.
If they were to be replaced today, a better choice would be an incandescent analog like 3000K LEDs in shielded, low-glare Full Cutoff luminaires.

[Cetary]

But wouldn't even the 3000k light scatter more readily then the LPS? Also, because there's essiantly no blue light, wouldn't it be better for our day/night sleep cycles as well? How about luminous efficiency? 200-180 lumins to the watt isn't bad. Just some thoughts.

[patric]

But wouldn't even the 3000k light scatter more readily then the LPS?

Any light with a blue component is going to exhibit a Rayleigh Effect.  The trick to reducing or eliminating the atmospheric scatter that causes skyglow is better shielding, avoiding excess, and better choices of light sources.
The much maligned High Pressure Sodium is criticized for it's orangish hue, but its much less damaging than it's blue rich counterparts Metal Halide, Mercury Vapor or early LEDs.

Also, because there's essiantly no blue light, wouldn't it be better for our day/night sleep cycles as well? How about luminous efficiency? 200-180 lumins to the watt isn't bad.

The lumens-per-watt of LPS reigns king, but LED is making gains in leaps and bounds.  Unlike yellow-only LPS, LED can be tailored for just about any color, and has already replaced some LPS in eco-sensitive areas.  I could envision amber LEDs along the river near Least Tern and Eagle habitats, for example (cough..River Spirit...cough...Blue Rose...cough..cough).  Even PSO's Riverside Station uses *some* amber LEDs (but we could still take it further).

[Cetary]

I found something that made me think, though.

"LPS light, being nearly monochromatic, provides essentially no color perception. This is clearly a drawback for visibility, though it is also essential to its low environmental impact, low sky glow, and advantage for professional astronomy (see below under LPS and Astronomy). In application in the real world, however, LPS light is in most situations supplemented by other light sources such as roadside commercial lighting or automobile headlights, which provides for quite adequate color perception. In many applications, particularly in the Flagstaff and Tucson, AZ areas, fixtures or poles combining LPS with another lamp type (fluorescent or metal halide) have been used. An investigation by R.M. Boynton and K.F. Purl ("Categorical colour perception under low-pressure sodium lighting with small amounts of added incandescent illumination," Lighting Res. Technol. 21(1) 23-27 (1989)) shows that categorical color perception (placing colors accurately into categories, such as "red," "yellow," "green," etc.) is restored by the addition of 5-10% broad-spectrum light (such as incandescent or LED) to LPS light."

http://www.flagstaffdarkskies.org/low-pressure-sodium-lighting/

It would seem then that the principle weakness of LPS, it's monochromatic color rendering,could be easily, or at least partly,be remedied. Wouldn't such a composite system of LPS and warm white LEDs have less scattering, skyglow, then an all 3000k system? By extension, wouldn't that also mean less of risk of carcidian disruptions?

Also, there was another point brought up in the webpage that was also brought up in the IES guide. LPS maintains it's light lumin output over it's lifespan rather then the light getting darker as time goes by. What of that?

Just some more thoughts.

[Townsend]

Patric - are you Tim Huntzingering with this Cetary posting?

Just curious

[patric]

Patric - are you Tim Huntzingering with this Cetary posting?

Just curious

Nyet.  I dont think it's someone local, though, but that's OK because it still gives me an idea of different perceptions people have.
Maybe someone could give us their local situation by introduction?

[patric]

It would seem then that the principle weakness of LPS, it's monochromatic color rendering,could be easily, or at least partly,be remedied. Wouldn't such a composite system of LPS and warm white LEDs have less scattering, skyglow, then an all 3000k system? By extension, wouldn't that also mean less of risk of carcidian disruptions?

If your city can only afford a patchwork quilt -type of system, then that's what you are dealt.  I still think a purpose-built streetlighitng system would yield more predictable results.

Also, there was another point brought up in the webpage that was also brought up in the IES guide. LPS maintains it's light lumin output over it's lifespan rather then the light getting darker as time goes by. What of that?

That might answer your earlier question about why they are still around:  Reliability.  Contrast that to Mercury Vapor that will still be burning for 20+ years, but it's light output gradually falling off while it still consumes the same amount of power.

When choosing lighting for public places, you have to take into account some aesthetic.  Is it an inviting look, and does it render colors accurately?  LPS is gawdawful by itself.  They used to use it at TU at one of the mechanical buildings.  You just have to see it to understand why people dont like it.

[patric]

Seattle's new LED-lit streets: Blinded by the lights


Our new streetlights save money and energy, help police and give Seattle early-adopter bragging rights. But do they have to be so glaring?

This is a good news-bad news-good news story. The first good news: Seattle is leading the nation into a bright new future of energy-efficient, cost-saving LED street lighting — a future limned with truer colors, better visibility and, maybe, safer streets. The bad news: despite extensive, much-touted prior testing, the city has been installing these new streetlights in crude one-size-fits-all fashion with little regard to Seattle's hilly terrain, bombarding many residents, outside and sometimes inside their homes, with intrusive, blinding glare. The other good news: It can and will correct these problems — if you call to complain.

Seattle stands with Los Angeles as a pioneer on the road to LED streetlights, which it began trying out clear back in 2007. Its efforts hit overdrive in 2009 when the Nickels administration secured a stimulus grant to start converting about 41,000 lights on residential streets to LEDs. Mayor McGinn upped the ante last June when he and LA's Antonio Villaraigosa introduced a measure adopted by the U.S. Conference of Mayors urging that every city switch to LED streetlights — presumably with suitable federal funding. Edward Smalley, Seattle City Light's chief streetlight engineer and a longtime LED booster, is the director of the U.S. Department of Energy's Municipal Solid State Street Lighting Consortium — the point man for LED conversion nationwide.

The advantages of the new technology are manifold. LED displays use as little as 40 percent of the electricity that high-pressure sodium bulbs, the old standard, use to produce as much light. Though they cost more upfront, they last about three times as long, which saves labor replacing them and disposal costs. They don't get jiggled to an early demise by vibration, as bulbs do; this makes them especially well-suited to bridges and other bouncy sites. City Light expects to recover the capital cost of converting in 7.7 years; it originally expected to save $2.2 million a year in energy and labor, but now hopes to save $3 million.

LEDs can deliver not only cheaper and more durable but better quality and more versatile lighting. High-pressure sodium bulbs, with their pale-orange glow, operate at the warm end of the light spectrum, about 2,100 kelvin; incandescent and "soft white" fluorescent bulbs emit in the mid-range, about 3,000 kelvin, and office fluorescents show cooler at 3,500. (Cooler light is thought to be stimulating — bad for sleep, but good for work.) LEDs can be made with your color temperature of choice; the cooler the temperature (i.e., the bluer the light), the less energy they consume.

Seattle considered an icy 6,000 kelvin but opted for a merely chilly 5,000, the temperature of moonlight.

Many people find this cool light unsettling, at least at first. But it also makes for truer colors. Police like LEDs because they help witnesses accurately report whether a suspect drove a blue or green car or wore a black or brown hoody. Politicians like any excuse to proclaim that they've made the streets lighter, brighter and safer. Street lighting is like long, determinate prison sentences: More is always presumed to be better, and no politician ever lost an election calling for it.

But for many residents living under them, the new lights are a mixed bag. For some, they're a nightmare. When the new lights arrived in Wallingford in late 2011 (the city installed them north of the Ship Canal first, and then started working up through the South End), the Wallyhood blog lit up with comments, from "a bit better than the yellowy light we used to have" to "HATE the color...HATE the sharp glare...HATE that it makes everything under it look cold and blue."

For many the shock of the blue fades with familiarity. "I don't hate them so much as I did at first," says software engineer and light-pollution watchdog Bruce Weertman. "I actually like the white — it's more natural." The bigger problem, for Weertman, the Wallyhood bloggers, and your correspondent, is the new lights' blinding glare and surprisingly intrusive reach.

"We can't sit comfortably and read in our living room without the curtains drawn," one Wallyhooder noted after the LEDs arrived. Worse yet, I could sit and read in my living room with the curtains open — by the glow of the streetlights. The streets outside (we're on a corner lot) were lit up like a prison yard, and suspended mini-novas pierced the eye with glare when you stepped out to the sidewalk.


It's not supposed to be that way. Another argument for LEDs is that they can be precisely targeted where light's needed, rather than scattering and trespassing where it's not. But these good intentions sometimes collide with the shakeout state of the industry (the technology's always improving, and the city keeps seeking better makes), the nature of the technology and the hills and dales of a city like Seattle.

Rather than a single bulb, whose emissions are reflected and directed by the backing fixture, an LED fixture has 120 little diodes —"like an array of small spotlights," in the words of Ballard-based lighting engineer Dan Salinas — variously pointed to cast what's supposed to be a composite block of even light.

From some angles the results are amazing: You can stand bathed in light and look straight up into one of the new streetlights without blinking. From others, they're excruciating: Step back and that same fixture will glare like a headlight. (See photos.) "That's because the peripheral lights are directed horizontally," explains engineer and lighting maven Terrence McCosh, "and LED optics defeat the inverse square law" — which holds that the intensity of a property (in this case light) is inversely proportional to distance from its source.

Steep slopes complicate the angles and compound the effect. An LED fixture a block or two up a hill can glare brighter than one across the street.

Seattle City Light is swapping out the city's traditional streetlights for LEDS rated at the same light output. City Light spokesman Scott Thomsen says that's at the direction of the Transportation Department and City Council, and in keeping with national standards for street lighting. But it's also deceptive. "You really can't judge lighting by its output," says Salinas, who sits on the board of the national Illumination Engineering Society, the leading professional group. "You can't say this amount of LED is going to replace this amount of high-pressure sodium. You have to consider the total system — do a photometric calculation so you can see how the light is distributed."

Because their output isn't lost to back-glow and dispersion, LEDs are effectively brighter than nominally equivalent traditional lights. City Light Thomsen acknowledges that there's an emerging view in the field that "because of the higher quality of light [with LEDS], you can reduce lumen output," and that the city may look at doing so in the future.

Right now, however, it's switching the lights over lumen-for-lumen — effectively upsizing Seattle's residential street lighting. They then tinker with individual lights — reducing output or adding glare shield when residents complain and city engineers confirm a problem. "That's not necessarily the best way, not the way I would do it," says Salinas. "But they think it's more efficient."

Thomsen says the city received complaints about fewer than 2 percent of the 31,000 LED residential streetlights it installed through 2012. (It has about 10,000 more to install this year.) "We don't feel it's that much of a problem," says engineer Ahmed Darrat, who oversees the conversion from SDOT's side.

But I wonder if some complaints got lost or overlooked. Bruce Weertman says he duly filed an online complaint form with City Light — and never heard back.

Maybe things are better now: "Over the last several years we've made concerted effort to improve our web report response," says Thomsen. Or maybe phone is the way to go. I called City Light's streetlight complaint line (206-684-7056). One of the operators I spoke to admitted that the office was getting "lots" of complaints about new, overbright lights. Within a week a ladder truck was out changing out the fixtures. (Their output is adjustable, but that's done in the shop.)

Now our block looks like a neighborhood again rather than a prison yard. I'm glad to help the city save a little more on its electric bill, but maybe they could have gotten it right the first time?

View this story online at: http://crosscut.com/2013/03/18/energy-utilities/113476/streetlights-seattle-led/

[carltonplace]

Why do we keep our highway lights on all night? Seems like a waste of money and resources to keep them on when very few drivers are on the roadway.

[Red Arrow]

Why do we keep our highway lights on all night? 

Because it's dark all night.

[patric]

Why do we keep our highway lights on all night? Seems like a waste of money and resources to keep them on when very few drivers are on the roadway.

For pedestrians that shouldn't be there.  Seriously.

Almost all highways handle faster speeds -- and are unlit (except for interchanges).

[patric]

Now I really do like what the city did on Cherry Street, but...


Warm-white LED street lighting photo:

http://twitpic.com/ecq2ut/full

...because cold blue isnt the only option.

[sauerkraut]

I liked those old Mercury lights that cities used in the 1970's & 1980's. Then they switched to those ugly orange Sodium lights. Street lights on freeways don't seem that critical, your cars headlights is all ya really need-- but on surface roads  street lights  are helpful.