STREETLIGHT & COMMERCIAL LIGHTING
Thank you for your interest in protecting dark-skies in your area! As the information below isn't yet widely available, most lighting engineers of major cities are unaware of it and the harms of blue-rich, white LEDs. The recommendations below are mostly a combination of dark-sky recommendations from the IDA, FDSC, and information I have gathered from lighting experts, engineers, scientists and manufacturers. I hope you will find this a helpful resource!
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BEFORE READING FURTHER, PLEASE GIVE YOURSELF A QUICK OVERVIEW OF THE DIFFERENT TYPES OF LIGHTS BY READING OR SKIMMING NOAO'S TYPES OF LIGHTS AND FAMILIARIZE YOURSELF WITH FLAGSTAFF DARK SKIES COALITION'S POST ABOUT THE DIFFERENT LEVELS OF LIGHT POLLUTION PUT OUT BY EACH TYPE OF LIGHT.
Streetlights cause the majority of light pollution. Know too that blue/white light creates more light pollution than any other light spectrum, and at night, it's also bad for our health, wildlife, and can cause drivers dangerous disability glare. The American Medical Association (AMA) recommends using streetlights with the lowest blue light possible.
The best advice currently for cities is to *wait!* LEDs are quickly improving, and you'll be glad you did! New and improved LEDs with lower kelvins but a higher CRI (Color Rendering Index) are continually coming out, so check back!
NBA LEDS (NARROW BAND AMBER) & LPS (LOW-PRESSURE SODIUM)
These will give off the least light pollution, contain no harmful blue light, and are used by a city of over 70,000 which can still see the Milky Way--Flagstaff, AZ. They mostly use LPS (low-pressure sodium), or NBA (narrow-band amber) LEDs. LPS can be hard to find and maintain, and NBA is still very expensive. Both are quite orange, but Flagstaff uses both successfully. Flagstaff is the model city when it comes to dark skies. For NBA LEDs, please talk with Matt Root at KIM LIGHTING (based in the USA).
PCA (PHOSPHOR-CONVERTED AMBER) & FLEDS (FILTERED LEDS)--WHAT I SEE AS OUR CURRENT BEST AND PRACTICAL SOLUTION
Last updated: February 2018. For affordable, efficient, dark sky compliant lighting for today's cities, PC Amber is what I see as our current best solution, followed by FLED (a warm white LED of 3000K or less with a filter cutting out all blue light to less than 1 or 2%).
I am happy to report that PCAs are picking up momentum! More towns are installing them, and more companies are manufacturing them as well as more research coming out about their benefits. Christopher Kyba tweeted in regards to Fabio Falchi’s work revealed at the LPTMM2017 that a huge improvement in light pollution was seen when cities chose PC Amber LEDs rather than white LEDs. See a compilation of PC Amber Tweets with photos here, and then scroll down.
AMBER LED SOURCES
For a list of sources/companies making amber LEDs for streetlights, landscaping, etc., please click here.
If PC Amber or FLED aren't possible, your best option is to wait!
WARM WHITE LEDS
While many cities are currently switching their HPS (orange) streetlights to warm white LEDs with a CCT of 3000 Kelvin or less, as recommended by the AMA and IDA, sadly, many are switching to 4000K or higher. The higher the Kelvin, the cooler (whiter) and more blue light it has. Please know that even a warmer (more yellow/orange) white LED of only 2400K still gives off too much blue light and has nearly twice the amount of light pollution as current HPS lights--even if the LEDs are fully shielded. This is due to the lights reflecting off roads, humidity, etc. However, it's possible that the blue light from warm white LEDs can be reduced to HPS levels or less *if* the lights are carefully reduced in brightness and the lumen output is reduced to 50% of full output, like Tucson, AZ is currently experimenting with and seeing good results using 3000K. Follow @John Barentine, Program Manager for the International Dark-Sky Association, for updates on how this affects the sky glow of Tucson. However, for this to work, the lights must stay dimmed. My concern is that the lights will not stay dimmed and light pollution will greatly increase. A study done by the Institute of Astrophysics of Andalusia (IAA-CSIC) shows that 3000K LEDs would need to have their power cut by 58% for their light pollution levels to be reduced to the levels of traditional sodium lamps (our orange HPS lights). In this same article, the IAA recommends amber LEDs or warm white LEDs of 2200 Kelvin or less, however, any warm white LED will still have too much blue.
HPS (HIGH-PRESSURE SODIUM) & METAL HALIDE
For cities still using HPS or metal halide, lucky you, as when you decide to switch to LEDs, they will have dramatically improved both in color and efficiency. In the meantime, I'd like to encourage you to use HPS where possible. Not only does it affect light pollution much less than the blue-rich, white light of metal halide, but they are also more affordable and efficient.
WHAT ABOUT RADIANCE, OR BRIGHTNESS?
As Flagstaff can see the Milky Way in their city of over 70,000, we should all look to their Outdoor Lighting Standards. DIN EN 13201 (European Road Lighting Standard) suggests 2 to 15 lux for resident streets, but many say 3 to 5 lux would be adequate. You can read further details in this booklet.
DO STREETLIGHTS REALLY MAKE US SAFER?
Isn't safety the main reason we have streetlights? This interesting video, by Peter Vercauteren, might have you questioning that, as well as all the results that England and Wales have seen over the many years in which many of their authorities have stopped using streetlights. Here is a study that analyzed 14 years of data from 62 authorities.
Simon Nicholas, who fights light pollution in the UK, recommends the book, "Understanding LED Illumination" by M. Nisa Khan. Fellow readers say that although it's technical, it's also written in a way that a layperson can understand.
All lighting should be reduced in brightness, fully shielded and only used when needed.
OIL FIELDS & NATURAL GAS FLARING
McDonald observatory in has some great suggestions in their report, Oilfield Lighting Can Coexist With Dark Skies as well as in the study Upgraded Rig Lighting Improves Night Time Visibility While Reducing Stray Light and the Threat to Dark Skies in West Texas.
Bakken Flaring Alternatives & Gas Capture--watch their YouTube video here. Natural gas flares create enormous amounts of light pollution, so this technology is exciting. Zeeko makes enclosed ground flares. I do not have experience with either of these technologies or know anyone who has used them, but they look worth looking into!