Streetlighting Concerns

I submitted the following letter to the editor to the Dodgeville Chronicle this evening:

Dear Editor:

Have you noticed the gradual transformation of our streetlights in Dodgeville, Mineral Point, and other communities in SW Wisconsin?  The light source in our streetlights is changing.  High Pressure Sodium (HPS), which has been in use for decades and produces a orangish-white light, is being replaced by light emitting diodes (LEDs), producing a whiter light.

What’s not to like?  LED’s many advantages include: efficiency, longevity, instant-on and instant-off, and dimmability, to name a few.  But Alliant Energy is installing new streetlights that produce white light that is too blue, and the illumination levels are about 2.6 times as bright as the high pressure sodium streetlights they are replacing.

Lighting specialists use a term called “correlated color temperature” or CCT (in Kelvin) that allows us to compare the relative “warmness” (redder) or “coolness” (bluer) of  various light sources.   The illumination provided by candlelight has a CCT around 1500 K, HPS around 2000 K, an incandescent light bulb around 2800 K, sunrise/sunset around 3200 K, moonlight around 4700 K, and sunny noon daylight around 5500 K.  The higher the color temperature, the bluer the light.

Higher color temperature illumination is acceptable in workplace environments during the daylight hours, but lower color temperature lighting should be used during the evening and at night.  Blue-rich light at night interferes with our circadian rhythm by suppressing melatonin production, thus reducing sleep quality, and several medical studies have shown that blue light at night increases the risk of developing cancer, most notably breast cancer.  Even low levels of blue-rich light at night can cause harm.  While it is true that something as natural as moonlight is quite blue (4700K), even the light of a full moon provides an illumination level of just 0.01 foot-candle, far dimmer than street lighting, parking lot lighting, and indoor lighting we use at night.

LED streetlights are available in 2700K, 3000K, 4000K, and 5000K.  I believe that Alliant is installing 4000K streetlights in our area—I certainly hope they are not installing any 5000K.  What they should be installing is 2700K or 3000K.  These warmer color temperature lights are no more expensive than their blue-white counterparts, and the slightly higher efficiency of the blue-white LEDs is entirely nullified by over-illumination.

Even considering a modest lowering of light level with age (lumen and dirt depreciation), these new LED streetlights are considerably brighter than the HPS lights they are replacing.  Just take a look around town.  What is the justification for higher light levels in our residential areas, and when was there an opportunity for public input?  In comparison to older streetlights, the new LED streetlights direct more of their light toward the ground and less sideways or directly up into the night sky, and that is a good thing.  But now the illumination level is too high and needs to be reduced a little.

If you share my concerns about blue-rich lighting and illumination levels that are often higher than they need to be, I encourage you to contact me at oesper at mac dot com.  I operated an outdoor lighting sales & consulting business out of my home (Outdoor Lighting Associates, Inc.) from 1994-2005, and wrote the first draft of the Ames, Iowa Outdoor Lighting Code which was unanimously adopted by the city council in 1999, so I am eager to work with others in the Dodgeville area who are also interested in environmentally-friendly outdoor lighting.

David Oesper
Dodgeville

Dodgeville Streetlights

Has anyone else noticed how Alliant Energy is gradually replacing our orangish-white-light streetlights with bluish-white-light ones? The orangish-white-light streetlights are high-pressure sodium (HPS) with a correlated color temperature (CCT) of 1900K, whereas the bluish-white-light streetlights that are replacing them are LED with a CCT of 4000K, and, most notably, they are two and a half times as bright.

Even though I have written to both Alliant Energy and the City of Dodgeville, nothing has changed.

My questions, which are still unanswered:

What is the justification for increasing the streetlighting illumination level by two and a half times over what it has been for decades?

Why are we going from 1900K to 4000K (cold white), when 2700K or 3000K (warm white) is readily available and being used in many communities in the U.S. and Canada?

This same transformation is happening in Mineral Point, and probably many other communities in SW Wisconsin as well.

Is anyone else noticing how this is profoundly changing the rural character of our nighttime environment? Is anyone else concerned about this? The increase in glare and light trespass onto neighboring properties from these new LED lights is quite noticeable to me, even though they are nominally full-cutoff. Why? They are too bright, and too blue.

If anyone locally is reading Cosmic Reflections (and sometimes I wonder if anyone is…), and if you have noticed and are alarmed by these streetlighting changes, please contact me on blog or off blog (oesper at mac.com) and let’s meet and discuss a plan of action. Something needs to be done before it is too late and we are stuck with this very negative change to our nighttime environment.

The LED Lighting Revolution

Solid state lighting, namely light-emitting diodes (LEDs), are completely revolutionizing indoor and outdoor lighting.  Here’s why:

  1. White LEDs on the market today have a system luminous efficacy ranging from 50 (least efficient) to 80 (average) to 140 (most efficient) lumens per watt.  This far exceeds the luminous efficacy of incandescent (5-35 lumens/watt), and generally exceeds compact fluorescents (45-60 lumens/watt).  Prototypes of the next generation of white LEDs have luminous efficacies up to 150 lumens/watt, and theoretically 200-250 lumens per watt may someday be achievable.  Since the traditional white light source of choice for outdoor lighting has been metal halide with a luminous efficacy of 65-115 lumens/watt, white LEDs are well on the way towards replacing metal halide.  Even the more efficient orange high pressure sodium (HPS) lights, with an efficacy of 150 lumens/watt, are nearly matched by the best white LEDs.  Only monochromatic low-pressure sodium (LPS) with an efficacy of 183-200 lumens/watt will give more lumens per watt than the best white LEDs.
  2. White LEDs last much longer than other light sources: 50,000 to 100,000 hours (between 12 and 24 years, operating dusk-to-dawn 365 days a year).  In comparison, high pressure sodium typically lasts about 5 years, and metal halide a little less at 4 years.
  3. Unlike high-intensity discharge (HID) sources such as metal halide, HPS, LPS, and mercury vapor, white LEDs are “instant on / instant off” with no warmup time to full brightness, so they can be switched on and off as often as you like with no shortening of bulb life; and they are easily dimmable. LEDs will render dusk-to-dawn lighting a questionable option rather than an operational necessity.

My only concern is that we finally “get it right” with LEDs instead of blindly following the “more is better” philosophy as we have with every lighting efficiency improvement in the past.  Low levels of white light (fully shielded to minimize direct source glare) is the most effective and efficient way to provide adequate illumination.  This shouldn’t come as a surprise, however.  Think of the light provided by a full moon as we have this week.

Unfortunately, most places that is not what is happening.  Light levels are increasing, as is the amount of lighting.  We seem well on the way towards eliminating anything resembling a natural nighttime environment for most people.  I don’t know about you, but that is not a world I want to live in.

References
DIAL (15 June 2016). Efficiency of LEDs: The highest luminous efficacy of a white LED.  Retrieved from https://www.dial.de/en/blog/article/efficiency-of-leds-the-highest-luminous-efficacy-of-a-white-led/.

Kyba, C., Kuester, T., et al. 2017, Science Advances, 3, 11, e1701528

Two Predictions About Outdoor Lighting Technology

Here are my (ever hopeful) predictions about the future of outdoor lighting technology.

(1) Dusk-to-dawn lighting will soon become a thing of the past.

Ever see the irony that as outdoor lighting efficiency has greatly improved over the last several decades, we have moved from “light only when you need it” to “lights on all night long”?  An incandescent light, if operated less than 3 hours per night, will use less energy than even the most efficient light source operated dusk to dawn.  Yes, that’s right.  Three hours of incandescent light (which is horribly inefficient) each night throughout the year uses less energy than an LPS, HPS, Metal Halide, or LED source of comparable lumen output operated dusk-to-dawn.  Just think of the energy savings we could realize by using an efficient light source that is used only when it is needed!

Passive infrared (PIR) switches, which are rather prone to false triggering, will be replaced by image analysis software that will do a much better job of deciding when a light needs to be on and when it does not.

The HID (high intensity discharge) light sources in common use today such as HPS (high pressure sodium) and metal halide have two drawbacks.  They prematurely age if you frequently turn them on and off, and they take a while to reach full brightness after having been off for a while.  These drawbacks do not exist with efficient “instant on” sources such as LEDs, which are even dimmable.

These new technologies in lighting and control will make it both easy and affordable to have reliable light only when it is needed.

(2) Security lighting will soon be replaced by much better crime prevention technologies.

Soon, flooding a premises with light will be one of the WORST things you can do to deter and prevent crime.  As security systems improve and become more sophisticated and affordable, security lighting will only be needed when an intrusion is detected, and maybe not even then if you want the perpetrator to be detected without them knowing they have been detected.  Fixed visual recognition systems or even mobile peripheral devices (MPDs)—as Bill Gates likes to call “robots” to avoid all the anthropomorphic connotations—that operate with ambient light (visible, infrared, etc.) will soon obviate anything so primitive as security lighting. And, if the stationary or mobile sensing device is inactivated by a hostile (or non-hostile) event, its connection with the base station inside the home or business would be broken and appropriate action could be immediately taken.

As both lighting technology and lighting control technology improve, it is my hope that dusk-to-dawn lighting will be rendered obsolete.

Avoid Blue-Rich LED Lighting

As Dodgeville (and many other towns and cities) are planning to replace their streetlights with LED luminaires, it is imperative that we use LEDs with a CCT (correlated color temperature) of 3000 K or less (Jin et al. 2015).  This is a “warm” white light (similar to incandescent) rather than the “cold” blue-rich light often seen with LEDs.  Outdoor LED luminaires often come in at least three “flavors”: 3000K, 4000K, and 5000K.  For example, American Electric Lighting’s Autobahn Series.  5000K luminaires provide the bluest light, and should be avoided at all costs.  Of these three, 3000K would be best, and if 2700K is offered, use that.

Why does this matter?  On June 14, 2016, the American Medical Association issued guidance on this subject.

High-intensity LED lighting designs emit a large amount of blue light that appears white to the naked eye and create worse nighttime glare than conventional lighting.  Discomfort and disability from intense, blue-rich LED lighting can decrease visual acuity and safety, resulting in concerns and creating a road hazard.

The detrimental effects of high-intensity LED lighting are not limited to humans.  Excessive outdoor lighting disrupts many species that need a dark environment.  For instance, poorly designed LED lighting disorients some bird, insect, turtle and fish species, and U.S. national parks have adopted optimal lighting designs and practices that minimize the effects of light pollution on the environment.

Recognizing the detrimental effects of poorly-designed, high-intensity LED lighting, the AMA encourages communities to minimize and control blue-rich environmental lighting by using the lowest emission of blue light possible to reduce glare.  The AMA recommends an intensity threshold for optimal LED lighting that minimizes blue-rich light.  The AMA also recommends all LED lighting should be properly shielded to minimize glare and detrimental human health and environmental effects, and consideration should be given to utilize the ability of LED lighting to be dimmed for off-peak time periods.

Incidentally, for your residential lighting needs, a good local source for LED bulbs that are not blue-rich is Madison Lighting.  They have many LED bulbs in both 3000 K and 2700 K. I use 2700K bulbs exclusively in my home, and the warm white light they provide is an excellent replacement for incandescent and compact fluorescent bulbs.  Never purchase LED lighting without knowing the color temperature of the lights.

If you’re skeptical that the color temperature of LEDs is an important issue, I suggest you purchase a 2700K bulb and a 4000K or 5000K bulb with the same output lumens and compare them in your home.  I believe that you will much prefer the 2700K lighting.  If 2700K lighting is best for your home, then why should it not be best for outdoor lighting as well?

Besides, most streetlighting is currently high pressure sodium (HPS), which is inherently non-blue-rich.  You will find that 2700K LED lights offers better color rendering than HPS without the need to go to even bluer lights.

If you have ever been irritated at night by an oncoming vehicle with those awful “blue” headlights, you’ve experienced firsthand why blue-rich light in our nighttime environment must be minimized.

Why are 4000K and 5000K LED lights so prevalent?  They are easier and cheaper to manufacture, but with increased demand of 2700K and 3000K LED lights, economies of scale will reduce their cost, which today are generally slightly higher than blue-rich LEDs.

Now, a bit more about why blue light at night can be detrimental to human health, and the primary reason why the AMA issued a guidance on this subject.

In addition to image-forming rods and cones, there exist non-image-forming retinal cells in the human eye called intrinsically photosensitive retinal ganglion cells (ipRGCs) that help regulate our circadian rhythms.  Studies have shown that blue light is far more disruptive to our circadian rhythms than redder light (Lockley et al. 2003).

Now, on to the environment.  Using a clever technique that compared sky brightness at several locations on several nights both with and without snow cover, Fabio Falchi (Falchi 2011) determined that at least 60% of light going up into the night sky is direct waste lighting, and 40% or less is reflected light.  This is as good an argument as any that we still have a long way to go towards using only full-cutoff luminaires that do not produce any direct uplight.  Blue light scatters much more in the night sky than red light, and this is due to Rayleigh scattering which tells us that the amount of scattering is proportional to the inverse of the wavelength of light to the fourth power, σs ∝ 1 / λ4.  This also explains why the daytime sky is blue.

Bluer wavelengths of light thus increase artificial sky glow to a much greater extent than redder wavelengths do.  Not only is an increase in blue light bad for astronomy, but its impact on the natural world is likely to be adverse as well.

Falchi recommends a total ban of wavelengths shorter than 540 nm for nighttime lighting, both outdoor and indoor.  He goes on to say that, at the very least, no more light shortward of 540 nm should be allowed than that currently emitted by high pressure sodium lamps, lumen for lumen.

References
Falchi, F. 2011, MNRAS, 412, 33
Falchi, F. 2016, The World Atlas of Light Pollution, p. 44
Jin, H., Jin, S., Chen, L., et al. 2015, IEEE Photonics Journal. 7(6), 1-9
Lockley, S. W., et al. 2003, J Clin Endocrinol Metab. 88(9), 45025