Finally, a Better LED Streetlight
A major lighting company has announced a street light that uses LED technology with less output in the blue wavelengths. While municipalities have rushed to install LED lights for their efficiency and lower operating costs, the inaugural lineup of LED products inherently emitted the undesirable blue light. Any LED light promoted as being white but dubbed "blue-rich" has significant downsides, ranging from human health concerns to a negative impact on the envirornment.
Cree stated it has designed a streetlight that "enhances the lighting experience with visual comfort, reduced glare and high color contrast. It provides the warm, inviting dark sky friendly lighting that makes good economic sense." That's welcome news for taxpayers and the people who have to live with capital investments for decades. In several communities that previously replaced yellowish high-pressure sodium lights with blue-rich LED fixtures, residents rebuffed the new LED lights because the lights were so harsh.
If Buying New Lights...
Cities that are considering installing new outdoor lighting should consider three three simple guidelines:
All outdoor lighting should be full cutoff, or fully shielded.
If LED lights are used, they should be rated under 3000K.
Lights should minimize glare, sky glow, and light trespass.
The spec sheet for the new Cree RSW series suggests it meets those criteria. While I have not yet seen this light in action, I'm encouraged by the numbers for the cobra head style fixture.
Streetlights are just one source of lights that can impinge on your well-being. Individuals can act to lessen the blues to which they are exposed at night, such as installing a simple app on electronic devices and purchasing LED lights rated no higher than 3000K. The temperature rating (look on the packaging) indicates the light's color--5000K is the bluer "cool light;" 2500K is the yellower "warm light."
LED Color Basics
Light-emitting diode (LED) lights have much promise because they consume significantly less energy and the light can be directed, thereby reducing light trespass and glare. Many people quickly embraced LED lights for the global benefits--even the Nobel Prize in Physics for 2014 went to the co-developers of blue-rich LED lights.
A technical article from Cree, LED Color Mixing: Basics and Background, describes some of the challenges of making LEDs that are colored consistently. You can add the brightness (lumens) and color (chromaticity) of several diodes of a comparable bin to build an array with an average value (image below) and homogenize the light with secondary optics. Or you can buy a batch in which the diodes are all of the exact same characteristic. The latter is more expensive because exactness is harder to achieve in manufacturing, whereas the former mixes different batches to yield an overall desired effect.
ADDED March 10, 2016:
Debra Briggs Luginbuhl writes, "There is better. Kim Lighting Warp 9 LED is available at 2000K, 580nm amber. We have some here in Flagstaff. Very similar to LPS. 3000K has way to much blue AND green in it. While 3000 is not *as bad* as 4000+K it's still bad for skyglow and the environment."
