Transitions in Outdoor Lighting and Its Effect

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SEmert
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Joined: Mon May 31, 2004 2:48 pm
Real Name: Steve Emert
Location: White Bear Lake, MN

Transitions in Outdoor Lighting and Its Effect

Post by SEmert »

Tonight I ran across this pair of well researched and well presented YouTube videos which cover the differences between high pressure sodium vapor and low pressure sodium vapor street lighting and the various types of LED lighting that have been introduced recently along our streets and highways, and discusses both their efficiency and their effect on people and the environment (including, of course, our main concern --- light pollution).

https://www.youtube.com/watch?v=U1dMlVwUsrA
The High Pressure Sodium Light: Ubiquitous, effective, but good?
Technology Connections, Published on Jun 4, 2018

https://www.youtube.com/watch?v=wIC-iGDTU40
The LED's Challenge to High Pressure Sodium
Technology Connections, Published on Jun 19, 2018

In the two videos, he covers our eye's sensitivity to various wavelengths in photopic (daylight), scotopic (night) and mesopic (low light, as in driving at night) conditions, and how the various lighting types (primarily high pressure sodium vapor and LED) affect our ability to see and react to situations when driving or walking at night, the relative efficiency of the different light sources, light pollution and lighting fixture placement and design.

Bottom line, it's not a simple subject. LEDs are generally more efficient. High color temperature (5000K) LEDs make it easier to see and react while driving, but many people feel they are "harsher", they can adversely affect both us (circadian rhythm and ... drumroll please, ... light pollution effects on observing) and wildlife (the example of hatching turtles being drawn toward street lights instead of being directed by moonlight to the ocean). I highly recommend watching both videos to get a fairly comprehensive summary of the pro's and con's of various outdoor lighting.

We all had hoped LED street lighting would reduce the light pollution we experience, as LED lighting "must be" directed downward for greatest effectiveness. But as many municipalities have been selecting 4000-6000K lights with blue-white light which is the same wavelength as most stars, LED lighting cannot be filtered with skyglow filters. Before watching these two videos, I had been complaining that municipalities should use 2700 to 3000 K lights mimicking incandescent lighting, so at least it can be filtered by light pollution filters. Unfortunately, as pointed out by these videos, "it ain't that easy" since that is the portion of the spectrum our eyes are less sensitive to under scotopic conditions. Therefore, using 3000K lights is less efficient and requires more lighting for the same effect as less wattage of 5000-6000K. Sigh. We just can't win.
Steve Emert
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