Growing up in a small town, I could see thousands of stars on a clear night. In a major metropolitan area where I live now, it’s hundreds. When I visited Beijing for three weeks, I think there was one night where the pollution cleared sufficiently to see any stars at all; I think I saw three or four.
LED’s are causing an exponential ramp in lighting pollution right now. (They’re more efficient, so people install them in more places and leave them on longer.)
People are convinced that their towns are "safer" if the lighting is bright enough to read a newspaper in the middle of every street in the middle of the night by street lamp alone, and think their oversized SUV seems tougher if the headlamps sear the eyeballs of everyone else on the road.
For actually necessary amounts of outdoor lighting at nighttime, LEDs are not any more power efficient than low-pressure sodium lamps, and considering how bright LEDs are often made, total power consumption is significantly higher.
The lighting industry has absolutely zero respect for human ergonomics, and is happy to sell as much new lighting as they can as often as they can with marketing spin built on pseudo-scientific nonsense. Surely there must be some engineers in the industry with basic understanding of human vision, but they aren't calling the shots. Policymakers are happy to channel Federal subsidies and local tax revenue through to the lighting industry, tossing out PR announcements about how "green" and "modern" they are being along the way.
The issue with LEDs is that they are broad spectrum, whereas sodium lights always fall in a very narrow band in the spectrum which is easily handled with a physical filter.
