It's a good video, but it's also a case study in being 'almost right'. The almost-correct interpretations cascade and result in a faulty conclusion: that blue-white LED streetlights are better than orange-white streetlights. Various comments object to the faulty conclusion ([1], for example).

At the end he at least addresses his ignorance:

> [18:39] You may have noticed that I didn't talk about the blue light from LEDs, and how this is supposedly ruining our eyes. That's because the "science" behind this is questionable, at best.

> [18:55] [discussion of chart with percentage blue light of various light sources]

> [19:04] [...] but considering that our eyes can withstand the intensity of sunlight, which is far far greater than any normal artificial light source, and also has a lot of blue light, and ultraviolet, which definitely is harmful, I think the 'blue light' thing is just fear-mongering. If someone can point to some verified, peer-reviewed research supporting this, and not a dodgy website, I'll consider changing my stance. In any case, the high flexibility of LED technology means it can be tuned in pretty much any way we like.

The research on the harm of blue light is out there -- For example, one of the comments links to "Effects of blue light on the circadian system and eye physiology" [0]. (only partially read at this point - I don't know if this paper gets into the mechanism of damage done by blue light, as I understand it...)

The sun hangs high in the sky and casts light on everything. We never need to look at the sun directly, we use the sun's light indirectly, after it bounces off of things. The atmosphere scatters the sun's blue light before it gets to us [2]. Artificial lights hanging on poles emitting photons we can't avoid having beamed directly into our eyes... Blue photons have relatively higher energy levels, and different physiological effects, than orange photons... [note to self: expand on this.]

The preceding video was about High Pressure Sodium lights, which I thought was good too:
https://www.youtube.com/watch?v=U1dMlVwUsrA

My transcription of the video's faulty conclusion (italics added):

> To conclude: although the High Pressure Sodium light is very efficient, its primary output color is misaligned with our nighttime visibility. Only about 1/4 of its light is actually effective at stimulating the cells in our eyes. Although the cool color temperatures of many LED replacements is harsh and aesthetically displeasing, studies have shown that it is not only more efficient, but also makes driving at night safer. There is, however, the potential for greater circadian rhythm disruption and larger amounts of skyglow, using these bluer light sources.

> Still, it seems clear that the High Pressure Sodium is on its way out. Advancements in LED technology are happening at a breakneck pace. Just 10 years ago, they weren't seen as viable, but today even the least efficient of LED replacements ends up emitting the efficiency of High Pressure Sodium once scotopic light output is considered.

> As it stands in 2018, we are faced with the choice of efficiency over aesthetics. I'm pretty sure I'd enjoy roadways lit with relatively-warm 3000K LEDS, and these also wouldn't disrupt sleep much. But you can save a lot more energy, and potentially have safer roadways, with 5700K lighting.

> Either way, it seems clear that LED technology will very soon overtake the tried-and-true High Pressure Sodium lamp, just as the High Pressure Sodium itself replaced the mercury-vapor lamp. And in 40 or 50 years, who knows what technology might light our roadways.

[0] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4734149/pdf/mv-... - "The radically different power spectrums can look similar when viewed directly by the eye, irrespective of how much blue emission is present."

[1] https://www.youtube.com/watch?v=wIC-iGDTU40&lc=Ugx6MYdsMY6I_...

[2] https://en.wikipedia.org/wiki/Rayleigh_scattering#Cause_of_t...

edit: this page has a discussion of drop-sag lights vs. proper fully-shielded lights: http://www.skykeepers.org/good-bad-lights-cv.html