Studies have found that cool white LED street lights, as well as legacy metal halide and mercury vapor sources, suppress melatonin levels much greater than HPS bulbs or warm white LEDs.

The American Medical Association suggests residential street lights to be no higher than 3000K, which means 4000K+ LED, metal halide, and mercury vapor are technically not recommended for residential streets. My area (Columbus, OH) seems to mostly use 3000K cobra head cobra lights but post tops seem to be 4000K. However, some parts of Ohio seem to use 4000-5000K LED street lights and I actually prefer the cool white.

Do you prefer 3000K or 4000K street lights?

Kiryat Ata uses mainly 3000K LED streetlighting, but Haifa also have 4000K and 5000K.
Most LED floodlights here are >6000K.
I think LPS and HPS, are the best for streetlighting. MV streetlighting usually was dimmer than LPS and HPS, thus didn't affected the melatonin that much like MH and LED.

... off topic: it's very interesting to me how a good amount of fellow Lighting enthusiasts, live in Ohio, myself included. I'm beginning to notice
this, and that is pretty epic. A decent amount of people on Lighting Gallery, seem to live here in Ohio...
Anyways, back on topic, my area, as well as most places I've been to here in Dayton, seem to use what appear to be 4000k LED street lights. Seems
like the majority of those replacement LED street lights give off a harsh color. They also appear to be much more glary during the night time, in
comparison to the HPS lit roads. Or... maybe they are 3000k, but my eyes are so use to the much deeper orange glow from the previous HPS street
lights, that even 3000k seems to appear a bit harsh in comparison...? I'm not sure. Or maybe the LED street lights have color shifted due to degrading
phosphors. Regardless, I prefer 3000k, easily. But of course between LED and HPS, I'd choose HPS, easily.

I prefer 3000K for LED street lighting. It’s the perfect balance between efficiency, visibility, and visual comfort. 4000K is slightly more efficient but I dislike the stark white colour and I feel that it should be restricted to only pedestrian crossings.

Most streetlights in our town are 4000K, but all new installs here now are 3000, and they look so much better 😎

Definitely 3000K or even less!, while driving late at night it surely makes a difference between a cold white glow and a warm orange glow and you could easily notice it, when looking at a street light closely but not directly, the power the cool white one gives could give more discomfort to your eyes than the warm orange color. Ambience-wise, the orange color gives a much better feel around the city, here's a little comparison between a white Philips street light compared to the traditional HPS color (apologies for the bad quality):



Sure, white light does supress melatonin levels, but tell me that when you start to have trouble falling asleep, sleep is very important!

For me I'd have to say 4000k, though an Astronomer I know would beg to differ haha. I like 4000k because it really isn't that harsh (my whole city is lit with 80,000 4000k leds or neutral white PL/T, which are actively being replaced). I find that 3000k streetlights look too yellow, though they do make a very positive impact for night sky visibility.

I do prefer 3000K or even less in street lighting, this Tc creating very nice atmosphere during night walks and causing less stress for the eyes during driving a car, warm LEDs and warm MHs ruling for me in street lighting, HPS too.
My town as most others in Poland pick 4000K for street lighting which is boring

Melatonin suppression while driving on the highway is a good thing, i guess.

Residential streets often had 3000k PL, and now have 3000k LED for the most part. Random streets might still have HPS here and there, i don't know yet what those are getting as replacement. Some cycle paths around nature areas have either 2700k tiny LED lamps, or lamps that exclusively produce red and green light to interfere less with animals living in the parks and preserves.

The 2700k LEDs are also used in some commuter roads within the city, with houses on both side. They are really pleasant.

I do think blue light in street lights is an issue, but not so much for the melatonin issue. That is certainly a real effect, but with most people looking at a TV or phone screen at night before going to bed, that is going to have a much bigger impact on melatonin levels than the street light outside.
Warm white lighting is just better overall. It's less harsh on the eye because of the lower blue content. It is slightly less efficient than cool white but most of the time that difference is negligible. Cool white lighting does have its purpose, but the roads aren't really the place.