@Lcubed3 - Yes, WSDOT has not yet issued a complete LED conversion, which is cool. I'm guessing as the HPS luminaires die, they'll just get spot-replaced.

Yes and no!, I grew up with predominantly SOX, it was these that spurred my interest in street lighting, so I miss that, we only went with SON here on the A roads, with one or two spot replacements in and amongst the SOX, although granted, the bulk SON installations were brighter than the SOX

With the LED installed though, it was also nice to go back to the white light of the early 70s😎

Ofcourse.

But it still exists here so its not like i cant go dowm the street and see some mercs and sodiums in action. The only technology that is basically extinct here now is metal halide. Aside from stadium lights and large factories. And a couple store parkinglots. And some interior factory and store lighting.

In 10 years im sure it will be virtually gone. Honestly at this point in life i got greater things to worry about and i cant control the march of LED in any major extent. I can control it partially at my places of employment and home. And I make sure of it.

Okay, so for me HPS is a bit of a double-edged sword. I think it's more effective at lighting major expressways and thoroughfares (especially in the rain), but MV/LED are far superior in every other application. Residential areas should[/b] be white or at least some form of white in color– things look kind of drab and even apocalyptic in the 2100K of HPS.

So, for me, the personal preference is to keep older mercury fixtures alive through retrofits (think the GE PowrDoor), and to keep expressways and major thoroughfares LED-free. Unfortunately, however, my opinion means diddly squat, so I guess I just have to learn to adapt to the harsh light of 4000K-5000K freeway LEDs. It was good while it lasted, however. Philadelphia only started going LED in 2023/2024, which is far later than nearly every city across the country.

I'll always miss them a bit. Although I will have to admit that the 3000K LEDs are a very nice upgrade.The difference in colour rendering is night and day, you can actually see things much better under them. Unfortunately my local municipality decided to get 6500K LEDs, which also are only 10 or so watts each, so unfortunately in my local area the lights actually became worse. 10 watt LED's or whatever they installed really isn't enough, it's terribly dark. I don't like super cool white street lighting, it's extremely sore to the eye at night. 3000-4000K is alright, but definitely not anything higher.

It'll be interesting to see how the led stret light hold up. I'd be surprised if any last more than 10 years

The street I live one is a mix of HPS and warm white LED streetlights at the current date, along with utility-rented yard lights. I honestly don't mind these LED's as there not too bright or too dim, or put out tons of glare like some of the new steetlights, but of course I love HID fixtures too  . I'm not sure how long these LED's and there driver boards are going to last during our extremely hot and humid summers here however. As for my opinion on high pressure sodium, I think there okey for street lights and yard lights where you just need to have illumination, but I would definitely take something with a higher CRI for any kind of task lighting, or anywhere where you must be able to see colors and detail clearly. One could also argue that HPS is better for residential streets, as the lower color temperature (the red to yellow output) is better for sleep compared to higher color temperature (cool white and daylight) light sources. The only thing that bothers me is when there is an entire street full of EOL bulbs that are cycling, or greened-out and providing no usable illumination. What a waste of electricity!

Yes, agreed.

As for LED reliability, I've seen some 5+ year old LED lights in the desert town of Alice Springs, where temperatures get over 50°c regularly working fine, admittedly these lights are Australian designed (and thus designed to operate in high temperatures).

One could also argue that HPS is better for residential streets, as the lower color temperature (the red to yellow output) is better for sleep compared to higher color temperature (cool white and daylight) light sources. The only thing that bothers me is when there is an entire street full of EOL bulbs that are cycling, or greened-out and providing no usable illumination. What a waste of electricity!

My country has used 2700 or 3000k fluorescents (in the last 20 years mostly PL) for residential streets since forever, because the concept is that at night, the streets also have to be comfortable places to be. I know of a few residential streets that have or had HPS, but those are definitely the minority.
HPS with its bad color rendering is not seen as approprate for a place where people live. It can get dark here at 16:00 already in the winter, so lots of people have to be outside when it's dark here.

@Laurens did not state this, but one particularly serious reason is Netherlands have rather mild sea climate with no serious frosts at winter. Fluorescents are helpless at cold, as they are not 'hot blooded' as HIDs and heavily depend on the environmental temperature. You probably still can force them to ignite at winter by whacking with a resonant ballast, but good luck getting any useful light at -35C, as is often gets in Astana in the middle of continental Eurasia. Well, even Moscow is considered relatively mild climate, but it becomes -25C at winter from time to time.

There are multiple factors at play. First, Philips insisted lamps used outdoors have to be in sealed fixtures, ensuring that their own waste heat would help keep up lamp temperature.
Second, if really low temperatures were expected, they advised the lamps with an internal starting strip like the TL-S. I have a fixture that has no starters, no resonant tricks, but uses the TL-S lamps.

Of course the light output still gets lower if they get colder. I think that's one of the reasons behind the popularity of PL here, because those things run fairly hot to start with. Standard linear fluorescents were already well on their way out in my childhood. The street where i used to live got converted from fluorescents (3x 40w) to HPS (70w or 150w, idk which one) around the year 2000, with residential cone shape street lights being converted from circline lamps to PL.
The last few years, the PL cones have been replaced by nearly identical cones, but now with LEDs in them.

I have no clue down to which temperature Philips would recommend PL or standard fluorescent. Probably at -35 they wouldn't anymore. At work i have a freezer that sits at -30, i could chuck a PL in there...

Here you can see how different kinds of fluorescent tubes behave over ambient temperature range, from Sylvania Australian catalogue. Good old F40T12 holds for longer, but still gives up at sub-freezing temperatures, dropping to ~10% (!) output at -20C.  T5s are especially helpless at cold.

You see a really strong heat insulation is needed to keep reasonable light output at cold winter even for T12 tubes. Keeping at least 15C of temperature rise for T12s, more for thinner lamps. That is not easy assuming you need to pass most of the light out at the same time, and also you run into sub-optimal temperature at summer (though not that bad as at cold numerically).

Interesting. I expected the thinner tubes to perform better because they're hotter to start with. Though i can attest to T5 tubes doing poorly in cold weather - there's a motion sensor activated waterproof fixture in the bike shed at work. It's always very dim.