Yeah 50W HPS seems to be less popular than 70W HPS overall, though 50W HPS is all over the place in RI and southeastern MA. Here, 100W MV was replaced with 50 (or 70) watt HPS, 175W MV was replaced with 100W HPS, 400W MV was replaced with 250W HPS, and 1000W MV was replaced with 400W HPS. 250W and 700W MV were never used here so consequently 150 and 310W HPS don't exist here. There actually ARE a few 150W HPS lights that were installed in the 80s as new original street lights (they weren't used to replace another light) but those fixtures are not maintained anymore since there's so few of them. So they slap up a 100W HPS (or once in a while, a 250W HPS) in its place. Not sure why there was never 250W MV here, since there are places where I think something between 100W HPS and 250W HPS would be appropriate. I don't know the wattages for any of the incandescents except for the 105W incandescents, which were replaced by 100W MV in the 60s (I know, a lot of energy savings, right? A lot more light too) so a lot of the areas with 105W incandescents kept them until the 1990s changeout where 50W HPS lights went up. I guess the municipalities couldn't justify switching to MV just to save a few watts.

Were they big 400W silverliners (OV-25) or smaller 100/175/250W ones (OV-15)? What about the seven GEs?

I currently have eight GEs, four Westinghouses, and two Coopers. My oldest street light is either my Westinghouse OV-25 remote ballast or my Westinghouse OV-10IB clamshell light. Both are from the early 60s. I think the OV-25 might be a little earlier though. My newest light is my 1997 GE M-400A2. It was originally 400W HPS with a 277V ballast but the shopping plaza it was in converted all the lights (400W HPS, 250W HPS, 1000W MV, and 400W MH) to 320W PSMH around 12 years go. Then a couple of years ago they replaced the lights (whole poles and everything) with LED shoebox lights. I missed out on some M-1000s and a Hubbell RLG but I was able to score two of the M-400A2s, one I kept and the other I gave to another collector. Fortunately the PSMH ballasts were all multi-tap so I could keep it PSMH. A PSMH cobrahead is pretty cool even though it's not OEM. I gave it a new coat of paint and added a photocell socket since it didn't have one. It's a big light and uses quite a bit of juice so it stays outside in the shed. Not the ideal way to display the collection but it'll have to do until I can get my own place with lots of room for all my lighting "junk".

275W HPS? Wow that's something new to me! I have no idea when the first HPS fixtures popped up here. the RI department of transportation had installed a bunch of poles on Interstate 95 with 400W HPS lights of all various makes and models back in the early-mid 80s. However when they went HPS in the 90s like the electric company, they replaced the already-HPS lights on those poles with 400W HPS M-400R2s. No logic at all behind that. I assume it was just so that the lights would all match? But who else would notice but us enthusiasts? Until the 80s all the RIDOT lights were on short poles and were 400W MV (with 250W HPS spot replacements). When they went all-HPS in the 90s they kept the already-existing 250W HPS lights, since by the 90s they already had some new installations of HPS lights (brand new poles and all) with contactor cabinets controlling them.

Interestingly enough, the freeway lighting around here always used individual photocells on each light. It wasn't until the 80s that RIDOT began using contactors to control the freeway lighting. Now it's all they use for new installations. There are still plenty of PC-controlled lights though. Some of the PC-controlled systems were retrofitted with a contactor cabinet and the PCs were swapped out for tall white Intermatic shorting caps but most still use the PCs. The only lights that were always contactor-controlled here were on major bridges such as the Newport Bridge. If you look on the left, you'll see two hacked-down poles. Way back when, there were twice as many poles. They removed every-other pole. I'm thinking there were traffic signs on those poles so they kept them up. If you look closely, half-way between each pole is a platform for a pole that doesn't exist. The mast arms attached to the two columns were actually welded into the structure, so those were simply left headless. Those lights in the streetview are 250W MH Cooper OVYs that were installed in the early 90s. This is the only installation of MH cobraheads in RI on a public road/freeway. The poles not on the actual bridges got replaced with 250W HPS GE M-250R2s. As you can see, they still got rid of every-other poles even off the bridge. And check this out: they missed two of the M-400s when they went HPS/MH in the 90s! This is at the Jamestown end of the bridge, where the freeway lighting is owned and maintained by the DOT. However, they replaced all the bridge lights with LEDs recently and this time this did not forget about these two.

at the Newport end of the bridge, the freeway lighting is actually owned and maintained by the electric company. The lights are leased to the state like wood pole lights are leased to the city/town. Newport Electric was the electric company (now it's NGrid) and Newport Electric kept installing brand new MVs until NGrid bought them out in ~2000. Since then NGrid has spot-replaced with HPS. Turn this shot left about 120 degrees and you'll see a nice incandescent radial wave with a remote PC socket.

MV lamps have a nice blue, but not very good for streetlighting along with HPS. The scotopic efficiency of such lamps is low compared to 4000k+ metal halide. Maybe the new photonics tech can improve the efficiency of MV.

@ streetlight 98,

Sorry that it has taken me so long to respond.

As to the Westinghouse cobraheads, I had (1) 400w MV, OV-25, and ( OV-15 lumenaires 175 MV. The GE's were (3) M-400, drop lens MV's made in 1984, 480/240V. The other 4 were M-400, FCO  HPS, made in 1988, and were also 480/240V. These lumenaires were brand new out of the box and I got them in a trade for some other electrical/lighting junk that I was getting rid of. I got the better end of the deal, that's for sure.

As a adolescent, I used my parents place as an outside lighting laboratory. The yard consisted of two acres with out buildings, one central utility pole and numerous large evergreen trees. Needless to say, I had a good portion of my collection of streetlights installed out somewhere in the yard. No one else in all of my neighbor hood even came close to fixture count. (There was an electrician who lived 3 miles away who came close though.) Had up to eight cobraheads installed outside. One 400w MV, and seven 175W MV all Westinghouse OV's. (My dad would joke that the Soviets heat seeking missiles would lock one to our place instead of there intended target  )

Interesting array of lights! Awesome that the GEs were NOS but too bad they weren't 120V. I suppose if you had 240V readily accessible you could have still lit them and kept them original. I assume the GE M-400s were the split-door type? (they looked like Powr/Doors with two doors but the ballast was still mounted in the top housing instead of on the door like a true Powr/Door.) I have a split-door M-400. It's 400W MV 120/240V and also NOS, from March 1973. Of course stupid me had tinkered with it when I first got it in the 6th grade so the socket wires are spliced.

LOL about the Soviet missiles.   I have to semi-permanent street light installations in my backyard. One's on the deck and the other is across the yard on the shed. They're hooked up to extension cords. The one on the shed has my 1965 GE M-250R, 175W MV 120/240V (the original ballast was 100W MV 240V but I had an OEM GE ballast that I put in so I could use it on 120V yet keep an authentic look. I just had to fabricate a capacitor strap. The on one on the deck I change put periodically. Right now it's got my 400W HPS Cooper OVX. Neither of the lights are used on a regular basis. Just when I feel like running them. I unplug them before I go to bed to avoid bugging the neighbors. I haven't lit the OVX yet. That sucker's gonna light the whole neighborhood. The neighbors might call the fire department on account of all the orange light. I'm surprised no one has done that when I run my HPS lights in the basement with the windows open in the summertime lol (the HPS makes less heat so in the summer I typically have a HPS light on display indoors and MV in the winter, when I can use the extra heat). I've always been leery of using my MH street lights indoors. I know the risk of a rupture is small but it still scares me.

...
When I mentioned the optical losses of a lumenaire, I'm taking about the coefficient of utilization. You're talking about lumens, but how many lumens are lost in the lumenaire?  My point is HPS may throw out a lot of lumens, but is it light that you can really see by? The lumen level may be high, but the awful color rendering makes most of the lumens generated pretty useless to the human eye (not as bad as LPS which has a negative CRI). If the light source instead was  MH, I think your argument for legacy technology would have a better leg to stand on, especially if it is ceramic. The reason why LED works as a replacement for HPS, is that it delivers the same amount of useful lumens for us to see with. You may not agree, and that's alright, but if HPS was so much better that LED, why is it that utilities are replacing in mass (its not just for energy conservation)? This reminds me of when MV was replaced in mass with HPS in the early 1980s. Many people complained about the yellow light (and a guy I knew at a local utility complained about the high maintenance cost and short lifespan of HPS). Now people are complaining about the high CRI LED, and are nostalgic for HPS. Who want the street lit with yellow light?

The major advantage of LEDs is not the optical losses in the luminaire. A good reflector has already an efficiency >90% and normally only about half of the light is reflected, the other half is directly emitted. The major advantage in street lighting(for indoor is not that important) is the great uniformity in luminous flux on the road which allow to use less total lumen, which is impossible to obtain with other light sources.

The Electric Co. In my area (Ameren Illinois) has officially confused me.  For one example, they replaced an EOL 175w merc with a 100w HPS Bucket, but two weeks after that, replaced the same Bucket with a 400w M400R3 cobra.  Down the road, he replaced an EOL 175w merc with a 250w HPS M250R2 (M2RR), which is what has been used for years, but a small portion of the M250s have been M2RC FCO versions.  So now I have no idea what is going to replace what.  All I know (at this point) is that it will be a GE luminaire and the lamps are made by EYE (Iwasaki).

Eh at least they're using quality lamps. A MV bucket down the street was dayburning. Popped a new PC in and it's fine. One lost its lens to trees. New lens and tree service and it's fine. One went completely dead (American electric bucket). It lost its lens and bulb for a week and a 100w HPS SA filled its place. Hopefully it stays. One 100w sa around here is missing half its lens due to tree damage. Wonder what it's fate will be.

Well at least they're keeping it interesting. It's kinda boring when you know exactly what will replace what. Yeah sometimes if a merc is datburning they'll replace the PC but other times they'll replace the whole light.