I miss low pressure sodium street lights

[traffic-light-man]

Of course, if it is possible for off-the-shelf LED lanterns to be modified with NBA LEDs, then SOX-like illumination might continue to be viable for private and commercial estates, where SOX seems to have been most resilient.

I recall in the early days of LED street lighting, there was a company at TraffEx that exhibited amber, amber/white and white LED lanterns - I assume an attempt to replicate the current options at the time.

From a road safety point of view, full colour differentiation from white light is a massive tick.

Hence the 'special' white lights that several companies dished out specifically for pedestrian crossings, and of course, the little floods and spots that you used to see attached to Belisha beacons.

Red LED lanterns have been utilised to help bats at night. I haven't seen these in person, but I imagine the resulting output has fairly similar traits to SOX (not the colour itself, but the limited rendering of other colours).

[Gareth]

^^ That looks like very murky SON. It does show that LEDs can be adaptable to specific local situations.

Something I thought about with regards to this circadian rhythm thing: LED lanterns that can change colour temperature depending on the time of day. So in winter, when it's dark when people get up in the dark and commute home in the dark: a full spectrum light could be used. From after 6pm or so and until 6am, it could switch to a more warm colour, more akin to incandescent or gas lighting.

In fact, with todays technology, you probably could have a central computer that could regulate or override the settings, down to the individual lightning columns. Bryn mentioned fog - I'm not exactly sure what the science is behind SOX being more effective in the fog but if LEDs could emulate the properties that SOX has in this respect, the central control could initiate a 'fog programme' so to speak. A bit like how traffic signal control centres have separate programmes from rush hour to unexpected congestion or planned one-off events.

[nowster]

Broad spectrum LEDs do it by exciting phosphors using blue or UV LED chips, in the same way fluorescent lights do using mercury vapour.

[ManomayLR]

I do think smart motorways should be fitted with 'adaptive LED lighting' where the lighting is as follows:

Sunset - lights turn on.
Before 8pm - lights white in color.
8:30pm to 8:45pm - gradual transition to an HPS color (Warm white).
11pm to 11:15pm - gradual transition to an LPS color (Yellow).
3:45am to 4am - gradual transition back to an HPS color (Warm white).
5:30am to 5:45am - gradual transition back to white.
Sunrise - lights turn off.

[traffic-light-man]

...HPS color (Warm white).

I'd say the average HPS SON colour is definitely orange rather than warm white. Although its colour rendering is superior to SOX, it's nowhere near as good as a proper white-light source.

I'm not sure I see any practical advantage to a colour changing fixture in this context.

[Truvelo]

Warm white is generally considered to be that of incandescent bulbs are 2700K. SON is definately more orange than that but not as yellow as SOX 1800K.

[ManomayLR]

I'm confused now about terminology and acronyms: Is LPS/HPS the appropriate acronym for low/high pressure sodium respectively, or SOX/SON?

To my understanding, SOX and SON are types of LPS/HPS lamps respectively, so I use the latter pair when referring to low-pressure or high-pressure lamps generically.

Is this correct?

[traffic-light-man]

I'm confused now about terminology and acronyms: Is LPS/HPS the appropriate acronym for low/high pressure sodium respectively, or SOX/SON?

To my understanding, SOX and SON are types of LPS/HPS lamps respectively, so I use the latter pair when referring to low-pressure or high-pressure lamps generically.

Is this correct?

Yes, you're absolutely correct. It's likely I'm the one confusing matters with SOX and SON, so apologies, just habit!

[Gareth]

SOX is a type of LPS lamp. More efficient that earlier ones, though I'm not sure of the technical differences. That said, I'm pretty sure hardly any LPS lamps that aren't SOX are in regular use in this country nowadays, so this distinction is not that important. So far as I'm aware, HPS and SON are the same thing. SON being a pun on "sun", to complement SOX.

Americans always talk in terms of HPS and LPS though.

[Raggit_Rich]

We have a quiet car park in my local town that is still mostly lit by SOX lights on concrete poles (one of the last in my area to still have SOX). The orange glow is quite marked and I do enjoy walking past it & bringing up memories of travelling in the 90s when I was young.

Our local council has lots of tall SON lights on the A22 that are still orange in colour.

[ManomayLR]

Before we moved house in 2015, our old house had LPS lighting on the street. There was a mix of steel and concrete columns. After we moved out, they were all replaced with LED. Sad times.

[Patrick Harper]

TBH, my enthusiasm for LPS was probably an extension of misguided nostalgia. Lighting akin to HPS or ceramic metal halide does the job just fine for all but the most demanding applications, so long the luminous output is not excessive and the lanterns prohibit light above the horizontal. That being said, given that the main purpose of street lighting in urban areas is to enhance the perception of safety, the standardisation on 4000K+ LEDs seems a bit unfortunate, it's kinda unforgiving in the other direction.

[traffic-light-man]

We've got some locally (I think they're a Philips product) that I'd say are around 3800K which are nice. I'm above the lantern hight and they certainly don't spill upwards from the lantern directly.

Outside of the city centre though, the Hardie kit (both the Beta 5 look-a-like and the long tube type) that is prominent seems to be closer to 4500K, perhaps even 4700K. Given they also tend to spill sideways a fair deal from both lantern types, they're pretty harsh on the eyes!

[Gareth]

The Hardie stuff is crap. Cold, dim, toothpaste white. Was always a relief to see the odd SOX survivor add some colour to the streetscene and, indeed, some brightness.

The gear the city's using now is much better and gives out a far more pleasant light and ambience. Thankfully, my area wasn't in the first tranche of upgrades from SOX and so we have the current better version.

It's just a shame the lanterns, sleeves and new columns have to be fugly. It's not like I expect the average street column or lantern to be a work of renaissance art. Just a bit of style would do it.

[ManomayLR]

But what was the main thing that led to the end of LPS?

[Gareth]

The advent of LED.

Although it was never popular in most of the world to begin with due to the poor colour rendering.

[Patrick Harper]

But what was the main thing that led to the end of LPS?

From the early 90s onwards, SON and other HID sources slowly nibbled away at SOX's market share, largely due to much better colour rendering. At the advent of mass-market LED lanterns in 2008, the split between SON and SOX in the UK was around 50/50. SOX has declined much faster since then due to the end of production of SOX equipment and the rising cost of SOX lamps, which by then negated any benefit in reduced energy consumption. LEDs may have hastened their demise but even without them, it was only a matter of time anyway.

[ManomayLR]

But what was the main thing that led to the end of LPS?

From the early 90s onwards, SON and other HID sources slowly nibbled away at SOX's market share, largely due to much better colour rendering. At the advent of mass-market LED lanterns in 2008, the split between SON and SOX in the UK was around 50/50. SOX has declined much faster since then due to the end of production of SOX equipment and the rising cost of SOX lamps, which by then negated any benefit in reduced energy consumption. LEDs may have hastened their demise but even without them, it was only a matter of time anyway.

On motorways, how many working LPS installations remain?

[Gareth W]

I miss SOX and Mercury - we still have some SOX on the back roads and courts of the sixties ex-Naval estate i live on together with the odd Mercury one in the concrete walkways and “nooks and crannies”.

But they and the SONs are slowly but surely being replaced by LEDs and CFTs which I hate.

[ManomayLR]

I miss SOX and Mercury - we still have some SOX on the back roads and courts of the sixties ex-Naval estate i live on together with the odd Mercury one in the concrete walkways and “nooks and crannies”.

But they and the SONs are slowly but surely being replaced by LEDs and CFTs which I hate.

What does CFT mean?