What colour should streetlamps be?

[pipnina]

We all know (or at least... 99% will) the pain the orange sodium lamps bring us when we lug our scopes outside. And fortunately there are very good filters out there to remove their effect on the sky. But it seems like these new LED lamps that emit light in just about every wavelength are going to become more common (already being put in place in Plymouth D:). These lamps can't be filtered...

This lead me to a thought. If these LED lamps eventually take over as the most common street lamp... Could we at least persuade our councils to put specific colour filters/LEDs in them? It makes sense to me that they might be a narrowband shade of green since that puts it far away from Ha and Olll (or is it OIII, I'll never know...)

I think, if these LED lamps have very narrow wavelengths, they'll be extremely easy to filter out. Do you think we could make it happen if the LEDs take over?

[FunkyKoval35]

Unfortunately, LED lamps are lighting in full spectrum.

[DaveS]

Black!   

Unfortunately LEDs are just too simple and cheap for the morons in local councils to think about anything else. To my mind the best are still LP sodium in full cut-off housings, but try telling that to the sheeple.

[pipnina]

Unfortunately, LED lamps are lighting in full spectrum.

Unfortunately, they are. It saddens me.

Although, on the bright side, all the LED lamps that have been put up in my area send much more light downwards than any other type of lamp I've seen prior. And even though 10/20% ofn the city now has these white lamps, the sky is still VERY orange.

(p.s. I was talking about filtering them, I.e. what specific colour should they be to best filter them out)

Black!   

Unfortunately LEDs are just too simple and cheap for the morons in local councils to think about anything else. To my mind the best are still LP sodium in full cut-off housings, but try telling that to the sheeple.

In all honesty, the sodiums probably are the best we have at the moment in terms of filterability. They emit quite a narrow band of frequencies.

[HD-AP]

The best colour for streetlamps is Black

and / or off !          

[ronin]

The answer to the question "what colour should streetlamps be?"  is: White.

The lights are there to enable people to see and be seen as they walk and drive, and certainly the new LED ones that have replaced the yellow sodium ones on roads I use have made things a lot easier and more visible. I am impressed by the general improvement. However that is driving a car but that is what the street lights are intended for.

The key word is "streetlights". They are there to function as streetlights. The lights used are not related to astronomy in any way and no consideration will have been given over to astronomy by any council, they are street lights and as street lights they are there to illuminate footpaths and roads.

[pipnina]

The answer to the question "what colour should streetlamps be?"  is: White.

The lights are there to enable people to see and be seen as they walk and drive, and certainly the new LED ones that have replaced the yellow sodium ones on roads I use have made things a lot easier and more visible. I am impressed by the general improvement. However that is driving a car but that is what the street lights are intended for.

The key word is "streetlights". They are there to function as streetlights. The lights used are not related to astronomy in any way and no consideration will have been given over to astronomy by any council, they are street lights and as street lights they are there to illuminate footpaths and roads.

I have to say. I didn't expect that side of the fence to show up on an astronomy forum!

It is true, the white light does make for better visibility when walking around compared to the standard sodiums. And the primary purpose of a streetlamp is in the name, as you suggest.

Although. I think the LED lamps emitting at 100% of the visible spectrum is overkill. Let's not forget that we can just choose 3 narrowband colours for the lamps to emit in and the light will still appear white because of our eye's natural bayer filter.

[pipnina]

The best colour for streetlamps is Black

and / or off !          

I was wondering when this response was going to show up! Maybe they should be turned off after a certain point. My mother used to work the night shift and she said there was rarely a problem with the lights going off at 11 and coming back on at 4.

[Scooot]

Many councils have already started doing that. Not sure if yours has started yet but it looks like they have plans to if they haven't already

https://new.devon.gov.uk/streetlighting/part-night-lighting/

[HD-AP]

Many councils have already started doing that. Not sure if yours has started yet but it looks like they have plans to if they haven't already

https://new.devon.gov.uk/streetlighting/part-night-lighting/

hI

The streetlight's on my road go off at 1 am and come back on at 5 am.

[HD-AP]

The answer to the question "what colour should streetlamps be?"  is: White.

The lights are there to enable people to see and be seen as they walk and drive, and certainly the new LED ones that have replaced the yellow sodium ones on roads I use have made things a lot easier and more visible. I am impressed by the general improvement. However that is driving a car but that is what the street lights are intended for.

The key word is "streetlights". They are there to function as streetlights. The lights used are not related to astronomy in any way and no consideration will have been given over to astronomy by any council, they are street lights and as street lights they are there to illuminate footpaths and roads.

True but council streetlighting is a hammer to crack a nut approach .

When streetlight's intrusively illuminate 50 yards behind them to 10 lumens ,bright enough to read a news paper in your back garden then this is unacceptable .

It's ok to illuminate roads and footpaths ,but when poorly designed streetlights intrude / illuminate onto private property ,it's a different matter altogether.

[DaveS]

I suppose it would be possible to have RGB streetlights, like theatre LEDs with the wavelengths selected to miss the important emission lines.

Just a quick note, our eyes don't have a Bayer matrix but a random array of RGB cones + rods.

Streetlights don't have to be white, all they need to do is give *just* enough illumination so people don't trip up or walk into things, and monochromatic sodium does that just fine. Cars don't need streetlights, that's what their headlights are for.

[pipnina]

I suppose it would be possible to have RGB streetlights, like theatre LEDs with the wavelengths selected to miss the important emission lines.

Just a quick note, our eyes don't have a Bayer matrix but a random array of RGB cones + rods.

Streetlights don't have to be white, all they need to do is give *just* enough illumination so people don't trip up or walk into things, and monochromatic sodium does that just fine. Cars don't need streetlights, that's what their headlights are for.

Well, true, it's not quite a bayer filter. But it works in a similar way at least. I seem to remember reading that there are tubes in front of each cone that filters the light by wavelength.

Although. LEDs right now ARE in RGB. They're just RGB in the sense of a computer monitor: They display a fairly wide range of frequencies in each colour. But I see what you mean, give the sub-LEDs filters that are as far away from emission lines as possible.

[DaveS]

"White" LEDs are actually a combination of an intense blue exciter LED and a phosphor. The blue LED peaks at about 450-470 nm, then there's a dip around the 500 nm mark (The Stokes Gap) then the phosphor has a broad emission peaking in the yellow I think.

Theatre RGB LEDs have discrete Red (630nm) Green (550 nm) and Blue (Usually 470 nm) LEDs Something like this could be done for streetlights, perhaps even just running the red LEDs after a certain time.

[Beulah]

I suppose it would be possible to have RGB streetlights, like theatre LEDs with the wavelengths selected to miss the important emission lines.

CMYK ones would be even better.

[D4N]

Wouldn't the green LED's be able to operate at a much lower level as our eyes are much more sensitive to green light?

I can drive quite adequately without streetlights, my car has headlights

What strikes me as crazy is when you have areas of motorway with streetlights. Why would you do that? It's just wasting money.

Sent from my iPad using Tapatalk

[FenlandPaul]

I run the UK operation of an LED lighting manufacturer (please don't lynch me). As someone who's in the industry, I'm afraid that there really is no better affordable technology out there at the moment for providing reliable, very efficient lighting with excellent colour rendering. So we're not going to see it disappear any time soon. The best thing we can do is persuade our councils and local business owners to use lighting in a better way - with good quality lighting designs directing the light where it's actually needed (not just a 1-for-1 replacement) and also when it's needed (with simple but effective control systems that turn off or dim the lights during non-core periods).

Control and design is key. If we do this properly, the effects of stray light should be significantly reduced. Clearly as someone who loves the night sky, I would love people to just "turn off the lights" - but I know that's not plausible.

Interested in the RGB mix idea - not heard of that before. I wonder why it's not used anywhere (I'll ask tomorrow and let you know if I get a good answer!).

Paul

[pipnina]

I run the UK operation of an LED lighting manufacturer (please don't lynch me). As someone who's in the industry, I'm afraid that there really is no better affordable technology out there at the moment for providing reliable, very efficient lighting with excellent colour rendering. So we're not going to see it disappear any time soon. The best thing we can do is persuade our councils and local business owners to use lighting in a better way - with good quality lighting designs directing the light where it's actually needed (not just a 1-for-1 replacement) and also when it's needed (with simple but effective control systems that turn off or dim the lights during non-core periods).

Control and design is key. If we do this properly, the effects of stray light should be significantly reduced. Clearly as someone who loves the night sky, I would love people to just "turn off the lights" - but I know that's not plausible.

Interested in the RGB mix idea - not heard of that before. I wonder why it's not used anywhere (I'll ask tomorrow and let you know if I get a good answer!).

Paul

An insider!

It would be interesting to know what you find out. Can't wait!

I just thought. You mentioned using control systems... What if the street lamps had motion sensors on them and motion under any lamp would turn the next 4/5 on in front and behind that lamp? It sounds like it could be very efficient and greatly cut down on stray light.

All just ideas. Probably too expensive to just replace all the streetlamps with that system, though...

[DaveS]

Thanks Paul, that would be interesting to know.

RE: stage lanterns, only the cheapest use bare RGB, it's increasingly common to add white, for pastel shades and / or amber for better warm colours. Some go to RGBAW, and there's a new trend for adding "UV" which is actually just 405 nm violet, to give better deep blues (Congo Blue for those who know). ETC use up to 7 discrete colour LEDs in their top end (ie. expensive!) lanterns.

Sorry to take this OT!

[FenlandPaul]

An insider!

It would be interesting to know what you find out. Can't wait!

I just thought. You mentioned using control systems... What if the street lamps had motion sensors on them and motion under any lamp would turn the next 4/5 on in front and behind that lamp? It sounds like it could be very efficient and greatly cut down on stray light.

All just ideas. Probably too expensive to just replace all the streetlamps with that system, though...

I've seen some companies that have developed those sorts of systems. There was one not far from here that developed a motion-sensing control system that did precisely that. It relied ona wireless mesh control network and they had some success on new-build roads and tunnels in China but I've not seen it anywhere else. It's definitely possible for car movements; not sure about people movements but I don't see why it couldn't work with a little effort. Suspect the capital outlay puts people off, though.

P

[laser_jock99]

The key word is "streetlights". They are there to function as streetlights. The lights used are not related to astronomy in any way and no consideration will have been given over to astronomy by any council, they are street lights and as street lights they are there to illuminate footpaths and roads.

LED street lights are indeed currently very directional and this is good for astronomy. However, where they have been installed many residents are starting to complain about this - presumably they are used to the awful light spill from the older light fittings lighting up everything in wide area.

http://www.thenational.scot/news/led-up-a-dark-alley-by-cost-saving-measures.2411

Comments like "it's dark all the way up to my front door" or "I need to use a torch between the new street lights" are not uncommon.

The typical (and correct) council response is that it is their responsibilty to only light the streets and not people's gardens or private property.

Worryingly though, concerns about the controlled directionality of the current generation of LED street lamps may well lead to LED street lamps being designed to throw white light in all directions.......

[wxsatuser]

The compact flourescent ones here are dropping like flies.

Some went kaput in a matter of two weeks and there are two out tonight near our house.

Hope a few more bite the dust and they don't bother to fix them.

[bitnick]

I just thought. You mentioned using control systems... What if the street lamps had motion sensors on them and motion under any lamp would turn the next 4/5 on in front and behind that lamp? It sounds like it could be very efficient and greatly cut down on stray light.

 

All just ideas. Probably too expensive to just replace all the streetlamps with that system, though...

There are at least experimental municipal lighting that works that way. This is a quote from an article about the Danish Outdoor Lighting Lab:

Along one bike path, the lights were dim until sensors picked up the presence of a jogger — the lights brightened in sequence following the runner down the path, then dimmed again to save energy once he had passed.

The article can be found here.

[bitnick]

I think the LED lamps emitting at 100% of the visible spectrum is overkill. Let's not forget that we can just choose 3 narrowband colours for the lamps to emit in and the light will still appear white because of our eye's natural bayer filter.

Actually, broadband lighting is necessary for acceptable colour rendition. Let's say your 3-narrowband-colours LED lights up something that happens to reflect light only in between two of those narrow bands (an orange maybe?). That object would appear black (if very narrowband reflectivity) or at least murky or weirdly colored under that illumination. So even if our eyes only differentiates between three parts of the colour spectra, those parts must be "broadly"/completely illuminated spectrally for things to look natural.

[Vega]

This is a very informative and interesting thread. I fear though that council's really wont be interested in changing street lighting solutions based on what wavelengths are most effective to the human eye or most easily filtered. It would be far too costly to invest in something that will result in a product that wont do their intended job any better (lighting up the streets). The only way we could convince council's to make any changes is if there was a clear financial benefit (the only reason we see come council's having switch off periods or the installation of 'intelligent lights' as mentioned above).

It's a miracle that some council's have even thought about more downward directional lights... lets just count our blessings there. 

Sorry if I sound negative. I would love for council's to consider light pollution issues more seriously as much as the next fellow astronomer but at the end of the day, money talks when it comes to council's priorities.

Put in to perspective, no street light is as a bad a light polluter as our very own moon when she's full. Naughty Luna!

Matt