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White street lights and light pollution


earth titan
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Northamptonshire County Council are gradually replacing all of the sodium street lights with white LEDs. Alternatives for saving money, such as turning lights off are not, as far as I know, under discussion.

Before I dash off a letter to the local county council, does anyone know:

The effects the new white LED street lights have on light pollution?

Any academic papers which show reduced lighting reduces street crime?

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I can't tell you how depressed your posting has made me. I knew this day was coming, but I didn't know it was so close at hand. Make no mistake, LEDs will kill deep sky astronomy from the UK.

As I'm sure most people reading this forum will know, the photoreceptors in our eyes are made up of rods and cones. The rods are the more sensitive photoreceptors that we use at night. The cones are what we use during the day and give us colour vision. The high resolution spot at the centre of our vision - the fovea - is packed with cones:

rcdist.gif

This is why we use averted vision to view deep sky objects, so we can view with our light-sensitive rods. Our rods have peak sensitivity at 495nm, which is turquoise:

conesens1.gif

The response curves for our red, green and blue cones are also shown. So when we use a red light to read a chart we can read it using the red cones in the fovea and not loose dark adaption in our rods, because our rods are largely insensitive to red light.

The current situation with light pollution is that it is mainly confined to a few emission lines from street lights. See this link showing the transmission curve for a UHC filter. Most of the emission lines are towards the orange and we are used to the orange glow of light pollution - however the overlap between the rod response curve and the streetlight emission lines is not too dire. This was brought home to me when I took a photo of the milky way from Tenerife. The milky way was very prominent to my eye, but when I looked at the photo, the light pollution was much more prominent. The reason was my eye was not so sensitive to the orange light pollution. Going back to the UHC filter, you can see why the OIII and Hb lines are so important visually, because that is what our rods are sensitive to.

LED are much more broad band sources than discharge lamps. The worst sort of white LED is the most common - these are phospher based and have a spectrum like this:

350px-White_LED.png

I guess there is a bit of a dip around 495, but it's still going to blast our rods. Even the RGB 'white' LEDs will blast our rods:

350px-Red-YellowGreen-Blue_LED_spectra.png

So basically I reckon LEDs will interfere with our rods much more than current street lights do. They are so broad band that filtering them out will be impossible. As I say, I think it's the end of deep sky astronomy from the UK.

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I guess despair isn't too helpful. What can we do about it. Obviously politicians care little about minority interests like astronomy so I guess we've got to try to focus their minds on making energy savings by only shining the light where it's needed - i.e. down - and also dimming or switching them off late at night. LEDs tend to be quite directional, so I guess that's a good thing.

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We had LED lights fitted in my neighbourhood in 2007 or so, and I'm convinced the sky here used to be darker than it is now hen we had the old lights. I'm not 100% sure, though.

If I understand light pollution correctly, it's light escaping upwards from the source instead of being directed down to the ground where it should be. (am I right?) If that's the case, then how difficult would it be for the local councils to fit some sort of shroud to the street lights to keep the light directed towards the floor and away from the sky? Or is the light being reflected back from the ground?

Edited by peteuplink
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Think that the maps we see of light polution are a little misleading. They show how bright a town/city is from above. As observers we are sat in the light looking through it. A small but different situation.

Most light pollution is the light escaping upwards from the lamp, with the sodium lamps a fair bit as no-one was bothered about it at the time.

Problem with the new lights is that they are white and more is directed down. In effect we are sat in white light and as more is directed downwards we are in quite a bit of it.

But even if directed down there will be reflected light. White light will reflect off of more surfaces then yellow will. A red surface will reflect the red component of white light whereas absorb most of the narrow Na yellow component.

Recall someone saying about a year ago that the sodium lamps we are so happy to moan about are a lot easier to filter out, they have a fairly narrow band. The white ones cannot be filtered.

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Well here is the link

http://www.northamptonshire.gov.uk/en/councilservices/Transport/roads/Documents/PDF%20Documents/Information%20(PDF%20Format%2023KB).pdf

Reading the document, they claim light pollution to be less and as they are directional they may be right.

I'm lucky enough to have a big back garden and can get away from the lights, but I wonder if the general levels of light will be greater? Spillage from the current lights in the street (sodium) creates a good swathe across my back garden but I can hide behind a couple of trees to be in the shadow.

I can feel an FoI request coming on however. Has any research been done in to the interests of minority groups, such as astromers, as councils are supposed to take the views of others into the consulation process.

All I can hope is PFI is becoming such a costly exercise, they will abandon it in favour of something else.

As a last point, one of the old arguments for not turning off sodium lights is the intitial start up and warm up costs so it was cheaper to leave them on all night. This argument would not exist with LEDs so we might be able to get them switched off at night.

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I'm reminded of John Betjeman's poem 'Inexpensive Progress' written in the 1960s, which had the lines ...'When all our roads are lighted - By concrete monsters sited - Like gallows overhead - Bathed in yellow vomit' The 'yellow vomit' which we all used to hate is the Sodium lighting. But the great thing for us astronomers is that you can filter out most of the 'yellow vomit'. You can't do that with white light.

With a lot of large urban fringe developments being planned, the chances are that this will result in large areas having the new white street lighting. Even if they are shielded to reduce upward light pollution, as planning policy generally requires (although the new UK government seems intent on dismantling the planning system and removing regulation), there will inevitably be some unfilterable light spill upwards.

The CPRE is big on light pollution. It will be worth seeing what their take is on this.

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Unfortunately councils will be able to say 'look, we've reduced your council tax bills with these low-energy lamps, and improved your lighting at the same time'. Big Society, my a**e. A group of fringe amateur astronomers are hardly going to swing anything.

But there is a much more serious issue here, and that's the continuing loss of connection urban people, and increasingly rural people, have with their environment. And that loss of connection leads to a loss of care or respect for the environment, which is everyone's loss. Towns are noisy busy places, but at night you can still get a certain reminder that there is more than the hustle and bustle of the city. You might get a glimpse of some stars, and the lower light level makes you more sensitive to other senses, such as being able to hear a distant owl hooting or fox barking, or leaves in the trees rustling. Floodlighting everything just swamps those senses and desensitises people from their surroundings, and indeed makes them MORE nervous of dark places. Society must understand that darker places aren’t necessarily scary and that darkness can be beautiful. I feel that I'm a lone voice here. Must have a word with Bill Bryson, CPRE President, who I occasionally see in my local Waitrose!

I'll get me coat. ('Fast Show' reference, for those not acquainted with the term. Meaning I've said too much, I'll get out of here to avoid any further embarrassment)

Edited by lukebl
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Light pollution - Wikipedia, the free encyclopediaVery interesting thread! I've long wondered why society seems so hell bent on lighting up the night everywhere. I've railed against it long before any interest in astronomy arose.

I came to manhood 50 years ago. As a youngster, it was still possible to go into the countryside and have virtually no light pollution. That is no longer possible except in the desert areas in the American southwest.

In the area where I live, we no longer have a central business district where high levels of light used to be concentrated 50 and more years ago. Now there are shopping centers and malls scattered around town. Each of these areas has a large parking area lit up like a landing zone for alien aircraft. To maximize the light, the lighting posts are scattered geometrically and light spreads around far beyond the periphery of the properties. I have often thought that municipal regulations should force the developers/owners to place their posts on the edges of their properties and focus it back onto their properties with penalties for any direct light escaping their property. I realize that reflected light couldn't easily be controlled, but allowing them to cast light outside there properties is wrong. In some cases, such lighting actually distracts drivers exiting from expressways. My wife has particular problems in some areas as her blue eyes gather far more light than do mine.

I've researched the subject a little to write an opinion piece for newspapers. I believe that the tax authority of municipalities - and the narrow number of decision makers who spend those funds - have been co-opted by power companies. Towns make a very dependable source of revenue for power companies and their shareholders. I had suffered from the mis-apprehension that crime rises if light is reduced. There have been numerous scholarly studies disproving the notion. In fact, a meta study by one group hypothesized that the link between crime and lack of lighting was the result of a well-funded campaign by power industry trade groups going back to the '50s. There was a rapid expansion of generation capability to meet peak daylight factory loads and the marketers came up with the lighting-crime link to sell the excess capacity going unused at night, during off-peak periods. It worked far too well.

I once lived next door to a very paranoid lady who bathed her property in floodlights all night long. She refused our requests to tone it down; so I took it to the town council only to learn that I would have to prove it a nuisance (beyond my opinion) and they would do nothing. Our neighborhood association did have bylaws that banned such lighting past mid evening, but I could never get them to act because the lady was such a well-known neurotic.

Here's a link to wiki on the subject: Light pollution - Wikipedia, the free encyclopedia

Edited by rabbithutch
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Have to agree with Beulah's comment, the image of the street being lit up like that is just plain ridiculous. Surely crime can't be so bad that we need to make night look like day?

I'm not an expert on these things but it must have a negative impact not only on animals but also humans - I'm sure there's a reason why we sleep at night when it's dark.

If they install these in my area I think it's going to be time to find another country to live in which isn't so paranoid and scared that they think the only way to be safe at night is to light up the entire country (sorry for the rant but that image has really annoyed me :()

Dean

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We have these "new" lamps going up all over Wareham. We have one behind our house and about 70 odd yards away. Does the light go up? No, infact it all goes down. Problem being is the strength of the pure, white light that is being chucked out. Somewhat like a 1,000 watt garden search light!!

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It's not the image that annoys me, it's the writer's words of "fantastic improvement" and the like that really shows the mentality of the masses. It's like a kneejerk reaction, turn night into day and people feel safe, no matter what the stats.

I´ve heard the LED lights should be more directional and the comment by Marchpane sounds encouraging in one sense, but we have to remember the ground will reflect a lot of light back upwards.

You never know, the actual crime stats might rise after such streets are bathed with such over-lighting; not that I would ever wish for burglaries & muggings to happen on anybody, but it would have a certain irony if crime went up after the new lights go live.

Edited by PortableAstronomer
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Generalisation, but here in Shropshire, public opinion seems to be slightly more in favour of turning lights off. Perhaps because it is a largely rural county so people are more used to lots of dark bits.

The negative spin is coming from a lady called Louise Ellman, chairman of the House of Commons transport select committee. She seems to think less street lights will mean more accidents. Plenty of roads around here have no lights at all - amazingly people seem to be able to use their headlights not to crash into things.

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Those LEDs look and sound awful and it's a sign of the times that a local council think that a saving of a few quid a year is good while conveniently forgetting that they cost £57m to install them in the first place. In general though street lighting is a thing very few people think about at all except to hold a vaguely formed opinion that more is a good thing and it's quite hard to argue against it without people looking at you like you're a nutter.

The really worrying thing is that the company responsible for suppying the Northants LEDs makes a big thing about how they save money so councils won't need to switch them off or dim them at night.

Here is Uttleford crime has fallen year on year since the midnight switch-off but the police have specifically refused to link the two, which is probably fair enough, as it's a rural part of the country, levels of crime were very low anyway and most of the villages in the area never had street lighting in the first place.

Edited by PeterM
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Here is Uttleford crime has fallen year on year since the midnight switch-off but the police have specifically refused to link the two, which is probably fair enough, as it's a rural part of the country, levels of crime were very low anyway and most of the villages in the area never had street lighting in the first place.

I don't want to get too political/cynical but ascribing a drop in crime to changes in streetlighting won't allow the local constabulary to claim any credit for it... :(

Our local newsletter has an article in it where our local constable advises that the best thing for security is to put "security" lights around the outside of their house.... sadly this is in amongst some other really rather good advice that most probably won't notice. I'll try and have a chat with him and see what arises from it.

I spent a week at the beginning of September in Jard sur Mer on the west coast of France which is littered with white LED streetlights (and white coloured buildings). To be honest there was a fair amount of LP for what is a smallish town at that time of year but nowhere near as much as I expected. This is probably because all of the lights were full cutoff and pointed the right way. On the flip side it's probably unfilterable... :(

I still have a lingering fantasy of spray painting bright orange half the hillside on the other side of the valley that Taunton sits in and waiting for people's complaints... :(

James

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Here in Texas, many are quite good marksmen and like to tune their rifle scopes before hunting season. Bright lights might make good targets. Not that I'd EVER do such a thing nor condone such property damage .:(

During hunting season, our roadsigns really take a beating. I wonder if overly bright street lights might not suffer similar fates. We've read at least one report of a red light camera being lassoed and pulled off a post - and our legislature hasn't even decided yet if they are legal.

But, this is Texas and not the UK . . .

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I dont much like the prospect of this in Northampton, nor do i like the prospect of a commited 25 year contract when technology moves on 4 generations a year! it does seems dumb! i live in the heart of the town but suppose being in a parsih wont have to have the damn things outside my house for a few years more according to the writing in the link. Bu that dont stop the pollution..maybe i should just invest in the Solarmax instead!

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Quick update on the situation and will continue to follow on this.

Just had a chat with the guy in charge of the project in Northamptonshire. Very nice chap and very helpful.

The start of the project is June 2011. It will take around 5 years and all lights (low pressure sodiums - the yellow ones) will be replaced by the Philips Cosmopolis. The plan is for these to be dimmed to 40% power after 22:00 hours and the anticipated light spill onto surrounding properties will be less than current lamps.

Before and after shot below:

http://www.newscenter.philips.com/pwc_nc/main/lighting/resources/press/press_cosmopolis_case_study_june/press_be_af_05_600.jpg

We have two lamps visible from our garden, one of which shines directly down the garden. I can currently filter this out and I see little prospect of changing the councils mind on this. Energy bills reduced by 40% and 'improved' lighting.

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One must applaud any government savings (assuming rates are lowered), but why must the solution include over lighting the area? Is there not some way to use fewer lights or reducing their wattage? Was this plan made with or without citizen awareness and participation?

These questions are mostly rhetorical, but I anticipate the day when even American municipalities crawl out of the pockets of vested interests and begin to change street lighting. I want to learn all I can about the experience of early-adopters in the hope of influencing changes here. (insert wishful thinking smiley here)

I can see our municipal government going ahead with such a plan on their own and Heaven take the hindmost. We already allow council members to conduct business with the city on a large scale and without appropriate transparency. Much of this has arisen in good economic times due to apathy. I'm hopeful - even at my advanced age - that we can overcome the apathy.

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