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Battling Light Pollution—From Smart Street Lamps to Dark-Sky Preserves
Thursday, 05 July 2012 10:00  |  Written by Dawn Marshallsay | Blog Entry

Light Pollution: Same View of Starlit Sky in City (left) and Country, photos by jpstanleyWe save energy by turning off the light when we exit a room, but how about switching off street lights when we exit a road? The USA’s street lamps use enough electricity to power 1.4 million homes, and generate as much greenhouse gas as two million cars do in a year. By reducing the number and length of time streetlights are lit, we can save energy and money—and help save the planet.

Switching Off Street Lights
Although local authorities have yet to install street lights that turn on and off using motion detectors, they are starting to launch a range of other energy-saving practices, including switching off every other light, certain lights after midnight and residential lights that aren’t at a street corner. Saving money may be their ultimate motive, but at least it saves the environment at the same time.

These practices are being implemented across the globe. Santa Rosa, California, plans to save $400,000 by removing 6,000 of its 15,000 street lamps, and turning 3,000 off between midnight and 5:30 a.m. Similar schemes are taking place in Montgomery (Pennsylvania), Dennis (Massachusetts) and South Portland (Maine), and in 2008 the Daily Mail reported that one in five local authorities in the UK are switching off some of their street lights.

Crime and Accidents
Following public complaints that turning off street lights will increase crime and road accidents, Cochrane Collaboration released a report suggesting that switching off street lamps ‘could triple road deaths.’ The international organization pooled findings from 14 scientific trials carried out since 1948 in Britain, Australia, the US and Germany, and suggested that the introduction of street lighting reduced the number of accidents by an average of 45%.

However, the report did not study the effect of existing street lights being switched off, and David Spiegelhalter, professor of the Public Understanding of Risk at Cambridge University, told the Daily Mail that the figures could have been skewed if the lights were installed after an abnormal amount of accidents had occurred on that road. After this, the number of accidents would probably have decreased, even if streetlights hadn’t been installed.

Villagers in the German burg of Dörentrup can turn on particular streetlights using their cellphones. Once they’ve registered with the Dial4Light scheme, they can make a free phone call, key in the code of the streetlight, and wait seconds for the light to come on, after which it will stay lit for 15 minutes. Data collected by the local council suggests that the system should reduce the village’s CO2 emissions by almost 20 tons, according to The Guardian.

LED Street Lights
An alternative to eliminating or switching off streetlights is to replace them with energy-efficient LED lights. The largest green streetlight retrofit to date is Clinton’s Climate Initiative, a five-year project that will replace 140,000 streetlights in Los Angeles with LEDs by 2013. This is predicted to reduce CO2 emissions by 4,500 tons annually, and save $10 million each year.

Light Pollution
Besides saving money and decreasing carbon emissions, turning off lights has other advantages. It reduces light pollution. Certainly, it’s easy to forget that light itself can be polluting. This occurs when it hides the stars and keeps birds awake all night—they don’t have curtains. The main culprits are buildings that leave their lights on overnight for security reasons. There are alternatives, such as hiring guards and investing in better locks and alarms.

Dark-Sky Preserves
Such energy-wasting, star-erasing practices are not tolerated in the world’s dark-sky preserves, where artificial lighting is minimized or banned to help wildlife and promote astronomy. Named differently by various organizations, these areas of darkness are labeled as Urban Star Parks (USPs) and Dark-Sky Preserves (DSPs) by the Royal Astronomical Society of Canada (RASC), while the International Dark-Sky Association (IDA) differentiates between International Dark-Sky Reserves (IDSRs) and Preserves (IDSPs).

The RASC’s guidelines on creating a dark-sky area suggest using coniferous trees, buildings, berms (barriers) and bushes as natural shields against nearby lighting. They also suggest shielding the bulbs in streetlamps to prevent light shining above the horizon. This helps make stars more visible.

When it comes to limiting streetlights, there are many alternatives to blanket switch-offs. To quell fears over safety and security, cities have variously tried timers, switching off every other light only, installing timers, setting up lights to be turned on by cellphones on demand, replacing them with LED lights, creating light barriers and shielding bulbs to stop glare. With so many options, there is no reason we shouldn’t choose one, thereby reducing CO2 emissions, saving money and helping the surrounding wildlife. And, as a nightly bonus, we’ll get back our chance for a majestic peek at the stars.

Additional resources:
Dial4Light BBC video
Dark Sky Guidelines from the RASC
CNN: Who turned off the stars? Light pollution
Restore the Night Sky: Do Your Lighting Right

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Comments (3)add
Written by Climate change and energy efficiency , June 09, 2010
Nicely written by you. Good article. Thanks for sharing your informative blog. Today's pollution is a global problem.
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Written by Julian Pollock , May 23, 2010
Thanks for this nicely written and presented article. I generally agree with all ideas for energy conservation. What would be nice would be to highlight some sites with petitions one can sign up to - to register this desire for world governments to increase these types on initiatives and projects to conserve energy. After years of living in remote places in India, I get used to moving around/walking inside and outside without light at night. One becomes more aware of the moon cycles (not only because I'm loony) so you know if you'll need a torch. In the West, most people don't know squat about moonlight!
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Written by JBL , May 20, 2010
One of the things I hate about cities is the unnecessary light they radiate that blots out the magnificent starry heavens.
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