Lemming Tracks: Designing Better Street Lighting

"Overexposed"
Charles Linn, FAIA, Architect Magazine (March 1, 2012)
"A newfound appreciation for dark skies, a model lighting ordinance, and LEDs may help maintain night vision by reducing outdoor illumination levels.
Lemming Tracks: Designing Better Street Lighting
"In cities around the world, telling a child, 'I used to see stars from my backyard,' may soon sound as credible as, 'I used to walk 10 miles to school in 6-foot-high snowdrifts uphill in both directions.' Sky glow, light pollution, and light trespass are the consequences of development and outgrowth in urban and rural landscapes. The damage isn't merely aesthetic. Research suggests that excess night light can harm nearly everything living under the sun. The offender may be as simple as stadium lights fatally mistaken by fledgling birds for the moon, or the neighbor's porch light that beams into your bedroom, resulting in fatigue and diminished productivity...."

What the Lemming noticed second about this article was the long paragraphs. If this wasn't written for and published in an ink-and-paper magazine, and then posted: It's the Lemming's guess that it was written by someone who learned the craft before the Information Age started.

So did the Lemming: and that's another topic.

The first thing the Lemming noticed was that this is another 'light pollution' article. These have been popping up at intervals for years. Some make sense, some tell more about the author than the subject, a few make good points.

This one, in the Lemming's opinion, makes sense. And makes good points.

Another trio of massive paragraphs, then the Lemming will opine.

Gigawatt-Hours, IDA, and Tradeoffs

"...The amount of energy and money expended to illuminate what is essentially water vapor and floating particulates in our atmosphere is not trivial. According a 2009 document published by the nonprofit International Dark-Sky Association (IDA), the U.S. expends 22,000 gigawatt-hours of electricity—the equivalent of 3.6 million tons of coal—each year in light pollution. At the rate of 10 cents per kilowatt-hour, this energy translates to $2.2 billion annually....

"...In the past half-century, the light source of choice for streets and parking lots was high-intensity discharge (HID) lamps, which included mercury vapor and low-pressure sodium lamps, but mostly the ubiquitous yellow-orange high-pressure sodium (HPS)....

"...It is difficult to design optics that can control stray uplight and glare without significant tradeoffs in luminaire efficiency. Despite their notoriously poor color rendering, HPS lamps are inexpensive, can last up to 24,000 hours, and output a lot of light initially; the output declines as they age. In the last 30 years, the use of metal halide, an HID source that produces whiter light than HPS, has increased, but HPS still dominates...."

This article gets points for discussing the technologies involved in outdoor lighting, the legal and regulatory situations: and, particularly, the awkward economic decisions folks need to make.

Is sky glow a real problem? Even though the Lemming's read some angst-filled articles about frightfully vital wildlife, and slightly-restrained rants by amateur astronomers who can't see through the haze overhead: yes, the Lemming thinks there's a real problem here.

Maybe not on the 'and we're all gonna die' level: but it does look like human beings are designed with 24-hour lighting cycle in mind: one where the lights are out for several hours each night. Humans are adaptable critters, and can survive bright light 24-7: but they do seem to thrive better with regular darkness.

Amateur Astronomers and the Asteroid Patrol

At the risk of being overly dramatic, the Lemming thinks it's prudent to recall that the bit of debris that upset the dinosaur's world wasn't alone.

Amateur astronomers often are the first to notice some new bit of cosmic stuff swinging by Earth's neighborhood. Most new asteroids and comets don't come particularly close to this planet. A few do.

And, every once in a while, one of their orbits gets them up close and personal with Earth. When that happens, something like the Tunguska event happens.

So far, humans have been lucky. The explosions haven't happened near cities. Of course, there are a few ancient civilizations that simply stopped being there: and that's probably another topic.

Right now, there's a chance that an amateur astronomer would notice something big enough to make an inconvenient gap in, say the eastern seaboard. Before it got so close that everybody could see it. For a few seconds, anyway.

Here is where 'light pollution,' sky glow, whatever comes in. All amateur astronomers that the Lemming knows about are on Earth. If the sky gets so bright at night that they can't 'see out:' well, we could lose more than some really good science.

Enough said.

On the 'up' side, quite a few folks have been working at finding practical solutions to bright city skies.

Allegedly-related posts:

• "Lemming Tracks: Toxic Light Bulbs For a Brighter Future"
  (January 16, 2012)
• "Bright Lights of Broadway: On Another Planet?"
  (November 7, 2011)
• "IceCube Neutrino Observatory: Again"
  (December 28, 2010)
• "Ben Franklin and Daylight Saving Time: Even Homer Nods"
  (November 7, 2010)
• "Big Impact on Jupiter: Astronomers' Field Day"
  (July 21, 2009)