By Laura Hunt Miller
PART 2: Let there Be (Less) Light
I used to live next to a school parking lot that was occasionally used for drag racing late at night. The powers-that-be decided to curb the young racers’ enthusiasm by installing lights that stayed on ALL night. Every night. All year. Once we could, we moved.
Ruston currently has a Bortle Scale rating of 6.8, a tool used to measure light pollution. Anything above a five means backyard stargazing is limited, with 1 being a “pristine dark sky” and 9 being bright “inner city sky glow.” A 6.8 puts us in the “bright suburban sky” category, where only the brightest stars are visible. Things like the Milky Way? You’re not likely to see it here.
That’s not to say lighting is bad. Humans instinctively associate light with safety and darkness with danger. It’s primal; early survival depended on it.
Civic design from the 1960s onward followed the “more light = less danger” policy, building on the assumption that a brightly lit place is a safe one.
Overly bright streetscapes have negative consequences too, such as making neighborhoods less hospitable. Relocating like we did, is surprisingly common according to studies done by the London School of Economics. And in downtown areas, excessive lighting can shift a space from feeling safe, to feeling unwelcomingly on display.
Over-lighting costs us literally as well. Let’s just say that the parking lot from my past had ten light fixtures. At 200 watts each, and $0.13/kWh (the current average cost of electricity in north Louisiana), that’s an annual energy consumption of $1,139 a year.
But what if that parking lot had been equipped with motion sensor lights? The average light usage could be reduced by 80%, cutting that $1,000-plus bill to about $200 a year.
Upfront these upgrades cost about $100-200 more per a fixture. So for that 10-light parking lot, adding motion sensors would raise the initial cost by $1,500–$2,000. But sensors can also prolong the life of the light bulb by five to ten years, according to the U.S. Department of Energy, resulting in less maintenance, less disruption, and less energy waste.
Now apply that math to every city or parish-funded parking lot with fixtures on a similar lighting plan. In theory, over $10,000 in annual power bills would drop to $2000.
This kind of cost reduction benefits both public and private sectors. But energy use is only part of the equation. The color temperature of light matters as well.
Most modern LED streetlights emit a cool-spectrum, bluish-white light. They look brighter but it come with tradeoffs:
• Blue light disrupts night vision more than warm light. That harsh “screen glow” we’re told to avoid? Modern society put it everywhere, sorry folks.
• Blue light worsens glare, especially for older drivers and those who have had eye surgeries.
• Blue light suppresses melatonin, disrupting natural sleep cycles.
• Blue light washes out the night sky more. So long, stars.
In contrast, warm-spectrum LEDs are softer on the eyes, more biologically compatible, and still highly energy efficient according to studies done by Harvard University.
So why don’t we use more of them? When warm LEDs first hit the market, they were more expensive and less efficient. That price gap has narrowed, but the old perception lingers, while some cities are playing catch-up installing warm lighting as old cool LEDs burn out.
Then there is the actual brightness of the bulb. Many cities didn’t account for the improved performance of LEDs when they upgraded older lighting. One high-efficiency LED can match the light output of two or even three older bulbs. Swapping fixtures one-to-one, and keeping the same pole heights resulted in well-lit streets that suddenly became overly-lit ones; a change that was welcomed without fully understanding the long-term consequences.
When we talk about light pollution, color temperature, intensity and light spread are big players, but let’s not overlook the simplest fix of all: point the light down, not up.
Whether it’s floodlights on a business sign, “safety lights” illuminating a wall, or lights shining up trees, upward-facing lights create glare, further obscure the stars, and spill across yards and windows where it doesn’t belong.
Progression from most light pollution-causing-lighting to least.
Good security lighting illuminates only the areas needed, avoids casting harsh shadows criminals can hide in (although it’s great for hide-and-seek), reduces contrast blindness, and doesn’t blind passersby or drivers.
Yes, a glowing building or tree look cool. But one that glows intensity all night, year-round, and can be seen from over a mile away? That may be a bit much. Even simply converting up-lighting to warmer or to a less intense bulb can go a long way.
So if we think we may have sound and light pollution problems, what can we do about it? We will explore what other communities are doing in the next installation of this article.
