Bright Moves: Road Safety, Environmental Sustainability, and Tax Savings through Better Lighting

Many years ago, I was hitch-hiking east from San Francisco. (It was 1967, the summer of love – but that’s another story.) Somewhere in Wyoming, at around 2 am, with no houses or streetlights for hundreds of miles, the car started making funny noises which, given our collective state of mind, sounded ominous. We pulled over, got out, and there it was – the biggest sky I, a city dweller, had ever seen. It was both darker and brighter than I would have thought possible. Stars. And more stars. Bursting out from a background that was beyond black. It was so amazing, so surprising, so beautiful that it almost felt spiritual. I ignored the car and just stared.

I’ve never seen anything like that again. Even worse, according to the International Dark Sky Association, unless something changes it’s unlikely that I ever will. Nationally, over-illumination is growing at more than a compounding 2.2% a year; actually, even higher because sensors don’t seem to register the short-wavelength blue light that is an increasing component of brighter LED and other sources. Some Massachusetts communities are brightening at ten times that rate! The skyglow of artificial light causes the sky to be 5–10 times brighter in urban areas than a naturally dark sky. We are losing sight of between 25 and 80 stars every day, between 1 and 3 per hour. About 80% of Americans, and at least a third of the world’s people, can no longer see the Milky Way. It’s a kind of blindness that we shouldn’t let ourselves suffer.


Probably it was our evolutionary past that made us wary of the dark in the night and in the back of the cave – it held the unknown, the scary and dangerous, the lairs of monsters. We loved the sun, embracing its warmth and sightfulness – until we learned that too much can burn, or disfigure, or even make us ill.

When electricity replaced air-fouling torches and candles, we did the same with artificial light; installing more and more, illuminating every corner of our homes and communities in a pursuit of security, safety, comfort, and access. Until we overdid it, again – putting in way more than needed with unnatural brightness and spectrums, distorting nature, increasing social stress, causing personal illness, and hiding the stars. Commercial store facades, roof-top displays, and advertising panels are a big and growing part of the light-pollution problem, including the increasing levels of “light trespass” that disrupts neighboring homes. But the most widespread source of unnecessary illumination, especially of wasted “uplighting”, are our streetlights.

Proper lighting is vital for night-time and bad-weather driving, walking, and cycling. It helps reduce the potential for crime (or at least our perception of that potential). It allows safe use or viewing of public spaces, monuments, sports, and other events. It helps decorate our holidays and identify our homes. But lighting, like many things, is not always a “more is better” phenomenon. In fact, like overeating apples, it causes rather than prevents problems, causes rather than prevents health and safety complications, even causes rather than prevents street crime and traffic accidents. Improving our quality of life, protecting both ourselves and our environment, requires a series of simple, low-cost (in fact, money saving), incremental steps – replacing blubs as they burn out, installing shielding, controlling timing – tied together by careful planning. We only need the awareness and will to do it.


But the poisoning goes beyond vision. The American Medical Association has issued several research reports showing that exposure to blue-rich white light or over-intense light at night distorts hormone production thereby increasing the risk of cancer (especially breast and prostate), diabetes, and cardiovascular disease and disrupting sleep patterns, impairing daytime functioning, triggering fatigue and migraines, promoting stress-related over-eating, and even interfering with sexual functioning. The mechanisms seem to be fight-or-flight-type increases of adrenaline and distortion of the pineal gland’s release of melatonin, all of which disrupts our circadian rhythms, cardiac arrhythmias, immune systems, cholesterol levels, and mood – as well as the thyroid, pancreas, ovaries, testes and adrenal glands. Humans are simply not evolutionarily prepared for electricity! (Office workers know that fluorescent bulbs have their own set of problems, including fatigue – although that may be related to the nature of most office work as much as anything else!)

And it’s not just human health that is affected. As Kevin Anderton wrote in Forbes, “In the animal kingdom somewhere around 30% of vertebrates and 60% of invertebrates are nocturnal and artificial lighting effects the life and sleep cycle of these life forms. Feeding and hunting become more difficult, mating habits get thrown off, and much more. It's not just animals, plants are affected as well. Street lights can negatively affect the insect population that is responsible for pollinating plants at night. Plants can experience late leaf loss and extended growing periods.”

Trees grow poorly or out of sync with the seasons. Migrating birds and turtles lose their way. Plants and their pollinators become uncoordinated. Light is not only energy, it is information and the disruption of natural patterns can throw off entire ecosystems, making them vulnerable to otherwise manageable threats.


Problems come from the direction, brightness/amount, timing, and spectrum/color of the lighting. Omni-directional blubs need to be shielded, or placed in properly structured fixtures, so that illumination only goes down. (A big advantage of contemporary LED lights is that they can be made unidirectional and can therefore provide the same level of surface illumination as a legacy High-Pressure Sodium (HPS) streetlight with only one-third the lumen output.) Sports field illumination should be limited to the playing surface and adjacent viewing stands. Whenever possible, lights should be placed below eye level instead of overhead. Lights for externally-lit signs and billboards should be placed above and shine down; internally lit signs should have the smallest possible size, the lowest possible brightness (measured in lumens), be positioned to avoid spill-over to residences, and not flash or blink or strobe or move at less than 30-second intervals. Commercial and public places that close after a certain hour can have their exterior lights dimmed or even turned off. IDA’s model municipal lighting code also says that “The maximum wattage for most commercial applications should be 250 watts of high intensity discharge lighting, but less is usually sufficient.”


Spectral distribution is described as Correlated Color Temperature (CCT) and is measured in degrees Kelvin (K). The lower the CCT the longer the wave-lengths, the “warmer” the light, and the less bluish (or intensely white) it appears. Blue-intense lights, like some of the white LED and Metal Halide street lights now taking over the market, have been shown to be five times more disruptive to our sleep than old sodium blubs. And blue light more readily scatters and reflects from street surfaces, increasing its spread and glare. (Because of the possibility of damaging ultra-violet exposure, its high intensity, and the availability of better alternatives, the International Dark Sky Association recommends that mercury vapor lamps not be used at all.)

(Many digital screen manufacturers of phones, computers, and other devices have already begun lowering the blue-spectrum content of their products, sometimes allowing even more “night-light” emphasis on the comforting red-yellow end of the rainbow.)

For street lights, the current recommendations are to aim for fixtures that emit no more than 3,000K and preferably no more than 2,700K, with more of the yellow spectrum. The old fashioned High Pressure Sodium (HPS) street lights were about 2,000K. Low-pressure sodium lights have slightly higher K levels, but their monochromatic color may make things less attractive. Most of the first generation of LED street lights were a blue-intense 4,000K or more. Today, it is possible to buy energy-efficient LEDs that measure in at 2,200K and some cities (e.g. Sherbrooke, Quebec have adopted those as the standard.

(While Boston was an early adopter of LEDs, they are still using the former standard of 4,000K and, even more problematically, are setting fixtures at unnecessarily --and expensively -- very high levels of brightness. Although the new “acorn” fixtures installed in Cambridge’s Harvard Square have better directional focus and therefore less glare than Boston’s, the fair city’s new lighting policy still uses a 3,500K standard for CCT.)


“Light trespass” is an increasing problem in urban areas where the blare of commercial billboards and signs intrude into people’s homes and backyards. Spotlights installed for display or safety can leak beyond their appropriate footprint. The spillover can come from indirect or reflective brightness as much as direct beams. The development of rapidly flashing or changing LED panels has made this problem enormously worse. Heavy curtains and blackout shades are some help, but what if you want to open your window?

On the road, we’ve all been temporarily blinded by the glare from an approaching huge pick-up or SUV whose super-bright headlights make it impossible to see the road – or from a regular headlight that’s slipped and points too high. Research shows that light-glare is particularly bad for older drivers. In some towns, data analysis revealed that poorly lit intersections with severe glare by unshielded lighting had the highest accident rates. Even for pedestrians, overly bright light in one spot can make it impossible to see what may be lurking in adjacent darker areas. Ironically, both situations reduce the overall visibility and safety they were intended to improve. The Federal Highway Administration says, “...scattering tends to superimpose a luminous haze over the retina...The effect is termed ‘disability glare’ or ‘veiling luminance’...Disability glare is one of the most important elements to control in a lighting system. It affects your ability to adequately see, particularly for older drivers.” 

Many state Department of Transportation infrastructure guidelines already acknowledge that in rural and residential areas where vehicles typically go at less than 30 mph, the standard 300 feet of normal headlight reach should make street lighting unnecessary except for spot illumination at intersections, bridges, or other potential danger spots. At those locations care needs to be taken to avoid creating a “brightness barrier” that makes it hard to see what comes after the lit location, similar to what happens when a vehicle with headlights that are too bright or aimed too high approaches. Road edges and curves can be delineated by passive methods such as signs, reflectors, reflective striping, etc. There is little research about the impact of lighting on accident rates, but most evidence points to distraction, alcohol-impairment, and exhaustion as the primary cause of crashes, not lighting.


Each 100 watts of night-time High-Pressure Sodium streetlight usage results in 460 pounds of CO2 emissions, according to the US Department of Energy. (Sodium lights also contain toxic mercury!) New products from progressive companies allow zero-glare, time-controlled, dimmable LED streetlights. Using Dimmable LED Streetlights allows a preset dimming of 30, 50 or 70 percent, usually set to start at midnight and coming back to full output at 5 AM before morning rush hour starts. When an LED streetlight is dimmed, the dimming reduces the heat in the fixture. With less heat, the life of the streetlight is expanded, thus reducing maintenance and replacement costs. In Tucson, Arizona, all new LED streetlights are set to dim by 30% from midnight to 5 AM.

Even without dimming, LEDs can reduce power consumption by up to two-thirds. When Tucson switched to LED street lights, energy usage – and therefore the need for fossil-fuels to produce power -- dropped nearly 80%. Los Angeles, Chicago, and Phoenix have policies requiring LEDs with 2,700K for streetlights in residential areas and no more than 3,000K for commercial applications. Other cities that have adopted 3,000K or lower limits include New York, San Francisco, San Diego, Toronto, Montreal. In Massachusetts, Gloucester, Melrose, Needham, Salem, and Wellesley have the same rule. Some cities – including Chicago, Davis (CA), Seattle and New York -- have even been forced into expensive retrofits to replace relatively new but offensively bright streetlights. (In addition to the LED’s reduced need for lumen output, other key factors in selecting LED streetlight make and model are 1) maximizing energy conservation by using fixtures with high “lumens per watt” ratings, and 2) minimizing glare by using fixtures with low glare ratings. such as certain styles from AE, LeoTek, and others.) 

Safety only requires the right amount of lighting in the right place at the right time. Anything more is potentially dangerous and definitely a wasted expense. All lighting purchases – for use on the street or in publicly-visible places – should be fixtures that have received the International Dark Sky Association’s Fixture Seal of Approval, which set a clear standard and provide a reliable third-party evaluation. Even beyond the level of brightness, care has to be taken to prevent sideways escape – it is usually necessary to focus the light so nothing goes higher than 80 degrees from the vertical, or even less, since the light can travel sideways for miles in the atmosphere, scattering as it goes, creating both glare and sky glow.


So far, most Dark Sky activity has happened at the municipal level. But there is some state-level movement – even here in Massachusetts! A bipartisan bill, introduced by Senator Cynthia Creem (bill number S.1937) and Representative Sean Garballey (bill number H.2858) has gotten 24 cosponsors and been sent to the joint Telecommunications, Utilities, and Energy Committee to be included in a future public hearing. The identical bills are both correctly called “An Act improving outdoor lighting and increasing dark-sky visibility.” Although there are no active opponents, the Massachusetts Legislature is neither fast-moving nor risk-taking. So those hearings are not likely to happen until deep in the current two-year session. And it will take serious advocacy and lobbying to get it through, particularly Speaker DeLeo’s House of Representatives. People interested giving their opinion should contact the TUE Committee (c/o [email protected]) or the Massachusetts chapter of the International Dark Sky Association (c/o James Lowenthal, [email protected]).


Thanks to Leo Smith, James Lowenthal, and Paul Valleli for comments on previous drafts.


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