Xcel Energy will be replacing our current stock of high-pressure sodium lights with energy-efficient LED bulbs (“Xcel Energy unveils LED streetlight vision,” Oct. 16, 2015). That will save energy and reduce the carbon footprint from our street lighting needs, but we can do much better than simple replacement. LED street lighting has been around for more than a decade, and a growing body of evidence indicates that adopting best practices in street lighting will mitigate health and environmental hazards associated with the blue-white color of LED lights. We can also take advantage of the programmable nature of LED lights to make our cities more livable after dark.
Blue-white (or full-spectrum) light is beneficial during daylight hours. At night, however, it disrupts our circadian rhythms, the internal clocks best known for syncing up our sleep and awake hours with the 24-hour cycle of daylight and darkness. Recent studies indicate that blue light from electronic devices and LED lights can affect DNA damage response and increase the chances of breast cancer, results that prompted the American Medical Association to issue a policy statement on lighting and human health.
Blue-white lights also produce more light pollution than warmer-hued streetlights. In a blog post for Tech Insider, writer Julia Calderone says: “Astronauts aboard the International Space Station are snapping pictures of Earth at night, and the images are telling a troubling story.” She followed up with before-and-after photos of Milan, Los Angeles, London and other cities that have switched to LED lighting. In each animation, the difference in reflected light is dramatic.
And that extra light may not be making citizens safer or more comfortable. Recent findings challenge the long-held belief that bright lights mean safe nights. In 1998, the city of Chicago began a multistage plan to reduce crime by replacing 90-watt lights in most city alleys with 250-watt bulbs. The city asked the Illinois Criminal Justice Department to evaluate the impact of increased alley lighting on crime. The conclusion: “[I]t is difficult to point to any conclusive evidence that increased alley lighting had an effect on crime.”
We may even be overlighting our streets, according to a research paper done for the city of Pittsburgh. “Lighting standards … require uniformity of illuminance between poles in a misguided attempt to replicate daylight conditions and improve visibility.”
“It is not possible to replicate photopic (full daylight) conditions at night,” the report continues. “Rather, it is better to eliminate glare … in an attempt to meet the visual comfort” of a wide range of citizens. The report specifically notes the impact of glare on the eyes of older people.
We could realize additional savings in energy consumption through the use of intelligent or adaptive street lighting. First introduced by the city of Oslo, Norway, 10 years ago, adaptive street lighting uses cameras and sensors to detect movement, similar to security lighting on residential property. If a person or motorist moves into an area, the streetlights brighten to create a safe environment, then dim or shut off when no motion is detected. Additional technology allows communication between adjacent lights so a pedestrian could walk through a large, well-lit safety zone while more-distant streetlights remain dark.
These and other reports don’t imply that lights serve no purpose in the safety of citizens, but they demonstrate that increasing the intensity of lighting doesn’t automatically decrease the number of crimes or accidents, and that strategies to reduce the overall amount of light on our streets could save money and reduce carbon emissions with no noticeable impact on resident safety.
The Pittsburgh report also recommends that cities look beyond energy savings to take advantage of the unique benefits of LED technology. For example, the highly directional and programmable nature of LED lights gives communities the option to provide safer and more pleasing lighting for bicyclists and pedestrians.
LED lights can be more than an energy-efficient replacement to our current street lighting; they could be the catalyst to rethink lighting to create more-livable communities.
Doug Shidell, of Minneapolis, is a freelance writer and publisher of the Twin Cities Bike Map.