Los Angeles uses its excess electricity to charge electric vehicles. Copenhagen goes even further, with a fully integrated traffic system that prioritizes buses and bikes – and can even flash lights to protect people biking from drivers.
The energy-saving technology that’s making this possible? LED streetlights.
At least 221 cities worldwide are switching their street lighting to LEDs, including a full 30 percent of outdoor lights in the United States, according to 2016 numbers from the U.S. Department of Energy. LEDs are up to 50 percent more energy efficient than traditional sodium bulbs and can last 15 to 20 years. And there are other unexpected benefits.
Better street lighting could potentially make riding public transportation easier by reducing the perception of danger, as well as improving visibility on roads. Driving at night is three times more dangerous than driving during the day, according to the National Safety Council. This is particularly bad for people walking, with most pedestrian fatalities occurring at night. Streetlights could improve this, as well as make streets places where people want to be.
Detroit, rebuilding from post-industrial decline, has been transformed by the new lights. In low-income neighborhoods far from the city center, LED streetlights have facilitated increased transit use and placemaking. Because of the increased visibility, residents feel safer waiting for the bus at night or walking to businesses and restaurants, which can now stay open later.
It’s a similar story in New York City, where LED lights in the Queens neighborhood of Corona have made residents feel safer spending time outside.
Changing over our lighting from pressurized gasses and vacuum tubes to semiconductors is not just a tweak, it’s a revolution. LED technology is already changing how we get around and how we live at night, with more promising changes just around the corner.
However, there’s mounting evidence that if not properly controlled, light from LEDs can negatively affect our health and the environment.
For the last decade or so, as large American cities began to change over their streetlights, LED lights have received pushback. In terms of color temperature, light from first generation LED streetlights is very cold and white. Unlike light from pressurized gas bulbs or even fire, it contains a lot of “blue light.”
In 2016, the American Medical Association warned that LED streetlights might have “adverse consequences.” AMA physicians were concerned by the blue light’s potential to cause glare, which they said could potentially make streets more dangerous at night.
They also cited a growing body of research about blue light’s ability to suppress the hormone melatonin and a person’s circadian rhythms. And blue light’s effects aren’t limited to humans: The AMA warned that it negatively affects flora and fauna, potentially causing ecological havoc.
According to Dr. Richard Stevens, a professor of medicine at the University of Connecticut and a coauthor of the AMA report, “it is now quite clear that circadian biology is central to all biology for all organisms on the planet.”
Stevens says that blue light inhibits the human body from transitioning from daytime to nighttime physiology. This is why you’re supposed to avoid your computer, smartphone, and television before bed. The effects of this delay are still being studied, but researchers believe that too much light at night could affect a range of health outcomes, including obesity and depression.
But blue light can be controlled. “LED is not the problem,” Stevens says. “It’s the specific products that are the problem.”
Since the first generation of LED streetlights, new technology has allowed for more sophisticated temperature controls. Some cities, including New York City, adjust the temperature of individual streetlights upon request. The city of Davis, California, replaced all its new LED lights with a warmer-feeling model after many complaints.
Cities can adjust the warmth and intensity of LED lights to match the weather and circadian rhythms.
According to a Department of Energy report, the median temperature of outdoor area lights in the U.S has fallen by more than one fifth since 2010, but remains much cooler than the standards recommended by the AMA.
When Pittsburgh first considered LEDs in 2010, city officials asked researchers at Carnegie Mellon University to study the options. Stephen Quick, an adjunct professor of architecture led a team observing 3,000 LED lights the city installed as a trial.
“We learned a lot from the installation,” says Quick. “We did measurements before and after to see how they were performing.”
Quick and his team came away cautious about the glare and cool temperature of the lights. Five years later, they came back and tested again, this time also looking at the potential of creating an integrated, “smart” system for controlling the lights.
LED streetlights, or even just the updated electronics and wiring in the poles, can be outfitted with sensors — measuring conditions like air quality — as well as cameras and other devices. Norway’s capital, Oslo, employs an elaborate control system that automatically dims lights with the weather and reports outages instantly.
After the second study, the Carnegie Mellon researchers recommended lower, warmer temperatures and limited controls because the technology was changing so fast. Pittsburgh is including these recommendations in its final negotiating with contractors for their LED conversion. The lights will also deliver a range of services, including public WiFi.
Quick believes that LED streetlights should also be adjusted to lower intensity and be dimmer.
“We know that everybody sees better with lower light levels,” says Quick. “Your eyes don’t take as long to adjust.”
The reflective light is much higher for LEDs, and finding the right brightness may take trial and error. Having lights be less bright would most likely decrease light pollution overall, provide more visibility and save more energy. But dimmer lights might not feel as safe to residents, especially in cities like Detroit.
In Arlington, Va., which is in the process of switching over to LEDs, the new streetlight system will dim lights to a quarter of their full power overnight. It might take awhile – and a lot of public input – to get the perfect recipe of temperature, dimness, and intensity right.
See original photo here.