Philly’s new energy-saving LED streetlights may reduce crime and fatal crashes. But what about light pollution?

Philadelphia has embarked on its largest energy conservation initiative to date, aiming to replace all old streetlights with new LED ones.

Since August, city crews have been methodically swapping out high-pressure sodium lights for LEDs, a move expected to significantly reduce energy costs and cut greenhouse gas emissions — equivalent to taking more than 2,000 cars off the road a year. While research suggests benefits such as reduced crime and enhanced traffic safety, concerns arise over the brighter, bluer light potentially being a nuisance, health hazard, or contributor to light pollution.

The Inquirer consulted with experts across fields to delve into the pros and cons of LED street lighting.

The Philadelphia Streetlight Improvement Project will replace 130,000 high-pressure sodium streetlights found around the city with brighter, more energy-efficient, and longer-lasting LED lights. It will also connect to a lighting management system providing the city with real-time data on outages to replace bulbs faster and a “smart” system that can be dimmed, brightened, and modified more easily.

It’s been a decade in the making as the Streets Department and Office of Transportation, Infrastructure, and Sustainability (OTIS) have been looking to upgrade the lighting system to be on par with peer cities around the country, and to take advantage of energy and maintenance savings, according to Katie Bartolotta, vice president of policy and strategic partnerships for the project’s funder, the Philadelphia Energy Authority (PEA).

The upfront cost will be $91 million, but with a new lighting system using half the energy the old system did, the city estimates it will save $8 million a year — making back the money in a decade, said Bartolotta.

The upgrade will cut the city’s carbon emissions by 9% a year, equivalent to the emissions of 1,000 homes.

It also includes clearing alleyways for new installations and prioritizing local, minority, and women-owned businesses for contracts. Beyond energy savings, the project focuses on enhancing safety in areas with high gun violence and road fatalities by improving lighting.

The selected LED lights for Philadelphia will be more durable and energy-efficient than the traditional high-pressure sodium lights, offering a cooler, brighter color than the familiar orange glow.

Quick facts about the LED lights selected for Philadelphia:

Studies indicate that street lighting can lower certain crimes but not violent crime. A 2022 review by criminology professor Brandon Welsh and a team at at Northeastern University and the University of Cambridge analyzed 21 studies over 50 years, finding a 14% drop in crime in well-lit areas, specifically in property crimes, with “no significant effect on violent crimes.”

This suggests that lighting can prevent break-ins and car thefts. Bill McGeeney, from the Pennsylvania Outdoor Lighting Council, argues that brighter lights may not reduce gun violence but can make people “feel” safe.

He also highlights a U.K. study showing that dimming or turning off lights at night can save energy without increasing crime.

“I would love to see a follow-up on this 10 years down the line to see if crimes were thoroughly reduced or if other factors played a role,” McGeeney said.

Once the light installations are finished, researchers at the University of Pennsylvania will be reviewing the new lighting’s effect on crime, traffic, and other measures.

The Federal Highway Administration (FHWA) notes that although fatal crashes occur equally during the day and night, nighttime driving is three times deadlier due to fewer drivers on the road. Half of all fatal crashes occur at night, attributed to factors such as drunken, tired, and faster driving, said Erick Guerra, an associate professor at the University of Pennsylvania who studies transportation planning.

Research indicates that street lighting can lower nighttime pedestrian injuries and intersection crashes by about 40%. And although lighting can’t compensate for impaired driving, studies over the last 20 years show it can lessen the frequency and severity of nighttime crashes.

In general, shining light in dark places at night is going to cause light pollution, and so will streetlights, said McGeeney. The issue is that society at large doesn’t view light as a source of pollution that can have devastating effects.

The natural day-night cycle is crucial for humans, wildlife, and ecosystems, regulating behaviors from sleep to migration. Artificial lighting disrupts this cycle, with significant consequences. Birds, for instance, which migrate at night, can become disoriented by city lights, leading to fatal crashes into buildings. In Philadelphia, such incidents are notably problematic (a four-block area in Center City claims the lives of 1,000 birds alone). It’s the reason why conservationists organized Lights Out Philly, a voluntary initiative during migration seasons to turn off or block as much indoor and outdoor light as possible to reduce mass bird deaths. The most successful building in the program reportedly reduced bird crashes by 70% since 2020, reported WHYY.

“Does it mean we shouldn’t have light? Of course not, we’re human. We need to both see where we’re going at night and feel safe,” McGeeney said.

For humans, excessive artificial light disrupts the circadian rhythm, affecting sleep patterns and increasing the risk of cardiovascular disease, cancer, and lowered immunity. Luckily, humans can turn off lights, close the blinds, or wear sleep masks. Animals and insects can’t.

Light pollution also limits the ability to see the night sky, with two-thirds of the U.S. already having lost the ability to observe the Milky Way with the naked eye.

Philly’s streetlight upgrade is a good start, say light pollution educators, but there’s always more to be done.

The city maintains that through years-long community input, sampling multiple lighting fixtures, and incorporating industry best practices (such as those set forth by DarkSky International), this new street lighting system is “the best of both worlds,” said Bartolotta.

“We did a couple of things to address some of the concerns, like picking a warm color temperature for lights city-wide that are DarkSky compliant, the gold standard for a do-no-harm approach to LED lighting,” Bartolotta said. “Another thing that folks bring up a lot with LED lighting is the discomfort of looking at it head-on and we ultimately went with a fixture that has lens diffusion that helps cut down on glare.”

DarkSky International is an industry-leading light pollution policy organization that helps governments install more environmentally friendly light solutions. It developed five key principles for responsible outdoor lighting.

Philly’s new streetlights will use DarkSky-compliant cobra head light fixtures that reduce the amount of “uplight” that shines toward the sky, focusing its light downward at the roads and streets, according to Bartolotta.

DarkSky advises against using LED lights that are colder in color temperature, suggesting that lights be 3,000 Kelvin or lower. Philly’s street lights will be 3,000 Kelvin, just clearing the threshold. However, McGeeney and other members of the Pennsylvania Outdoor Lighting Council would rather see warmer lights closer to 2,700 Kelvin. The new LED lights will be brighter in many cases, though.

“The project identified data-driven locations for ‘boosted’ illumination to provide more lumen output, by design, in areas with higher instances of nighttime crime and vehicle crashes,” said Bartolotta. “Perception of light levels is highly subjective but we anticipate most observers will likely experience an increase in illumination.”

Bartolotta mentioned that additional upgrades can be made down the line and that feedback is welcome.

“LEDs in and of themselves are actually quite remarkable, they offer a tremendous amount of light for a tiny fraction of the energy and be more easily controlled to modify lighting” McGeeney said. “The city will be able to control many aspects of that light and one easy solution is to only put light where its needed, don’t use a tremendous amount of light, and only have them on when needed.

He said an example is boosting light during rush hour times, but reducing or turning off lights between 2 a.m. and 5 a.m., when the majority of businesses are closed and people are at home sleeping.