Denmark Tests Red Streetlights to Protect Bats Without Sacrificing Night Road Safety

A neighborhood north of Copenhagen just made a pretty wild change to its streets at night: red streetlights instead of white ones. In Gladsaxe, officials have been swapping out regular streetlights for red-spectrum LEDs. Not for looks. There's actual science behind it and it's part of how cities might start thinking about the environment when building infrastructure.

Street lighting has always been about brightness equals safety. White light, maximum visibility for drivers and pedestrians. Makes sense. Problem is those same wavelengths are terrible for nocturnal wildlife, bats especially.

Research shows nighttime light screws with bat behavior in ways that depend on the wavelength. Red light with its longer wavelength seems to mess with them way less while still giving drivers enough light to see. Denmark knows bats are critical for mosquito control, so the red lighting is their way of trying not to screw up behaviors bats need to survive.

Designing Roads for Everyone

Red LEDs got installed on a stretch of Frederiksborgvej about four-tenths of a mile long. Road cuts through tree-lined areas and a colony with seven bat species living there. Trying to balance roadway visibility for safety with lighting that doesn't wreck the ecosystem.

Gladsaxe project isn't just about switching light colors. Part of a bigger rethink of how cities interact with nature. Specifically tied to the EU-funded Lighting Metropolis – Green Mobility Program that aimed to get LED lighting rolled out faster across the Øresund Region in Northern Europe. Involved infrastructure in Denmark and Sweden from 2019 to 2022.

Denmark's pretty serious about environmental stuff. They even investigated BMW's sustainability claims a few years ago. Since then the EU's backed off several big environmental commitments like the 2035 combustion engine ban, so whether world leaders actually care about the environment is up for debate. At least these red lights help the bats.

Will It Actually Work?

Success won't be measured by how people feel about red streetlights but by what the data says. Researchers in Gladsaxe are watching bat activity and traffic conditions along the red-lit road to see how lighting affects local wildlife. Those findings decide whether this approach actually cuts down on disruption and whether other cities in Denmark and beyond can do the same thing.