How Denmark’s red street lamps do much more than just save energy – Jalopnik

Denmark, a picturesque neighborhood north of Copenhagen, has radically changed its nighttime streetscape: red streetlights in certain areas instead of the usual white streetlights. In the municipality of Gladsaxe, officials have replaced traditional street lighting with red spectrum LEDs. This change is rooted in real science and reflects a deeper shift in how cities can ultimately consider environmentalism in their infrastructure.

Historically, most street lighting systems equated brightness with safety, using white light to maximize visibility for drivers and pedestrians. These same light wavelengths are increasingly recognized as harmful to nocturnal wildlife, especially bats.

Research shows that light at night affects bat behavior in wavelength-specific ways, with longer wavelength red light appearing to minimize behavioral disruption while still providing sufficient functional illumination for drivers. The Danes recognize the crucial contribution of bats to mosquito control, and the red lightning represents an attempt to reduce human-induced interference with the behavior that bats depend on for survival.

Red LEDs were specifically installed on a stretch of Frederiksborgvej more than four-tenths of a mile long. This road passes through tree-lined corridors and through a colony that is home to seven species of bats. The goal is to balance road visibility for safety with a lightning-fast approach that minimizes damage to the surrounding ecosystem.

The Gladsaxe project is not just about light spectra; it is part of a larger reevaluation of how cities interact with the natural world – namely the ambitions of the European Union-funded Lighting Metropolis – Green Mobility Program. The program aimed to accelerate the implementation of LED lighting in the Øresund region of Northern Europe, and covered infrastructure in Denmark and Sweden between 2019 and 2022.

Denmark’s commitment to environmental integrity is no secret; the country even went so far as to investigate BMW’s sustainability claims a few years ago. Since then, the EU has rolled back a number of high-profile environmental commitments, such as the 2035 ban on combustion engines, and it is questionable whether the environment is a priority for world leaders. But at the very least, these red lights are in the bats’ best interest.

Ultimately, the success of the project will not be judged by what the red lights look like to residents, but by what the data reveals. Researchers in Gladsaxe are actively monitoring bat activity and traffic conditions along the red-lit corridor to evaluate how the lighting affects local wildlife. These findings will determine whether the approach meaningfully reduces disruption and whether it can be implemented in other cities in Denmark and beyond.