Whet Moser on Chicago’s changing streetlights:
On Wednesday, City Council signed off on its $160 million plan to change the color of Chicago, replacing its 270,000 high-pressure sodium lights, which give the city its, um, distinctive orange glow, to LED. Right now Chicago is one of the most orange cities in the world; when the project is done, it’ll look completely different, on the street and from space.
Chicago’s been orange for about 40 years. It started with an experiment on the Dan Ryan in 1969, about the time high-pressure sodium-vapor lights were perfected enough to go into widespread use, and a handful of the blueish mercury-vapor lights were replaced. Three years later the Lawndale People’s Planning and Action Conference proposed their light installation on Roosevelt Avenue as a crime-fighting tactic. But it was unclear if the investment would pay off. In 1973, UCLA astronomer Kurt Riegel, concerned about light pollution, correlated rising crime to increased outdoor luminosity in a piece for Science, concluding that “the selling has also been very succesful—most people now believe that outdoor lighting buys them security.” (He found that the evidence was mixed.)
The history behind Chicago’s streetlights is unexpectedly interesting, as is the blowback from some quarters on shifting to more modern, starkly bright, and, in my opinion, better looking white lights:
Chicago followed the [American Medical Association]’s guidelines and is getting 3000K LEDs. It’s close to the 2700K lights the city of Davis, California, got after its citizens revolted against the “prison lighting” of their new 4000K LEDs, or Phoenix, which switched to warmer lights under public pressure, not the only city to field complaints about cool-temperature lights.
[…]Incandescent lights are beloved because they’re warm and their color-rendering is excellent, so they feel natural and have a good warmth for nighttime lighting—but, they’re extremely inefficient. High-pressure sodium lights are warm, but their color rendering is terrible (“the ugliest light known to the cinematographer”). LED streetlights have much better color rendering, but it’s unnatural to have the night lit like the day—in ways we can perceive, and perhaps in ways we can’t. Chicago’s 3000K LEDs are an attempt to have it both ways: familiar enough in rendering colors to not look like “frightening futurism,” warm enough to be appropriate for the night.