I grew up near the steel mills in Middletown, Ohio, and if the clouds were just right at nighttime I would see a few minutes of bright orange glow in the sky when a ladle of molten metal was tapped. I didn’t see anything comparable until I was just out of college and moved to Washington, D.C., and had my first jarring experience with big city “mugger” streetlights. You know the type: the ones now used in nearly every major city that create a orange creamsicle-colored dome nightscape over a metropolis that can be seen dozens of miles away.
The hideous hue and intensity from these sodium vapor lights, as I recall, caught on in a big way in the early 1970s and was justified because of their purported ability to cut crime by eliminating dangerous shadowy areas in urban areas. They were also cheaper and more durable than the alternatives back then. Regardless, city residents got used to them and they seemed to have found a permanent home in urban–highway architecture.
But some US cities are looking for a change in their night sky schemes. Chicago, for example, recently announced that it is replacing 16,300 of the old sodium vapor lights with ceramic metal halide lights. That 16,000+ number may sound like a lot, but its only a relatively small step forward for the city will still have nearly ten-times that amount of the old luminaries. Chicago is also converting 1,000 stop lights (another small portion) to LEDs.
Although this is just an incremental step, it’s a step in the right direction. Planners say they will save $40-$70 in electricity per light, and the ceramic metal halide versions will last about 50 percent longer than the old models. Between the new streetlights and stoplights, the city expects to save $1.8 million per year and cut CO2 -related emissions by 15,000 metric tons. The actual transition is taking place now because of the availability of a $13.8 million DOE grant. Lower maintenance costs are also expected.
The city’s department of transportation says it will eventually replace all of its streetlights.
Besides the monetary savings, the city says in a news release the CMH lights provide an improved light spectrum and reduce light “pollution,” noting, “Despite the lower wattage, the lights appear as bright or brighter to the eye than the old light fixtures, and offers truer color of objects… Additionally, Chicago’s metal-halide fixtures reduce ‘sky glow’ (light traveling up, instead of down) by between 50 to 100 percent depending on the type of fixture. They also reduce ‘light trespass’-light shining into unwanted areas, like nearby buildings or homes.” (Note, whoever calculated that 100 percent reduction number needs help with his/her gazintas and gazoutas.)
Regarding performance, one website notes regarding the CMH-or-LED debate that “Neither are as bright as the 150W and 250W lamps that typically light residential roadways in Chicago, but they seem perfectly adequate to me. The dimmer white light gives the blocks with CMH and LED a more suburban look.”
Regarding the source of the new lights, Chicagomag website claims they are CosmoPolis made by Philips although others think it’s a GE product. Lux magazine did a comparison of the Phillips and GE CMH products earlier this year.
But what about the secure feeling that the sodium vapor light ingrained in urbanites? Thanks for asking. The Chicago Tribune reports that old lights didn’t perform so well:
“Since the large-scale adoption of sodium vapor lights in the United States and elsewhere, studies have been done showing that they can hamper police identification of suspects because they decrease people’s ability to tell one color from another, because they make everything look orange at night.”
According to the Atlantic magazine, the list of other cities looking at replacing their streetlights includes New York, Anchorage, San Jose, Pittsburgh and Los Angeles.