Where's the solution for LED traffic signals that can't melt snow?
We know from last week's storm that freezing rain, snow and high winds are a recipe for an epic fail with usually dependable LED traffic signals.
Drivers did a double-take as they neared signals so obscured with snow it was hard to tell if a green or a red was showing. On at least four occasions, crashes occurred with minor injuries, begging the question -- how do we solve this problem before someone gets killed?
There's no shortage of ideas to fix the flaw in LEDs but no magic bullet yet, local and national experts say. LEDs generate much less heat than old-fashioned incandescent bulbs, which melt ice and snow.
"The issue of snow on LED signal heads is something that municipalities have been concerned with for years," Lake County Traffic Engineer Jonathan Nelson said.
One promising idea is a heater activated by a built-in thermostat made by an LED manufacturer, Nelson said. The county installed the heaters in four signals at Peterson and Midlothian roads near Libertyville in 2016 as a pilot project.
It wasn't put to the test until the storm Nov. 25 and 26 when Nelson found the device was able to melt some but not all the snow.
"The red signal was slightly visible," he said. "There was still snow blocking full visibility -- but it was better than nothing."
Nelson contacted the manufacturer last week only to find it was no longer making the product, sending the county back to square one.
Other fixes range from specialized visors to telescoping lens brushes.
"All of these solutions seem to help, but it's not a quite a home run," Kane County Traffic Operations Engineer Stephen Zulkowski.
"We are also going to continue to work with our vendors and manufacturers to push for a technology-based solution," Nelson said.
Some LEDs being manufactured right now are equipped with heaters that work reliably, Argonne National Laboratory's Principal Building Scientist Ralph T. Muehleisen said.
The trick is retrofitting the existing versions, a task that's got to gall communities who were sold on LEDs in the first place because they were supposed to be low maintenance.
Another twist is that LEDs with heaters won't be as energy-efficient as those without.
Asked if we should have stayed with old-fashioned bulbs, Muehleisen explained, "You always save more energy with LEDs than with incandescents."
You should know
Why can't LEDs melt snow and ice?
Typically, cooler LEDs used in traffic lights use about 10 watts of power compared to 135 watts in heat-producing incandescent bulbs, Zulkowski said. "That math suggests a 90 percent reduction in the wattage and a 90 percent reduction in the heat," he said.
LEDs came into general use after a 2005 federal law requiring traffic signals to be more energy-efficient. Although they are brighter and longer-lasting than incandescents, the word's been out about their weather-related vulnerabilities since at least 2010 when the U.S. Department of Transportation convened a workshop with traffic engineers.
A 2014 DOT report that studied storms in Wisconsin, Colorado, Utah, South Dakota and Canada, as well as Oswego, found "a common requirement for snow- and ice-covered LED traffic signal lenses is a wind of sufficient speeds to blow the snow at an angle toward the signal lens and below the visor. LED lights were typically obscured with strong winds over 10 mph from the north, high humidity and moisture, and temperatures near freezing that fell rapidly."
Fast forward to Nov. 25 and a storm with "a unique combination of rain/ice first, strong winds and heavy, quick snowfall which created worse than usual obstructions for all signals regardless of bulb type," Schaumburg Transportation Director Karyn Robles said.
"The blizzard covered anything facing north including all southbound signals, signs, posts, etc. with almost a foot of snow and ice," Nelson said.
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