Snow-covered LED traffic signals: traffic hazard or not?

Several newspapers in the Midwest carried an Associated Press story in December headlined: “Energy-Efficient Traffic Lights Can’t Melt Snow,” with the subhead, “Traffic accidents are blamed on energy-efficient traffic lights getting covered with snow.”

The report noted that during an Illinois snowstorm last April, one motorist, Lisa Richter, could see she had a green light and began making a left turn. A driver coming from the opposite direction did not realize the stoplight was obscured by snow and plowed into Richter’s vehicle, killing her.

The report added, “Dozens of similar collisions have been reported in other cold-weather states, including Iowa and Minnesota.”

In Green Bay, Wis., street maintenance crews clean the snow off LED signals by hand during blizzards. In St. Paul, Minn., meanwhile, city crews use air compressors to blow snow and ice off blocked lights.

Highway departments in several snow states are reportedly testing potential solutions to the problem, including installing weather shields, adding heating elements like those used in airport runway lights, or coating the LED lights with water-repellent substances.

A blogger in Québec, Canada wrote in response to one of the news articles: “Sometimes when the snow is just the right consistency and falls in the right direction, it sticks to the traffic lights lenses, obscuring them. In the past, the heat generated by the incandescent bulbs would melt the snow, but the new LED lights don’t produce enough heat. A city worker has to remove the snow with a kind of small broom attached to a long pole.”

But the issue of snowstorms and LED traffic signal safety “is very much overblown,” said Scott McMahan, writer and editor for LIGHTimes Online-LED Industry News (www.lightimes.com), a Web site that covers the LED industry. “The fact that LED traffic signals have been around for years all over the world, and we’ve only heard about this snow issue once in all those years — well, that says something. Non-LED traffic signals are out very frequently, and the amount of time that they are out is much more significant than the amount of time that the LED signals would be out,” McMahan told GovPro.com

The severity of a storm is a factor, said Lonnie Tebow, director of the Newark, N.Y.-based International Municipal Signal Association’s (IMSA) Transportation & Traffic Programs Office. “I spoke with IMSA-certified traffic signal maintenance supervisors and managers in the Denver, Colo.; Toronto, Ontario; and the Indianapolis, Ind., metropolitan areas of the U.S. and Canada. They told me, frankly, that it was really not much of a problem in any but the most severe snowstorms,” Tebow said.

Traffic signal crews take a variety of steps to clear LED signals, added Tebow. “On those rare occasions and at those few locations where snow drifted over LED signal indications, several agency personnel told me that they used Super Soaker-type squirt guns filled with anti-freeze or some similar-acting chemical to melt the snow from the lens without ever needing to leave the ground. Most of the others simply wiped the lenses clean with a rag or brush from an aerial truck. And as a preventative measure some agencies were applying a chemical compound like Rain-X to the signal lenses.”

Daren Marceau, P.E. of Forensic Traffic Specialists, PLLC offered similar views to GovPro.com: “LED signals have been used all over North America for about a decade, and this is the first time I’ve heard of this problem. It does kind of make sense as the LEDs give off less heat than a traditional incandescent bulb. But, my initial thought would be why, if there are many thousands of the LEDs in service in areas that see a fair amount of snow, we haven’t heard much about this to date?”

Cary, N.C.-based Forensic Traffic Specialists is a forensic engineering firm that provides investigation, reconstruction and expert witness services for crashes involving traffic control devices.

Manufacturers are developing products that melt snow on LED signals, said Tom Griffiths, publisher of LIGHTimes Online and Solid State Lighting Design. “If you put in the heating elements that would then remove the occasional snow situation, then you start to get rid of the power advantage of LED signals compared to incandescent signals.”

That power advantage can be huge, Griffiths said: “Typically, you see 90 percent energy efficiency in LEDs compared to incandescent.” LEDs are also more dependable, Griffiths said: “The LED traffic signals seem to have an incredible ability not to fail (seven-plus years and counting for many). Incandescents failed regularly.”

Scott McMahan, of www.lightimes.com, offered this traffic safety tip for motorists: “If there is a problem (with snow obscuring an LED traffic signal), then there are laws in place that say that motorists treat that non-working traffic signal as a stop sign. So, it probably is not that much of a safety concern in the long term.”