Safety concerns have been raised nationally about led traffic lights
Iowa motorists need to be extra careful during winter storms because of the possibility that energy-efficient traffic lights could be obscured by snow, traffic engineers say.
"We can't design for every potential weather scenario out there. So there has to be some shared responsibility" by motorists, Welch added.
Safety concerns have been raised nationally about led traffic lights. A woman was killed in Oswego, Ill., in April when her vehicle was struck by a pickup truck driver who didn't realize a red stoplight was covered by snow.
Lisa Richter, 34, died and four other people were injured in the crash as she was making a left-hand turn in an intersection that used LED traffic signals, authorities said.
Many Iowa cities — including Cedar Rapids, Des Moines, Sioux City and West Des Moines — are using LED traffic signals. Iowa Department of Transportation officials said they haven't linked any traffic fatalities to use of LED bulbs, and they believe the benefits of using the modern lights outweigh potential negatives.
Iowa cities have discovered a windfall in savings on electric bills by installing new traffic signals that use light-emitting diodes, better known as Leds, state and city officials said. But a drawback is the environmentally friendly bulbs don't melt snow on traffic lights like old-fashioned incandescent bulbs.
"It's absolutely an issue" because of the possibility that red lights on LED traffic signals can't be seen by motorists, said Tom Welch, traffic engineer for the Iowa Department of Transportation in Ames. He urges Iowans driving in adverse winter weather to approach each intersection as though it has a conventional stop sign in place.
Welch said LED traffic signals provide safety benefits because they are much brighter than conventional traffic lights. The newer bulbs are especially beneficial in urban areas where people may be distracted by commercial Lighting and other background objects, he added.
Des Moines uses LED bulbs on most of the 4,000 traffic signal heads in the city, saving about $100,000 yearly in electrical bills, said traffic engineer Gary Fox.
"We haven't noticed much of a problem" with snow obscuring traffic signals, Fox said.
"The conditions have to be just right," he said. "We have visors over the signal lenses and generally that protects the face from getting snow on it. But if it is a wet, sticky snow and the wind is blowing, the snow can get on there and it can stick for quite a while."
Scott Logan, Sioux City's city engineer, said he has had a similar experience with LED traffic signals.
"If there is a problem, we just go out and tap the head and the snow falls off," Logan said.
The same heavy snow conditions that could obscure a red light on an LED traffic signal could also cause a stationary metal stop sign to become snow-covered, traffic engineers said. They note that LED traffic lights last much longer than conventional bulbs, trimming labor costs to replace them.
West Des Moines Traffic Engineer Jim Dickson said almost all of his city's traffic signals now have led lights.
One of the positive factors is that the bulbs use so little energy that they work well with battery backups, which are gradually being installed to keep traffic signals working during electrical outages, he said.
The Colorado Department of Transportation believes it has found a cheap fix to the problem of snow-shrouded traffic signals.
It has bee installing a $20 device known as the "Snow Scoop Tunnel Visor" that prevents snow buildup from blocking LED traffic lights.
A louvered vent on the top of the visor and an open bottom contribute to the increased vertical movement of air across the face of the signal lens, generating a resistance to snow deposits.
The visor device, manufactured by McCain Inc. of Vista, Calif., is being used on traffic signals in the Denver metro area and in some mountain communities which host ski areas, said Mindy Crane, a Colorado DOT spokeswoman.