One example of such a failure is just now drawing attention.  Across the country, many counties have adopted LED traffic lights as an energy efficient replacement to traditional bulbs.  While accomplishing their energy saving billing superbly, the deployment had an unintended side effect.  In northern states like Wisconsin, snow and ice have been building up on the new bulbs creating a road hazard.  The critical factor appears to be that normal bulbs produce enough heat to melt the snow -- but the energy efficient LED bulbs, thanks to their efficiency, do not.

In Wisconsin, the winter weather has obscured the lights so badly that several accidents have occurred, leading to at least one fatality.  Describes Duane Kassens, a Wisconsin driver from West Bend who was involved in one of the fender benders, "I've never had to put up with this in the past.  The police officer told me the new lights weren't melting the snow. How is that safe?"

There are some options that could fix the potentially life-threatening oversight.  Weathershields or water-resistant coatings remain two leading candidates.  Heat elements also are being considered, but they could largely negate in the winter the 90 percent power savings that the LED bulbs deliver.  And there's an old-fashioned alternative -- Green Bay, Wis., police Lt. Jim Runge describes, "As far as I'm aware, all that can be done is to have crews clean off the snow by hand.  It's a bit labor-intensive."

The alternative, though, can be deadly. In Illinois a driver plowed through a blocked traffic light in April, hitting 34-year-old Lisa Richter who had the right of way.  She died from injuries sustained.  Oswego police Detective Rob Sherwood, who was involved in the Richter case comments, "Would the accident have occurred if the lights had been clear? I would be willing to bet not." 

The allure of the LED designs, though is hard to resist.  Unmodified LED bulbs save Wisconsin $750,000 a year in energy costs and they last 7 years or more, whereas traditional bulbs must be replaced every 12 to 18 months.  Describes Dave Vieth of the state Transportation Department, "With LEDs we have energy savings in excess of 80 percent, and we don't have to have crews replacing them as often. So it's clear the overall savings are pretty significant."

Some traffic engineers are defending the designs, saying accidents are the fault of bad drivers, not poor engineering.  They say that drivers should know that the law mandates drivers to treat obscured or non-functional lights as a stop sign.  States Dave Hansen, a traffic engineer with the Green Bay Department of Public Works, "It's the same as if the power is out.  If there's any question, you err on the side of caution."