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Power Transportation

Midwest Seeing Red Over 'Green' Traffic Lights 839

theodp writes "Many municipalities have switched to LED traffic signals because they burn brighter, last longer and use 90% less energy than incandescent bulbs. But they also emit less heat, meaning they sometimes have trouble melting snow, causing problems across the Midwest. In Wisconsin, snow blanketed LED traffic lights in some towns, leading to crashes at intersections where drivers weren't sure whether to stop or go. The unintended consequences of the green technology were also identified as a 'contributing factor' in the death of an Illinois woman hit by a driver who blamed the snow-covered energy-efficient signal for giving the appearance of a normal green light instead of a left-turn signal. 'We can remove the snow with heat, but the cost of doing that in terms of energy use has not brought any enthusiasm from cities and states that buy these signals,' said the CEO of an LED traffic-signal manufacturer. 'They'd like to be able to take away this issue, but they don't want to spend the money and lose the savings.' In the meantime, some towns are addressing sporadic problems by dispatching crews to remove snow or ice from signals using poles, brooms, and heating devices." We were discussing these recently at the office — several folks in the building are red/green color blind and different street lights are differently distinguishable.
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Midwest Seeing Red Over 'Green' Traffic Lights

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  • Simple (Score:2, Interesting)

    by Thelasko ( 1196535 ) on Wednesday December 30, 2009 @11:02AM (#30593510) Journal
    Put a small heater in the traffic signal that turns on below 0C (32F). Problem solved.
  • Remove the shroud? (Score:1, Interesting)

    by Anonymous Coward on Wednesday December 30, 2009 @11:05AM (#30593552)

    It seems the obvious solution is to remove the shroud surrounding the LEDs. The LEDs are bright enough and directional enough to not need a shroud, unlike the incandescents.
    Remove the shroud, the snow has no place to accumulate and the lights can be seen. Everyone is happy.

  • Propaganda? (Score:5, Interesting)

    by CrazyDuke ( 529195 ) on Wednesday December 30, 2009 @11:10AM (#30593626)

    I read this and I almost immediately thought "propaganda." Why? A appeal to fear based on a insignificant and easily fixable event, then attempting to tie the fear to larger political concepts. Fear change! Fear green! Equals death! Keep same! Same is warm! Same is reliable! Same is safe! You don't have to think about same!

  • Re:heating element (Score:3, Interesting)

    by mariushm ( 1022195 ) on Wednesday December 30, 2009 @11:15AM (#30593702)

    An article said changing to LED lights in an intersection brought about 100$ a month economy in electricity costs, for that particular intersection.

    It would cost several hundred dollars to make changes to the semaphores (like changing the regular glass to glass with wire inside that would heat it and have sensors that would turn on the heating elements only when needed). Some towns only get that heavy snow once every few years or for just a few days each winter so when you think about it, it's cheaper to just send people with brooms to clean them when needed. If drivers would have more common sense and be more careful, there wouldn't be any accidents.

  • Hmm... (Score:4, Interesting)

    by neowolf ( 173735 ) on Wednesday December 30, 2009 @11:15AM (#30593704)
    I wonder if there is some other design factor that is causing this problem, beyond just the LED lights not putting out as much heat as incandescent ones. I live in Colorado and most of the traffic lights here (Denver area) now use LEDs. I don't believe I have ever encountered one that was clogged with snow or ice. Not to say it doesn't happen, but I wonder if the traffic lights here are simply designed differently (better covers/shielding, spacing, ?).

    It seems like a simple solution would be a small heater incorporated into the LED lamp assembly that only turns on below a certain temperature. Better yet- perhaps a sensor could be used to detect if the lamp was covered, perhaps by reflectivity. This would probably still use a lot less electricity over the course of a year.
  • by Lord Bitman ( 95493 ) on Wednesday December 30, 2009 @11:23AM (#30593862) Homepage

    the shroud is there to prevent mistakenly thinking you have green when the lane going in a different direction has the green. The top/bottom of those is utterly useless, though. The whole thing should be a flat surface aside from the blinders on the side.
    and yet...
      1) that sign is still completely covered and unreadable due to snow
      2) No solution is offered for the sign
      3) Nobody even mentions the sign. Without the information from the sign, people are expected to just practice safe driving.

  • by Microsift ( 223381 ) on Wednesday December 30, 2009 @11:31AM (#30594006)

    I agree, I haven't taken a written driving test in over 15 years. When I did take the test, one of the questions was (paraphrasing) "How often do you have to get your license replaced." What a ridiculous question (give me my license and I'll read the answer off of the front). I wonder what real question got crowded out by this irrelevant question (If it's not obvious, I missed the question).

  • by Anonymous Coward on Wednesday December 30, 2009 @11:33AM (#30594034)

    Add a dome of snow, that gets illuminated green by the bright LED's beneath, and it stops being an arrow. We used to use this trick by filling an old gallon milk jug 1/3 to 1/2 full of water (which will freeze), add in a large bulb christmas light on the top, and string them around your house (one bulb per jug). Even though its a point light source, the whole jug glows the color and lights up the snow bank in the winter.

  • Don't blame the installers. Based on my experience, I would wager 100 bucks it was a voted in politician that made the decision, against the recommendations of professionals.

  • I half agree.

    I think I favor less enforcement, and less laws overall. Most of the driving rules, in terms of real safety, are overly cautious
    "Best Practice" guidelines at best. Speed limits are just ridiculous, in general. People are going to drive the speed they feel safe, regardless of what the stupid sign says. That speed is usually 10-15 MPH higher than the sign. Yearly safety inspections? I can see emissions checks every few years, or a safety check after 5 or so. However, regular safety inspection really is beyond the pale of what the state really needs to do. Stop signs? Please. Much of the time simply slowing down and treating it like a yeild is appropriate. Much of the time when that isn't true, it works just the same if you plan to do that, and end up having to stop anyway. The only REAL danger at those intersections are people who... weren't paying attention anyway.

    We have rotaries here in MA. They are safer than normal intersections, but... so many people just don't get them. They arn't hard. If your inside, you have right of way. Its simple. Yet, nearly every morning I am honking my horn at people who are yielding in the middle.

    I blame drivers ED. We need much stronger drivers ed, and incentives to take refresher courses. Instead, if you get 5 tickets in 3 years, even if they are paperwork violations (like not having your registration on you, or driving on an expired license) they ASSUME your main problem is your attitude and agression, and send you to a "defensive driving" course.

    The NSC (national safety council) course MIGHT be useful IF and ONLY IF your problem is really rage. Its utterly useless for everyone else. They don't barely even talk about driving rules. Just how you need to adjust you rattitude if you think its ok to break them.

    Its not even close to whats really needed on the road.


  • by SeaFox ( 739806 ) on Wednesday December 30, 2009 @11:49AM (#30594318)

    idiot driver should be prosecuted since everyone knows the third light from the top is regular green and not a turn signal.

    Are LED fixtures made to follow these same rules? On an LED light, the same light can easily be used to display both by simply not turning on all the LEDs.

  • Re:heating element (Score:4, Interesting)

    by Guysmiley777 ( 880063 ) on Wednesday December 30, 2009 @12:00PM (#30594570)

    I was up in Fargo, ND visiting family for Christmas (yah shoor ya betcha) and a traffic light was out on a 6-lane intersection. Guess what? Everyone was calmly proceeding as if it was a 4-way stop. No drama, no retardation.

    This whole thing is a non-problem. It's just that lazy journalists love it because it's "irony". It's not really ironic unless you're Alanis Morissette, but it makes for an easy, shitty space filler. Notice how in that story the SIGN is also covered in snow? ZOMG! We need heated road signs! Woe is me! Signs can sometimes become obscured by snow, the horror! The HORROR!

  • A danger... (Score:2, Interesting)

    by Anonymous Coward on Wednesday December 30, 2009 @12:05PM (#30594642)

    Yes, it's true: if a traffic signal is obscured by snow, treat it like an all-way stop. I live in Florida, so all we have are blacked-out traffic signals during power failures.

    But there's a danger:

    Fast north winds mean the southbound signals are covered with snow, but the other directions' signals are visible.

    You're driving south, your signal is covered with snow, and you are unaware that you have a red light. You come to a complete stop, treat it like an all-way stop, and keep going through the intersection. The cross street has a green light, and it's crash time.

    This is also possible if the right lights burn out in the wrong combination. LED traffic signals are more reliable in this matter, so there's a safety improvement right there.

    As for snow and ice melting, I assume that outfitting LED signals with heating devices thermostatically set to 36F is a LOT cheaper than switching back to incandescant beacuse of this "advantage". Even if you live in the coldest climate, you're still better off with fluorescent lighting at home, since incandescent lights are wasteful lights AND wasteful heat sources.

  • by Terje Mathisen ( 128806 ) on Wednesday December 30, 2009 @12:18PM (#30594890)

    Here in Oslo (Norway) we've had these LED lights for several years, and the snow shields have never (afaik) had any problems keeping the lights visible, even during our regular snow storms.

    Here's a detail from a photo of a local junction which I took for my wife. She is responsible for making public transport in the region as efficient as possible, which includes giving priority to buses and trams in all intersections: []


    PS. Here's a link to the least useful program I have even written, pi-search, which can locate digit strings anywhere within the first 1e9 digits of pi: []

  • by fuzzyfuzzyfungus ( 1223518 ) on Wednesday December 30, 2009 @12:26PM (#30595048) Journal
    It isn't just about energy costs(though those are a significant factor). Incandescent bulbs, even the ones that trade off efficiency for durability, have crap lifespan. Estimates vary somewhat(depending on local labor costs/municipal contracting efficiency, and chosen relamping interval); but $50 per bulb replacement, with bulbs replaced annually, seems to be a common enough number. By comparison, reasonably engineered LED modules are supposed to give you a decade without replacement. Even if energy were free, there'd be a good case to be made.

    As it is, this seems to be a story (depending on whether the fuckup occurred on the engineering side or the buying side) either of shortsighted buyers opting for false economies, or lazy engineers failing to think through likely failure modes.

    Electrical heating of transparent enclosures(either by a resistive film applied directly to the enclosure surface, or just a heater inside the enclosure) is not exactly rocket surgery. We've been doing it for decades in car windows, among other places. Nor is measuring the opacity of a given surface all that difficult. There are a number of robust approaches you could employ(optointerrupters around the rim testing for interruptions caused by material on the lens, photosensors scattered in the LED matrix, measuring intensity of light reflected back to the emitter array, etc.) These would modestly increase emitter and energy costs; but would easily eliminate the problem, and still come in cheaper than the incandescents.
  • Interesting. (Score:2, Interesting)

    by hallux.sinister ( 1633067 ) on Wednesday December 30, 2009 @12:52PM (#30595568)
    Or better yet, how about mandating red AND yellow lights be bigger and brighter than green. From a distance, it would look like this:

    O (red)

    O (yellow)

    . (green)

  • Re:heating element (Score:3, Interesting)

    by ArsenneLupin ( 766289 ) on Wednesday December 30, 2009 @01:44PM (#30596580)

    We need heated road signs!

    Ever wondered why stop signs are octogonal in shape?

    The answer: being the most important traffic sign, they have this unique shape so that they are distinguishable from all other signs even when covered in snow.

    So snow covered signs are a real concern, and yes, designers did think about the issue!

  • by DJRumpy ( 1345787 ) on Wednesday December 30, 2009 @01:46PM (#30596616)

    Every image people are showing here shows the snow building up from the bottom towards the top. If snow was so easy to stick to such a surface, we should see at least SOME accumulation on the top of the lens, which isn't the case, unless the bottom of the lens is already full of snow/ice.

    Everyone here is basing their logic on a guess. There is no light casing without this lip in any of the sample images from TFA or posted here otherwise. They simply assume that the heat from the old style lights is the only factor.

    I think it's far more likely that the old design was adequate for an incandescent light due to it's heat output, but inadequate for an LED light since it doesn't emit as much heat and it doesn't get any heat to the hood/lip surface areas.

    The lip and horizontal surface angles at the bottom of the hood are the root cause IMO.

  • Building a new power plant will make electricity cheaper? I do not see that happening in the short term. Power plants are not cheap to build.

    Now that the problem of sticky snow has been discovered the obvious solution is to add heaters to the traffic lights that can be turned on in winter. The minor extra cost of a heater just means the pay back on using LED's and saving electricity takes a few more months.

    Having an SUV does not make it easier to drive in the snow. Having good snow tires does, having chains if required, and learning to drive in snow: no sudden movements, don't stop when going up hill, stay way back from the car in front, and slow down well before corners. Take your foot OFF the brake if skidding so you can steer.

    We only get big snowfalls every 2 or 3 years so most drivers here are really bad at driving in snow. SUV's and 4 wheel drives make up 80% of vehicles in ditches due to the "over confidence factor". It seems many people with 4 wheel drives don't realize ALL cars have 4 wheel brakes.

    Going green generally saves money, and makes your life easier.

  • by hazem ( 472289 ) on Wednesday December 30, 2009 @02:26PM (#30597244) Journal

    Red-green colorblindness should not affect the ability of a person to correctly observe a traffic light.

    Under ideal conditions, you're correct. (But this whole article is about non-ideal conditions)

    I have some color blindness and I can describe the problem I have. When it's raining and at night, it's difficult for me to tell a green light (non LED) from a nearby street illumination light (from a distance). I know that sounds crazy. Because it's dark, it's hard to see the rectangular enclosure, so I can't tell by the green-light's position. Only after it's changed to yellow then red can I tell which light was the illumination light and which was the green light.

    And I can't just assume that lack of a yellow or red means I have the green, because it might be burned out.

    The new LED lights use a different color of green that has a higher blue component that makes them completely obvious. Plus the LED lights are more intense than the other lights. This may be due to the light from an LED being a smaller set of frequencies (or a single one?) compared to a filtered incandescent, though I really don't know much about the physics of LEDs.

    So, I expect it was mentioned in this context because when it's dark it's harder to tell the position of the green light against the dark enclosure, especially when there are nearby white lights. And the blue-green used makes them easier to see. At least that's my experience.

  • by plover ( 150551 ) * on Wednesday December 30, 2009 @03:13PM (#30597952) Homepage Journal

    How does the cost of potential lost human lives figure into this equation? I mean, due to them not working, the wrecks increase...possibly risking life and limb of taxpayers.

    Human lives have a value assigned to them by the Department of Transportation. Last I heard it was $5,800,000 per year []. That meant that if some hazardous road condition caused someone to die, they would change it if it cost less than $5.8M to do so. And it adds: if four people went off a cliff in one accident, and six people went off the same cliff in a different accident in the same year, they would put up guard rails, or rebuild the road, or whatever improvements it takes, up to $58 million.

    By that logic, the city of Oswego, where the victim died due to the snow-covered LED signal, would spend money to swap bulbs or add heaters or spray cooking oil on lights or whatever it takes, up to $5.8 million.

    It may sound cold and unfeeling to put a dollar figure on a human life, but it has to be done. Considering that a set of stoplights at a single intersection can cost over $750,000 to buy and install, cities have to spend their money wisely. Just because the neighbors ask for a stoplight because the cars go too fast doesn't mean the city has the money to give them one. But if someone should actually get injured or killed, it obviously needs to affect their priority for spending. It's just how it's done.

  • by Anonymous Coward on Wednesday December 30, 2009 @05:53PM (#30600026)

    We have had LED traffic lights in Sweden for over 10 years now.

    I have never seen one blocked by snow, and never heard of any cases where there were problems like these.
    And we get plenty of snow here.

    Sounds like the Americans are just buying crappy lights, or maybe the wrong models.

  • Re:Stop signs? (Score:3, Interesting)

    by toddestan ( 632714 ) on Wednesday December 30, 2009 @09:59PM (#30602014)

    That's why stop signs are the only road sign that's hexagonal in shape. So even if it is covered in snow, you should still be able to recognize it as a stop sign.

"I will make no bargains with terrorist hardware." -- Peter da Silva