LED traffic lights don't melt snow, do cause accidents
By Vlad Savov 
posted December 17th 2009 9:16AM
posted December 17th 2009 9:16AM
A number of cold weather American states are reporting their dismay at finding out that LED traffic lights are so energy efficient that they do not produce enough excess heat to dissipate any snow that covers them. It turns out, perhaps in an homage to bad engineering everywhere, that the inefficiency of incandescent light bulbs was previously relied upon to keep traffic signals unimpeded. The new LEDs do not achieve the same effect, which has resulted in a few accidents and even a death being blamed on obstructed traffic lights. Feel free to apply palm to face now. It's not all gloomy, though, as the majority of people are said to treat a dysfunctional traffic light as a stop sign (how clever of them), and a tech fix is being worked on as we speak.
They could use a capacitive layer which detects the conducting snow. If it is cold enough to beat the resistance of the layer they discharge to melt the snow in very short pulses.
This uses little power, only works when it snows or freezes.
Alternatively the could have the transformator cooled by alcohol which dissipates the heat through channels in the lens.
@Pyronick Or they could just put the old Halogen light bulbs back in. ; ^ )
On the truck trailers i have built with ledlights there is a heater that starts if temperature drops bellow freezing point.
Don't you Americans understand that led lights don't melt snow.
I don;t know about the U.S. but in Canada you are told when you get your learners permit that wehn traffic lights are out they automatically become a 4 way stop.
btw why is the snow in the picture black?
>YukonJack Posted Dec 17th 2009 11:43AM
>
>chalk another brainy idea up to those idiots who work inside all day >hiding inside their 4 walls behind their nice desk. sometimes it is >necessary to go outside and actually see what goes on in the real >world.
Your comment holds no truth, and your thinking is broken.
Not everything is applicable everywhere. You don't use a butter knife for brain surgery, the same way you don't apply every Engineering invention anyplace in the world.
People seem to forget the layers of people that approved the use of this device. The city council recommended it. The city Engineer evaluated it, the city Clerk approved it, and the city worker screwed it into the traffic light (probably mumbling the whole time how it wouldn't work, but telling no one else). And it still failed. By god, it must have been the Engineers fault. Did no one in the long chain of people using the product stop for one second to think about the application of the product? Didn't they test it in a few lights 1st? If they did, and there were problems, was it approved anyway due to political pressure?
And I guess you still want to blame Engineering, because we didn't tell you every possible application it could and couldn't be used for.
Maybe a butter knife *IS* appropriate for brain surgery on some people. You'd likely not be able to tell the difference afterward!
why not then treat it like a stop sign?
you snow people dont know how to drive
Where I am in Canada this is not an issue. I guess they must have foreseen this happening since we get a lot of snow.
I'm wondering if maybe you couldn't replace every third or fifth or n-th LED with something a little "hotter" in order to ameliorate the condition. In fact, if you pattern it as "X" for red, "--" for yellow, and " O" for green then you are ensured of visibility as well as color-blindness differentiation.
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I remember hearing about this issue 2-3 years ago on NPR's CarTalk. How has it gone unnoticed so long by these municipalities that this is just the first winter where it's become an issue?
This may be oversimplifying the solution but isn't there a way to simply make the LEDs brighter, thus making them hotter and ridding of the ice? All that would be needed is ONE temp sensor, when the temp drops below X degrees LEDs get brighter/hotter until temp is back up to a degree that snow wouldn't be a problem.
Ice is gone, energy use remains efficient. Thoughts? Is this feasible/possible?
Just get rid of the overhang, or whatever it's called. Make the surface super slippery, and no snow will stay there.
DUH
A transparent shield over the traffic light cowl would be a good solution to this problem. The material would have to be non-reflective and have a non-stick coating something similar to SNO-FLO. The main reason why this solution would be best is because it's practical and easy to implement. If you design a heater solution, you would have to retrofit all the lights and that would lead to some immense costs.
i live in toronto where it's pretty chilly and we use LED traffic lights exclusively without a problem. Maybe their is some particular model which implores ice melting filaments or something?
@insuranceguy: Making the LEDs brighter does not make them hotter at least not in a way which would help to melt snow (though it would drastically shorten the life of the LED). LEDs don't generate heat the way that an incandescent source does.
For an LED, any energy not used to produce visible light is released from the back of the chip-set as heat. This heat must be conducted or convected away to ensure that the LED P/n junction temperature doesn't exceed mfg specifications. The cooler that junction temperature, the longer the LED will last. Regardless, an LED radiates almost 0% IR. In other words, the light beam is cool - no matter how bright - and simply cannot melt snow.
By contrast, over 70% of the energy not used to produce visible light from an incandescent source is radiated as IR which most definitely can melt snow...
If we could only find a way to capture and transmit the white-hot fury and anger generated by nerds arguing in comment sections about the best way to melt snow on traffic-lights......
ummmm all the lights are white, does that mean go?
:-/
Do not dismiss the idea of adding heaters to the traffic lights so quickly. Although LED bulbs do use less power, they are still quite a bit more expensive than incandescent bulbs. They are not using these bulbs because they are more efficient. The real savings in having these bulbs used in traffic lights is that they don't need to be changed nearly as often. It is expensive to change a light bulb at a traffic intersection. The added cost of a heating element is probably worth it to avoid the cost of sending work crews out to change the bulbs more frequently and the accidents caused when a light bulb goes out.
this diserves the picard face palm haha
And how about to agreed with the Kyoto Convention? or the Copenhagen Conference?
Please forward this story to big Al Gore, the one who penned "A Convenient Lie."
There is a simple solution to this....use lights that have larger signals (meaning more heat) and a significantly wider gap at the bottom of the hood. The slope of the hood below is more than enough to prevent snow covering the signal above. UK lights have always been designed like this (and the new LED ones don't have the problem either...I just walked out an checked) and I've seen ones like that in the states as well....
That's actually SAD! How stupid can people be! do you want to save a tenth of a watt of electricity or save someone's life!
How about a clear plexiglass cover so that snow can't collect? We're working with geniuses.
Let me just say LED lighting is great to save power but for cold wintery areas like Massachusetts, New Hampshire or Maine, it's useless. I've seen that thing piled up with snow a bunch of times. Put in a defroster or something with a temperature sensor to solve that problem. But honestly for cold climates... use incandescent lighting. Building that temperature sensor/defroster is just a waste of money unless somehow they were able to make a very efficient and cheap Sensor/Defroster unit.
In Fort Collins, CO they started switching entirely to LED traffic lights around 2000, but they have recently started switching back. There are two main reasons:
- Snow melt, like in this article.
- Premature failure
It seems that the LED lights were not properly designed to handle rapid temperature changes (like we sometimes get in Colorado); most of the LED lights in the city had individual LEDs fail, and many of them even failed to the point where they needed to be replaced.
If they are saying it causing accidents and death, yes its a design flaw, but what is the law says if its not working, power is out or an obstruction in the light. The intersection becomes a four way stop. Just because people don't know how to drive and understand the laws, its there fault also. Yes, they need to install some type of heater to the lights when it goes below a certain temperature so they don't do this anymore.
@jsiani no heater is required... a roof is what they need xD
i find it doubtful that designers didn't think of this happening...
Or If People Were Actually Smart Drivers Accidents Wouldnt Happen.
@EthanExplosion
pff if they would make cars visibly unsafe everyone would think twice before doing anything risky
I live in hawaii and we do not even use these
In hawaii volcanic ash and sun makes the classical lightbulbs overheat, so there's it a bad idea to use classical, so they do.
The funny thing is that this has been researched years ago, I question the news article a bit... The FAA banned LED lights on runways because of this same issue. It wasn't until someone came up with a heater built into the housing that they allowed LED fixtures on the runway.
My guess is that they are using cheaper methods due to budgets, not because they didn't know this could happen.
Someone else posted this on Flickr. It's what the railroad crossings in my area looks like. I think it would work with the traffic lights.
http://www.flickr.com/photos/drpep1024/2902426865/
The lights just need to be redesigned.
Plenty of LED traffic lights here in the Netherlands, and also plenty of snow right now. Our traffic lights are just covered on the top and sides, and the lenses are curved and smooth enough to prevent snow from sticking to them even if the snow is directed straight at the light.
I used to date the daughter of the Chief District Engineer of my area and he had said that using LEDs caused issues with the wiring itself to the lights. The condensation on the power connections didnt evaporate due to the heat resistance from the LEDs, so they had to install resistors to pull more current through the power lines to the traffic lights! I'd assume that removing the resistors and installing some kind of current-limited heating element would still heat up the lines enough to remove condensation and melt snow.