LED Lights Don’t Melt Snow on Traffic Lights, Hiding Signals From Drivers
Jan. 8, 2010
A huge swath of the country is getting snow and it’s raised an unusual and potentially dangerous problem for motorists.
Click picture to see report
Communities across the country are converting to LED traffic lights, but these lights don’t emit heat, so snow doesn’t melt like it would with a regular incandescent bulb. In some cases, Drivers then can’t see the signals.
During a snow storm last year, Lisa Richter of Oswego, Ill., had a green light and was turning left. But police say a driver in the oncoming lane blew through his red light and plowed into her, killing her instantly.
This wasn’t a regular accident. Police said this traffic light, blocked by snow, contributed to the crash. The light was an LED signal, which doesn’t emit heat, so snow doesn’t melt like it would with a regular incandescent bulb.
Cities and states across the country that have converted to LEDs report an energy cost savings of up to 80 to 90 percent.
In Green Bay, Wisc., where all traffic lights are now LEDs, December’s incredible snowfall caused many to be packed with flakes.
After their intense storm last month, some drivers in Madison, Wisc., noticed their neighborhood LED signals were hiding.
“I know that the stoplights are there, but if I didn’t, it would have been very easy to fly right through them,” one driver said. “And especially with the off ramp right on the interstate, it could be a very dangerous situation.”
The state of Wisconsin switched to LEDs in 2002 to achieve the massive energy cost savings. Maintenance costs are also much lower because LEDs last a long time. Incandescent bulbs usually have to be replaced every 2 years.
“With LEDs, we have some of our heads that were installed in 2002 still operational today,” said Wisconsin state traffic signal systems engineer Joanna Bush.
Another advantage of LEDs: Bush said the old incandescent bulbs could pose safety problems of their own.
“When they fail, they go dark, like a light bulb at your house. There’s no warning and it’s dark. With the LEDs, it’s a string or two that starts to go out and the driving public might not even notice a change in the LEDs and we can get our crews out to change it.”
LEDs?
How are those snow/ice covered solar panels working out for you?
A case of retrofitting an old physical traffic control light design with a new ‘bulb’/illumination device without considering other factors, like, the old designs factored-in the melting of snow/ice via incandescent bulb heat …
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Gail Combs (08:21:11) :
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What does this illustrate? Sloppy engineering.
If the current media crisis was “Oh my there is a coming Ice Age”, someone might have considered the icing up problem of these new lights and produced a decent, VALIDATED engineering design.
Au contraire; this was a decision by some bean counter to save beans. A retrofit of existing traffic control lights to an illumination/light source which promised to save money in replacement work and in power consumption.
I don’t think the city did a speck of ‘engineering’ with regard to suitability in the variety of weather types experienced in a northern climate.
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latitude (13:05:09) :
The 35 and 36 were nighttime lows (look at color ledger at the top of the map) and the 88 was a daytime high. But still I understand your point. The heat sources at the airport made an inaccurate temp reading. It wasn’t 88 yesterday in West Palm Beach, only at the airport.
Still doesn’t get you close to “20% savings” figure cited.
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Jim
2010/01/09 at 1:55pm
mikelorrey (13:49:45) :
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While I agree that waste heat produced in WINTER is useful (albeit that lighting is an inefficient heater), waste heat in SUMMER is quite the opposite and increase ..
“Still doesn’t get you close to “20% savings” figure cited.”
.Actually, given the reduction in air conditioning load in summer will be greater than the increased demand for heating in the winter, the savings should wind up being greater than 20%.
Seems this problem prompted a potential solution: http://www.ledsmagazine.com/news/7/1/4
seems like this red dot in Florida issue would make a good post for WUWT.
Philip T. Downman (08:53:33) :
Another thing: Why are most signals, lanterns, lighthouses and so on based on red/green? More than 5% of males and 0,25% of females have a red-green color vision defect. For example blue and yellow had worked for practically all people. Impaired blue vision is extremely unusual.
It’s all about the sensitivity of the rods and cones in your eye. The eye is extreamly sensitive to red, for example. Glance around a room and you notice the red thing straight away. Green is the same: you’ll notice a green thing much quicker than, say, a blue thing.
It’s an evolutionary construct. Back when proto-humans were running around the African Savanna, you essentially had a big green jungle and a bigger blue sky. Small changes in the sky don’t mean much, so you don’t see them. If you saw a flash of red or anything else close to the wavelength of red (eg. yellow), you need to register that instantly, because it is probably dangerous.
The same goes for changes in green: different plants mean different things.
So, red/green is where it’s at.
I don’t know about the US, but here in Australia our traffic lights are all arranged vertically, with red at the top and green at the bottom, so colour registration is supplimented by position. Lose colour, and you can still see what the lights are saying.
When I was in Japan, though, I noticed that some lights were arranged horizontally. I’m sure there was a consistenancy there, too, but it does require a level of interpretation that the Aussie system removes.
mikelorrey (13:49:45) :
While I agree that waste heat produced in WINTER is useful (albeit that lighting is an inefficient heater), waste heat in SUMMER is quite the opposite and increase power consumption in air conditioning loads, so averaging annually, and considering that it is easier and requires less energy to heat than to cool, that its still to a benefit to use efficient lighting technologies like LEDs.
This is entirely dependent on location. Alaska, for example, has very few “hot” days… In California near the coast, when it is hot during the day, it often becomes cool at night; when you need both heat and light. In Phoenix, yeah, pretty much LEDs win all the time. In frozen high mountains, not so much…
And that is why any decision on what lightbulb to use ought to be left firmly in the hands of the customer doing the buying and using.
“One size fits all” doesn’t.
(Not mention I don’t want mercury in my fridge so the CFL bulb is a really dumb idea and I don’t want to put a gazillion hour $40 LED light in a basement closet that MIGHT get used 1 hour a year, maybe. Oh, and the various chick hatchery, cat warmer, lizard warmer, etc. “heat and light” choices. Not to mention that the $12+ CFL “dimmable” bulbs are not smoothly dimmable and have more of a “step function”… And did I mention that they give some migraine sufferers headaches? I know one such person. Then there is the fact that you get 10,000 on/off cycles as a limit – not just years – so things like motion sensor yard lights are going to be dropping like flies if near any foot trafic [and any other place with frequent on/off cycling like fridge, bathroom, kitchen…] . And then there is the “time to repair” issue. At the mechanic yesterday a guy came in with a brake light that would flicker on once, then off. Instead of a 2 minute “change bulb” (it being LED not bulb) for a couple of bucks he was told “It has a card with electronics on it, bring it back Monday and we will put it on the analyser” …)
Individuals need to make choices, not governments with “one size fits all” prescriptions that don’t.
While traffic lights like these might need the heat for a few hours when being pummelled by wind blown snow, this accounts for less than 1% of the operational time of the light so its still a waste to have it generating heat 24/7 in winter. At best, I’d recommend that the bezel in front of the LED panel utilize a small heating element that utilizes a capacative sensor that senses when there is appreciable bulk water in front of the light.
Seems pretty complicated to me. Why not just put a clear plastic snap on cover over the front of the ‘can’ and not let the snow in in the first place? Easy retrofit too. (The “can” is there to control who can see the light, but seems to me there is no reason not to move the “bezel” to the front on new designs.)
E.M.Smith
2010/01/09 at 2:10pm
“This is entirely dependent on location. Alaska, for example, has very few “hot” days… In California near the coast, when it is hot during the day, it often comes cool at night when you need both heat and light. In Phoenix, yeah, pretty much LEDs win all the time. In frozen high mountains, not so much…
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Individuals need to make choices, not governments with “one size fits all” prescriptions that don’t.”
“Seems pretty complicated to me. Why not just put a clear plastic snap on cover over the front of the ‘can’ and not let the snow in in the first place? Easy retrofit too. (The “can” is there to control who can see the light, but seems to me there is no reason not to move the “bezel” to the front on new designs.)”
I agree 100%. My conclusions are based on overall averages of the nationwide installation base of lighting. Having worked as a professional lighting designer and energy analyst (featured on a Washington Post cover story), I’m quite aware of the complexities of the issue and the broad range of individual siting requirements.
While lighting does also heat a building, usually that heat is in a place where it is not able to be used effectively. It typically winds up radiating upward from ceiling or wall installations into crawlspaces and is never used for warming the working spaces of a building.
In the specific case of these traffic lights, its clear that incandescent traffic lights utilized the heat to keep the lenses clear of snow on the rare occasions when that risk existed (even in Alaska), but as another reader here pointed to a shroud that uses louvers to create wind vortexes inside the shroud to keep the lens clear of snow, it is entirely possible to solve the engineering problem without consuming energy… This is smart design and demonstrates that sticking with the way we’ve always done it isn’t the most effective thing when implementing new technologies.
photon, the high was 73.3F at Palm Beach Gardens yesterday
That’s as close as I could find to the WPB airport, and a long way from
a 88F record high.
http://www.kflwhk03.com/wx5.html
I think there are some false assumptions in that. First, it must assume that all current lighting is incandescent. It isn’t. Most commercial buildings are already lit with non-incandescent lighting and many homes already have fluorescent lighting in places like the garage and possibly the kitchen. Switching to incandescent of what might amount to 10% of the 22% of the US electricity consumption would then reduce consumption overall by an amount barely measurable in the total electric consumption scheme and, as another commenter noted, result in simply shifting of some energy to other sources when the primary climate control is heating. You can consider incandescent lighting to be dual purpose in winter where they provide both light and heat.
The idiotic CFL craze is fed by people wanting to feel like they are “doing something” to “save the planet” when they are actually doing nothing at all and the planet might not need “saving”. It is an emotional “lotion” to mollify people’s anxiety and doesn’t *really* do anything about energy consumption.
Switching to CFLs at my office, for example, would save exactly NOTHING since all lighting is already fluorescent anyway.
crosspatch (2:29pm):
“Switching to CFLs at my office, for example, would save exactly NOTHING since all lighting is already fluorescent anyway.”
If CFLs were the only most efficient alternative, you would be right. However, you aren’t. Fluorescent technology saves about 50% over incandescent technology. LED saves 80-90% over incandescent technology, therefore it saves 60-80% over fluorescent technology. For a given capital investment, you get the same return on investment to upgrade to LED from Fluorescent as you do to go from incandescent to fluorescent. And this is just in the energy savings. It turns out that the labor savings of LEDs over incandescent is about 95%, with an 90% savings over fluorescent in maintenance man hours and labor dollars. This makes the return on investment to upgrade to LED even greater from fluorescent, than from incandescent to fluorescent.
One thing I would suggest is that all new building use DC lighting. Every building would have a 48 volt AC feed which would be rectified to DC at the building entrance. This would allow people to add PV or wind turbine energy to the system much more easily. It would also allow battery backup at the premises. In case of power shortages, the 48VAC circuit could be shut down first. This circuit would provide power for such things as lighting, a new style of “wall warts”, etc. Various appliances would still be powered by the conventional 110 or 220 volt feeds. You could then do a different sort of “brownout” where you shut off the 48vac feed and reduce energy demand from the utility and that shuts off only people’s lighting (except maybe for an emergency lamp) but leaves their freezer and any required life support systems working. Homes that elected to install a battery backup and possibly have local PV or wind capacity might not even notice the disruption at all.
crosspatch
2010/01/09 at 2:37pm
“One thing I would suggest is that all new building use DC lighting. ”
Meh, not terribly smart. Going from 240v AC to 48v DC (or from 120vAC) requires all the wiring in the building to be changed, as lower voltage requires greater amperage for the same wattage. Forex, 120vac to 48vdc requires the guage of the wire to be three times greater. This would be a boon for the copper industry, as the price of copper would skyrocket, and wiring anyplace would become insanely expensive.
Until they can make a white LED that doesn’t suck, LED lighting is not an option for me. The color is not white and it gives me a headache.
I think it likely that having had the issue brought home to them, the traffic light design engineers of the world will come up with a relatively easy and ingenious design change for the future.
Let me try that again:
The easy fix is to not have the shield that collects the snow, especially since LED’s shine brighter and don’t need to have the light directed.
An easier fix would be the addition of a ceramic (or similar) type heater that modulates its heat output according to the surrounding temperature. Solid state. Low tech (at the point of application).
Meh, dont need the heat ALL the time in the winter, Simon, you just need it when water is present. That says you need a capacitance sensor.
but as another reader here pointed to a shroud that uses louvers to create wind vortexes inside the shroud to keep the lens clear of snow, it is entirely possible to solve the engineering problem without consuming energy…
If you don’t count the cost of replacing the traffic light fixtures or the cost of modifying them in the city/county where they are installed.
Meh, dont need the heat ALL the time in the winter, Simon, you just need it when water is present. That says you need a capacitance sensor.
Then you have the problem of sensor reliability and the reliability of power control electronics. And water is not the problem. Snow/ice is the problem. Why turn the heat on in a rainstorm?
Engineering wise I think it is worth a few extra watts in winter to reduce the risk of killing people.
I’m of the KISS school of engineering. Aerospace division.
Me too. The capacitance of liquid water is going to be different from snow.
And they want anyone to believe that 20 miles in between
those two record lows, 35F and 36F, it was 88F.
Not to worry. After homogenizing, the temperature record will show that Florida was a comfy 75°F.
Anyone else notice that WordPress now has a built-in spell checker?
(And it just underlined “WordPress”)
@ur momisugly Neil O’Rourke (14:06:59) :
In Japan all traffic lights are arranged horizontally, green on the left en red on the right. Yet the lights for pedestrians are arranged in the usual vertical configuration. Although there green is often a bit on the blue-side.
Everyone that is posting about having a different shield – the problem is driving, wet, sticky snow, that will stick to pretty much everything and anything.
To me the obvious solution is to put at least one small halogen light in with the LEDS – enough to provide enough heat to warm the glass and stop snow sticking, or not use LEDs altogether. Or just go back to halogens in snow prone areas. There’s no cost savings in LEDS if you have to send out crews to clean the snow off – human hours and vehicle hours are much, much more expensive than electricity. I’m sure if someone did a study, they’d find it would only be a handful of maintenance trips to clean snow before the LED cost savings were lost. That’s before you even factor in the cost of a single fatal accident due to snowed over lights. In heavy snow, it’s not easy to see anything, let alone a traffic light with no lights on.
The suggestions to incorporate a heating element are probably a good idea, but then you’d have to look at the total cost of ownership. The LEDs are doubtless already more expensive to install, adding electronics and a heating element would increase the cost further. And if an expensive LED set gets wiped out in a traffic accident and has to be replaced, does that further negate the cost savings?
Someone needs to do an engineering study and work this out properly, taking into consideration all costs, including installation, maintenance, electricity usage and unexpected occurences like snow and accident damage.
If a study was done like this (and ignored the ’emissions’ side), then a decision could be made with data rather than emotions. Even if you believe in the emissions problems, then the local authorities could plant a tree for each light they installed.
I thought I suggested it for NEW construction, not retrofitting existing buildings. New buildings would have a 48VAC feed and it would be only for low current applications such as lighting much like an RV circuit. I think having a separate low-current feed that can be locally backed up / augmented is a good idea.
I would want one.
crosspatch (3:10pm): I thought I suggested it for NEW construction, not retrofitting existing buildings.
So you did. Even so, the mass of copper in wiring is going to be triple (if the grid AC is 120v, sextuple if 240v), so your wiring cost is going to cost at least three times as much. If 48v homes becomes required by code, then the cost of copper is going to go through the roof and you could wind up paying ten times the current price or more to wire your building. Very inefficient and (at risk of sounding green) nonsustainable.
crosspatch (14:37:56) :
A 48 VAC feed into the building? That seems incredibly wasteful in wiring and gauge. Industrial buildings almost always have their own transformer and could make their own. If you just want a full-wave rectified DC output, then you have a suite of other problems. If you want conditioned DC, then you may not want to start with 48 VAC, as the extremes are 48 x sqrt(2), or 68. An efficient switching power supply makes more sense.
If the building has 3 phase power, then simple rectification would get a pretty decent DC.
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mikelorrey (13:49:45) :
Incandescent lights are 100% efficient heat sources as long as the light (a small fraction of energy used) is kept inside.
Not as efficient as heat pumps which are > 100% efficient and the heat from lighting may not go where you want it.
latitude (14:12:11) :
photon, the high was 73.3F at Palm Beach Gardens yesterday
I was hoping Anthony would pick up on our exchange and make this red dot in record cold Florida in to a post. It does show vividly the UHI problem. Everyone in America knows about the cold in Florida. For people to find out that there was record heat at an airport in Florida would make the UHI case crystal clear to laymen.
Why is no one talking about infrared LED’s? We use them in TV remotes. Make the traffic light lens from a material that is not transparent to IR, but will absorb it and heat up. On the cheap you could incorporate the IR LED’s with the others in a single-unit replacement for an incandescent or older LED bulb, use a bi-metal temperature switch, suitably set, for “just in case” heating. Otherwise an IR LED unit could keep the heating at the lens, where you want it, and away from the LED’s. Then you can switch on the IR unit however you want.
Are all the available IR LED’s so weak they cannot be used this way for heating?
kadaka
2010/01/09 at 3:41pm
“Are all the available IR LED’s so weak they cannot be used this way for heating?”
AFAIK, wrong part of the IR spectrum. You need an LED whose emission curve correlates with that of H2O’s absorption spectrum.