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.”
I wouldn’t use a temperature sensor and a heater to fix the problem because that would just waste a lot of electricity in cold climates. 32F is t-shirt weather now. Ideally a change to the protective covers and surface of the lamp would resolve most of the problem passively. The best active approach seems to be some sort of emitter and a photodiode to catch the reflection if snow/ice have built up in the cowling or just a timer and a photodiode to see if there’s sufficient sunlight coming through at say, noon. If there isn’t, then turn on the heater and do some melting. Hmm, what DOES the patent office have to say on the issue…
I can also say that here in Minnesota I personally haven’t seen any issues, but I believe the accounts.
The simplest solution, IMHO – if the light needs to be shrouded, use a single shroud that arches over the topmost light, and goes down the sides of all three. This prevents side glare, and leaves no shelves for snow to collect in front of the lights.
I haven’t read all of the comments, so I don’t know if I’m too late with this suggestion?
photon without a Higgs (10:02:57) :
The map is from the last 2 days
http://mapcenter.hamweather.com/records/2day/us.html?c=maxtemp,mintemp,lowmax,highmin,snow
Now a second red dot, at West Pal Beach International Airport, is from yesterday, Friday.”‘
That WPB red dot says a new record of 88F on Friday.
Friday’s high in WPB was 76F.
All they have to do is seal the traffic light fixtures then pump them full of CO2. Then they will be snow free in the winter.
As was already suggested their are solutions to this problem. LED lights are the way to go but in cases like these extra measures must be taken to create a safer environment. There’s no excuse by the relevant authorities for not taking these measures. They need to learn from their mistakes and act. If they don’t then they are culpable.
A good fix would be to install electric heaters behind the led lights.
starzmom (06:26:37) :
“A small heating element in the light fixture, perhaps?”
The law of unintended consequences strikes again. LED’s, being a solid state device, will be damaged by excessive heat. > 300 deg K will lead to their early failure, and > 375 deg K will destroy them in an hour. Heat is the mortal enemy of all semiconductors. Compare this to as high as 3,300 deg K for the tungsten filament of an incandescent light bulb. Since just slapping a heating element inside the LED traffic light an inch behind the polymeric cover will be an engineering failure, a viable defrosting system would have to be a clear cover with an imbedded filament heater, much like the design of the rear window defroster found on automobiles with a hatchback instead of a trunk. Such designs apply more heat to the outside surface of the glass than to the interior surface. The imbedded heater design would also rule out any polymers for the composition of the cover due to the intense spot heating that will occur nearest the heating filaments, so a tempered heat resistant glass cover would be required. In order to be effective, the heater would have to initiate automatically, triggered by an optical sensor that detects a decrease in light intensity a short distance in front of the clear cover. Then the engineer has to figure out a way to prevent the optical sensor itself from becoming snowbound. The sensor circuit would also have to “know” when the particular bank of LED’s are energized or not. Also needed is a temperature sensor to prevent false triggering due to rain, fog and dust. Oh the expense!
Now, if someone would discover the formula for clear Teflon for which to make a cover, problem solved without heat! Until then, I think the best remedy is the retro solution, remove all red LED traffic lights in snow-prone areas, and reinstall the incandescent red light models.
Schools still indoctrinating students on the global warming meme with the help of ABC.
Ask you child when he or she comes home and preaches about Man-made global warming ad CO2, Are you a climate scientist? Can you show me the peer reviewd science? What, no to both questions? Then shut the hell up.
Cold Can’t Shake Global Warming Faith of ABC’s Blakemore
http://newsbusters.org/blogs/matthew-philbin/2010/01/08/cold-cant-shake-global-warming-faith-abcs-blakemore
I’m not against the LED Traffic lights, in addition to energy savings and reduced maintenance costs, unlike regular lights, the LED have a graceful failure. That is they start to dim and some lights go out as the start to fail.
HOWEVER like all engineering, some trade offs are needed.
(1) The light needs to be open on the bottom, to drop any snow that might try to gather. (See link below.)
http://www.greenwichukip.org.uk/assets/images/traffic_light_led2.jpg
(2) In some areas, heaters may be needed when temperatures drop below freezing.
The problem is NOT unsolvable, it just takes more effore to make sure the system works properly.
Also, STUPID drivers need to be trained, if we don’t see a light, STOP FIRST!!!!
At last a BBC weatherman questions the computer models
\\\ A frozen Britain turns the heat up on the Met office. ///
http://www.bbc.co.uk/blogs/paulhudson/2010/01/a-frozen-britain-turns-the-hea.shtml
Which begs other, rather important questions. Could the model, seemingly with an inability to predict colder seasons, have developed a warm bias, after such a long period of milder than average years? Experts I have spoken to tell me that this certainly is possible with such computer models. And if this is the case, what are the implications for the Hadley centre’s predictions for future global temperatures? Could they be affected by such a warm bias? If global temperatures were to fall in years to come would the computer model be capable of forecasting this?
latitude (11:32:34) :
That WPB red dot says a new record of 88F on Friday.
Friday’s high in WPB was 76F.
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the red dot says West Palm Bch Intl Ap
so that would be the airport
http://www.climate-charts.com/USA-Stations/FL/FL089525.php
so it was 12 F warmer at the airport
what would the temp anomaly by without UHI??
P Gosselin (06:53:02) :
“For Americans, a roundabout is a so-called traffic circle.”
Except in Boston. Beware the sign that says “Rotary Ahead.”
A couple of small sections of nichrome wire run accoss the light that are turned on automatically would solve the problem Most traffic lights are run by a housing that has timers, etc. for how long the lights are on each direction and when they go on blink in the middle of the night. Adding a thermistor that turns on a heater to those would be a no brainer.
This could be accomplished easily enough with a “hybrid” lamp. One that has both LEDs and an incandescent bulb. At a certain temperature, a bi-metal contact such as this(not exactly that device but one like it set for the proper temperature) would close causing the incandescent bulb to illuminate when the signal is active in addition to the LEDs. When the temperature rises above freezing, the bi-metal would open and the incandescent bulb(s) would no longer operate. The sensor could be mounted to the lens someplace near the edge with thermally conductive epoxy.
As the incandescent bulb(s) would operate only when the lens temperature was below the activation temperature of the temperature sensor, they would last much longer and if they failed, would still continue operating with the LED lamps.
Making a hybrid assembly with several smaller incandescent bulbs mixed in with the LED lamps is how I would approach the problem.
pwah, yep
The WPB airport reported 88F yesterday.
Here’s the airport temp site.
Go to the bottom and look at past 24 hours.
http://www.usairnet.com/weather/conditions/?station=KPBI
Which is quite impossible, since places 10 miles away reported record lows.
I would just like to address all these “hey, stupid… STOP if you can’t see the light” comments.
It’s one thing for a light to be out. People usually deal with this quite well.
But a fixture covered with snow can blend right in with background and falling snow in much the same way that a camoflage wallet in the bushes is the most money you’ll ever lose until fall.
It’s made all the worse when the people before you go through without anything happening to them or anyone else. No one sees the light fixture, let alone a light, so they see no reason to slow down. So why would you?
Steve in SC (06:32:51) :
“LEDs do emit heat, just not a whole lot.
They are more efficient and thus produce the same light with less wattage dissipated in heat. They are substantially more visible in situations where glare is a problem. Which poison do you want?”
I’ve never had a serious problem due to an encounter with an incandescent traffic light, yea there has been a few times where the sun was shining in my eyes and I had difficulty seeing the light, but I dealt with it. On the other hand, I’ve encountered a few overzealous LED traffic lights at night that absolutely blinded me, causing me to lose my “dark adapt”. It’s the same effect you get by staring at the sun or having someone shine a 10 megacandela spotlight in your eyes. I’ll take the red pill.
West Palm Bch Intl Ap explains one red dot in Florida over the past two days. Now what about the other one from Thursday in the Pan Handle?
January 7 and 8, 2010:
http://mapcenter.hamweather.com/records/2day/us.html?c=maxtemp,mintemp,lowmax,highmin,snow
86 F, previous record 82 F in 1998
at this station
Marianna Caa Ap, Fl
I believe this is the station
http://www.nc-climate.ncsu.edu/cronos/?station=085367
Anyone live in Marianna, Florida?
http://pics2.city-data.com/city/maps/fr5207.png
latitude (12:49:19) :
Which is quite impossible, since places 10 miles away reported record lows.
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Shesh! Unbelievable!
UHI—it’s worse than we thought!
photon
considering that right above WPB,
Stuart set a record low of 35F,
and right below WPB,
Ft Lauderdale set a record low of 36F.
And they want anyone to believe that 20 miles inbetween
those two record lows, 35F and 36F,
it was 88F.
In Florida, with the wind blowing
If co2 makes it warmer,
why is dry ice so damn cold ?
{ Hank Hancock (11:37:09) :
All they have to do is seal the traffic light fixtures then pump them full of CO2. Then they will be snow free in the winter.}
At 100% co2 you risk Venus air temps…
You’ll melt more than just the snow…
“Goodness, gracious, great bulbs of fire !!!”
On that theme, just fill multi-pane windows with co2 between the glass. A little sunlight on the window will create runaway temperatures like on Venus, high enough to heat our homes, or cook a roast… throw another shrimp on the window sill for me, would ya?
I’d say that roundabouts in the UK have been successful, by and large. I think we have always had more of them than other comparable countries. They come in all sizes, e.g. mini-roundabouts (which some people admittedly detest, but I like).
I think that provided drivers treat them in the spirit intended, they can work very well. As someone else has said, on the larger, busier roundabouts, they have installed traffic lights, which kind of defeats the purpose. IMHO, traffic lights “deskill” the driver, who tends to just look at/for the lights, and not at what’s on the road.
Sadly also, traffic lights generally do seem to be making a bit of a comeback here. In my town (which used to be relatively traffic-light free), they introduced a big new traffic scheme, supposed to tackle congestion, heavily dependent on linked traffic-lights. Needless to say it increased congestion…
Antilock brake system will not stop you as fast as locked up wheels in loose gravel and deep snow.
There are also warnings in published materials that in some conditions they lengthen stopping distances at the trade off of maintaining steering control.
The Subaru WRX had over sensitive antilock brake design in the early models that resulted in a recall for reprogramming. Some users including myself experienced near total brake failure due to the defect in certain conditions, where the computer would misinterpret wheel lock signals when crossing rail road tracks, manhole covers, and small patches of sand on pavement. This is due to the split traction problem where one wheel is on a very slippery surface but all other wheels are on high traction surfaces. Some ABS systems will interpret the wheel lockup on the wheel with low traction as an indication that all wheels are on low traction surface and lower braking effort to suit the lowest common denominator wheel. The result is that all 4 wheels braking effort is reduced so they would not lock on that slick surface greatly increasing stopping distance. This problem resulted in a “consumer satisfaction” recall by Subaru where you could have the ABS computer reprogrammed to reduce the problem. Most found the better solution was to remove the electrical fuse for the ABS system and go back to predictable brake performance of a mechanical hydraulic system that did not try to out think the driver.
With the ABS shut off the car had much higher braking effort and did not at random refuse to decelerate at traction limited rates.
http://www.abs-education.org/faqs/faqindex.htm
http://www.iihs.org/research/qanda/antilock.html <— see item #3
http://www.nhtsa.dot.gov/cars/rules/regrev/evaluate/808206.html
http://www.thetruthaboutcars.com/nhtsa-abs-braking-increases-fatal-run-off-road-crashes-by-34/
http://www.harristechnical.com/articles/abs.pdf
Larry
Airports are diligently converting their taxiway lighting systems to LED. The LED TW lights had the same problem with icy glaze, but heaters were added. Further research may eliminate the need for discrete heaters; see:
http://www.lrc.rpi.edu/resources/newsroom/enews/fall07/Research41.html for example.
Incorrect conclusion; false economy; straight-line projection failing to take into consideration other factors.
It assumes, perhaps, that the waste heat produced does no one any good, but let me say, with the outside temperature at 25 deg F today this is _not_ waste heat (as I heat with ‘clean’ electric as do many others in my ‘planned’ subdivision do).
.
.
Jim
2010/01/09 at 1:39pm
mikelorrey (06:56:59) : …
According to this: http://www.cee1.org/eval/db_pdf_es/275es.pdf
22% of US electric consumption is in lighting. Converting to LED lighting nationwide for everything would therefore reduce consumption overall by 20%.
/
“Incorrect conclusion; false economy; straight-line projection failing to take into consideration other factors.
It assumes, perhaps, that the waste heat produced does no one any good, but let me say, with the outside temperature at 25 deg F today this is _not_ waste heat (as I heat with ‘clean’ electric as do many others in my ‘planned’ subdivision do).”
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.
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.