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 don’t understand why anyone designs a PWM for LEDs that’s low enough to visibly flicker. I generally go for something above 1kHz (often significantly above, my last design was 50kHz) and this totally eliminates visible flicker. It’s not exactly hard to achieve these frequencies efficiently, you just need to use the right size MOSFET.
120Hz is too low, I can easily see 120Hz flicker in my peripheral vision and I assume many others can too. (Peripheral vision seems to be more sensitive to flicker…).
I’d double it at a bare minimum, but really, what’s wrong with 1kHz?
As for why a heater? Well if the incandescents didn’t have this problem then the simplest thing to do is emulate them when necessary. Other solutions MAY be superior but you’d have to prove that they work at least as well as simple heat I’d say. I’d be worried that the wind-based solution could fail if wind is low or if there’s just a huge amount of snow.
I may be missing something in this story but the first question that entered my mind was: How did this all weather product make it out of product development without undergoing adverse weather testing?
It seems basic to me.
photon without a Higgs (07:20:55) :
Record cold and snow in the past two days, Thursday and Friday, in the US. Florida is getting it the worst. But Watts Up With that red dot in Florida??
Location: West Palm Beach International Airport. What could be wrong there?
I went back for a week:
http://mapcenter.hamweather.com/records/7day/us.html?c=maxtemp,mintemp,lowmax,highmin,snow
2 record high temps in the south amonst record cold…both airports. I was in Charlotte, NC on Friday, and they tied and probably broke the record for most days in a row below 20. I’m at home again and watching snow fall for the 7th day in a row. It hasn’t gotten above freezing here in 10 days, for an area with average temperatures in the 40s for this time of year.
signing off from the “weather is not climate” channel.
Steve
A classic case of
“Sub-optimising the whole system by optimising a subsystem”
Why don’t the traffic folk ensure that they have someone who thinks ‘systems’?
Redesign the LED light elements to be installed at an angle so that snow/rain falls off, and redo the hoods to make sure that snow/ice can fall directly down and out of the beam. While you are at it, design an LED unit that has Red, Orange, Green arrays all together. You will then only need one lamphouse!
Attempts to put heating elements in existing housings seems to be a retrograde bodge. How does anyone tell if the heating element fails and the LED ices up? Why not use an incandescent bulb? Wow, light and heat at the same time, and anyone can tell if it has failed! Duh ….
And while you are at it, install more roundabouts. Replace those scary mutiple lane light-controlled X-roads, and the frightful T-bone smashes. Make the traffic flow better.
For those who question the temperature at Palm Beach Airport, or other airports… The ASOS/AWOS temperature sensors are fan aspirated. Since, when they installed the new Dewpoint Sensors, they did not turn off the mirror cooler in the HO 1088 temperature sensor, if an aspirator fan failed, you would, especially during low wind conditions, get high erronious temperature readings from the temperature sensor.
Been there, done that. We had it happen at an airport out west, a couple of months ago… The indicated high temperature was in the 50s and 60s, while highs at other sites surrounding it were in the 20s and low 30s. Also, some other sites (RAWS and Highway measuring sites) in the vicinity were in the 20s and 30s.
All this was without a “fault indicator flag” being set on the ASOS site. Apparently, there is no sensor/air flow sensor in the HO 1088.
“Butch (04:03:02) :
I may be missing something in this story but the first question that entered my mind was: How did this all weather product make it out of product development without undergoing adverse weather testing?”
Some design decisions are bizzare to say the least. The center LED brake light array on my car is not readily user replaceable. In fact, it requires the total replacement of a trim panel, including painting and finishing. In my case, it took two attempts by (2) body shops and two complete trim panels. The panels used are adhesive and must be replaced if removed.
Steve M. From TN (05:53:02) :
jimH (07:05:31) :
Ok, ok,……but what about the red dot in Roswell? 😉
“jimH (07:05:31) :
[…]
All this was without a “fault indicator flag” being set on the ASOS site. Apparently, there is no sensor/air flow sensor in the HO 1088.”
I always had the impression that it’s pretty safety critical for an airport to monitor temperatures. Is that not so?
supercritical (06:20:20) :
A classic case of
“Sub-optimising the whole system by optimising a subsystem”
Why don’t the traffic folk ensure that they have someone who thinks ’systems’?
Redesign the LED light elements to be installed at an angle so that snow/rain falls off, and redo the hoods to make sure that snow/ice can fall directly down and out of the beam. While you are at it, design an LED unit that has Red, Orange, Green arrays all together. You will then only need one lamphouse!
Then you get the added advantage that folks who are red green color blind will lose their location clue (ie which color light is which based on position rather than color ) and will have no idea what the light is trying to tell them under some conditions. And you have the added advantage of introducing a single point failure, if that one light goes out you lose all three lights, where on a conventional 3 element light if one dies, most of the time the other 2 are still working.
That is also a systems decision ( and a human engineering consideration ). What is most efficient for the electronics and engineering may not be an ideal human interface design because of human factors.
Larry
Someone should have consulted an engineer before plunging headlong into the new green jobs of “scraping snow and ice off the led traffic lights”.
Redesign the fixtures at huge costs, else you need heaters for the new “green” energy saving lights. Isn’t this how it works out, green is more costly than what is done now.
Come to think of it, I wonder if any engineers were consulted about ethanol, windmills and solar panels. They could calculate for you whether you were actually gaining in the energy equation, or were you simply adding ‘green make work jobs’.
“tarpon (10:18:48) :
[…]
Come to think of it, I wonder if any engineers were consulted about ethanol, windmills and solar panels. They could calculate for you whether you were actually gaining in the energy equation, or were you simply adding ‘green make work jobs’.”
They all produce more energy than was needed to set them up. It’s just pretty expensive because often it’s not that much MORE energy than was used to create them. As i said in a different thread: At the beginning of the oil age, they got 100 calories back for every calorie invested. ATM they’re down to 1:10 because the low hanging fruit has been eaten and new developments are more energy-intensive.
I don’t have actual numbers for the ratios in wind and solar, but an estimate for bio fuel was about 1:3. In mankinds history, societies have collapsed when their energy harvesting efficiency fell below 1:3 so biofuel is surely barely viable energetically, and unviable economically.
This isn’t the only oversight with LED’s the same goes with street lights. Communities all over the country have converted to LED street lights. The problem is that the street lights were spaced the coverage offered by incandescents. When the convert to LEDs which offer less coverage the street and side walks have darks spots. Criminals all over the country, drug dealers, prostitutes, muggers are figuring out that they can use the dark sports to their advantage.
Jeff Id (07:45:22) :
“All they need to do is put a sensor which detects when temps drop below 32 and activate a resistive non-light emitting heat source. Problem solved.”
Why not be logical and activate a light-emitting heat source, like an incandesescent bulb, to help visibility and signalling?
DirkH (09:33:43) :
“jimH (07:05:31) :
[…]
All this was without a “fault indicator flag” being set on the ASOS site. Apparently, there is no sensor/air flow sensor in the HO 1088.”
I always had the impression that it’s pretty safety critical for an airport to monitor temperatures. Is that not so?
Absolutely true. Aircraft takeoff and landing performance planning are based on pressure altitude (a function of temperature), and calm winds coupled with the local temperature converging with the dew point means you can expect fog in the summer and frost in the winter.
And you haven’t lived until you’ve encountered ice-fog during your approach to the airport…
I wonder how much gas energy is wasted by unnecessary stopping in zero cross traffic conditions. More lights should be blinking caution and not mandetory stops at all times, besides, a blinking caution yellow will use 50% less energy than a stop or go light.
Snow has to fall horizontally enough to cover the traffic light (usually protected from vertical snow). This is not an usual snow fall, but rather a snow storm.
In such condition, all vital traffic signs like STOP are covered too.
And train warning lights can be covered too, because they are turned on only when there is a train, and off most of the time->snow won’t melt.
I just wonder who, after a snow storm covered all vertical signs, is stupid enough to go through a crossroad fast enough to kill another driver.
LED traffic lights is a good idea. It just need an additional system to prevent this specific problem. We talk here about billions watts being spent for nothing. We don’t talk here about uber green senseless technology, but efficiency improvement. Light bulb is maybe the only electrical device which remained mostly as primitive as 100 years ago.
You want light? Use a LED.
You want a heating system to remove snow 1 day per year? Add a heating resistor and a sensor, or simply a soft, light transparent film hanging in front of the light so snow won’t stick.
And don’t forget that incandescence light bulbs heat is certainly a problem in summer, and traffic lights have to be designed to take this into account. There is certainly a cost related to heat protection too.
Being color blind has required me to observe traffic movement well in advance of the intersection. If the other ignorant drivers would do likewise instead of fixating on their hood ornament, this would not be a problem.
Progress. Most solutions have tradeoffs. We also had a lot of ice thrown from windmill blades during the storms. The tip of a wind generator blade can hit 180 miles per hour and toss ice build op a long distance.
But the brochures claim they are perfect and safe.
Well anybody who thinks LED traffic lights save energy, just hasn’t sat behind enough RED lights, with absolutely no traffic moving through the intersection in any direction. Any two year old child can make a better traffic decisions than most of these traffic lights. Remember they are programmed by the same sort of people who give us Micro$oft Windows.
The problem with LED traffic lights is that RED came first, since GREEN was hard to make, and yellow even harder. So most traffic lights are set up to be mostly red in most directions most of the time.
Of course it wouldn’t hurt to give drivers a driving test before giving them a driving license.
Every place I have ever lived in the USA, any time traffic lights were out for any reason, drivers were supposed to treat them as a four way stop sign. Usually when that happens, the traffic moves better than when the lights are working.
City politicians don’t know any way to improve traffic, other than putting in more lights. And they breed; you put in lights at one intersection, and it creates a traffic problem at another intersection, so you go and put some more in there.
The trouble is, these days US public schools don’t teach simple problem solving any more. They are into these group projects, where nobody is required to think for themselves, and solve a problem on their own. If they put up traffic lights to tell people when to jump off a cliff, a whole lot of people would follow the lights instructions.
Talk about a non problem; snow covering a traffic light. Those hoods are put there to stop drivers from seeing the cross street lights so they can’t tell which direction has the green light. If you drive into any intersection without knowing who has a green light, then you are a candidate for a Darwin award.
Two videos from Youtube: One an intersection without traffic lights and one with. Interesting results:
http://www.youtube.com/watch?v=_Yj36G9ukDc without lights
http://www.youtube.com/watch?v=H2JFL1Sk21Y with lights
The LED system does save power, but that is not their primary advantage.
They also fail less often, but more often than manufacturers claim. (OK they have a warranty).
**The Main Safety Advantage to LED traffic lights is that an entire intersection can be battery powered in an electric outage. These batteries last 4-6 hours, and are automatic. If the outage lasts longer, the DPW just sends a man by with a charged battery. This simple fact has very likely saved lives.
After hurricanes have passed through here, we had cops at major intersections directing traffic for hours. They used cartons of road flares at night. What a scene it was! This cost of overtime alone probably excedes the price of the LED retrofit.
One last thing….why not de-ice like they do with airplanes? Just think how the kids would like to see a truck come by squirting a hose line at the lights!
This is a very small issue compared to the benefits of the units. I always thought that traffic lights were a perfect match to LEDs, a single wavelength light source.
On the rare occasion you have horizontal snow to the extent required to cover the lights, it’s not just the lights that get covered but every safety sign, etc. Not to mention general visibility is going to be terrible while it happens.
In all the years I’ve seen the LEDs I’ve NEVER seen this problem, and we get plenty of snow and snow storms here.
No government, or company for that matter, builds out infrastructure for the express purpose of taking care of the 0.01% event, “make due” is usually the only cost effective way. If it is actually common in an area, I’m sure a solution will be forthcoming to resolve this apparent deficiency. I would say, available winter maintenance money is better spent in prompt good snow removal.