Technological innovation has cut many of the trickiest environmental Gordian knots. As readers of SuperFreakonomics know, at the end of the 19th century the American city was tottering on the brink of environmental catastrophe. The cause: byproducts of transportation, specifically the horse-drawn variety (more here). Manure, flies, accidents and disease abounded, until the timely arrival of a technology which at the time was hailed as an environmental savior -- the internal combustion automobile.
Of course, those who celebrated did not fully realize that the miracle technology would bring troublesome consequences of its own. Today we face the specter of global warming, to which the automobile is an important contributor.
Just like our ancestors in the fin-de-siecle city, we are using new technology to fight the shortcomings of the old. And unsurprisingly, like our ancestors, we are bound to find that our technological fixes can have unintended, malign consequences of their own.
Consider the seemingly noncontroversial replacement of conventional traffic signals with LED bulbs. What
I'm surprised - in fact, shocked - that you didn't do a basic cost vs. benefit analysis using statistical values of life for the US. (I think SF even throws out $7M/life but you could use a range from some of the major papers in this field.). From what I can tell, you have all the info to at least pencil out an estimate rather than saying "Is it worth it? Probably, but that is little consolation for those hurt and killed in these crashes." That is a lame argument. This is supposedly an economics blog.
ResponderEliminarI read LED Ashtray and was quite intrigued as to what the purpose would be. Still an interesting case of unintended consequences.
ResponderEliminarYou know, I noticed the traffic lights near my apartment getting gummed up with snow a few times this Winter, but I never thought to attribute it to them being switched to LEDs a few months ago.
ResponderEliminarIt's just a little luminaire engineering problem. I am sure they already have begun making changes to prevent this from happening.
ResponderEliminaryeah, 100 years from now people are gonna giggle at this problem- automated transportation systems made this obsolete- brought a new wrinkle to the problem of crashing, however
ResponderEliminarAs well espoused in SuperFreakonomics the simplest answers are usually the best. In this case if we rethink our traffic light fixture I'm sure we could come up with a design that would prevent snow/ice buildup. I'm no engineer, but I would think angling the light fixture downward would help allow snow to slide off easier, minimizing buildup. Maybe IV can come up with something even more simple and cheap!
ResponderEliminarLEDs are also an issue at airports. They don't give off heat and thus many FLIR heads up display systems used to aid pilots in low-visibility aren't able to pick up new LED runway lights through the fog because they don't create an IR signature for the systems to pick up.
ResponderEliminarYour advice 'motorists should know to exercise caution and treat them as if they are stop signs' is the same one that should be followed when the lights are out, but is simply not enough for this situation.
ResponderEliminarBear in mind that unlike when the lights are out in ALL directions, snow obscured lights are usually only a problem in ONE direction, thus the obscured person is treating the intersection as a stop sign and other drivers think the intersection is operating normally and are obeying their signals. If it is your direction that is obscured, do not assume that traffic that is stopped will stay stopped or that traffic that is moving toward the intersection will stop. Treat the intersection as if you are the frog in a real-life version of Frogger.
This doesn't sound like a problem without a solution. I don't understand why an additional heat coil is such a problem in terms of energy. It would not be difficult to tie this to a temperature sensor, or even better a sensor that detects how much light gets in and out of the fixture, so that the extra energy use is minimal and LED's would still save energy/money.
ResponderEliminarI'd like to know the stats on how many lives are saved because the LED's don't burn out.
ResponderEliminarIf the LED is covered in snow wouldn't the proper thing be to treat it as a stop sign? This seems like kind of a non-issue because we already have guidelines for what to do if a signal is out.
It's amazing how fast we forget the past. A simple solution to a reoccurring problem. In the late 50's, heating elements were poured into sidewalks outside entrances of large department stores to help melt ice and snow. A simple application of a heating element which is triggered by two factors of temperature combined with an optical sensor. The sensor sends an infrared light via a LED across the opening if it is diffused it turns on the first triggering, the next is by the temperature. When the snow builds up, on goes the heating elements. Clear ice is not a factor as it still allows the light to be seen. A 1950's solution to a 2010 problem. 60 years in teh making.
ResponderEliminarThe article states: "Heating up the LEDs would help defeat the purpose of saving energy."
ResponderEliminarFirst, it would not defeat the purpose of saving money by having less need to replace burnt-out bulbs.
Second, could not the LED heaters be hooked up to thermostats or switches? During summers, no energy would be wasted on heat. During winters, the heaters could run constantly, or only when it was a cold day, or only when it was snowing, or some other such variation. The technical equipment needed for each variation I just mentioned would probably vary in design and cost, but I have to imagine that at least some of those solutions would be reasonably easy to implement and cost effective overall.
Would electric-powered cars have problems in very cold weather? I know gasoline has a low freezing point which allows cars to keep running. Do currents run significantly slower in low temperatures?
ResponderEliminarP.S. I don't drive so forgive any ignorance.
Just seems like more of the same to me. You do realize that traffic lights can go out for other reasons and in many types of weather.
ResponderEliminarIf they would just go back to having a cop at every intersection, this could be solved I tell you!
Really, isn't it more the fault of the drivers not paying attention to the road?
Make the green lights LEDs, but keep the red and yellow as the regular hot ones. It doesn't matter much if you can't see a green light.
ResponderEliminarYou only save maybe 40% as much, but the change isn't instantaneous anyway. By the time you've changed all the green lights to LEDs, a technical solution might be available for the others.
IMHO, any analysis of accidents caused by snowed-up LED lights would be useless without a comparison to the number of accidents caused by burned-out incandescent bulbs.
ResponderEliminarAlso, as for the energy penalty of having a heater on the light...it could be designed to only come on when needed. You could have a sensor that would detect the decreased light output and switch on the heat, or at least notify the DPW to come and clean the light. It would probably not add that much to the cost of the light, especially compared to the cost of a large array of high-efficiency LED emitters.
Wow, the manufacturer and the customer(government) forgot to do the proper engineering. Having been an engineer on a Satellite earth station network in Alaska I can safely say that the heaters were built in to the antennas and feedhorns. They only run under the right combination of moisture and temperature. This is some of the worst places in the world for rime ice and snow. Building a little heater- sensor in to a streetlight would be a piece of cake and it would only run 1% of the time annually. This is not economics. This is common sense.
ResponderEliminarThis is a 'humans not following the rules' problem. If you can't see the traffic light or it is not functioning, you are supposed to treat the intersection as an all-way stop.
ResponderEliminarOne of the best punny titles ever on this blog.
ResponderEliminarThis is pretty funny since hand held devices used by drivers cause far more deadly accidents than LED lighting...by the way the LED products do not leach toxic mercury into the water supply.
ResponderEliminarIf people paid attention to safe driving habits and observed rules of the road and common courtesy, we may not need all the signal lights and distracting signage people require so they know how to behave behind the wheel.
Heating/snow removal tech has been around in security cameras for quite a while now, it should be easy enough to modify it and put it in traffic lights.
ResponderEliminarJust add a wiper, like a windshield wiper.
ResponderEliminarAlso, hyperbright LEDs have saved many lives in automotive accidents. Because they turn on instantly and don't need the 300mS or so that an incadescent filament needs to warm up, when used as brakelights they give following drivers an edge, especially with the eye-level lights that became common as LEDs spread. It's not many lives saved - one estimate is around fifty a year, worldwide - but the inventor of the hyperbright LED is on record as saying that this is the single most satisfying aspect of his work.
ResponderEliminarNot sure what he feels about frozen traffic lights.
R
Seems to me this calls for an application of Einstein's exhortation to the effect that things should be made as simple
ResponderEliminaras possible, and no simpler.
In places where heat as well as light is desirable, some of the time, simply fashion a hybrid signal, with a thermostatic
control that turns on the [primarily] heat radiating elements
only when needed. For the runway application, why cannot
the lighting units be arrays of both visible and infra-red emitting devices?
And anyway, while I was on a tour of a prominent lighting research center (admittedly this was about 8 years ago), the scientists indicated they were not ready to release their LED traffic signals because they got too hot. Apparently they sovled this problem. But, I did wonder at the time how the LED arrays were going to save electricity, if the efficiency ratio of light to heat (or visible to infra-red) was so low...
Here in Minnesota, we've had LED traffic signals for years. I started noticing them a decade ago. As far as I can tell, they don't seem to get occluded significantly more than traditional lights. Perhaps the folks in Chicago should find out what (if anything) the Minnesotans are doing differently.
ResponderEliminarPlease. LED traffic lights are not the only ones that have problems in heavy snow storms. I grew up in northern Wisconsin and the Upper Peninsula of Michigan. Heavy snow storms and/or blowing snow often blocked the lenses of the old incandescent traffic lights as well. Everyone knew to be extra careful and alert for traffic under these conditions.
ResponderEliminarFurther, installing heaters or other such devices to clear the snow is unnecessary - assuming that we really need to do anything besides take responsibility for our own safety. A redesign of the lens to deflect the snow rather than allowing it to accumulate is all that is necessary - and then only in areas where the problem may occur.
LEDs are much brighter than incandescent lights... surely that has prevented accidents where with the old lights, drivers would not know which light is on.
ResponderEliminarThen there's the task of figuring out how much less air pollution is generated by switching over to LED lights (don't need to burn as much coal, after all.). I suspect you'll come out roughly even in terms of overall effect to human health.
Professor Victor Petrenko at Dartmouth has come up with electrical de-icing technology that doesn't depend on heating the ice to melt it (changing the state of water is energy intense), but by changing the adhesive properties of ice using low power electric fields. This seems like a good possible application.
ResponderEliminarengineering.dartmouth.edu/news-events/ice-engg.html
"If you can
ResponderEliminarMy dad is color blind and can't see the green LED lights. Thankfully they haven't switched positions on him, so he knows which one is green. Just another thought to add to the discussion.
ResponderEliminar"Perhaps new technological solutions will be found, as has happened to an extent with the automobile. In the mean time, hopefully motorists in colder regions will lengthen their lives by adjusting to this new hazard. Or by moving from Chicago to LA, the way I did."
ResponderEliminarYes, let them eat cake.
LEDs don't emit heat
ResponderEliminarHeaters? Electric fields? So much complexity and over-engineering. More points of failure.
ResponderEliminarThe lights already have hoods. Put a glass window in the hood, sloping from the base of the light to the tip of the hood. Show and ice can't collect on it. Maybe vent it so the waste heat from the back of the LED array can seep into the enclosed space for some warming.
I should add; or, better yet, rebuild the intersection as a roundabout. No lights to maintain or de-ice. Just yield signs which, fortunately, keep their shape when iced over.
ResponderEliminar#25: The snow is colder in Minnesota and therefore less sticky.
ResponderEliminarThere are ~40000 traffic fatalities in the US each year, so perhaps 0.01% are due to this problem.
However, since there is a simple and cheap technical solution there is not reason to to implement it:
On the shroud over each light, a number of LED/photodiode pairs should be place. The LED can be blinked once every few seconds. The photodiode will detect significanly more light during the blink if there is snow packed into the shroud. If the controller detects packed snow it turns on a heater to melt it.
Even though this may sound complex, the parts required are cheap, especially compared to the cost of the traffic light as a whole.
LED stop lights can easily be redesigned to shed snow. The problem is using LEDs as replacement bulbs without modifying the lamp.
ResponderEliminarOverlooked in your equation is the extra pollution created to power conventional incandescent or halogen lights. An estimated 10,000 to 30,000 US citizens die every year because of pollution emitted by coal power plants. But air pollution and the people killed by it is merely an externality according to economists.
The first problems you stated -- manure, disease, global warming -- all have an environmental impact. The problem of crashing due to obscured lights is more of a problem of human fragility, and actually benefits the environment by slowing overpopulation. Just sayin'...
ResponderEliminarWe should bring the lights in out of the cold. I propose installing wireless access points at intersections. The WAPs will broadcast appropriate information that can be displayed on a small panel on the dashboard.
ResponderEliminarThis seems like a lot of work, but it's a great step towards allowing cars to automatically negotiate intersections. It would also require much less energy and maintenance than even LED lights. As an added bonus, we could completely get rid of the huge ugly poles.
The WAPs could also be configured to give much richer information than a standard light: traffic and road conditions, speed limits, or any other info the DoT would want to broadcast.
One problem it appears (I think) people are missing is that they spent all sorts of real money replacing the old lights with LED ones.
ResponderEliminarWhile it's easy to imagine a technological fix, it seems quite likely that that will cost extra money to implement (and take a fair amount of time too).
Anyway, "stuff" happens. Even if this change incurs an unexpected extra cost (one that will now have to be figured into the cost savings), in the long run, the LEDs will likely be better (and cheaper).
Of course, the problem that is occurring in some places isn't necessarily occurring everywhere.
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ResponderEliminarClearly, the best scenario would have been to have known about this issue before hand. That way, the LED light unit could have been designed with the heating coil electronics built-in. No doubt, future designs might incorporate it.
ResponderEliminarOf course, one could go to far in correcting this problem by putting in heating-coils where they aren't needed!
"My dad is color blind and can
ResponderEliminarIf it is snowing and you don't know the area, you would probably not know where a traffic signal is. Even being familiar with an area doesn't mean you would remember every signal location, especially at night.
ResponderEliminarI once read that experts predicted economic growth could be sustained a 3% rate for only a few more years. The reason given was at that point it would require all of the farm land in the world to feed the horses necessary to sustain that level of eonomic activity. NO thought to the elimination of the horse by the horseless carriage.
ResponderEliminarWe don't know what will come next as a solution to today's problems. As your article very clearly points out there may be another issue to deal with as a result of the solution.
Then we'll find another and another...
Simple: Just have a heater that goes on periodically. Then it doesn't waste energy all the time, but still will melt snow.
ResponderEliminarI live in Canada and we have LED traffic lights in Toronto and the surrounding area.... NO problems... Chicago traffic lights are likely designed in a way that this is an issue
ResponderEliminar"...some consequences, even deadly ones, will have to be lived with."
ResponderEliminarIs the irony in that statement intentional?
Um, wouldn't the same snow that covers the red lens also cover the green one, as well? Or do upper Midwesterner just assume that if they can't see the red light, then it is perfectly safe to plow right on through the intersection?
ResponderEliminarBut, to be fair, it might serve some evolutionary "purpose," helping us to sideline the weaker ones among us.
compare the number of deaths due to frozen/snow covered LED traffic lights to the number of deaths caused by a burned out light bulb. Then I will make my decision as to LED is "safer" or not.
ResponderEliminarWhy can't we just put a piece of glas or plastic over the stoplight housing so that snow can't get in there in the first place?
ResponderEliminarWhy all the waste of heaters that can burn out and thermostats that require electronics when a simple, small, lightweight, roof over the light along with slick glass would solve all but the most awful of snow buildup. This isn't rocket science and doesn't require the most complex of fixes.
ResponderEliminarAnother method would be to replace every other LED with a regular bulb thereby providing the heat necessary to melt the snow. Again, simple.
Another problem with "green" LEDs is that they apparently encourage stupidity:
ResponderEliminarAn office near me spent $200 on buying twinkle lights as decorations for their holiday party. They bought the expensive LED lights "because we're a green company".
The lights were in use for four hours. I figure that they spent an extra $100 to get chemically intensive "green" LEDs to save less than $2 in electricity.
Roughly, $101 per light times 3 times 4 = $1200 for a four-way traffic light.
ResponderEliminarledtronics.com/products/ProductsDetails.aspx?WP=C641K622
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ResponderEliminar(They
ResponderEliminarCars have had small heating elements built into the windshields (they look like wires in the glass, under the wipers on the front, across the entire window in the back) that produce just enough heat to melt snow and ice. It doesn't take much. They don't even feel warm to the touch. I can't see how it's possible that they use much energy, given that they work on a car's electrical system.
ResponderEliminarTraffic lights with similar heating elements should be developed for cities that experience cold snowy winters. I doubt that sensors to turn them on or off depending on conditions would be worth the cost and would be likely to fail. On the other hand, wiring some sort of switch could run into difficulties: fewer switches would mean lots of wiring, more switches would take more manhours to turn them on and off. But I'm sure there must be a solution.
why not just case the LEDs in a perfectly flat, vertical panel with no ridges for the snow to acculate on? Even better, an inverted pyramid shape.
ResponderEliminar"Second, could not the LED heaters be hooked up to thermostats or switches? During summers, no energy would be wasted on heat. During winters, the heaters could run constantly, or only when it was a cold day, or only when it was snowing, or some other such variation."
ResponderEliminarNorm,
the LED works well under cold condition (more efficient). When it get hot, it reduce the light emitting efficiency and change the wavelength of the output. Look like the problem is the lens (or cover glass), it might be in corporate some kindly of heating elements, such as the ice melting mechanism used in your car rare window. But keep the LED cool. Engineer of the traffic light design group should know the ins and outs of the device=LED prior to integrated into the lamp. Poor fundamental understanding of the technology is at fault. My view is that the quality of engineering force at USA went down hill last 20 years. The designers in particular. Scary time now, and wasteful resources in the grand scale due to poor training at University level have years to come. (Don't tell me SAT GMAT score or other university rating or patent counts. None of them is a good scale to measure the excellence of Applied Engineering work force).
Coat the exposed lens (slanted to shed snow and ice) with Teflon.
ResponderEliminar#38,39, et al,
ResponderEliminarOr ditch the majority of traffic lights (and resulting infrastructure costs of electricity, maintenance, crash repair, timing computer, etc) for the European style local travel round-a-bout yield only intersection. This would be safer for drivers too by eliminating red light running t-bone crashes for the lower speed fender glancing blow type crashes.
I never understood the round-a-bout until I saw one in Italy being constructed to ~replace~ a 4way light controlled intersection. US highway designers screwed up by originally using traffic circles in high speed state highways versus low speed local traffic areas where traffic calming benefits the nearby population.
#54- I have seen burn out traffic light bulbs - that is why most light controlled intersections have more than one light versus the original 1900s single 4 way light hung over the center of an intersection.