LED Signals Seen as Potential Hazard

NYTimes:

LED Signals Seen as Potential Hazard

CHICAGO — Last April, the driver of a pickup truck approaching an intersection in the far western suburb of Oswego went past a red light obscured by snow and struck a 34-year-old woman turning left in her car.
The woman died and four other people were injured in the accident, which was among the first to raise concerns here and around the Midwest about a relatively new driving hazard related to inclement weather: traffic signals, like those in Oswego, that use light-emitting diodes, known as LEDs.

The new lighting is part of a fast-growing trend in environmentalism. LED bulbs use less energy, last longer and are more visible than their predecessors. They are also known to require less maintenance. But they do not emit nearly as much heat as conventional bulbs, allowing snow and ice to accumulate more easily in certain conditions.
As winter storms roared through the country’s midsection and pummeled the East Coast, officials said they were on the alert for LEDs.

In Illinois, Iowa, Minnesota, Wisconsin and other states, special efforts are being made to ensure that the signals do not pose an undue threat to drivers.
“Do I think the accident would have happened if the light was not covered in snow?” said Detective Rob Sherwood of the Oswego Police Department, referring to the accident in April. “I’d be willing to bet that it would not have happened if the driver that went through the light had an unobstructed view of the signal. It was the first indication in this community that the LED lights were not melting the snow.”

In the last seven years, Wisconsin has converted more than 90 percent of the lighting under state control to LED bulbs.

For those of you in sunnier climes, this is how energy efficiency can be lethal:

http://graphics8.nytimes.com/images/2010/01/02/us/02lights_CA0/articleInline.jpg

I'm wondering about the lights on emergency vehicles which apparently are also switching to LEDs, they are now on a bar (which could easily be covered w/snow) rather than the old rotating lights.

Wow. Come on, it can't be that much more expensive to use regular bulbs! :shrug:

Whatever little expense is worth it if it saves lives.

Interesting.

The universal rule in cases when traffic lights are out of order is to treat the intersection as a four-way stop.

Seems to me the middle of a snow storm is a good time to be particularly alert to signals being out of order -- or obscured by snow.

Perhaps it is careless driving, not LED technology, that presents the hazard.

Just my $.02

I agree with the preceding post.

Strange as it seems, too, a little volunteerism might not hurt either, like getting a pole and cleaning the lights or with the ubiquitous cell phones, calling in the problem to the central dispatch or police.

Similar technology can be produced to detect and resistively heat such lights. In fact, all that is needed is to increase the current through an LED for the duration of the snow or ice period. LEDs are normally operated at an optimum current level for sake of energy. It would be almost trivial to increase the current for sake of inclimate weather. One added component would do it automatically, a thermistor.

It’s hard to tell from the story, but if she was driving through an active mid-western storm, about the only thing you usually can see are the lights themselves. The pole and casing can be completely obscured by the weather. We used to call them ‘ghost lights’.

[quote="crm114, post:3, topic:181727"]
Interesting.

The universal rule in cases when traffic lights are out of order is to treat the intersection as a four-way stop.

[/quote]

I saw another report on this and it appears that snow is not covering all the lights in all directions to the same degree. So one direction may see the lights as normal and another direction treating it as a four-way and you have a big problem.

I've lived my entire life in the snowbelt, and I say that if the snow and wind are such that you cannot see a "dead" stoplight in time, you are driving recklessly. Slow down and treat all dead lights as 4 way stops, per the law.

LED's last virtually forever and, over time will present FEWER 'no light' circumstances than incandescent bulbs that burn out far too often. This just another reporter looking to make a name for himself or a lawyer setting up for a lawsuit.

LED lamps may cost four to ten time more than a conventional lamp BUT “payback” occurs in most cases in less than 5 years…the LED lamps last…operating optimally around 30 years…of course that has yet to be tested since LED lamps have only recently been available due to technology. Within 10 years most lighting fixtures here in the US will be LED technology…a huge saving on energy.

Typically one can expect to get 75-100 watts of light out of a 6-10 watt lamp…the energy savings…which cuts down on expendible resources to generate the energy are phenominal.

None of which is why LEDs are being so quickly adopted for stop lights. That is more about instant illumination (versus the minute pause with conventional bulbs) and the drastic reduction in ‘burnt bulbs’ and the associated traffic hazards and labor costs.

[quote="manualman, post:10, topic:181727"]
None of which is why LEDs are being so quickly adopted for stop lights. That is more about instant illumination (versus the minute pause with conventional bulbs) and the drastic reduction in 'burnt bulbs' and the associated traffic hazards and labor costs.

[/quote]

10% the energy cost IS a compelling reason. It's a major part of why they are being adopted. Keep in mind, a typical traffic bulb is about a hundred watts, and a single head intersection runs 4 bulbs at a time. So about 400 watts. that's .4kwh per hour, 24 hours a day; 9.6 kwh a day, or around 30 to 80 cents a day. Given that a single intersection may be up to 5x as many heads... now drop the cost to 5 cents per day, multiply it out by the thousands of controlled intersections in a city... 500 to 8000 dollars a day saved... easily a million dollars a year in energy reductions for a major city. Chicago saves $2,500,000 a year on energy costs, and 100,000 on materials. (The article doesn't cite the reduced cost of materials installation.)

The reduced costs of LED over incandescent for hardware (12x use hours), reliability (less subject to vibration damage, LED arrays often remain functional after some damage), man hours for installation (takes about 10 min to change a bulb; if you're doing it 1/10th as often, you need about 1/8th the manpower, with manpoer loss due to longer travel times between bulbs), you need less storage space for replacements, and can have even lower energy costs for symbol-lights (arrows, etc).

And I've seen incandescent signals snow-blocked, too.

References
members.misty.com/don/lede.html
c40cities.org/bestpractices/lighting/chicago_led.jsp

We have lots of snow here in Ontario, and lots of the traffic lights use LEDs. I haven’t seen a single case of snow blocking the view of the traffic light yet.

Maybe the glare shield around the light is shaped differently here, so it doesn’t collect snow. I’ve never heard of this being a problem.

Everyone is using LED lights now, they make a lot of sense for all sorts of reasons.

[quote="Aramis, post:11, topic:181727"]
10% the energy cost IS a compelling reason. It's a major part of why they are being adopted.

[/quote]

No it's not. It costs about $175,000 to install signals at a significant intersection (with left turn, detector loops, emergency vehicle override, etc). I help design them in my job. When you are spending that kind of dough, nobody notices if you spend a few thousnad more on LED instead of conventional. The energy efficiency is a nice side benefit with PR pizzaz. The driving force is the reliability. It only takes moments to change a bulb, but it costs big bucks to stop the traffic, deploy the lift truck, etc......

If energy efficiency were the driving force, you'd see the same or MORE expense/effort going into replacing street light luminaires with LED lamps. The market share for LED light pole luminaires is about 2% versus nearly 95% for intersection signals. Mostly because it nearly doubles the cost of the fixture.

City PR departments like to crow about how green they are, but the truth isn't that hard to find. Look at the money.

There are “retrofit” companies which have developed LED technology to also retrofit “cobra heads” and “shoe box” luminaires. Not only are the housings and poles “saved” by being reused, thus decreasing the number of castings put into our landfills, but the energy savings are very substantial.

LED technology has developed “replacement” lamps for street lighting…they have integral LED drivers and screw in sockets just as normal incandescent lamps do…same fixture can be utilized…dramatic energy cost savings as well as drastic reduction in maintenance costs.

The only hardware being replaced is the bulb.

5 minitues with Google and the money IS accounted for. Chicago cites M$2.2 in enery savings and only K$100 in hardware savings. A factor of 20. Anchorage has had a similar (but much lower totals in both columns) savings, and I’ve not seen a head replaced. Only the bulbs.

And changing a bulb, even on a busy road, can often be done with only a single lane closed; I’ve never seen the highway closed for a bulb change (in fact, they park the picker on the sidewalk or the island for the Airport Heights and Glenn Highway intersection).

Some heads are even mixed… incandescent ambers, LED reds and greens, since the ambers haven’t burned out yet. It doesn’t matter to the extant switchbox whether the lamp is LED or Incandescent… a new one might be unable to switch the current for a 160w system, but that’s not a heap of current, and so even then it’s unlikely.

[quote="Publisher, post:14, topic:181727"]
There are "retrofit" companies which have developed LED technology to also retrofit "cobra heads" and "shoe box" luminaires. Not only are the housings and poles "saved" by being reused, thus decreasing the number of castings put into our landfills, but the energy savings are very substantial.

LED technology has developed "replacement" lamps for street lighting...they have integral LED drivers and screw in sockets just as normal incandescent lamps do...same fixture can be utilized....dramatic energy cost savings as well as drastic reduction in maintenance costs.

[/quote]

Now go price 'em and come backand we'll talk. I'm telling you, very few owners are choosing LED lights so far because the payback time is still extreme. The exceptions being owners wanting to make PR statements such as LEED certification, etc.

Oh, there is no doubt they are still expensive…however they have decreased by half in the last 5 years and as technology advances the price will continue to go down…the retrofits for street lighting are around $500.00…a new LED fixture is around $550.00…new construction taking place in cities where LEED certification is required is finding the retrofits very enticing…not only do they get their LEED certification but they can be “green” as well, reusing the existing housings/castings and tout sustainability as an added feature.

Payback has been calculated to occure in 5 years or less…with a life expectancy of 30 years…and energy becoming a premium…those architects and engineers who wish to make a name for themselves within the specifier community are taking advantage of LED specification on new projects.

That last paragraph sounds suspiciously like certain cut sheets I have read recently. What do you do for a living? ;)

[quote="manualman, post:18, topic:181727"]
That last paragraph sounds suspiciously like certain cut sheets I have read recently. What do you do for a living? ;)

[/quote]

I work for a lighting design agency. Some of the cities I've worked with here in the NW have discovered first hand the payback and sustainability of LED products aren't too far off what the manufacturers are touting...of course we haven't reached the 30 year mark to verify the life of LED's...I'll be "in the Presence" by then.:)

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