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.”
As the article said, the old incandescent bulbs would fail too. And not just during a heavy snow when folks know that they need to be cautious. Perhaps in the northern states the LED version could have a heat strip that would activate below a certain temperature. In the mean time, drivers that approach a stoplight protected intersection where neither red or green lights are visible should do as we did in the past when the incandescent bulbs failed. Be careful.
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There are roundabouts in the states–not many yet. They seem to work very well. Folks assume the responsibility for not crashing into each other instead of blindly responding to red and green lights.
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.
Tom (06:16:45) :
For once these are the unintended consequences of government doing something smart, than of government doing something stupid.
The proof is in the pudding. It was not smart.
Luke 7:35
“Yet wisdom is vindicated by all her children.”
Wisconsin of all places!
As an engineer for a city in western Oregon (the wet part of the state), I heard about the snow buildup issue on the LED lights a few years ago in trade publications. Since we don’t get much blowing snow it doesn’t pose a big problem here. I remember thinking that the folks in Wisconson and Minnesota might want to do something different. The LEDs are certainly much better lights since they are brigher and more reliable. Adding heating elements and some sort of temperature sensor is possible, but will almost certainly drasticly increase the cost for each LED “bulb”.
When the LED traffic signal bulbs start to fail, you will usually see a line or blotch of the individual LEDs “burned out” This is caused by a wiring fault somwhere in the LED bulb. The only fix to replace the entire bulb. I think some of that was the manufacturer’s learning curve since the problems took a few years to reveal themselves.
As far as energy use in absolute terms for traffic signals, I have always heard that the annual power bill for a non-LED traffic signal was around $1,500. A 80-90% reduction could add up for large cities with lots of traffic signals. Of course using 80% less power doesn’t lower you bill by 80% because of the base service charge the power company charges for just having a meter.
Also, the metal shields on the traffic signal lights are there to shade the lights from the sun for better visibility, not so much to direct the light forward (although it does help). Adding the curved plastic shield over the LED will keep the snow and ice off the LEDs, but I imagine that the plastic will get discollored over time, much like the headline covers on a used car, and make the lights appear less bright. I would also hate to have one fall off onto my car from 20 feet up.
This is an example of how changes in operations usually result in changes in secondary effects.
We do not live in a risk free society and every change you make in infrastructure leads to changes in risks.
For example the introduction of antilock brakes and stability control systems for cars do not significantly reduce the number of accidents, it just changes the type of accidents people get into. Before the antilock brake people would slide off turns they could not slow down for and stuff the car into some ones fence. Now they safely slow down enough to get most of the way through the turn and roll the car as it goes off the road. In some conditions the antilock brakes actually increase stopping distances, resulting in cars sliding into intersections that they should have been able to stop for, or increased numbers of rear end collisions at intersections, because of overshoot. It is all a choice of evils.
Here where I live, the law says if a stop light is not working or not visible, the intersection becomes a 4 way stop. The driver (if they recognize there is a blocked signal) should stop and look both ways before entering the intersection. That does not help much for the case where the driver does not recognize there is a signal and simply blows through the intersection, but the exact same failure can happen with the incandescent lights if they burn out, so this becomes pretty much a toss up.
Traffic signs like stop signs are also subject to exactly the same “covered with snow” problem when you have a wet blowing snow and temps are cold enough that the snow sticks to the front of the signs. People manage to figure that out too.
I have noticed here where I live that a good number of traffic lights no longer have the shades on them. Perhaps that is the reason.
Like all new technology over time they will figure out work-arounds for these problems like removing the shades, and heaters of some sort.
Larry
The LEDs are probably a good idea because they reduce cost for electricity and maintenance. And they should be more reliable since a failure of 1 LED will not cause the light to go black. I think an engineered solution can be found through better design of the hood and lens. Some plastics like Teflon and polypropylene are naturally slippery and would be more resistant to the sticking snow problem. I wouldn’t give up on the LEDs.
Most traffic signal LEDs are retrofits of existing traffic signal fixtures, and with the cost of energy today, these retrofits make a lot of sense economically. If the entire fixture had to be replaced, I’m afraid the economics would stop many of these changes.
However, as Gail Combs (08:21:11) : noted,
”
I’m sure a very smart engineer out there somewhere will develop a design that doesn’t allow snow to accumulate (or stick to the surface in the case of wind driven snow) and be cost-effective enough to allow the replacement of the older design fixture.
Then the fight will be with the government agencies that will have to approve the new design!
Sorry to be pedantic, but I think you’ve an extraneous apostrophe in the post title.
ABC used it to denote the “Stoplights’ … Problem” which is correct, if annoyingly anthropomorphic. It is unnecessary in your headline.
Also, it’s about -11F here; I’m attributing my grumpiness to that. Thanks!
[Fixed, thanks’ ~dbs, mod.]
I’ve noticed several LED stoplight conversions in New Hampshire over the past few years, but have never noticed a snowcovered lamp. Most of our windblown snow is cold and dry and won’t accumulate, I’m sure near the rain/snow line it could be a significant problem.
So, solutions might include heaters to avoid temperatures around freezing and not heat below 25F or so. Changes to the light shade and covers could work well too.
I’ve only seen failed strings in the green lamps, they do run at a higher voltage than red, but I’m not sure about their efficiency. Some of the high power 3W white LEDs that have popped up in the last few years are mounted on heat sinks, and the low power ones certainly generate heat. I bought a white LED Christmas tree light string on sale after the 2008 season (something like $0.10 per white LED, an awesome price) and mounted 50 LEDs on a piece of perf. board. The LEDs do get quite warm at the typical 20 ma current. LEDs are nowhere near 100% efficient, they’re just a lot better than incandescent lamps.
Steve in SC (08:10:36) : “…Temperature sensors that would turn them on would burn a lot of useless electricity…”
Wrong.
Gail Combs (07:53:57) :
Pamela Gray (08:14:13) :
The map is from the last 2 days
http://mapcenter.hamweather.com/records/2day/us.html?c=maxtemp,mintemp,lowmax,highmin,snow
The red dot in the Pan Handle is from Thursday.
Now a second red dot, at West Pal Beach International Airport, is from yesterday, Friday.
I sure would like to see the pictures of these two stations and the locale.
starzmom (08:18:19) :
Interesting comment.
Engineers Unite!
I live in France where they still usually have incandescent bulbs in the traffic lights, as far as I know (sometime you can see fluorescent coils and they seem to be better). The problem here is the setting sun shining directly into them, as they are very weak. I always slow right down or stop in such a case – get hooted at by the car following but don’t budge until I’m sure.
hotrod (08:59:10) : “…In some conditions the antilock brakes actually increase stopping distances…”
You’ll have to prove that. Please provide a link.
OT, but did anyone notice that Lake Okeechobee was ccalling Snow earlier? I’m sure it was a sensor issue due to the temperature at the time, but interesting nonetheless.
KOBE 091129Z AUTO 35009KT 10SM SN SCT060 OVC095 05/03 A3014 RMK AO2
KOBE 091109Z AUTO 35010KT 10SM -RA BKN060 OVC095 05/02 A3014 RMK AO2
KOBE 091050Z AUTO 35010KT 10SM SN OVC060 06/03 A3013 RMK AO2
The current estimated Lake temperature is 57F and the wind was blowing from the Northwest. The town is on the North end of the lake.
Crashex (08:25:07) :
News commentary and shows like 60 Minutes are usually presented from the perspective of the plaintiff’s lawyer.
There is also a big problem with trial by jury. The jury is supposed to be 12 peers, or something along those lines. But what a jury really is is 12 people who weren’t smart enough to get out of jury duty.
No wonder a lawyer who, in some cases, does little more than capture the attention of such a jury is able to win his case. Just presenting dry facts to a jury should be enough. It’s not. An entertaining presentation is needed.
What a world, hey?
Al Gore’s Holy Hologram (08:39:47) :
Pray we do have some global warming. If cooling continues we’ll use more energy and have less energy security.
We’ve got plenty of oil in Alaska. And plenty of coal in the Appalachians. Lots of other resources too. We just need to use them.
Many serious accidents happen at traffic lights, because people speed up to get through at the end of a cycle. Roundabouts are much safer because you have to slow down entering a roundabout, and because there is no reason to rush. You never have to wait for a light to cycle.
In England, many roundabouts are nothing more than a painted circle. Nothing expensive about that.
refers to braking on dry pavement…
onr such link
Al Gore’s Holy Hologram (08:39:47) :
Pray we do have some global warming. If cooling continues we’ll use more energy and have less energy security.
Sorry, no.
We are in more danger from self-styled elitists, pseudo-scientists and busy body intellectuals than we are from the climate.
James 5:17
Elijah was a man with a nature like ours, and he prayed earnestly that it would not rain, and it did not rain on the earth for three years and six months.
Polar Bears Forced to Land and Water
Holy smokes, the polar bears can, and are adapting, who would have ever guessed !??
Makes me all fuzzy and warm and…
jorgekafkazar (10:08:32) :
hotrod (08:59:10) : “…In some conditions the antilock brakes actually increase stopping distances…”
You’ll have to prove that. Please provide a link.
Road and Track did a test back in the late 80’s using a Mercedes with and without the anti-lock brakes. The results of the test were that for adverse conditions except on dry pavement the car stopped in a shorter distance by just locking up all four wheels. On glare ice locking up the wheels produced stopping distances three times less than the same car with the anti-lock enabled. They initially tried to modulate the brakes but they were thwarted by the wooden feel of the brakes through the anti-lock mechanism so they just locked the wheels up.
Chris C. (08:57:15) :
I hate to appear dense in asking, but are you trying to tell us something good or bad about these lights?
This is an easy fix. Just install a temp actuated heat element behind the lights. Problem solved. I have them in my rear view mirrors on both sides of my car.
[snip]
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