Ok I know there is several people who dislike LED's on the site so I though I'd give you a bit of laugh at a new problem with them, they won't melt snow and I just seen this in the national news at :>  http://www.cbc.ca/news/canada/manitoba/winnipeg-led-traffic-lights-snow-1.4377116 Yes winter is coming to Canada...

lol, thats lovely... not that i hate LED's but i see possible realizations in peoples heads that LED's aren't great for everything..

I've heard the same story only speaking about the tail lights on big trucks. The snow sticks to their rear end and the lights do not melt it. Over time, you lose the ability to see their tail lights. Very dangerous.

I don't remember if I read about it or if I heard someone talking about it.

Here in Israel. snow is common only at the north part of Israel, as well as in Jerusalem and nearby. In most parts of Israel, there is no problem to use LED for traffic lights: They are brighter and more noticeable than incandescent lights (And they are even glaring to look at, at night). But for locations with a lot of snow, incandescent is the only option if the snow covers the lights.
Isn't the upper part of the lights of the traffic signal, should prevent the snow to cover them?

Here in Israel. snow is common only at the north part of Israel, as well as in Jerusalem and nearby. In most parts of Israel, there is no problem to use LED for traffic lights: They are brighter and more noticeable than incandescent lights (And they are even glaring to look at, at night). But for locations with a lot of snow, incandescent is the only option if the snow covers the lights.
Isn't the upper part of the lights of the traffic signal, should prevent the snow to cover them?

high winds blow snow onto the lenses despite the guard above the lense.

Here in Israel. snow is common only at the north part of Israel, as well as in Jerusalem and nearby. In most parts of Israel, there is no problem to use LED for traffic lights: They are brighter and more noticeable than incandescent lights (And they are even glaring to look at, at night). But for locations with a lot of snow, incandescent is the only option if the snow covers the lights.
Isn't the upper part of the lights of the traffic signal, should prevent the snow to cover them?

I don't think you get the same amount of snow as Winnipeg, people in Canada really do own snowmobiles, ok not all of them, maybe the big snow fall of 1950 in Israel might barely compare to where these lights are being used they get 110 cm (43 inch) a year on average add some wind and all those covers do is give the snow somewhere to build up then add below zero temps to -40 for several months and it really has no were to go until spring, and Winnipeg is far from some other cities in snow fall, St Johns gets like 322 CM / year (127 inch) average Woody's Point Nfld gets 637 cm (251 inch) and we have had weather stations report average annual amounts of 1388 Cm (45.5 feet) and some towns can have snow on the ground for 300+ days of the year.. 

I've heard the same story only speaking about the tail lights on big trucks. The snow sticks to their rear end and the lights do not melt it. Over time, you lose the ability to see their tail lights. Very dangerous.

I don't remember if I read about it or if I heard someone talking about it.

Oh wow, I never thought of that for automotive applications.  Initially, I thought LED's are great for cars since they are lower maintenance and more energy efficient.  That's a significant design flaw for snowy and cold climates.  Some newer cars have entirely LED headlamps, so that would be a problem driving in a snowstorm.  The headlights might not be an issue due to heat from the engine bay, but I could totally see the LED taillights getting covered in snow and not melting.

I don't think energy efficiency is needed in automotive lamps,

I don't think energy efficiency is needed in automotive lamps,

It depends on if the car is running or not. Energy efficient lights in cars are not required when the engine is running and charging the battery.  Power for the incandescent or halogen lights is drawn from the battery and alternator as they have a constant charge from the running engine.

LEDs would be an advantage while the car is off.  Leaving the lights on by accident wouldn't drain the battery.  They would probably lead to longer battery life for the car, too.

I really hate LED tail lights because unless the driver is braking, they have a very annoying flicker when they are dimmed. You'd think something expensive like a car would have a decent dimmer for the LED tail lights, but not so. I'm not talking about inexpensive cars, I've seen the effect on Volkswagen, Audi, Mercedes, Volvo and the like as well as less expensive ones like Honda, Toyota, Ford, GM, etc.

LED in the instrument cluster is annoying as well, for the same reasons.

I didn't LED taillights would flicker.  I can imagine it's worst when the low brightness is on with the running light more than the high brightness with the brake pedal pressed.  I'm sure the car, especially the expensive brands like you mentioned with more electronic features has more irregular voltage and current.  A lot more devices in the car other than the taillights drawing power.  I notice in my car, the headlights will dim slightly when I roll up or roll down the window as power is drawn from the headlights to the window motor.  Same thing when you start the car with an interior light on.  It will flicker as the car ignites and draws a huge surge of energy to the ignition coils.

I know what you're talking about, but that is not what I mean. There are several mechanisms to dim LED, some of which work by 'chopping' the current in a similar fashion to standard incandescent dimmers. However, with incandescent, the flicker is much less noticeable because of the filament persistence. There are other ways to dim LED that don't cause flicker, and although slightly more expensive, would be worth it for above mentioned reasons. Normally, tail lights are about at half brightness and jump to full brightness upon brake pedal activation. There is an obvious dimmer in the circuit, and that is the culprit.

Oh, and while we're at it, there are wall dimmers that do the same, even if they are certified for LED. Makes for very annoying room lighting, worse than HID on magnetic gear.

LED traffic lights getting obstructed by snow has been a problem for a few years now. It is a problem with LED tail lights on trucks, as well.

Why using LEDs in tail lights: Contrary to marketing BS (and the car sale pricing strategy), the LEDs actually make the car manufacture cheaper to produce. The main reason is the huge hole in the steel body needed for the incandescent tail lights. This hole is a lot of rather expensive (in the perspective of the tail light) metal forming, plus it compromises the structural integrity of that part of the body (so to make it back means again more cost). The LEDs are way more compact, so need way less of the forming, plus without that hole the body structure is inherently stronger, so you may further cut back some bucks on there. The net result is, although the price of the lantern itself is more than double for LEDs, the incandescent would have to have significantly "negative" cost (so the car maker would have to get paid for using it) to make the total cost equal. The higher $$$ the customers are willing to pay for LEDs is just an extra bonus...

The flicker: Of course, it is possible to dimthe LEDs by just reducing the current, it would be even cheaper (and some cheap makers were using this approach). But the problem is, once the LEDs age for some time operated at higher current, they tend to develop a leakage,which then shunts the low current in the dimmed setting, making the brightness difference way bigger than original. This won't be as much a problem for a single LED, but with a cluster the individual LEDs each age at different rate, so the result would be irregular pattern on the lighting surface. Plus many LEDs te d to shift their wavelength (so color) when the current gets changed, so there would be a color shift as well.
The simplest remedy for both issues is then operating the LEDs all at the same current and do the dimming just by PWM.
Of course, the frequency needs to be high enough, but the problem is, the car industry needs to be very conservative (all things need to be thoroughly verified before used in mass and that is the hell expensive process), so they do just a small change at a time. So the first cars with LEDs were just used the dimmers originally designed for incandescents (they are part of the rear section control unit) and these operated just at 1about 100..150Hz (to keep switching losses low and meet the EMC requirements even with rather high currents associated with incandescents). Controllers designed for LEDs are already operating at 400Hz (lower currents allow steeper edges yet meeting the EMC, plus the switching losses could be relatively higher, as the overall power levels are lower). But the new controllers are only on some late car models...

The snow on the tail lights: Well,what I observe most is the tail lights not visible by just dirt and mud deposit. And there is no difference,  if it is incandescent or LED, both need regular cleaning during long drive in a bad weather. Noticeable difference would be only in case of really c,ean snow problem. Well, not many parts of the world have clean snow on the roads (where the incandescents won't need any cleqning), in most parts of the world it is just abrown muddy mess, where just the melting heat does nothing to make it visible.

Truckers love LEDs in the taillights and trailer lights and market lights.