Japanese LED traffic lights just too cool when snow falls

Energy saving traffic lights in Japan are failing to melt snow covering them
Energy saving traffic lights in Japan are failing to melt snow covering them

Energy-saving LED traffic lights seemed like a cool way to cut back on electricity costs, but Japanese police said Monday they might just be too cool—because they don't melt snow.

Light-emitting diodes (LEDs) account for around 45 percent of all of Japan's stop-and-go signals and that proportion is growing as local authorities cotton on to their economising possibilities compared with regular incandescent lights.

But in wintery northern Japan the lights have encountered a problem—drivers can't see them because they don't get warm enough to melt accumulated snow.

Akira Kudo of Aomori Prefectural Police said snow has to be removed manually between December and mid-February during blizzards.

"We don't have enough staff members to remove as more and more LED lights are being introduced," he said.

LED lighting is becoming ever more popular in public and private spaces because of its lower energy consumption.

The technology has been big news in Japan since three local-born physicists won the Nobel Prize last year for the development of the blue LED, the breakthrough that to the white LED now commonly used worldwide.

Children make snowmen in Iiyama city, Nagano prefecture on February 15, 2015
Children make snowmen in Iiyama city, Nagano prefecture on February 15, 2015

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© 2015 AFP

Citation: Japanese LED traffic lights just too cool when snow falls (2015, February 23) retrieved 21 May 2019 from https://phys.org/news/2015-02-japanese-traffic-cool-falls.html
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Feb 24, 2015
This doesn't seem to be an issue with LED traffic lights in Canada. I wonder what exactly is different.

Feb 24, 2015
This doesn't seem to be an issue with LED traffic lights in Canada. I wonder what exactly is different.


There's heaters installed in them.

De-icing system for traffic signals:
http://www.google...S7211771

There are simple heating wires with positive temperature coefficient, which are self-regulating in terms of temperature, much like the rear window heaters in cars. A simple thermostat switches them on below a pre-determined temperature where the heat from the LED bulb itself is insufficient to keep the glass clear.

These types of heaters are also necessary in cold and humid environments to prevent frost and fogging of the bulbs. Otherwise there would be ice and water build-up around and inside the enclosures which leads to corrosion and high maintenance costs.

Of course it wastes a bunch of energy, but what can you do?

Feb 24, 2015
This has however been a perennial problem all around the world ever since LED lights started to become substituted for incandecent bulbs in traffic lights.

For example, a news article from 2010:
http://abcnews.go...=9506449

It's down to the city planners whether they'll install heaters on the bulbs or not, and of course it saves money not to, or they may be ignorant of the option in the first place. Usually the lowest bidder wins and the traffic lights use plain LEDs that can and do get frozen during the winter.


Feb 24, 2015
Thank you. That was informative.

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