Someone asked me this the other day, so I'll share my answer as it involves some pretty impressive figures.
London has over 5000 traffic intersections, each one comprising an average of 10 traffic signals, making about 50,000 signals. If those were to be converted to LED lights, the resulting saving in electricity alone (assuming a cost of 6 p per unit) turns out to be almost £1 million a year, with an annual reduction in carbon emissions of more than 9500 tonnes.
Presently, light bulbs in conventional traffic lights are changed every year, so as LEDs can be expected to last up to 10 years they would avoid up to 8 maintenance visits over their lifetime. That's a lot of cherrypickers out of work.
If you want all the technical details, someone's explained it here which saves me the trouble.
Now just think how many traffic hold ups you could miss if all traffic lights were LED.
Of course, you could save even more energy, cut more carbon and reduce driver frustration too if you follow this example and just remove traffic lights altogether.
Ealing Council says "How many times have we waited at a junction and nothing is happening? No cars are moving, no pedestrians are crossing. Nothing. Just wasted time, adding to our frustrations. So we will bag over some traffic lights and allow motorists and pedestrians to trust each other." How refreshing!
You need to think through the design of LED Traffic Lights. During the winter, the heat from the light bulbs keeps the lens of conventional traffic lights free of snow. With traffic lights based on LEDs, the snow can build up on the lens and obscure the light.
I knew that there are advantages in using LEDs for a nummber of applications with traffic lights being one of the obvious choices. I never realised how much the benefit was to local councils until I read this. Admittedly the example quoted is London but imagine what would happen if we could get the technology right for street lighting and domestic lighting in any town or city. That sounds to me like a number of power stations going out of business. I had never thought of the disadvantage of using LEDs before but seeing that there is so much chaos anyway when snow comes in the UK will this make much difference? Has anyone checked what happens with traffic lights (of either sort) and snow?
I've emigrated to Spain, and I am also wondering what's the big deal with LED traffic lights?
I haven't seen a non LED traffic light here for years.
There are also advantages such as lights that change colour (green and red, or alternate yellow from two "lenses") and more resolution than just a light, such as pedestrian crossings where the "green man" can display a countdown of 10 seconds remaining to cross.
Are LED lights news in England?
. . . but have you seen how many LED traffic lights there are with failed LEDs? The LED manufacturers always quote "up to" 100000 hours' life, meaning they guarantee it to be LESS THAN 100000 hours.
This is pretty cool. There was a neat school project done in Pennsylvania where university students research the impact of switching from incandescent bulbs to LEDs, and some even provided policy recommendations for governments.
This is an article about it: Joshua M. Pearce, “Appropedia as a Tool for Service Learning in Sustainable Development”, Journal of Education for Sustainable Development, 3(1), pp.47-55, 2009.
Enjoy!
Regarding "A Buit"'s June 12th posting . . .
It's makes me disappointed how the title of the cited article is so typical of a government effort; that is, why isn't the article titled "A study of Incandescent lighting versus LEDs, including recommendations" instead of the confusing "Appropedia as a Tool for Service Learning in Sustainable Development”. I can hardly believe the two are related!
All and all the savings for led bulbs is huge compared to incandescent. When you compare them to replacement and labor.
Why do we leave our lights on 24/7 anyway?
In Germany, at night, the lights on a lot of junctions flash yellow and don't control traffic. The pedestrian crossings will switch the traffic lights off until someone pushes the button to cross as well.
They also have traffic lights without a green light too.
Makes no sense to me why we have to sit at a red at 1am in the morning!
Good points, Andy. I think three-phase lights are justified, but there is often too much road paraphenalia and control. Slightly off LED topic, but Camden council is starting an experiment in reducing road signage, and marking, to a bare minimum. Of course, the legal threat of "Health & Safety issues" hangs over this whole area... (as opposed to real health and safety)