Okay - all you city planning authorities out there, looking for ways to green your cities and reduce pollution, reduce congestion, and make life easier for your citizens. Lissen up, I have a thought for you.
I suggested, years ago, that a lot of traffic congestion could be reduced by designing the bigger better traffic light set. Once again, the Most Abject Pathetic Technology & Electronics Kompany I worked for looked at me as though I'd sprouted three legs and an extra head when I suggested it, and once more, this is an idea well worth taking on board when you next send out a tender for replacing traffic lights.
It isn't hard, these days, to separate a video image into frames, and search each frame for salient features. Such as "outline of a car," "outline of a motorcycle," and so forth. Any reasonable computer can do this with ease. Said reasonable computer can also compare one frame with a subsequent frame, and over a few frames, average the speed of all those detected salient features, as well as maintain a tally of how many such features are in frame.
So if you aim a camera back across the traffic lights at the oncoming traffic, the computer can tell how much traffic it has coming in, how fast that traffic is moving, and how much traffic has flowed in that direction for the last 24 hours.
Now suppose you have four such systems at each intersection, controlling the flow of traffic. It doesn't matter what time of day it is, the traffic lights react to the existing stream of traffic and try and schedule so that the least cumulative amount of time is spent idling at the lights in all directions.
That move alone could reduce fuel use and pollution from idling at lights to insignificant amounts. Since it takes a lot of energy to get rolling again once stopped, reducing the amount of times a vehicle has to stop makes an immense difference. This is also true for electric vehicles (EVs) because they chew huge amounts of juice to start rolling again.
As a bonus, if there is a traffic stream (or single vehicle) approaching the controlled lights at a speed exceeding the speed limit, you can always provide a red light to them. Then if they pass through the lights despite that, you have a picture of them running a red light, and also their speed at the time... %)
One last thought - if you don't want to waste the computing power needed for parsing images, perhaps you could respectfully ask car and immobiliser manufacturers to start placing a small piece of technology in their product - a Bluetooth beacon... You could count the number of BT beacons at traffic lights just as easily as images, you'd lose the ability to enforce speed limits and the red light camera facilities, but it would simplify things a bit.
If you like my idea and decide to use it, feel free to. But please also feel free to donate some money via my Paypal link so that I can continue to come up with new ideas...