Re: This is new?
A fascinating plunge into traffic sensors!
These days, the primary detection method is inductive loops. A long time ago, rubber bars with a hose in, a more permenant version of the sensus point, were popular.
These days, more advanced sensors are getting common, for instance radar sensors that can monitor multiple lanes without having to replace on resurface. Also infra red sensors for more accurate vehical profiling, height etc.
Another recent inovation are little wireless capsules, containing an electronic compas, that detect car type/speed/count based on the vehicals disruption of the earths magnetic field. The highways agency trialed them a couple years ago, and found them much faster than loops to fit, but battery life in field remains to be proven.
Another exotic technology is multi microphone sensors which use traffic noise to give a car, lane position, speed etc. Less accurate than loops but cheaper.
The UK uses automatic traffic control in cities. The individual lights all report back to a central computer which optimises traffic flow in quite a deterministic way.
It is much cheaper to link the lights to a central station because you can just use BT phone lines.
Of course, you could do self organising by linking the lights via a central hub at the same cost, but if you do that, you lose the redundancy anyway, so there doesn't seem much point.
IMHO, real progress could be made by harnessing data from peoples GPS devices to let you know where they were trying to go. Perhaps you could send instructions back to the GPS, routing people evenly accross varius possible routes. If this happens, it will come from the GPS/mapping industry, not the traffic lights people.