On Sun, Oct 27, 2013 at 2:31 PM, François Lacombe < francois.laco...@telecom-bretagne.eu> wrote: > > there are also objects that can be influenced remotely, like busses that >> can put certain traffic_lights to green >> > > Actually I'm not sure we can talk about remote control in this situation. > Because buses won't directly turn traffic lights green. A third part > (computer, industrial processing unit...) will know the bus is coming and > adapt lights following a few rules. >
The most common system is the 3M opticom, where coded infrared light is transmitted from the bus or emergency vehicle, to a sensor mounted on the traffic light. The traffic control computer (located in a box nearby) then adjusts the light as needed. Typically it calls for 4 way red when an emergency vehicle approaches, and delay or advanced green for high priority vehicles like a bus.
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