How are traffic signals coordinated in a system?

Traffic signal controllers are very sophisticated and use high-speed microprocessors that make thousands of calculations every second. Each coordinated intersection has a controller that is linked via a wireless network to a central server, which keeps all the traffic signals’ internal clocks synchronized. The coordinated signals run according to plans derived from vehicle counts. Typically, signals have four weekday plans—morning, off peak, noon, and evening—and one weekend plan. Coordinated traffic signals drop out of coordination in the evening when traffic volumes are lower.

However, in Missoula the seven downtown signals are fixed-time signals that run in coordination 24/7.

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1. How do traffic signals work?
2. How does a traffic signal sense cars?
3. Why do some lights stay green when there are no cars present?
4. How does an emergency vehicle, such as a fire truck or ambulance, change the signal to give them a green light in the direction they are traveling?
5. Can I make a light change to green by flashing my headlights?
6. What happens when a train approaches a traffic signal near a railroad crossing?
7. How are traffic signals coordinated in a system?
8. How do pedestrian buttons and walk signals work?
9. Why do I need to push a button to get a walk light?
10. What new technologies are coming our way?