Signal timing

The process includes selecting appropriate values for timing, which are implemented in specialized traffic signal controllers.

An actuated traffic signal relies on some mechanism for detecting vehicles as they approach the intersection.

The preferred wire is stranded copper with an insulating cover, which is then loosely surrounded by a protection jacket.

The 'switch' is normally closed (NC) in the de-engerized state but held open when power is applied to the circuit.

This is called 'Fail-Call' so that if there is a failure in the sensor electronics, the output will place a 'Call' to the controller as if a vehicle is present on the loop detector.

All detection methods except inductive loop detectors and magnetometers suffer in accuracy as the result of the concept of occlusion.

The whole intersection is then programmed to operate a fixed time every cycle, but the controller will service the other movements only when there is a 'call' or demand.

In COORD operation, short for coordination, the signal is running a background cycle length.

It can also be set to flash until made not too, allowing thee to essentially be converted into beacons if the traffic light is obsoleted enough.

The movement remains in the extendable portion as long as an actuation is present and the passage timer has not expired.

If there are no conflicting demands on the intersection, the controller will ignore the MAX and rest in the major street movement.

This is timed as the length of the crosswalk divided by a speed of 3.5 feet per second, minus the yellow clearance for the adjacent vehicle movement.

Coordination (the more correct term is progression) refers to the timing of the signals so that a "platoon" of cars traveling on a street arrives at a succession of green lights and proceeds through multiple intersections without stopping.

A well coordinated signal system can enhance traffic flow, reduce delay and minimize pollution.

In March 2020, the ITE adopted Beaverton, Oregon engineering consultant Mats Järlström's recommendations for yellow light timing.

Järlström had begun investigating the matter after his wife received a ticket from a red light camera in 2013.

Järlström, who has a degree in electrical engineering, filed suit in the federal District Court alleging violation of his First Amendment rights.