How Does Traffic Light Ladder Logic Work?


Quick Answer

Traffic lights are controlled either by a timer programmed to signal the light to change at specific intervals or by a controller programmed to respond to auto traffic. An EPROM chip that contains the program written for a given traffic light sends instructions to the controller.

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Full Answer

The most effective way to program a traffic light depends on the automobile traffic at a given intersection. Intersections with heavy traffic usually have traffic lights that work on fixed times; each signal at the intersection appears for the same amount of time regardless of whether the amount of traffic coming from all directions is equal. Programmers optimize fixed timers by determining the best order of lights for smooth and safe traffic flow.

Automobile-activated timers are much more common in areas where there is light traffic. These type of lights adjust the length of the signals based on traffic flow. In doing this, they are able to optimize traffic flow by providing more green light time to the part of the intersection that receives the most traffic at any given time. In addition to a controller, auto traffic controllers utilize a detector that sends a signal to the controller when traffic approaches the intersection.

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