How do traffic signals work?
Traffic signals are made up of many components and pieces of equipment to ensure that the signal operates safely and efficiently. Two of the most important components are the controller and detectors. The controller is a computer that is programmed with various parameters that dictate how the signal operates, such as minimum and maximum green times, pedestrian walk times, and cycle lengths.
The detectors determine when a vehicle, pedestrian, or bicycle is present and pass this information to the controller. There are various types of detection systems, including video, thermal, electromagnetic loops in the pavement, and radar. Once the controller knows that traffic is waiting to receive a green light, it will incorporate that information into its programming as it runs through phases and cycles.