Traffic signals, also known as traffic lights, use a combination of hardware and software to control the flow of traffic at intersections. They consist of three main parts: the controller, the detector, and the display. The controller is the brain of the traffic signal, using a computer program to determine the timing of the lights. The detector is a sensor that monitors traffic volume and speed, sending this data to the controller. The display is the actual lights, which are usually red, yellow, and green, and are controlled by the controller. The controller uses a fixed-time or actuated timing plan to determine when to change the lights. In fixed-time plans, the lights are set to change at regular intervals, while in actuated plans, the lights change based on the amount of traffic. Traffic signals can also be controlled by pedestrian signals, which have their own display, controller, and detector. These signals are designed to prioritize pedestrian traffic, allowing them to safely cross the road when the traffic is light. Traffic signal controllers are usually powered by electricity, but some are powered by solar panels or other alternative energy sources.

Robby Stein, a Google executive, will be speaking at TechCrunch Disrupt 2026 on the Builders Stage. The event offers a chance to save up to $200 before September 25th.