What type of traffic light changes its timing based on cars actually being there?

The type of traffic light that changes its timing based on cars actually being there is known as an actuated traffic light. An actuated traffic light is designed to respond to real-time traffic demand rather than operating on a fixed, predetermined schedule. These systems use various types of vehicle detection sensors to identify the presence of vehicles approaching or waiting at an intersection. The most common sensor is the inductive loop detector, which is a coil of wire embedded in the pavement. When a metal object like a car passes over or stops on this loop, it creates a change in the electrical current, signaling the presence of a vehicle to the traffic signal controller. Other detection methods include video detection cameras, which analyze images to identify vehicles, and radar or microwave sensors, which use electromagnetic waves to detect vehicle presence and movement. When a sensor detects a vehicle, it sends a signal to the traffic signal controller, which is the computer that manages the light changes. Based on these signals, the controller adjusts the timing of the traffic light phases. A traffic light phase refers to the specific sequence of green, yellow, and red lights for a particular direction of travel at an intersection. For example, if vehicles are continuously detected on a main street, the actuated light can extend the green light phase for that direction, up to a programmed maximum, to allow more vehicles to pass. Conversely, if no vehicles are detected on a side street, the light can skip its green phase entirely or provide only a minimum green time, allowing the green light to return more quickly to busier approaches. This dynamic adjustment based on actual demand helps to minimize delays and improve the overall efficiency of traffic flow by allocating green light time where and when it is needed most.