What device is designed to control the flow of traffic by allowing it to stop and proceed alternately?

The device that is designed to control the flow of traffic by allowing it to stop and proceed alternately is indeed referred to as a traffic-control signal. This type of signal is specifically programmed to manage and facilitate the orderly movement of vehicles and pedestrians at intersections by alternating the right of way. By utilizing colors, most commonly red and green, a traffic-control signal indicates when vehicles must stop and when they may proceed, thereby enhancing safety and reducing traffic congestion.

Traffic lights, while commonly interchangeably used with traffic-control signals, may refer specifically to the signaling device itself (the lights) rather than the broader category of traffic-control measures. Roundabouts and yield signs serve different functions in traffic management; roundabouts are designed to keep traffic moving with minimal stops and prevent head-on collisions, while yield signs instruct drivers to give way to traffic already in the intersection, rather than controlling the flow through directed signals. Therefore, the correct distinction is that a traffic-control signal encompasses the complete system used to alternate traffic flow effectively.