What term describes traffic control devices that tell drivers when to stop and when to go?

The term that describes traffic control devices that indicate to drivers when to stop and when to go is "signals." Traffic signals are designed to manage the flow of traffic at intersections and controlled points, utilizing a system of lights—usually red, yellow, and green—to convey clear instructions to drivers.

Red means stop, green means go, and yellow indicates caution or prepare to stop. This system allows for orderly traffic movement and significantly reduces the chance of accidents by providing standardized, easy-to-understand instructions for drivers.

While yield signs indicate that drivers must slow down and yield the right-of-way to other vehicles, they do not explicitly tell drivers when to stop or go in the same definitive manner as signals do. Barriers serve as physical obstructions to control or restrict the flow of traffic but do not convey traffic direction. Road markings, although they offer guidance and information, such as lane divisions and pedestrian crossings, do not have the active, directive function like signals. Thus, signals are the correct answer as they serve to directly instruct drivers on when to proceed or come to a halt.