What device is used by emergency vehicles to take priority control over a traffic signal?

Emergency vehicles use a system known as preemption to take priority control over traffic signals. This technology allows emergency vehicles, such as fire trucks or ambulances, to change traffic signals to green as they approach intersections, thereby enabling them to navigate through traffic more efficiently and safely.

The preemption system operates via various methods—often involving sensors or radio signals that communicate with traffic signal control systems. When an emergency vehicle approaches, the preemption system can override normal signal patterns to clear the path, reducing response times during critical situations.

Other options like the override controller and signal booster might involve signal control and amplification, but they do not specifically refer to the system designed solely for emergency vehicle priority control. A traffic timer typically controls the duration of signal changes rather than providing priority access to emergency vehicles. This is why preemption is the correct term associated with the practice of emergency vehicles gaining priority at intersections.