How is preemption control enabled during emergencies?

Preemption control is a critical feature in traffic management systems, especially during emergencies such as when emergency vehicles need to navigate intersections quickly and safely. Enabling preemption essentially means that the regular traffic signal operations are overridden to ensure that emergency vehicles can pass through intersections without delay.

Transferring normal operations to a special control mode is the correct method for achieving this preemption control. When an emergency vehicle approaches, the traffic signal control system can switch to a preemption mode that modifies the signal phases, typically turning the traffic lights to red for all directions except the path of the emergency vehicle. This allows the vehicle to proceed through the intersection without stopping.

In this special control mode, the traffic signals can be programmed to prioritize the movement of emergency vehicles, enhancing safety and response times in emergency situations. This contrasts with other options which either do not directly facilitate emergency vehicle movement or would not provide the required immediate response needed during an emergency.