In which scenario would signal preemption most likely be activated?

Signal preemption is a traffic management technique that prioritizes certain vehicles at intersections by momentarily overriding the normal traffic signals. This system is most commonly utilized for emergency vehicles, such as ambulances, fire trucks, and police vehicles, that need to navigate through intersections quickly to respond to emergencies.

In the case of an approaching emergency vehicle, signal preemption would be activated to change the traffic signals in favor of the emergency vehicle. This helps minimize delays, reduce response times, and enhance safety for both the emergency responders and the general public. The system ensures that the emergency vehicle can proceed through intersections without waiting at traffic signals, thereby facilitating a quicker response in urgent situations.

The other scenarios presented would not trigger signal preemption in the same manner. Heavy pedestrian traffic may instead necessitate pedestrian signals or other measures to ensure safety. A scheduled bus stop would typically involve regular transit operations but not an immediate need to change signals, while normal traffic congestion does not warrant prioritization and is managed through routine signal timing adjustments rather than preemption.