Which operation speed limit is enforced by ATC in yard mode?

The correct operation speed limit enforced by Automatic Train Control (ATC) in yard mode is 12 mph. This speed limit is carefully established to ensure safety within yard operations where trains maneuver in close proximity to each other and other equipment. The 12 mph limit helps to reduce the severity of potential accidents and provides operators with adequate time to react to any unexpected situations.

In the context of yard operations, trains are often stopped or moving at low speeds, and maintaining a controlled environment is crucial for both safety and efficiency. Speed limits are designed to accommodate the complexity of operations, allowing for effective communication between crew members and minimizing risks associated with switching and loading operations.

Other speed limits like 10 mph, 15 mph, and 20 mph might apply in different contexts or parts of the rail network, but within yard mode, 12 mph is specifically mandated by ATC regulations to operate safely in this high-density area.