Metropolitan Transportation Authority (MTA) Assistant Conductor Practice Test

The Automatic Train Control (ATC) system is responsible for ensuring that trains operate safely by monitoring their speed and enforcing compliance with speed limits, particularly as indicated by cab signals. In situations where a train does not reduce speed as mandated by the cab signals, the ATC system activates a penalty brake to bring the train to a safe stop.

This system is integral in maintaining safe train operations by automatically intervening when speeds exceed set limits, thereby preventing potential collisions or accidents. The ATC operates in conjunction with cab signals, which communicate necessary speed changes to the train crew.

While the Cab Signal System indeed informs the train of required speed adjustments, it does not implement a penalty brake; rather, it relies on the crew's response to the signals. The Manual Control System places the responsibility for speed management entirely in the hands of the train operator. The Yard Management System primarily focuses on managing train movements and logistics within train yards rather than enforcing speed regulations on mainline operations. Thus, the ATC clearly serves as the system that activates the penalty brake when necessary to ensure safe train operation.