When engaging the emergency brake, which of the following actions is NOT required?

The correct response highlights that activating the HVAC system is not a required action when engaging the emergency brake. In emergency situations, the primary focus is on stopping the train as quickly and safely as possible, which involves actions directly related to braking.

Pulling the emergency brake valves’ pull cords is crucial as it physically activates the emergency brake system and initiates braking. Similarly, placing the brake valve handle in the emergency position is necessary to ensure that the brakes are fully applied, facilitating a rapid stop. Additionally, releasing hand pressure on the master controller handle is essential since any application of power should cease to avoid further acceleration during an emergency stop.

In contrast, the HVAC system's operation is not directly related to stopping the train and does not contribute to the train's emergency braking procedure. Hence, activating HVAC is irrelevant in this context.