How long should you actuate the independent brake when initiating an automatic brake application?

The correct choice indicates that the independent brake should be actuated for at least 2 seconds when initiating an automatic brake application. This duration is crucial because it ensures that the braking system adequately responds to the activation command, maintaining a safe and controlled deceleration process. Actuating the brake for this time frame allows the system to properly engage, creating the necessary pressure differentials in the braking mechanism to stop or slow down the train effectively without causing abrupt movements that may lead to safety issues or mechanical strain.

The emphasis on a duration of 2 seconds reflects standard operating procedures intended to enhance safety and reliability. Proper training protocols stress adhering to these specific timings to ensure that all train personnel can respond consistently and effectively in situations that require a brake application.