What must be done when all brakes are released on all locomotives?

When all brakes are released on all locomotives, it is essential to observe the independent brakes release on all locomotives to ensure safe train operation and proper system functionality. This step is crucial because it confirms that the independent braking system is functioning correctly across all units in the train. The independent brakes provide a backup to the main automatic air brake system, and their reliable release indicates that the braking systems are operating as intended.

Monitoring the independent brakes allows for an assessment of any potential issues that may arise before proceeding with further operations. If any locomotive's independent brakes do not release, it could pose a risk during train movement, leading to unintended dragging or other safety hazards. Therefore, this step is critical for maintaining control and ensuring the safety of the train handling procedures.