What is necessary to check for leaks when preparing to depart a stopped train?

To ensure safe operation when preparing to depart a stopped train, checking the equalizing reservoir pressure is critical as it serves as an indication of the overall air brake system's integrity. The equalizing reservoir collects and maintains the necessary air pressure required for brake application across the train. If there is a leak in the system, the pressure in the equalizing reservoir would diminish, signaling a potential problem that needs immediate attention before proceeding.

Maintaining proper air pressure is vital; if the equalizing reservoir pressure drops below acceptable levels, it may result in inadequate braking and an increased risk of accidents during the journey. This check is a proactive measure in ensuring that all components of the air brake system are functioning correctly, providing safety for both the train crew and any passengers or cargo being transported.

While other options might relate to train operations or performance, they do not directly pertain to monitoring air brake system integrity or leaks as effectively as checking the equalizing reservoir pressure does.