During an emergency stop, what is a critical action besides applying brakes?

During an emergency stop, alerting train personnel and passengers is a critical action because effective communication can significantly enhance the safety and coordination of subsequent actions. Informing both the crew and passengers of the situation ensures that everyone is aware of the emergency and can follow necessary safety protocols. This action not only prepares passengers for potential hazards, but it also allows train personnel to respond appropriately, whether that means preparing for an evacuation or managing the situation until further help arrives.

Additionally, while other actions like assessing track conditions or ensuring passengers are seated may be important in a regular operational context, they may not be the immediate priority during a sudden emergency stop. Immediate communication helps to mitigate panic and confusion, facilitating an organized response to the emergency situation.