What can still be done even if the batteries on a train are dead?

Even if the batteries on a train are dead, applying the air brakes is still possible because air brake systems are typically operated using compressed air rather than relying on electrical power. These systems are designed to function independently of the train’s electrical systems, allowing for safe stopping in emergency situations.

The air brake mechanism relies on air pressure maintained in the train’s air reservoirs. Therefore, even without electrical power from the batteries, train operators can still engage the air brakes to bring the train to a halt. This is a crucial safety feature that ensures control over the train's braking system under various operational conditions.

In contrast, engaging the traction motors, activating the horn, and using the emergency lights generally require electrical power from the batteries, which would not be available if they are dead.