What happens if a car's air brake system releases before the signal is given?

When a car's air brake system releases before the signal is given, the correct course of action is to retest the system once after a minimum of three minutes. This response takes into account that the air brake system may not have maintained the necessary pressure or operation at the moment the signal was expected. By allowing a minimum waiting period, the system can stabilize, and the retest can provide an accurate assessment of the air brake's performance.

This process is crucial for ensuring safety and functionality in railroad operations. If the air brakes failed to hold pressure or released prematurely, retesting serves as a quality check to determine if the system can perform correctly under operational conditions, thus ensuring that it meets safety standards before returning to service. This approach allows for potential interventions or repairs if the system does not pass the retest.