Which light indicates that a local brake problem may exist?

The brake application light is designed to illuminate in situations where there may be a problem with the braking system. Its primary function is to signal that the brakes are engaged or being applied. If there is an issue with the local brake system, the illumination of this light serves as a warning to the operator that further investigation is necessary to ensure safe operation. When the brake application light is on, it indicates that the brakes may not be functioning optimally, which is critical information for the conductor or operator to act upon promptly.

Understanding the roles of the other lights can clarify why they do not indicate a local brake problem. The brake release light signifies when the brakes have been successfully released, while the status indicator light provides a general overview of the system's operational status. The air pressure light, on the other hand, refers to the pressure levels in the braking system rather than directly signaling a local brake issue. Therefore, the brake application light is the most relevant indicator for potential local brake problems, making it the correct answer.