What initial step must be taken during an Intermediate Air Brake Test?

During an Intermediate Air Brake Test, the first initial step is to perform a Rule 100.9 Brake Pipe Leakage Test. This step is crucial because it ensures that the brake pipe system is functioning correctly and that there are no leaks in the brake pipe that could affect the brakes' effectiveness. By verifying the integrity of the brake pipe, personnel can ascertain that the air pressure can be maintained adequately throughout the system, which is essential for safe train operation.

The Rule 100.9 Brake Pipe Leakage Test involves applying a specific method to ensure that the pressure in the brake pipe does not drop excessively over a defined time period when the air brakes are not in use. This step is foundational because any leaks would compromise the braking system's performance, potentially leading to unsafe conditions while the train is in operation.

While making a 15-psi brake pipe reduction, verifying the presence of all passenger cars, and inspecting for visible damage on the cars are also important procedures in ensuring train safety and performance, these actions follow the confirmation of the integrity of the brake system through the leakage test. Without confirming that the braking system is leak-free first, other checks may be irrelevant or conducted under unsafe conditions. Therefore, starting with the brake pipe leakage test is the most critical