What is the minimum reduction in PSI required for a Class III Brake Test to apply the brakes?

In the context of a Class III Brake Test, the requirement states that there must be a minimum reduction in pressure, measured in pounds per square inch (PSI), to ensure that the brakes are properly engaged and functioning. The correct answer is based on the standards set for brake tests which require a 20 PSI reduction to apply the brakes effectively.

This significant reduction is essential for ensuring that the braking system can be relied upon under standard operating conditions. A reduction of this magnitude indicates that the system has enough pressure drop across the brake lines to confirm that the brakes will engage thoroughly and safely, which is crucial for the successful operation of the train.

By requiring a 20 PSI reduction, the protocols help to eliminate any ambiguity regarding the operation of the brakes and ensure that all systems are functioning correctly before the train is put into motion. Thus, this standard helps maintain safety and operational efficiency in train operations.