Which method should be used for measuring leakage during a Class I Air Brake Test?

The correct choice for measuring leakage during a Class I Air Brake Test is the Air Flow Method. This method is primarily used because it allows for an accurate measurement of the flow of air through the brake pipe and into the various components of the braking system. By assessing the airflow, one can determine whether there is an acceptable level of leakage present.

The focus on air flow provides a precise understanding of how efficiently the braking system operates, which is essential for ensuring safe conditions for train operations. This method enables conductors to identify and quantify leaks that may not be noticeable through visual inspection or other means, thus contributing to the overall safety and reliability of the train's braking system.

Other methods, such as visual inspection, may not detect minor leaks, and while the Brake Pipe Leakage Method and Class III Application and Release Method could be relevant in different contexts, they are not the primary or most effective means for evaluating leakage specifically during a Class I Air Brake Test. The Air Flow Method, therefore, stands out as the best practice for this particular evaluation.