Union Pacific Air Brakes Practice Test

The correct choice emphasizes that a locomotive must have an Air Flow Method (AFM) Indicator that provides a direct reading of air flow with precision no greater than 10 cubic feet per minute (CFM). This level of granularity in measurement is important because it allows for precise monitoring of the air flow being used in the air brake system.

Using an indicator with such specific increments helps in ensuring that the air flow remains within the necessary operational parameters for effective brake performance. This is crucial for safety and effective train operations, as any deviation from normal air flow could indicate potential issues in the braking system that need to be addressed.

A direct reading capability makes the assessment of air flow more intuitive for operators, allowing them to quickly understand and react to the braking system's performance. The necessity for precise control and clear readings reflects the importance of these aspects in maintaining the safe and efficient operation of trains.