What percentage of air brakes must be operational before proceeding in a Class 1A air brake test?

In a Class 1A air brake test, it is required that all air brakes must be operational—this means that the percentage of functional brakes must reach 100 percent before a train is allowed to proceed. The rationale behind this requirement is to ensure the safety of train operations. Having all brakes in working order is critical to prevent accidents and ensure that the train can be controlled effectively under various conditions.

If brakes were to be functioning at a lesser percentage, such as 75, 80, or even 90 percent, it could lead to a significant risk due to the potential for inadequate stopping power or control, especially in emergency situations. Therefore, achieving complete functionality of the air brakes is essential for safe train handling and compliance with regulations.