What is a key requirement for any gauge used in air brake tests?

A key requirement for any gauge used in air brake tests is that it must be checked for accuracy regularly. This ensures that the gauge provides reliable and precise measurements of air pressure, which is crucial for the safe operation of the air brake system on trains. Regular checks help identify any discrepancies, wear, or damage that could lead to unsafe conditions if left unaddressed. Accurate measurements are essential for verifying that the braking system is functioning correctly and that it can respond appropriately under various operational conditions.

While real-time recording and other options may seem beneficial, they do not address the fundamental need for accuracy in measurements, which directly impacts the safety and effectiveness of the air brake system. Therefore, the regular verification of accuracy stands out as a critical requirement for maintaining the integrity of the testing process.