What is the maximum allowable air loss in a straight truck or bus with the engine off and brakes released?

The correct answer is that the maximum allowable air loss in a straight truck or bus with the engine off and brakes released is 2 psi in one minute. This standard is important for ensuring the integrity of the air brake system. A loss of air pressure greater than this threshold could indicate potential leaks or other issues within the system that might compromise brake performance.

In commercial vehicles, maintaining proper air pressure is crucial for safety and functionality. For example, if the air loss were higher than 2 psi in one minute, it could signify a malfunction that may lead to brake failure, which poses significant risks while driving.

This measure is specifically designed to detect problems early before they can affect vehicle operation. Requiring no more than 2 psi air loss allows for a safety margin while still confirming the reliability of the air brake system. The time constraint of one minute helps to standardize testing intervals for air loss, making it a consistent part of vehicle inspections.