What is the maximum acceptable air loss rate for a straight truck or bus with the engine off and brakes applied?

Answer: C — 3 psi in one minute

The maximum acceptable air loss rate for a straight truck or bus with the engine off and brakes applied is 3 psi in one minute. This standard is critical for ensuring the safety and reliability of air brake systems. A loss greater than this threshold may indicate leaks or inefficiencies within the air brake system, which can compromise braking effectiveness and overall vehicle safety. Maintaining this air loss rate is crucial for the vehicle's ability to hold pressure in the brake system when stationary, allowing for dependable operation under braking conditions. Understanding this benchmark helps drivers and mechanics identify when preventative maintenance or repairs are necessary, ensuring that the air brake system remains in optimal condition.