If the low air pressure warning activates while a vehicle is moving, what should the driver do?

Explanation

When the low air pressure warning activates, the driver should stop as soon as it can be done safely, because if air pressure keeps falling, the spring brakes will apply automatically once pressure drops into their activation range, and that can happen unpredictably while the vehicle is still moving. 49 CFR 383.111(b)(4) requires CDL applicants to know the implications of low air pressure readings, the required-knowledge area this question falls under; the paragraph names that knowledge area without itself spelling out the stop-immediately response, so the specific action is standard driver-training content, attributed to the manual. Continuing the trip is wrong because the warning signals a real risk to both the service brakes and the vehicle's ability to control an automatic spring brake application, not just the parking brake. Pumping the brake pedal is wrong because pressing the pedal uses air rather than restoring it, making the shortage worse. Relying on engine braking exclusively is wrong because it does not address a failing air supply and does not substitute for stopping and addressing the underlying problem.

Source: 49 CFR 383.111(b)(4)