Arizona Air Brakes CDL Practice Test

What happens when air pressure drops below a certain level during braking?

1. The brakes will automatically engage

2. You lose full control of the braking system

3. The warning light will not activate

4. The service brakes will function normally

The correct answer is: You lose full control of the braking system

When air pressure drops below a certain level during braking, the braking system may lose full control due to insufficient air pressure in the air brake system. Air brakes operate based on compressed air, which is essential for the functionality of the braking components, including the brake chambers and valves. If the air pressure falls too low, typically below the minimum threshold required for safe operation (often around 60 psi), the system may not function effectively, potentially leading to a loss of braking capability. This is particularly critical in air brake systems as they rely on air pressure to apply the brakes. At low pressures, the system may not be able to perform as required, which can compromise safety. In contrast, while warning lights and automatic engagement mechanisms are components of air brake systems, their operational status depends on the specific pressure thresholds and system design. Therefore, understanding the implications of falling below the required air pressure is crucial for maintaining control and safety when operating vehicles equipped with air brakes.