Michigan CDL - Air Brakes Practice Exam

What happens when the brake pedal is applied in a vehicle with air brakes?

1. The brake lights are turned on

2. The air compressor activates

3. The engine shuts off

4. Fuel injection is increased

The correct answer is: The brake lights are turned on

When the brake pedal is applied in a vehicle equipped with air brakes, one of the functions that occurs is the activation of the brake lights. This is an important safety feature that alerts other drivers that the vehicle is slowing down or coming to a stop. When the brake pedal is pressed, an electrical signal is sent to the brake lights, ensuring visibility and communication on the road, which is crucial for preventing accidents. In vehicles with air brakes, the air compressor operates independently and is not directly connected to the brake pedal. The compressor maintains the air pressure in the braking system, but pressing the brake does not trigger it. Similarly, applying the brake does not cause the engine to shut off or increase fuel injection, as these systems operate differently and are not affected by the action of applying the brake pedal. Thus, while the brake lights are a visible response to the application of the brake, the other options relate to systems that function separately from the immediate response of the air brake system.