CDL Air Brake - Commercial Driver's License Air Brakes Parking Brake System Questions and Answers

Question 1

What provides the force to apply the parking brakes in a vehicle equipped with an air brake system?

Accepted Answer

Large, powerful springs located in the brake chambers.

Answer

Air pressure from a dedicated parking brake tank.

Answer

Hydraulic pressure from the master cylinder.

Answer

The driver's physical effort applied to the brake pedal.

Question 2

A driver pulls the yellow, diamond-shaped knob on the dashboard to park the vehicle. What is happening within the air brake system?

Accepted Answer

Air pressure is being released from the spring brake chambers, allowing the springs to apply the brakes.

Answer

Air pressure is being sent to the brake chambers to apply the brakes.

Answer

The air compressor is being activated to build pressure specifically for the parking brakes.

Answer

An electrical signal is sent to lock the service brakes in the applied position.

Question 3

Which of the following conditions will cause the spring brakes to apply automatically?

Accepted Answer

Air pressure in the main system drops to a low level, typically in the 20-45 psi range.

Answer

The service brake pedal is pressed and held for more than 60 seconds.

Answer

The engine RPM drops below a certain level.

Answer

The vehicle exceeds the posted speed limit while descending a steep grade.

Question 4

Some vehicles are equipped with a control lever on the dash that allows the driver to apply the spring brakes gradually. What is this control called?

Accepted Answer

A modulating control valve.

Answer

An S-cam rotational controller.

Answer

A slack adjuster override.

Answer

An anti-lock braking actuator.

Question 5

A driver is operating a combination vehicle and needs to park. What is the correct procedure for using the parking brakes?

Accepted Answer

Apply the parking brakes for both the tractor and the trailer.

Answer

Apply only the trailer parking brakes to prevent stress on the tractor.

Answer

Apply only the tractor parking brake and leave the trailer brakes released.

Answer

Use the service brake pedal to hold the vehicle while shutting down.

Question 6

A key safety rule states that a driver should never push the brake pedal down when the spring brakes are on. Why is this?

Accepted Answer

It can damage brake components due to the combined force of the springs and air pressure.

Answer

It can cause the air compressor to overheat.

Answer

It will immediately release the spring brakes, causing the vehicle to roll.

Answer

It can drain the vehicle's battery by activating the stop lights.