The air brakes systems in commercial vehicles function differently than the brakes in your personal vehicle. They use compressed air and are a safe means of stopping heavy, large vehicles. Air brakes are actually made up of three systems: an emergency brake, a parking brake and service brakes.  Understanding how the air brakes system is essential to ensure it is properly functioning and when maintenance is required.

Due to this, federal law requires that you pass the air brakes tests and hold the appropriate CDL before driving a vehicle with full air brakes. The tests ensure that you have a general knowledge of the air brakes system and know how to properly inspect it and identify potential problems. Until you pass the tests, your CDL will have the L or Z restriction.

  • The L restriction prohibits you from driving vehicles with air brakes systems if you fail the air brakes knowledge test, can’t identify the system components or conduct an inspection, or don’t drive a vehicle with air brakes during the road skills test.
  • The Z restriction keeps you from driving air brakes-equipped vehicles if you drove a vehicle with an air-over-hydraulic brakes system during the CDL road skills test.

Some states require only Class A CDL applicants to take the air brakes tests. Other states also require Class B CDL applicants to pass these exams because some Class B vehicles have air brakes. Ask your local DMV whether or not your state requires air brakes tests for all commercial vehicle drivers.

Air Brakes Tests

To avoid the L or Z restriction on your CDL, you need to pass two air brakes tests: a knowledge test and road skills test. Learn what to expect on each of these exams in the sections below.


Topics Covered on the Air Brakes Knowledge Test

The first part of the air brakes assessment involves a multiple-choice knowledge test. It’s different in each state but generally has 20 to 30 questions and covers similar topics.

You must take this exam when you intend to drive a commercial vehicle with air brakes, whether you’re earning your CDL for the first time or removing a restriction from your CDL.

Take a look at the topics on the test so that you can be prepared:

  • how the system works,
  • what each component is and does,
  • what to do in certain situations, and
  • when to perform regular maintenance such as draining the air tank.


Topics Covered on the Air Brakes Skills Test

The second part of the air brakes assessment is the road skills test. You must take this exam before driving a vehicle with an air brakes system. To pass this exam, you need to properly identify the air brakes components and perform a full inspection of the system.

How to Prepare for the Air Brakes Tests

Now that you have an idea of what exactly you will be tested on, you need a way to learn the information. We recommend that you implement the following two-step study plan.


CDL Manuals

Each state has its own CDL manual. To learn everything that you need to know about air brakes systems, study the Air Brakes subsection of the Class A section.

Along with demonstrating how to identify the components of the system, this section will describe how to use the air brakes and how to perform the seven-step inspection. You can find the CDL manual for your state here.


CDL Practice Tests

It might be cliche, but practice really does make perfect. This is why air brakes practice tests are so important to your preparation for the real thing. Practice tests give you a better understanding of the phrasing that your state uses for its multiple-choice questions and allow you to see similar questions asked different ways.

Additionally, failing the tests mean that you pay extra fees the next time you attempt them. Utilizing the air brakes practice tests that you find here can give you a significant advantage to passing.


Essential Test-Taking Strategies

Tests are meant to be challenging, but along with studying and practicing, several strategies can help you achieve success. Preparing your body is one strategy, and this involves getting enough rest the night before and eating a well-balanced meal before you go to the DMV.

You can use the following strategies during your tests:

  • Carefully read the directions.
  • Fully read each question before choosing an answer.
  • Form your own answer before reading the choices.
  • Eliminate choices that you know are incorrect.
  • Don’t leave any questions blank.
  • Pace yourself so that you don’t feel rushed.
  • Try not to be nervous.

Even if you don’t intend to drive a commercial vehicle with an air brakes system, having the ability to drive one will make you a more versatile driver. Passing these tests could even open the door to job opportunities that you never dreamed of.