CDL Air Brakes Test

How air brakes work, how to check them and how to drive with them.

The hardest of the eight When California studied its own tests, 78% of first tries at air brakes failed, against 40% for general knowledge (California DMV, 2008, on tests from 2006 to 2007).

Start practicing · Topic Study · Sample questions

What's on the Test

  1. General air brake system nomenclature (3 questions): The Parts of an Air Brake System, Dual Air Brake, Inspecting Air Brake Systems
  2. The dangers of contaminated air supply (dirt, moisture, and oil) (2 questions): The Parts of an Air Brake System
  3. Implications of severed or disconnected air lines between the power unit and the trailer(s) (2 questions):
  4. Implications of low air pressure readings (2 questions): The Parts of an Air Brake System, Dual Air Brake, Inspecting Air Brake Systems, Using Air Brakes
  5. Procedures to conduct safe and accurate pre-trip inspections (5 questions): The Parts of an Air Brake System, Dual Air Brake, Inspecting Air Brake Systems
  6. Procedures for conducting en route and post-trip inspections of air-actuated brake systems (5 questions): The Parts of an Air Brake System, Inspecting Air Brake Systems, Using Air Brakes
  7. General operating practices and procedures (6 questions): The Parts of an Air Brake System, Using Air Brakes

How the Exam Works

Who takes it
Anyone who will drive a truck or bus with air brakes.
Format
25 questions, each with three options.
To pass
20 right (80%), as on every CDL knowledge test (49 CFR 383.135).

Frequently Asked Questions

How many questions are on the CDL Air Brakes test?

25, and you need 20 right to pass. A few states differ; your state's CDL manual says.

What if I skip or fail the air brakes test?

Your permit or CDL gets the L restriction: no vehicle with air brakes of any kind, air-over-hydraulic included (49 CFR 383.95(a)).

Are these the real test questions?

No. They're our own, written from the federal rules and the CDL manual's facts, in the real test's format: three options each and the same number of questions. We're not affiliated with any state, FMCSA or AAMVA.

After the Test

Passing the knowledge tests for your vehicle gets you a commercial learner’s permit (CLP). Hold it at least 14 days, finish entry-level driver training, then take the skills test. How to Get a CDL