CDL Practice Tests by Endorsement
The Federal Motor Carrier Safety Administration requires every commercial driver to pass a battery of knowledge exams before being issued a Commercial Driver's License. The exact tests you must take depend on the class of vehicle you intend to drive and the endorsements you need. Below are the eight knowledge tests covered on CDL Prep Hub. Click any category to begin practicing.
General Knowledge
The mandatory test every CDL applicant must pass: vehicle inspection, control, signaling, hazards, and safe operation.
Open practice test →Air Brakes
Required for any vehicle equipped with air brakes — covers compressors, governors, slack adjusters, and emergency systems.
Open practice test →Combination Vehicles
Class A endorsement test: coupling, fifth wheels, glad hands, off-tracking, and pulling tractor-trailers.
Open practice test →Hazardous Materials (Hazmat)
Required to carry placardable hazardous materials — paperwork, placards, segregation, routing, emergencies.
Open practice test →Tank Vehicles
Required for liquid or gas tanks of 1,000 gallons or more — surge, baffles, outage, and rollover prevention.
Open practice test →Doubles / Triples
Required to pull more than one trailer — converter dollies, pintle hooks, and crack-the-whip control.
Open practice test →Passenger Transport
Required for buses and other vehicles designed to carry 16 or more passengers, including the driver.
Open practice test →School Bus
Required to drive a school bus — danger zones, loading/unloading, and student management.
Open practice test →Which CDL tests do you need?
Every applicant takes the General Knowledge exam. Drivers who will operate a vehicle equipped with air brakes must also pass the Air Brakes test — failing it adds an "L" restriction to your license that prohibits operating air-brake-equipped vehicles. Class A applicants take the Combination Vehicles test, which covers tractor-trailers and other articulated combinations. The remaining endorsement tests are required only for the specialty work you intend to perform: Hazardous Materials (H) for placardable hazmat loads, Tank Vehicle (N) for liquid or gaseous bulk tanks of 1,000 gallons or more, Doubles/Triples (T) for multi-trailer combinations, Passenger (P) for buses with 16 or more seats including the driver, and School Bus (S) for any bus used to transport students to or from school.
Endorsements stack: a school bus driver typically holds the P and S endorsements, and a fuel-tanker driver typically holds N and H (often combined as the X endorsement). All endorsements except the air brake test are added to the license through the same testing process — pass the knowledge exam, pay the endorsement fee, and (for hazmat) complete the federal security threat assessment.
How the questions are organized
Each category page lists every question in that subject. Click any question to open a dedicated page that shows the question, four answer choices with the correct answer marked, and a written explanation that ties back to the AAMVA CDL Manual or to the specific section of 49 CFR that the question covers. Pages are linked sequentially so you can move forward or backward through the bank without returning to the index.
If you are studying for the first time, work through General Knowledge top to bottom — most state knowledge exams pull heavily from this bank. If you are renewing or adding an endorsement, jump straight to the relevant category. The questions you see here are representative of the AAMVA model exam; your state's specific test may include additional regional questions about state laws, weight limits, and routing.