CDL practice tests
Practice for the written CDL knowledge tests you take for the commercial learner’s permit. Every question shows the right answer and why, and your progress is saved on this device.
- General KnowledgeFollowing distance, stopping distance, emergencies, cargo securement, alcohol rules, inspections and hours of service.57 questions · real test: 50, pass with 40
- Air BrakesCompressor and governor, air tanks, low-pressure warnings, spring brakes, dual systems, brake lag and the inspection tests.30 questions · real test: 25, pass with 20
- Combination VehiclesRollover and rearward amplification, coupling and uncoupling, trailer air lines, the tractor protection valve and doubles.24 questions · real test: 20, pass with 16
- Hazardous MaterialsPlacards, shipping papers, hazard classes, attending and parking a loaded vehicle, railroad crossings and emergencies.30 questions · real test: 30, pass with 24
- TankerWhich tanks need the endorsement, leak checks, high center of gravity, liquid surge, baffles and bulkheads, outage and braking a tanker.35 questions · real test: 20, pass with 16
- Doubles and TriplesRollover and the crack-the-whip effect, converter dollies, coupling and uncoupling twins and triples, shut-off valves and air brake checks.33 questions · real test: 20, pass with 16
- PassengerBus inspection, baggage and hazardous materials rules, the standee line, railroad crossings and drawbridges, rider problems and prohibited practices.35 questions · real test: 20, pass with 16
- School BusDanger zones, mirror adjustment, loading and unloading, students crossing, evacuation, railroad crossings, student management and backing.35 questions · real test: 20, pass with 16
Which tests you need
- General Knowledge. Everyone applying for a Class A, B or C CDL takes this test first.
- Air Brakes. Needed to drive any vehicle with air brakes; without it the CDL carries an air brake restriction.
- Combination Vehicles. Needed for a Class A CDL: tractor-trailers, and trucks towing trailers over 10,000 lb.
- Hazardous Materials. Needed for the H endorsement, together with a TSA security threat assessment.
- Tanker. Drivers who haul liquids or gases in bulk take this test for the N endorsement.
- Doubles and Triples. Class A drivers who pull double or triple trailers take this test for the T endorsement.
- Passenger. Drivers of buses and other vehicles built for 16 or more people, including the driver, take this test for the P endorsement.
- School Bus. School bus drivers need the S endorsement in addition to the P endorsement.
How the real knowledge test works
You take the knowledge tests at your state’s licensing office, usually on a computer. Most states set 80% as the pass mark, and the General Knowledge test usually has 50 questions. The question pool is written from your state’s CDL manual, which every state bases on the same national model, so the facts are the same everywhere even when the wording differs. Read your state manual as well as practicing here.
Passing gets you a commercial learner’s permit. After at least 14 days with the permit and entry-level driver training, you can take the skills test. The CDL classes and endorsements page explains which class and endorsements a job needs.
How these questions were written
Each question tests a fact from the model CDL manual. Where the fact is also a federal rule (following-distance warning devices, tire tread, alcohol limits, hazmat placards and parking) the explanation cites the section of the Code of Federal Regulations, checked against the current eCFR text.