The CDL (Commercial Driver License) knowledge tests are a series of FMCSA-mandated written exams you must pass before operating a commercial motor vehicle (CMV) on public roads. Depending on the class of vehicle you plan to drive and the cargo you'll carry, you may need to pass the General Knowledge test plus one or more endorsement tests. Every state administers CDL exams at its local DMV or licensing office.
Studying with a printable PDF lets you review CDL material away from a screen — ideal for truck stops, break rooms, or anywhere you have a few minutes to drill questions. Our free CDL practice test PDF covers General Knowledge, Air Brakes, Combination Vehicles, and Hazmat so you can prepare for all four of the most commonly required knowledge tests in one download.
Each CDL knowledge test targets a specific area of commercial vehicle operation. Here is what you need to know for the four most common exams.
The General Knowledge test is mandatory for every CDL applicant. It covers pre-trip vehicle inspection procedures (engine compartment, brake system, lights, tyres, mirrors, and emergency equipment), basic vehicle controls (steering, shifting manual and automatic transmissions, backing and turning), space management and following distances, night driving and adverse weather operation, mountain driving and runaway truck ramps, and cargo securement rules including weight distribution. You must also know FMCSA hours-of-service (HOS) regulations: the 11-hour driving limit, 14-hour on-duty window, 30-minute rest break requirement, and the 60/70-hour weekly limits.
Any driver operating a vehicle with air brakes must pass this test or have the air-brake restriction removed from their licence. Topics include the dual air brake system (primary and secondary circuits), the air compressor and governor (cut-in/cut-out pressure), air reservoirs, the brake pedal (foot valve), slack adjusters, the low-air-pressure warning (activates at 60 psi), spring parking brakes, brake fade and heat buildup on long downgrades, brake lag distance (approximately 32 feet at 55 mph), and the full pre-trip air brake check procedure (leak-down test, low-air warning test, parking brake test).
Required for Class A drivers, this test covers coupling and uncoupling procedures for semi-trailers and full trailers, the fifth-wheel locking mechanism inspection, dolly/pintle hook connections, anti-lock braking system (ABS) trailer relays, rearward amplification and crack-the-whip rollover risk, off-tracking in turns, and safe backing techniques. Understanding the difference between a B-train and A-train combination and knowing weight distribution rules for tandem axle placement are also tested.
The Hazmat endorsement requires a TSA Security Threat Assessment (fingerprint-based background check) in addition to the written test. Test topics include DOT hazard classes and their placard requirements (explosive, flammable liquid, poison gas, radioactive, etc.), shipping papers (bill of lading, hazardous materials entry, emergency contact number), the Emergency Response Guidebook (ERG), loading and unloading rules (forbidden materials, quantity limits), the route restriction rules for tunnels and populated areas, and driver responsibility during a hazmat incident or spill.
A Class A CDL covers any combination of vehicles with a GVWR over 26,001 lb where the towed unit exceeds 10,000 lb — primarily semi-trucks and tractor-trailers. A Class B CDL covers single vehicles over 26,001 lb (city buses, dump trucks, straight trucks) plus vehicles towing units under 10,000 lb. A Class C CDL covers vehicles that don't meet Class A or B thresholds but transport 16+ passengers or placardable hazmat quantities.
Print the PDF and work through each section as a timed drill. For the General Knowledge section, aim for 50 questions in 60 minutes. For endorsement sections, hold yourself to 25–30 minutes. After scoring each section, flag every question you answered incorrectly and look up the relevant section in the FMCSA CDL handbook (available free at fmcsa.dot.gov).
Pair the printed PDF with our online CDL practice tests for immediate answer feedback and detailed explanations. The online tests also track your weak areas by topic so you can focus your remaining study time where it counts most. Many CDL candidates find that alternating between online and printed practice — using the PDF for final-day review — produces the best retention.
Pay special attention to the Air Brakes section even if you are not required to take that endorsement: understanding air brake systems helps with pre-trip inspection questions that appear on the General Knowledge test. Similarly, Hazmat placard questions occasionally appear as scenario-based questions in the General Knowledge test, so broad familiarity with all sections pays off.