Free CDL General Knowledge Practice Test 2026
The General Knowledge test is required for every CDL applicant regardless of class or endorsement. It covers vehicle inspection, basic control, shifting, communicating, space management, seeing hazards, and emergency procedures.
What is the safest approach to backing a commercial vehicle?
About the CDL General Knowledge Test
Every CDL starts here. The General Knowledge test is the one exam no commercial driver can skip, and it sets the foundation for every endorsement that follows. Expect questions on the multi-step pre-trip inspection, controlling a heavy vehicle's speed and space, keeping a following distance that grows with length and weight, scanning far down the road for hazards, and reacting to skids, brake failure, and other emergencies. Master this test and most endorsement material will already feel familiar.
What's on the CDL General Knowledge knowledge test
The General Knowledge knowledge test is written from Section 2 (Driving Safely) and Section 3 (Transporting Cargo Safely) of the national CDL manual, the text every state's CDL manual follows. Every CDL applicant takes it, whatever class or endorsement they are after.
Federal rules fix the pass mark at 80 percent for every CDL knowledge test, but leave the number of questions to each state, so check your own state's CDL manual for the exact count. This practice test uses all 25 questions in our General Knowledge bank, each checked against the manual page shown with it.
- Source manual
- National CDL Manual, Section 2 (Driving Safely) and Section 3 (Transporting Cargo Safely)
- Number of questions
- Set by each state: federal rules require a set number of questions, with a prescribed number from each knowledge area (49 CFR 383.133)
Manual sections this test is drawn from
- Section 2: Driving Safely - Vehicle Inspection, Basic Control of Your Vehicle, Shifting Gears, Seeing, Communicating, Controlling Speed, Managing Space, Seeing Hazards, Distracted Driving, Aggressive Drivers/Road Rage, Driving at Night, Driving in Fog, Driving in Winter, Driving in Very Hot Weather, Railroad-highway Crossings, Mountain Driving, Driving Emergencies, Antilock Braking Systems (ABS), Skid Control and Recovery, Accident Procedures, Fires, Alcohol, Other Drugs, and Driving, Hazardous Materials Rules for All Commercial Drivers
- Section 3: Transporting Cargo Safely
Sample questions from this test, with answers
Want to test yourself first? Take the test above before reading these. Every answer below is checked against the source shown.
1. What is 'controlled braking' in an emergency stop?
- A. Pressing the pedal to the floor and holding it there
- B. Pumping the brakes rapidly the whole time
- C. Braking as hard as you can without locking wheels (correct)
- D. Using only the trailer or parking brakes
Why: With controlled braking you brake as hard as possible without locking the wheels and keep steering movements very small. If you must steer more or the wheels lock, release the brakes and reapply as soon as you can.
Source: National CDL Manual, p.2-34 (PDF p.56), 2.17.2 How to Stop Quickly and Safely
2. How should you hold the steering wheel?
- A. With one hand at the bottom of the wheel
- B. Lightly, so the wheel can center itself
- C. Firmly with both hands on opposite sides (correct)
- D. With one hand, keeping the other free
Why: Hold the wheel firmly with both hands on opposite sides. If you hit a curb or pothole, the wheel could pull away from you unless you have a firm hold.
Source: National CDL Manual, p.2-8 (PDF p.30), 2.2.2 Steering
3. What is the safest approach to backing a commercial vehicle?
- A. Back quickly so it is over sooner
- B. Avoid it when you can and use a helper (correct)
- C. Rely only on the inside rearview mirror
- D. Back toward the right side when possible
Why: Backing is always dangerous because you cannot see everything behind you. Park so you can pull forward, use a helper when you must back, back slowly, and back toward the driver's side when possible.
Source: National CDL Manual, p.2-8 (PDF p.30), 2.2.4 Backing Safely
4. What three distances make up total stopping distance?
- A. Reaction, braking, and coasting distance
- B. Perception, reaction, and braking distance (correct)
- C. Perception, following, and braking distance
- D. Braking distance only, at any speed
Why: Total stopping distance is perception distance plus reaction distance plus braking distance. Vehicles with air brakes also add brake lag distance.
Source: National CDL Manual, p.2-13 (PDF p.35), 2.6.1 Stopping Distance
5. During a pre-trip inspection, how much tread depth do front tires need?
- A. 2/32 inch in every major groove
- B. 1/32 inch in every major groove
- C. 4/32 inch in every major groove (correct)
- D. 6/32 inch in every major groove
Why: Front tires need at least 4/32 inch of tread in every major groove, and other tires need 2/32 inch. Also check for bad wear, cuts, bulges, and wrong air pressure.
Source: National CDL Manual, p.2-1 (PDF p.23), 2.1.3 What to Look For (Tire Problems)
6. What causes brake fade?
- A. Brake linings wearing out over many years
- B. Excess heat from using the brakes too much (correct)
- C. Ice forming in the brake lines in winter
- D. Driving with brakes that are too cold
Why: Using the brakes too much instead of relying on engine braking overheats them. The heat changes the linings so they grip less and expands the drums, until the vehicle may not slow down at all.
Source: National CDL Manual, p.2-32 (PDF p.54), 2.16.3 Brake Fading or Failure
Other CDL Endorsement Tests
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