CDL General Knowledge Practice Test
The core knowledge test every CDL applicant must pass, covering safe driving, vehicle inspection, control, and hazards.
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About the CDL General Knowledge test
The CDL General Knowledge test is the one written exam every commercial driver must pass, no matter which class of license or endorsements you are after. It covers the safe-driving fundamentals from the federal Commercial Driver License Manual: inspecting your vehicle, controlling it, managing space and speed, and handling hazards. Because the same core material appears on every state CDL test, mastering it here prepares you wherever you test.
What the General Knowledge test covers
- Vehicle inspection: the pre-trip, en-route, and post-trip checks, and what common defects (like excessive brake-pedal travel or low air pressure) mean.
- Basic control and shifting: using controls and gauges, smooth shifting and double-clutching, and choosing the right gear on grades.
- Seeing and communicating: mirror use and visual search, signaling your intentions, and using your horn and lights correctly.
- Managing space and speed: following distance, total stopping distance (perception plus reaction plus braking), and adjusting for curves, hills, and load weight.
- Hazards and emergencies: night, fog, and winter driving, railroad crossings, skid recovery, controlled and ABS braking, and what to do at an accident scene.
Common mistakes to avoid
The questions people miss most are about total stopping distance (it grows with the square of speed, so doubling your speed roughly quadruples your braking distance), how a heavy load changes stopping and handling, and the right way to brake. Many applicants also confuse what to do in a skid and when to use engine braking on a long downgrade. Slow down and read each answer fully: the wrong options often describe something that sounds reasonable but is unsafe.
How to study for it
Take the full practice test until you are consistently above the pass mark, then run the exam simulator to rehearse under time. Use the topic breakdown after each attempt to see which areas pull your score down, and re-read those chapters of your state CDL manual. Aim higher than the minimum: general knowledge is the foundation the air brakes and combination tests build on.
Other CDL tests
Air Brakes
Needed by nearly all Class A and most Class B drivers.
Combination Vehicles
Required for every Class A (tractor-trailer) applicant.
HazMat (H)
Drivers hauling placarded hazardous materials.
Passenger (P)
Bus, transit, and shuttle drivers.
School Bus (S)
School bus drivers (requires the Passenger endorsement first).
Tanker (N)
Drivers of liquid or gas tank vehicles.
CDL General Knowledge test FAQ
How many questions are on the CDL General Knowledge test?
Most states use a 50-question General Knowledge test and require about 80% correct (40 of 50) to pass. Our full practice mode and exam simulator use the same 50-question length so you rehearse the real thing.
Is the CDL General Knowledge test the same in every state?
The core content is federal, drawn from the AAMVA/FMCSA model CDL manual, so it is nearly identical from state to state. A few details like the exact passing count or a handful of state rules can differ, so confirm specifics with your state CDL manual.
Do I need the General Knowledge test for every CDL class?
Yes. Every CDL applicant, whether Class A, B, or C, must pass the General Knowledge test. Endorsements like air brakes, combination vehicles, HazMat, or passenger are added on top of it.
Are these the real CDL test questions?
No. These are original practice questions written to match the topics, format, and difficulty of the official test. The real exam uses its own questions, but studying these prepares you for the same material.