CDL General Knowledge Practice Test: What's on It
The CDL general knowledge test covers 50 multiple-choice questions on safe driving, vehicle systems, basic vehicle control, cargo handling, and (for combination vehicles) coupling and air brakes, and every state requires a score of at least 80 percent, meaning 40 correct answers, to pass. Every CDL applicant takes this exam, no matter which class or endorsement they’re chasing.
The exact question pool differs by state because each one layers its own supplement onto the federal core content, and whether you also need an air brakes or combination vehicle section depends on the vehicle you plan to drive. That’s the part most practice sites gloss over, so we’re breaking it down section by section, with real sample questions and the actual state and federal pages you can verify this against.
What’s actually on the general knowledge test?
The general knowledge test draws from five core topic areas that every state builds into its CDL manual: safe driving practices, the vehicle’s systems and gauges, basic control and backing, vehicle inspection, and cargo securement. If you’re testing for a combination vehicle (most Class A drivers), you’ll also sit a separate combination vehicles section covering coupling, uncoupling, and how a tractor-trailer behaves differently from a straight truck.
Air brakes get their own section too, and it applies to anyone testing in a vehicle equipped with them. Skip the air brakes section and you’ll pass with a restriction (code L) that blocks you from driving any commercial vehicle with a full air brake system, so most drivers plan to take it rather than work around it later.
Most state manuals also fold basic hours-of-service and driver fitness material into the safe driving section rather than giving it its own heading, so don’t skip that chapter assuming it’s covered elsewhere. We’ve watched test takers miss two or three questions purely because they treated the fitness-for-duty pages as background reading instead of testable content.
How many questions are there, and what score do I need?
Fifty questions, and you need 40 correct, which is 80 percent. The California DMV’s Commercial Driver Handbook states this directly for its general knowledge section, and Virginia’s DMV puts it just as plainly on its 2026 site: “you must answer at least 80% of the general knowledge questions correctly” to pass. We checked both because state manuals occasionally reword their sections year to year, and the 80 percent threshold has held steady across every state we reviewed.
There’s no clock running while you test in most states, though a handful set a soft time expectation. Plan on 45 to 75 minutes if you’re reading each question carefully rather than racing through it.
Do I need ELDT training before I can take this test?
Only if you’re getting a Class A or Class B CDL for the first time, upgrading a Class B to a Class A, or getting a school bus, passenger, or hazmat endorsement for the first time. FMCSA’s entry-level driver training rule took effect February 7, 2022, and it is not retroactive: if you already held that CDL or endorsement before that date, you don’t need to complete ELDT to keep it, renew it, or move it to a new state.
Where ELDT does apply, training providers must be listed on FMCSA’s Training Provider Registry, and the theory portion has no fixed hour requirement. Instead, FMCSA’s ELDT curriculum standards require trainees to hit an overall minimum score of 80 percent on the theory assessment before moving to behind-the-wheel instruction, which itself is graded on proficiency rather than a set number of hours. That’s a meaningfully different bar than the “X hours in the seat” model a lot of state programs used to run.
Does the test differ by CDL class?
The core general knowledge content is the same whether you’re going for Class A, B, or C, since FMCSA sets one federal standard for it, last updated on FMCSA’s site February 4, 2026. What changes is which extra sections you’re required to add. Class A drivers pulling a trailer add the combination vehicles section. Class B drivers in a single vehicle over 26,001 pounds skip that section unless they’re also getting a passenger or school bus endorsement. Class C, which covers smaller vehicles hauling 16 or more passengers or placarded hazmat, only applies once you need one of those specific endorsements.
What does it cost, and how many times can I retest?
Fees are set state by state, not federally, so they range widely. Vermont’s DMV charges $39 for the CDL knowledge test and $17 per additional endorsement test, per its fee schedule posted April 10, 2026. Other states bundle the knowledge test into a single permit fee that runs anywhere from $10 to $90. Check your state DMV’s current fee page before you schedule, since these numbers move.
Retake policies vary more than fees do. Most states let you retest the next business day for a repeat fee. California is stricter: fail three times and your application is voided, which means starting the permit process over from scratch. Virginia draws a similar line for older failures: fail the general knowledge exam three times before February 7, 2022, and you had to complete the classroom portion of a state-approved driver training program before retesting, per Virginia DMV’s current CDL testing page. We’d rather you know that going in than find out at the counter.
How should I actually study for it?
Pull your current state’s CDL manual first, not a generic national guide, because state supplements cover traffic laws that don’t show up anywhere else. Then run timed practice sets and track which sections you’re missing, air brakes and cargo securement tend to trip up first-time test takers more than safe driving basics does. Give yourself at least a week of daily 20-minute sessions rather than one long cram; the material is procedural, and procedural knowledge sticks better in short repeated passes.
We rebuilt our own practice sets more than once after cross-checking three state manuals side by side, because wording that looked equivalent on paper tested differently in practice. Treat your state manual’s exact phrasing as the answer key, not just the general idea behind it, especially on air brakes and cargo securement questions where the correct sequence of steps matters as much as the concept.
CDL general knowledge test at a glance
| Item | Detail |
|---|---|
| Questions | 50, multiple choice |
| Passing score | 80% (40 correct) |
| Extra sections | Air brakes, combination vehicles, as applicable |
| ELDT required | Only for first-time Class A/B CDL or first-time P/S/H endorsement, since Feb 7, 2022 |
| Typical fee | $10 to $90+ depending on state (Vermont: $39 knowledge test) |
| Retake limit | Varies by state; California voids after 3 failures |
| Study source | Your current state’s CDL manual |
Sample questions we wrote to match the real test’s format
1. You’re driving a loaded truck down a long, steep grade. What’s the correct braking approach? Select a low gear before you start down the grade and apply light, steady pressure. Riding the brakes continuously overheats the drums and causes brake fade, which is the opposite of what you want on a long downgrade.
2. What’s the minimum following distance for a large vehicle at speeds below 40 mph? One second for every 10 feet of vehicle length. At 40 mph or above, add one more second on top of that.
3. What must a pre-trip inspection cover? Fluid levels, belts and hoses, steering and suspension, brakes, tires, lights and reflectors, and, on a combination vehicle, the coupling system between tractor and trailer.
4. At what air pressure does the low air pressure warning device have to activate? Before the tank pressure drops below 60 psi, or the value the manufacturer set, whichever is higher.
5. Your vehicle starts to hydroplane. What do you do? Ease off the accelerator and don’t brake. Let the vehicle slow on its own until the tires regain contact with the road.
6. How do you know if a load requires a hazmat placard? The shipping papers will identify the material’s hazard class, and federal placarding rules under 49 CFR Part 172 determine whether that class and quantity requires a placard on the vehicle.
7. What’s the safest way to back a straight truck or tractor-trailer? Get out and look before you back. Use a helper if one’s available, back slowly, and check your mirrors continuously. Avoid backing toward your blind side whenever the route gives you a choice.
8. Why does poor cargo weight distribution matter? Unbalanced or unsecured cargo raises the vehicle’s center of gravity, which increases rollover risk on curves or during emergency maneuvers. Weight has to be distributed and secured according to load securement rules, not just piled on.
9. Your brakes fail while you’re driving. What’s the sequence? Downshift, apply the parking or emergency brake gradually, and look for an escape route or open path. Avoid slamming the brakes, which can lock the wheels and take away what steering control you still have.
10. What sign of fatigue means you need to stop driving now, not later? Trouble keeping your eyes open, drifting between lanes, or missing exits and signs. Any of those means you pull over and rest instead of pushing to the next stop.
If you want to see where you actually stand before test day, run a full-length practice set on CDL Practice Hub and score it the same way your state does, at 80 percent. Pair that with the CDL Practice Hub study guide, which walks through every general knowledge topic in the order most state exams weight them, so you’re not guessing which sections deserve the most review time.
FAQ
How many times can I retake the CDL general knowledge test if I fail? Most states let you retest right away for a repeat fee, but a few, including California, void your application after three failures and make you restart the permit process from the beginning. Check your state’s CDL manual supplement before you schedule a retest, since waiting periods and retake caps aren’t federally standardized.
Is the general knowledge test the same in every state? The core content, safe driving, inspection, hours of service, cargo, is federally standardized, but each state adds its own supplement covering state-specific traffic laws. That means the exact question pool differs state to state even though the underlying skills being tested are identical nationwide.
Do I have to pass the general knowledge test before I get a permit? Yes. Passing the general knowledge test, plus any air brakes or combination vehicle section that applies to your class, is required before your state issues a commercial learner’s permit. You then hold that permit for a minimum waiting period before you can schedule the skills test.
Can I take the test in a language other than English? It depends on the state. Some still offer multiple languages, but Texas DPS announced it moved to English-only CDL and CLP knowledge testing for all exams scheduled on or after June 1, 2026, matching FMCSA’s English proficiency standard. Confirm your state’s current policy before you register.
I got my CDL before 2022. Do I need ELDT now? No. FMCSA’s entry-level driver training rule isn’t retroactive. If you held a CDL, or an S, P, or H endorsement, before February 7, 2022, you don’t need to complete ELDT for that same credential, even when you renew it or move it to a different state.
Bottom line: the general knowledge test is 50 questions, an 80 percent passing bar, and a question pool that’s federally consistent in substance but state specific in wording. Study your current state manual, run practice sets until the weak sections stop being weak, and confirm your state’s fee and retake rules before you walk in.