CDL General Knowledge Test: 50 Questions, 80% and How to Prepare

Here's something that surprises a lot of new drivers: the CDL general knowledge test isn't mainly about trucks. It's about judgment. How far ahead you look, how much space you leave, when to brake on a mountain grade, what to do when a tire blows. If you've driven a car for years, you already know half the vocabulary, and that's exactly why people underestimate it.

Every CDL applicant takes this test, whether you want a Class A tractor-trailer license, a Class B dump truck job or a school bus seat. Pass it (plus any endorsement tests) and you get your commercial learner's permit. Here's what's on it and how to study without wasting a month.

What the CDL general knowledge test covers

States build their CDL tests from the commercial driver's license manual that follows FMCSA's model, so the general knowledge material looks very similar from state to state. The test draws from three parts of the manual:

• Section 1, Introduction: license classes, disqualifications, and the basic rules every CDL holder lives under.
• Section 2, Driving Safely: the big one. Inspection, vehicle control, shifting, seeing, communicating, space and speed management, hazards, night and winter driving, railroad crossings, mountain driving, emergencies, skids, crashes, fires, and alcohol rules.
• Section 3, Transporting Cargo Safely: inspecting cargo, weight and balance, securing loads, and cargo that needs special care.

Sections for air brakes, combination vehicles, hazmat, passengers, tankers and doubles are separate tests. You don't need them for the general knowledge exam, though you'll likely take some of them the same day.

Format: 50 questions, 80% to pass

In most states, the CDL general knowledge test has 50 multiple-choice questions, and you need 80% to pass, which means 40 correct. Many states give it on a computer at the licensing office, and some let you skip and return to questions. Rules on retakes, waiting periods and fees are set by each state, so check your licensing agency before test day.

Section 2 of the manual: the heart of the test

If you only have time to master one section, make it Section 2. When we tagged the questions in our own CDL bank by topic, driving-safety topics and inspection topics made up the largest groups by a wide margin, which matches the manual's emphasis.

Within Section 2, give extra attention to:

• Vehicle inspection: the seven-step method, what to check on tires, wheels, suspension and steering, and when to inspect en route.
• Space management: following distance, space above and to the sides, and turning wide without swinging into another lane.
• Speed management: stopping distance, speed on curves, hydroplaning, and speed on downgrades.
• Hazards and emergencies: steering to avoid a crash, braking techniques, brake failure, tire failure, and skid recovery.
• Mountain driving: choosing a low gear before the downgrade and the "snub" braking method.

Section 3 deserves a solid second pass. Questions on cargo inspection timing, load balance and securement show up regularly and are easy points once memorized.

Numbers to memorize

Numbers are where most people drop points. Here are the ones the model manual uses; your state manual should match, but double-check if anything differs.

Read each number in context in the manual. Questions often hinge on a detail, like whether warning triangles go ahead of or behind the truck on a divided highway.

Common trap questions

The general knowledge test likes a few classic traps:

• "Which is NOT..." questions. Read the stem twice. The word "not" or "except" flips the answer.
• Brake failure on a downgrade. The answer is usually to look for an escape ramp or an escape route, not to pump the brakes hard all the way down.
• Hydroplaning. It can happen at speeds as low as 30 mph with enough water. Many drivers assume it takes highway speed.
• Hot engines. Don't remove the radiator cap on a hot engine; the safe-procedure answers involve letting it cool.
• Skids. Drive-wheel skids are corrected by taking your foot off the accelerator and, if on a slippery surface, pushing in the clutch.
• Railroad crossings. Never shift gears while crossing the tracks.

Trap questions get easier when you've seen the wording before, which is why practice tests matter as much as reading.

2-week study plan

This plan assumes about an hour a day. Adjust if you have more time.

Days 1–3: Read Section 1 and the first half of Section 2 (inspection through space management). Take one short practice set each night.

Days 4–6: Finish Section 2: hazards, night and winter driving, mountain driving, emergencies, crashes and fires. Make flash cards for every number you meet.

Day 7: Take a full 50-question practice exam. Write down every topic you missed.

Days 8–9: Read Section 3 on cargo. Re-read the topics from your missed list.

Days 10–12: One full practice exam per day. Aim for 90%+, which gives you a cushion over the real 80% cutoff.

Day 13: Review flash cards only. Start studying air brakes and combination vehicles if you're taking them.

Day 14: Light review, good sleep, and test.

Our free CDL practice tests mirror the topics in the manual, and Premium adds an exam simulator that draws questions you've seen least. After the general knowledge test, continue with the CDL air brakes test and read how to get a CDL permit so your paperwork is ready. For the official rules behind CDL testing, see FMCSA's commercial driver's license program.

Frequently asked questions

How many questions are on the CDL general knowledge test?

Most states use 50 questions and require 40 correct answers (80%). Check your state's CDL manual, since a few states format the test differently.

Is the CDL general knowledge test hard?

It's harder than a car permit test because it covers more numbers and more technical topics. Drivers who read Section 2 carefully and score 90% or better on practice tests usually pass.

Can you retake the CDL knowledge test the same day?

That's up to your state. Some allow a same-day retest, others make you wait a day or longer and may charge again, so check before you go.