What's on the CDL written test and how to prepare

The CDL written test covers vehicle operation, safety rules, and cargo handling specific to commercial trucks and buses. The test varies by the class of license you're seeking and the endorsements you need — a tanker endorsement test is different from a hazmat test, for example. Most states require you to pass a general knowledge test first, then tests for any endorsements you want to add.

The test is multiple choice, usually 50 questions for general knowledge, and you need to score around 80 percent to pass. You take it at your state's Department of Motor Vehicles or an approved testing location. Before you sit for the test, you'll need to study the CDL manual your state publishes — this is the actual source material the test questions come from, not a third-party guide.

Most states let you take the written test as many times as you need, but some charge a fee each time. Check your state's rules before you schedule, because a few states limit retakes or require a waiting period between attempts.

Key Takeaways

  • Your state's official CDL manual is the primary study material — test questions come directly from it, and you can usually read it free from your DMV website.
  • The general knowledge test covers vehicle inspection, safe driving practices, and braking systems; endorsement tests add specific rules for hazmat, tankers, doubles, or passenger vehicles.
  • You need roughly 80 percent correct to pass, and most states let you retake the test if you fail, though some charge a fee per attempt.
  • Many states offer practice tests online or at the DMV office so you can see the question format before test day.
  • You must have a valid regular driver's license and pass a medical exam before you can take the CDL written test.

How to get your state's CDL manual

Every state publishes its own CDL manual, and it's free. Go to your state's DMV website and search for "CDL manual" or "commercial driver's license handbook." Most states let you read it as a PDF, and some print physical copies you can pick up at a DMV office.

The manual covers the same topics the test will ask about: pre-trip vehicle inspection, braking systems, safe driving in different weather, cargo securement, and hours-of-service rules. Read through the entire manual at least once before you take any practice tests. The manual also explains what each endorsement requires, so you'll know which ones you need for your job.

Some states include sample questions in the back of the manual. These are worth doing, but they're not the same as a full practice test — they're just a few examples of the question style.

General knowledge test topics

The general knowledge test is required for all CDL applicants and covers the basics of operating a commercial vehicle. You'll see questions about vehicle inspection — knowing which parts to check before you drive, what to look for, and what makes a vehicle unsafe to operate. You'll also answer questions about braking systems, including how air brakes work, what happens if they fail, and how to brake safely on hills or wet roads.

Safe driving practices make up a large section: speed limits for trucks, following distance, turning, backing up, and how to handle skids or loss of brakes. The test also covers road hazards like railroad crossings, school buses, and driving in bad weather. You'll answer questions about vehicle weight and balance, tire safety, and securing cargo so it doesn't shift during transport.

Hours-of-service rules appear on the test because federal law limits how long you can drive without a break. The test asks about logbook rules, off-duty time, and what happens if you violate these rules. Some questions cover alcohol and drug use, because commercial drivers are held to stricter standards than regular drivers.

Endorsement tests and what each one covers

Endorsements are add-ons to your CDL that let you drive certain types of vehicles or cargo. You don't need all of them — only the ones required for the job you're taking. Each endorsement has its own written test.

Hazmat (H) covers rules for transporting hazardous materials. The test asks about labeling, placarding, loading, and what to do in an emergency. You'll study what materials are considered hazardous, how to recognize them, and safety procedures. This endorsement requires a background check in addition to the written test.

Tanker (N) covers vehicles that carry liquids in bulk tanks. The test focuses on how liquid shifts inside a tank during acceleration, braking, and turns, and how that affects vehicle handling. You'll learn about tank inspection, filling and emptying procedures, and why tanker vehicles are harder to control than box trucks.

Doubles/Triples (T) covers pulling two or three trailers at once. The test asks about coupling and uncoupling procedures, how to inspect multiple trailers, and how the extra length and weight change braking and turning. This endorsement is common for long-haul trucking.

Passenger (P) covers buses and vans that carry people. The test covers passenger safety, boarding and exiting procedures, emergency equipment, and how to handle medical emergencies or disruptive passengers. If you're driving a school bus, you'll need additional state-specific training beyond the CDL.

How to study effectively for the test

Start by reading your state's CDL manual from beginning to end. Don't try to memorize everything on the first read — focus on understanding the concepts. Take notes on topics that confuse you, and reread those sections. Many people find it helpful to read the manual twice: once to get the big picture, and once to focus on details.

After you've read the manual, use practice tests to see which topics you need to study more. Many states offer free practice tests on their DMV website. Some private websites also offer practice tests, but stick with ones that use questions from your state's manual, not generic CDL questions that might not match your state's test.

Take practice tests under test conditions: sit at a desk, set a timer, and don't look at the manual while you're answering. This helps you know what you actually remember versus what you can look up. When you finish, review every question you missed, not just the ones you got wrong — understanding why the right answer is right matters more than just knowing you got it wrong.

Study in short sessions rather than cramming. Spending 30 minutes a day for two weeks is more effective than studying for six hours the day before the test. If you're struggling with a topic, ask a truck driver or instructor to explain it in their own words — sometimes hearing it from someone who does the job makes it click.

What to bring and what to expect on test day

Bring your valid regular driver's license, proof of residency (usually a utility bill or lease), and any documents your state requires. Some states ask for proof of medical certification before you can test. Check your state's DMV website for the exact list of documents — showing up without the right paperwork means you won't be able to test that day.

The test is taken on a computer at a DMV office or approved testing center. You'll have a set amount of time — usually 60 minutes for general knowledge — to answer all the questions. You can't go back and change answers on most systems, so read each question carefully before you select your answer. If you don't know an answer, make your best guess rather than leaving it blank.

You'll get your score when ready after you finish. If you pass, you'll move on to the skills test (the driving test) and the pre-trip inspection test. If you fail, you can usually retake the written test after a waiting period that varies by state — some let you retake it the next day, others require a week between attempts.

Preparing for the skills test after you pass the written test

Passing the written test is the first step, but you also need to pass a pre-trip inspection test and a driving test to get your CDL. The pre-trip test requires you to walk around a truck and explain what you're checking and why — the examiner is listening for safety knowledge, not just whether you can point to parts.

The driving test happens on public roads and includes basic maneuvers like backing up, turning, and lane changes, plus highway driving. You'll be graded on safety, control, and following traffic laws. Many people pass the written test but fail the skills test because they haven't had enough practice behind the wheel of a commercial vehicle.

Before you schedule the skills test, get behind the wheel of a truck and practice. Some CDL training schools offer behind-the-wheel instruction, and some trucking companies will train you on the job. The more hours you drive before the test, the better your chances of passing.

Frequently Asked Questions

Can I use online practice tests instead of reading the manual?

No — the manual is the source material for the test, and reading it teaches you the concepts you need to understand. Practice tests are useful for checking what you've learned, but they're not a substitute for studying the manual. Use both together: read the manual first, then take practice tests to find gaps in your knowledge.

What happens if I fail the written test?

You can retake it. Most states let you schedule another test within a few days, though some require a waiting period. You'll pay the test fee again. Review the topics you missed and study those sections of the manual before your next attempt. Many people pass on the second or third try.

Do I need to take a class or hire a tutor to pass the CDL test?

No — the manual and practice tests are enough for many people. If you're struggling with specific topics, ask a truck driver to explain them, or look for free YouTube videos that break down concepts like air brakes or tanker dynamics. Paid CDL courses can help, but they're not required to pass the written test.

How long should I study before taking the test?

Most people study for two to four weeks, spending 30 minutes to an hour per day. If you have truck driving experience, you might need less time. If you're new to commercial driving, give yourself more time to understand the concepts. Take a practice test when you're scoring consistently above 85 percent, and you're probably ready for the real test.

Can I take the endorsement tests at the same time as the general knowledge test?

Most states let you take multiple tests in one visit, but check your state's rules first. Some states require you to pass general knowledge before you can test for endorsements. If you're taking multiple tests, budget extra time and consider spacing them out so you're not taking four tests in one day when you're tired.