The written test covers vehicle operation, safety rules, and cargo handling specific to commercial trucks

The Commercial Driver License (CDL) written test is a knowledge exam administered by your state's Department of Motor Vehicles. It tests your understanding of federal and state regulations, safe driving practices for large vehicles, and the specific endorsements you need (hazmat, passenger transport, tanker, doubles/triples). You must pass the written test before you can take the skills test, which includes a pre-trip inspection, basic vehicle control, and an on-road driving evaluation.

The test format varies slightly by state, but most use a computer or paper exam with multiple-choice questions. You typically need to score 80 percent or higher to pass. The number of questions depends on which endorsements you pursue — the general knowledge section is mandatory, and each endorsement adds additional questions.

Key Takeaways

  • You must pass the written test before scheduling the skills test, and you can retake the written test if you fail, though waiting periods vary by state.
  • The test covers general knowledge (braking, steering, cargo weight), air brakes if your truck has them, and any endorsements like hazmat or passenger transport.
  • Study materials are free: your state DMV publishes the CDL handbook online, and many states offer practice tests on their websites.
  • Bring a valid ID and proof of residency to the testing location; some states require you to schedule an appointment in advance.

What the general knowledge section covers

The general knowledge portion tests your understanding of vehicle control, safe driving practices, and federal regulations. Questions cover topics like how to brake safely with a heavy load, how to handle skids, how to position your vehicle on curves, and how to manage fatigue. You will also answer questions about vehicle inspection, load securement, and hours-of-service rules — the federal limits on how long you can drive without rest.

This section typically contains 50 questions, and you need to answer at least 40 correctly to pass. The questions are drawn from the CDL handbook your state publishes, so studying that handbook is the most direct way to prepare. Many states also post sample questions or full practice tests on their DMV websites at no cost.

Air brakes, hazmat, and other endorsements

If your truck has an air brake system, you must pass an air brakes test — this is not optional if your vehicle uses air brakes. The test covers how air brakes work, how to inspect them, and how they differ from hydraulic brakes. This section usually has 25 questions, and you need to pass with 80 percent or higher.

Endorsements like hazmat (hazardous materials), passenger transport, or doubles/triples are optional but required if you plan to haul those cargo types or vehicle configurations. Each endorsement adds a separate test section with its own questions and passing score. For example, the hazmat test covers how to identify hazardous materials, proper placarding, and emergency procedures. You do not have to take all endorsements at once — you can pass the general knowledge and air brakes tests first, then add endorsements later.

How to study and what materials are free

Your state's DMV publishes the official CDL handbook, which is the source material for all test questions. read it from your state DMV website — it is free. Read through the sections that explore to your vehicle type and endorsements. The handbook is written in plain language and includes diagrams of vehicle systems, braking techniques, and load securement.

Many states also offer free practice tests on their DMV websites. These practice tests use the same question format and difficulty as the real test, so taking them multiple times helps you identify weak areas. Some third-party websites offer practice tests as well, though not all are accurate — stick with your state DMV's official materials when possible. Study groups or online forums for truck drivers can also point you to reliable resources.

Testing locations, scheduling, and what to bring

You take the written test at your state's DMV office or an authorized testing location. Some states allow you to test at third-party locations like truck driving schools or private testing centers. Check your state DMV website to find locations near you and see whether you need to schedule an appointment or can walk in.

Bring a valid government-issued photo ID (driver's license, passport, or state ID) and proof of residency (utility bill, lease, or bank statement with your current address). Some states also require proof of Social Security number. Arrive early — testing centers often have specific hours, and you may not be allowed to test if you arrive after a certain time. Leave phones and study materials outside the testing room; most testing centers do not allow them at your desk.

Retaking the test if you fail

If you do not pass, you can retake the test, but waiting periods vary by state. Some states let you retake it the next day; others require you to wait one week or longer before your next attempt. Check your state's rules before your first test so you know what to expect if you need to try again.

When you retake the test, you are usually tested on the same subject areas but with different questions. Use your first attempt as a learning experience — note which topics gave you trouble and study those sections more thoroughly before your next test. The practice tests are especially useful for this: take them, review the questions you missed, and study those topics in the handbook.

Moving from the written test to the skills test

Once you pass the written test, you are cleared to schedule the skills test. This is a separate exam that happens on a different day and tests your ability to actually operate the vehicle. The skills test has three parts: a pre-trip inspection (you walk around the truck and point out safety-critical components), basic vehicle control (backing, turning, and parking in a controlled area), and an on-road driving evaluation (typically 30 to 50 minutes of actual driving).

You must bring the same ID and residency documents to the skills test. You also need to bring a vehicle that meets federal standards — it must be the same type of vehicle you will be driving commercially (a Class 8 truck for over-the-road hauling, for example). Some truck driving schools provide vehicles for testing; others require you to bring your own or rent one.

Frequently Asked Questions

Can I take the CDL written test online from home?

No. You must test in person at a DMV office or authorized testing location. The test is proctored to prevent cheating. Some states have expanded testing locations to include third-party centers, so check your state DMV website for options near you.

How long is the written test?

The test itself usually takes 30 minutes to an hour, depending on how many endorsements you are testing for. Plan to spend 1.5 to 2 hours at the testing location to account for check-in, instructions, and any wait time.

What happens if I fail one endorsement but pass the general knowledge section?

You pass the sections you scored 80 percent or higher on. You can retake only the endorsement you failed without retaking general knowledge. This means you can add endorsements one at a time if you prefer, rather than testing for all of them at once.

Do I need a CDL permit before I take the written test?

Requirements vary by state. Some states require you to hold a CDL permit (obtained by passing the written test) before you can take the skills test. Others let you go straight to the skills test. Check your state DMV website for the exact sequence in your state.

Is the written test the same in every state?

The general knowledge and endorsement tests are based on federal standards, so the content is very similar across states. However, each state writes its own questions and may emphasize different topics. Study your state's official CDL handbook, not a generic one, to match your state's test.