10 Things You Should Do Before Your CDL Knowledge Exam

Many people arrive at the DMV overconfident and underprepared, neglecting simple steps that would ensure they pass. Here are 10 steps every aspiring commercial driver should take to prepare for the CDL or CLP knowledge exam.

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1o things you should do before your CDL exam

CDL Classes and Endorsements Overview (July 2024):

As you earn your Class A, Class B or Class C CDL, you can also earn endorsements. Endorsements allow you to drive certain vehicles or groups of vehicles such as single or combination trucks, tankers, doubles, school buses and passenger vehicles. The more endorsements you hold, the greater your chances to make more money and advance your career. You'll need to pass a separate knowledge exam and/or road exam for each endorsement you want to get. Learn more about CDL endorsements and restrictions.

Type of EndorsementCodeDescriptionRequired test(-s)
CDL General Knowledge Test-Even though technically it's not an endorsement, it's the first of several tests that you will have to complete in order to get your CDL. Includes questions on road signs, traffic laws, safe driving practices, vehicle equipment, and other important topics.Knowledge test
CDL Air Brake TestA (L Restriction Removal)If your CDL application requires an air brake endorsement, you will need to pass an air brakes test. This test will test your knowledge of air brakes and other vehicle components and systems.Knowledge test
CDL Combination TestXThis Combination endorsement covers both Tanker and Hazardous Materials.Knowledge test
CDL Doubles and Triples TestTIf you want to operate a vehicle with more than one trailer attached (doubles or triples), you will need to pass a doubles and triples test.Knowledge test
CDL HazMat TestHThis test covers all you need to know about driving vehicles that can carry hazardous materials, such as poisonous liquids or materials, explosives and radioactive materials.Knowledge test
CDL School Bus TestSThis endorsement allows you to transport students in a full-sized school bus.Prior to obtaining an S endorsement, a P endorsement must be earned.Knowledge test and road test
CDL Tank TestNThis endorsement allows you to aperte a tank vehicle (a vehicle that transports liquids or gasses in bulk.)Knowledge test
CDL Passenger TestPThe P endorsement is needed to operate a vehicle that seats 16 or more people, including the driver.Knowledge test and road test

Practice on the go and offline with our CDL Genie app:

What's a Commercial Driver's License?

CDL License
A commercial driver’s license (CDL) is a driver’s license that authorizes a person to operate a class of commercial motor vehicles (CMVs). Federal standards define three classes of CDLs, each for a corresponding group of motor vehicles:
  • Class A (Combination Vehicles): Any combination of vehicles with a gross combination weight rating (GCWR) of at least 26,001 pounds provided the gross vehicle weight rating (GVWR) of the vehicle(s) being towed exceeds 10,000 pounds. Examples include tractor-trailers.
  • Class B (Heavy Straight Vehicles): Any single vehicle with a GVWR of at least 26,001 pounds, or any such vehicle towing another vehicle whose GVWR does not exceed 10,000 pounds. Examples include coach buses and transit buses.
  • Class C (Small Vehicles): Any single vehicle or combination of vehicles not included in Class A or Class B that is used to transport sixteen or more passengers including the driver or to transport hazardous materials. (For this purpose, federal regulations define a hazardous material as a substance that has been designated by the US Secretary of Transportation as a material whose commercial transportation may pose an unreasonable risk to health and safety or property.) Examples include sixteen-passenger vans.
Some US states also require CDLs for other purposes or other types of vehicles. Like other types of driver’s licenses, CDLs are usually issued by a state government’s DMV. In other respects, a CDL functions like an ordinary driver’s license. It can be used as a valid form of identification. The holder of a CDL may legally drive a passenger car or obtain a motorcycle endorsement on the CDL.

How to Obtain a Commercial Driver's License?

Obtaining a CDL
  • You must be at least 18 years old.
  • Have a valid driver's license (or learner permit) for the state in which you are applying.
  • Pass the CDL written knowledge test.
  • Complete your medical exam and get your physical.
  • Get fingerprinted by law enforcement with ID verification, or go to an authorized third-party vendor that provides computerized fingerprinting services.
  • Go to a DMV office and pay the required fee to take the skills test

What Are All the Truck Parts Called?

Tractor truck parts explained

CDL Test Questions and Answers: What To Expect?

  1. Study your state's CDL handbook. Sometimes it's hard to find the official source, so we've put together a list of the most recent official CDL handbooks for every U.S. state. If you prefer a hard copy, you should be able to pick one up at your local DMV office.
  2. Take a lot of practice tests. Taking practice tests that simulate your state's actual knowledge test will give you confidence and prepare you for the actual thing. Our CDL test questions are based on your state's official manual, so you'll know what to expect. These tests are valid for both commercial driver license and CDL permit (CLP).
  3. Watch CDL videos. YouTube is a fantastic resource, especially for pre-trip inspection.

Apply for a Commercial Driver's License (CDL)

A Commercial Driver's License is required to drive commercial vehicles such as tractor trailers, semi-trucks, dump trucks, and passenger buses (including school buses). The minimum age to apply for a CDL is typically 21. To become a truck driver, you can apply for a CDL at a local DMV office. Learn more about the three classes of CDLs that determine the kinds of commercial motor vehicles you’re permitted to drive: Class A, Class B, and Class C. There are strict federal guidelines for obtaining a CDL, and each state has its own requirements that need to be also met. You must pass both a written knowledge exam and a driving skills test, which are designed by your state.

CDL Written Knowledge Test

Your CDL test is the first step to a professional truck driving career in a trucking company. After you've studied your state's CDL handbook, the best thing you can do is either sign up for a costly CDL training program or take a free CDL practice test that simulates your state's actual knowledge test. provides a general knowledge test, as well as practice tests for specific commercial vehicle endorsements, such as air brakes test, school bus, and hazardous material (HazMat endorsement). There's also a practice test for pre-trip inspection - it will come in handy before your CDL road test. These tests are valid for both commercial driver license and CDL permit (CLP).

Choose your state from the drop-down menu above, and you’ll be provided with a test for all CDL license types that is closely based on your state’s manual, state and federal laws, and practice questions provided by the state if available.

How Is the CDL Practice Test Structured?

Think of this as your own CDL study guide for each endorsement. Every practice test has multiple-choice questions in the same format you’ll find on your state’s CDL test. These questions are phrased like the ones on your state’s official knowledge test. Most of the questions come with a hint to help you choose the right answer. Each correct answer comes with an explanation that has been carefully written to help you become more familiar with the topic of the question. We want you to be able to answer questions on those topics correctly even if they are worded a bit differently. Please read each explanation; it is based on your state’s CDL manual and DMV/DOT website.

Which Topics Are Covered?

This practice exam covers a wide range of topics that you’ll need to know about to pass your CDL knowledge test and enter the trucking industry. These topics include aggressive drivers, braking techniques, cargo safety, distracted drivers, drunk driving laws, emergency preparedness, road and weather conditions, and safe backing. No, we certainly did not forget about air brakes, combination vehicles, or hazardous materials! These topics are complex enough to deserve separate treatment. Just as states typically require you to pass specialized knowledge tests on those topics, we offer our own specialized practice tests on air brakes, combination vehicles, and hazardous materials. By studying our CDL practice tests, you'll be on your way to obtaining your Class A CDL, Class B CDL, or Class C CDL license. Remember that you'll also need to fill out the Medical History portion of the MER form (MCSA-5875) and also obtain a copy of the Medical Examiner Certificate form (MCSA-5876).

How Many Times Should I Take the CDL Practice Test?

We recommend that you keep taking the test until you become fully comfortable with the subject matter and receive a score high enough to boost your confidence about your upcoming CDL exam. A high score will bring you closer to passing your CDL knowledge test, so practice as many times as you’d like. There are no fees, and you won’t even have to register. Good luck now and on your CDL test. Drive safely!

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