Commercial Driver's License

Preparing for the CDL Knowledge Test

About the CDL

In 1986 the US Government passed the Federal Commercial Motor Vehicle Safety Act, which set minimum standards that anyone applying for a commercial driver's license must meet. To comply with these standards, each state must:

  • Test driver's knowledge and ability to safely operate commercial motor vehicles
  • Issue a special “commercial driver's license”
  • Share licensing information and convictions with other states
  • Disqualify or suspend the commercial licensing privileges of drivers who are convicted of certain offenses under new national guidelines.

The benefit of this act for potential CDL drivers is a common set of laws and requirements that must be understood by all drivers regardless the state issuing your commercial license.

Requirements For Obtaining a CDL License

Age: You must be 21 years old to obtain a commercial drivers license, however, in most states you can obtain a CDL at 18 with the exclusion of the Hazardous Materials Endorsement (Endorsement H) and you would be restricted to driving in that state only.

Residence: You must be a resident of the state you are applying for a CDL in.

Physical Exam: Some drivers will require a medical card depending on their state to operate a commercial vehicle.

Understanding CDL Class Licenses

Depending on the vehicle you are looking to operate, you will need one of three different CDL class licenses - A, B or C. The following should help you better understand which license you need and the appropriate study material based on the license:

Class A Any combination of vehicles with a gross vehicle weight rating, GVWR, of 26,001 pounds or more, provided the GVWR of the vehicle or vehicles being towed is in excess of 10,000 pounds.
  • Tractor-trailer
  • Truck and trailer combinations
  • Tractor-trailer buses
Class B Any single vehicle with a GVWR of 26,001 pounds or more, and any such vehicle towing a vehicle with a GVWR not in excess of 10,000 pounds.
  • Straight trucks
  • Large buses
  • Segmented buses
  • Trucks towing vehicles with GVWR of 10,000 pounds or less
Class C (Passenger) Any vehicle not described in Class A or B above but is: Designed to transport 16 or more passengers, including the driver;
Class C (HazMat) Any vehicle not described in Class A or B above but is: used in the transportation of hazardous materials that require the vehicle to be placarded under C.F.R., Part 172, Subpart F.

CDL Endorsements

If you plan on operating a special type of commercial vehicle, you must pass additional tests to obtain an endorsement that is placed on your CDL. Some endorsements require passing only a knowledge test, while others require a knowledge (i.e. written) as well as a skills exam (i.e. road or in-field test).

  • T - Double/Triple Trailers (Knowledge test only)
  • P - Passenger (Knowledge and Skills Tests)
  • N - Tank vehicle (Knowledge test only)
  • H - Hazardous materials (Knowledge test only)
  • X - Combination of tank vehicle and hazardous materials endorsements
  • S - School Bus (Knowledge and Skills Tests)


To obtain your CDL, you need to pass the knowledge tests with a score of 80% or better, followed by a skills test. You can take the knowledge test at most driver license office locations and typically need to schedule a skills test in advance. Plan on 1.5 - 2 hours for the knowledge test and 2 hours for the skills test.

Knowledge Tests

The CDL manual is 10 sections that you may be tested on to obtain your commercial license. The sections you need to study are dependent on the Class of license you are applying for:

Class A
  • Section 1: Introduction
  • Section 2: Driving Safely
  • Section 3: Cargo
  • Section 5: Air Brakes
  • Section 6: Combination Vehicles Section
  • Class B
  • Section 1: Introduction
  • Section 2: Driving Safely
  • Section 3: Cargo
  • Class C - Passenger
  • Section 1: Introduction
  • Section 2: Driving Safely
  • Section 3: Cargo
  • Section 4: Passenger
  • Class C - Hazardous Materials
  • Section 1: Introduction
  • Section 2: Driving Safely
  • Section 3: Cargo
  • Section 9: Hazardous Materials
  • If you plan on driving a truck with air brakes, which most drivers will encounter, you will also need to study Section 5 - Air Brakes, which is required for a Class A license but recommended for the other Classes as well.

    Skills Test

    After passing your knowledge tests, you can then schedule a skills test. The skills test consists of:

    • Pre-trip inspection test
    • Basic control skills test
    • Road test

    You will take these tests in the type of vehicles you are looking to get licensed for.

    Studying For The CDL Test

    Get The Manuals

    As painful as they are, reading the manuals is a must for passing the CDL knowledge tests and obtaining your commercial driver's license. Each state offers their own manual, free of charge, and typically through their website. Find your state's CDL manual and take the time to read through each relevant section, referring to the above chart to determine which sections you need to know.

    Take The Practice Tests

    Once you have studied the material, make sure you are prepared for the actual DMV exam. The exam takes time and money, and showing up unprepared is a waste of both.

    Fortunately, we offer the most up-to-date CDL study material on the web. Our experienced drivers have expertly prepared a complete series of study material - including comprehensive online practice tests and visual aids - making it quick and easy to prepare for your test.

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    Commercial Driver's License (CDL) Articles