CDL classes: A, B and C explained

The three groups, as the rule defines them

49 CFR 383.91 calls them Group A, Group B and Group C. Almost everyone says Class A, B and C, and the license itself is printed that way, so the two words mean the same thing here.

Group A is a combination vehicle. 383.91 defines it as any combination of vehicles with a gross combination weight rating of 26,001 pounds or more, provided the vehicle or vehicles being towed are rated over 10,000 pounds. Two separate numbers decide it: the rating of the whole rig, and the rating of whatever is on the back. A tractor pulling a semi-trailer is the obvious case.

Group B is a heavy straight vehicle. 383.91 defines it as any single vehicle rated at 26,001 pounds or more, or one of those towing something rated at 10,000 pounds or less. A dump truck, a box truck and a transit bus all sit here. The vehicle is one unit, or one unit with something small behind it.

Group C is the small vehicle group. 383.91 defines it backwards, by what it is not: any vehicle or combination that meets neither the Group A nor the Group B definition, but which is either designed to carry 16 or more passengers including the driver, or is used to carry hazardous materials as defined in 383.5. So Group C is not a light or beginner license. It exists because of what the vehicle carries, not because of what it weighs.

One detail catches people out. These are ratings, not weights. 383.133 tells states to use the gross vehicle weight rating or gross combination weight rating when deciding whether a vehicle represents a group, not the weight the vehicle happens to be carrying that day. An empty trailer does not drop you into a lower class.

Which knowledge tests each class needs

Everyone takes general knowledge, whatever the class. 49 CFR 383.111 lists 20 general areas that every commercial driver must know, covering vehicle inspection, basic control, shifting, backing, visual search, communication, speed and space management, night driving, extreme conditions, hazard perception, emergency maneuvers, skid recovery, cargo, mountain driving and fatigue. That list is federal, which is why the test barely changes across state lines. Work through the general knowledge practice test first, because nothing else can be issued without it.

After that, the class adds tests.

Class A adds combination vehicles. 383.111(c) sets out three areas for anyone driving a combination: coupling and uncoupling, the inspection steps that are unique to a combination, and general operating practice including air brakes. This one is not optional for Group A. 383.135 states that an applicant who fails the combination vehicle portion of the knowledge test must not be issued a Group A permit or license. Practice it on the combination vehicles practice test and the Class A practice test.

Air brakes apply to A and B, and sometimes C. 383.111(b) lists seven air brake areas, from system parts and contaminated air supply through to low pressure warnings and parking brakes. It follows the equipment, not the class. Failing it does not stop you getting a license; 383.95 says the state must instead print an air brake restriction, which bars you from driving any vehicle with air brakes of any kind. That usually rules out the job you wanted, so treat the air brakes practice test as part of the main run rather than an extra. The Class B practice test mixes the straight-truck material with it.

Class C is general knowledge plus whichever endorsement puts you there. Because 383.91 defines Group C by passengers or hazardous materials, a Group C applicant is always sitting an endorsement test too: passenger under 383.117, or hazardous materials under 383.121. The Class C practice test is built around that pairing. Hazardous materials also needs a Transportation Security Administration background check, which runs on its own schedule and cannot be sped up by studying, so start it early and sit the hazmat practice test while it is in progress.

The pass mark is the same everywhere. 383.135 requires at least 80 percent correct on each knowledge test. On a fifty-question paper that is forty right.

Endorsements sit on top of the class

Endorsements are separate from class and are listed in 383.93: double and triple trailers, passenger vehicles, tank vehicles, hazardous materials, and school buses. The same section sets out what each one costs you in testing. Doubles and triples, tank, and hazardous materials each need a knowledge test. Passenger and school bus need a knowledge test and a skills test.

Passenger endorsements are tied to a class. 383.117 requires the skills test to be taken in a passenger vehicle that meets the group you are applying for, and 383.95 says that if you test in a smaller passenger vehicle than the group you applied for, the license is restricted to match what you drove.

Moving between classes later

383.91 covers this directly. A driver who has passed the knowledge and skills tests for Group A may operate a Group B or Group C vehicle, and a Group B driver may operate a Group C vehicle, in both cases provided they hold the endorsements the vehicle needs. Going the other way, or moving to a group your license does not cover, means retaking and passing all the related tests.

That is the practical argument for testing in the biggest vehicle you can get access to. A Class A covers the Class B and Class C work as well, as long as the endorsements are there.

How to tell which one you are after

Ask about the vehicle, not the job title. Three questions settle it nearly every time.

Is anything being towed, and what is the towed unit rated at? Over 10,000 pounds with a combined rating of 26,001 or more, and you are in Group A under 383.91.

Is it a single unit rated 26,001 pounds or more? That is Group B.

Does it carry 16 or more people including you, or move placarded hazardous materials, without meeting either of the first two? That is Group C.

If you are still unsure, ask the employer for the rating plate figures rather than guessing from the look of the truck. The rating is stamped on the vehicle, the class follows from it, and the tests follow from the class. The CDL practice test index lists every test in one place once you know which ones you need.