A commercial driver's license has three layers: the class, which sets the size of vehicle; the endorsements, which add types of vehicle or cargo; and the restrictions, which take equipment away. Each is defined in federal rules that every state must follow, in 49 CFR 383.91 to 383.95, and the letter codes are fixed in 383.153. This page gives all three, with the thresholds exactly as written.
The three classes
383.91(a) defines the vehicle groups:
- Class A, combination vehicle. Any combination with a gross combination weight rating of 26,001 pounds or more, provided the vehicle or vehicles being towed have a GVWR of more than 10,000 pounds. A tractor-trailer is the typical case.
- Class B, heavy straight vehicle. Any single vehicle with a GVWR of 26,001 pounds or more, or such a vehicle towing something of not more than 10,000 pounds GVWR. Dump trucks, box trucks and city buses.
- Class C, small vehicle. A vehicle or combination that meets neither A nor B but is designed to transport 16 or more passengers including the driver, or is used to transport placarded hazardous materials.
The test is the rating, not what the truck weighs today. 383.133(c)(3) says so directly for the test vehicle: GVWR or GCWR, not actual weight, decides which class a vehicle represents. A 26,001-pound-rated box truck running empty still needs Class B.
What a higher class lets you drive
383.91(c): a driver who passed the Class A tests may operate Class B and C vehicles, and a Class B driver may operate Class C, in each case provided the driver holds any endorsement the vehicle requires. The reverse is not true: moving up a class means retaking the related tests.
The endorsements
383.93(b) requires an endorsement to operate double or triple trailers, passenger vehicles, tank vehicles, vehicles carrying hazardous materials, or school buses. 383.93(c) sets the tests, and 383.153(a)(9) the codes:
| Code | Endorsement | Test required |
|---|---|---|
| T | Double/triple trailers | Knowledge |
| P | Passenger | Knowledge and skills |
| N | Tank vehicle | Knowledge |
| H | Hazardous materials | Knowledge (plus the TSA security threat assessment) |
| X | Tank vehicle and hazardous materials combined | Both knowledge tests |
| S | School bus | Knowledge and skills |
A tank vehicle under 383.5 is one designed to carry liquid or gas in a tank of more than 119 gallons individually and 1,000 gallons or more in total, whether permanently or temporarily attached. An empty storage tank not designed for transport, strapped to a flatbed, is not one.
The hazmat endorsement has a step outside the licensing office: under 49 CFR 1572.13(a) no state may issue or renew it without a Determination of No Security Threat from TSA. That process has its own page.
Endorsements on a learner's permit
383.93(a)(2): only P, S and N may appear on a commercial learner's permit, and each comes with limits: no passengers other than examiners, trainees and the supervising CDL holder, and tank vehicles only when empty and purged. H is not allowed on a permit at all. Details are on the learner's permit page.
Restrictions, and how the test vehicle creates them
Most restrictions on a CDL are not penalties. They follow from the vehicle the skills test was taken in, under 383.95, with codes from 383.153(a)(10):
| Code | Restriction | Why it is added |
|---|---|---|
| L | No air brake equipped CMV | Failed the air brake knowledge test, or took the skills test without air brakes (383.95(a)) |
| Z | No full air brake equipped CMV | Skills test in a vehicle with air over hydraulic brakes (383.95(b)) |
| E | No manual transmission | Skills test in an automatic (383.95(c)) |
| O | No tractor-trailer | Class A test with a pintle hook or other non-fifth-wheel connection (383.95(d)) |
| M | No Class A passenger vehicle | Passenger skills test in a Class B vehicle (383.95(e)) |
| N | No Class A and B passenger vehicle | Passenger skills test in a Class C vehicle (383.95(f)) |
| V | Medical variance | The state was notified of a medical variance (383.95(g)) |
The note to 383.95 adds that a driver with a V restriction may not operate a CMV in Canada.
Removing a restriction later
383.135(b)(7): to remove the E, L or Z restriction the state may give a modified skills test rather than the full one; removing L or Z also requires the air brake pre-trip inspection and the air brake knowledge test. 383.135(b)(8): removing the O restriction means retaking all three skills test segments in a tractor-trailer. This is the reason CDL schools usually test in a manual, air-brake, fifth-wheel tractor: it avoids restrictions that cost a second test to remove.
Choosing a class
For most over-the-road jobs the answer is Class A without restrictions, because it covers B and C and fits every tractor a carrier may assign. Class B suits local delivery, construction and transit work. Before paying for training, ask the school which vehicle the skills test will be taken in, since that decides the restrictions. CDL schools and testing locations are listed by state and town in this directory.