From eHow:
In most states, licenses fall into A, B, C and M classes. Classes A, B and C are further broken down by commercial and non-commercial vehicles. These three classes cover cars, trucks and tractor trailers. In addition, the A, B and C classes each have separate weight restrictions for both the main operational vehicle and any items being towed.
The basic Class C license allows you to drive two and three-axle vehicles up to a certain weight (in California, 26,000 lbs. and 6,000 lbs., respectively). The Class C license is the standard "driver's license." With a Class C, you can transport up to 16 passengers. A commercial Class C license can contain endorsements that allow the driver to transport hazardous materials or more than 16 passengers.
Illustration on how to count axles. Class of truck as shown above is based on the truck's weight.
3-axle vehicle
2-axle vehicle:
(CDL) Commercial Driver's License
Class A: Combination vehicle--tractor plus trailer--of 26,000 lb (11,790 kg) or more. Includes split (coupled) buses.
Class B: Single, straight vehicle of 26,000 lb (11,790 kg) or more (includes most buses including articulated buses; see articulated vehicles: any vehicle with a pivoting joint for greater turning radius). Also includes combination vehicles for commercial use weighing less than 26,000 lb GVW.
Articulated bus
Class C: Commercial vehicle that doesn't fit classes A or B, but is placarded for hazardous materials or is intended to carry more than 15 persons (excluding Georgia.) May include heavy-duty non-commercial vehicles with trailers capable of carrying over 16,000 lb, and all vehicles that can carry over 16,000 lb but not more than 25,999 lb.
Class C licenses are issued in most states in both commercial and non-commercial status. A non-commercial Class C license may not be used for hire. Most recreational vehicles that do not fall into the class D/E category, such as converted buses or full size (greater than 40 feet) campers require a non-commercial Class C license.
CDL ENDORSEMENTS:
According to Wikipedia, "Professional drivers are usually required to add endorsements to their CDL in order to drive certain types of vehicles that require additional training, such as those equipped with air brakes. CDL endorsements are also common among all states, and the training and testing requirements are regulated by the US Department of Transportation. Endorsements are as follows:
P: Passenger Transport (buses carrying 16 or more persons, vans for hire carrying 11 or more persons in California)
H: Hazardous Materials (requires a TSA background check as well as an extensive written exam. The driver must be a US Citizen or permanent lawful resident to obtain an H or X endorsement.)
M: Metal coil
N: Tank Vehicles (Required for carrying liquids in bulk.)
T: Double/Triple Trailers (Road trains) (Class A licenses only.)
X: Hazardous Materials and Tank Combination
L: Air Brakes
S: School Bus (In addition to a standard bus endorsement, more stringent TSA and CORI background checks are required.)
With a Commercial Class A license, you can operate all Class B and C vehicles and tow all commercial vehicles, regardless of weight. On the non-commercial side, a Class A license allows operation and towing of all vehicles and trailers except commercial vehicles, motorcycles and other vehicles that require additional endorsements.
Driving a motorcycle requires a Class M license. Depending on the state, M licenses may fall into more than one category. In California, for instance, an M1 license is required to operate standard motorcycles and an M2 license is needed for motorized bikes.
In most states, licenses fall into A, B, C and M classes. Classes A, B and C are further broken down by commercial and non-commercial vehicles. These three classes cover cars, trucks and tractor trailers. In addition, the A, B and C classes each have separate weight restrictions for both the main operational vehicle and any items being towed.
The basic Class C license allows you to drive two and three-axle vehicles up to a certain weight (in California, 26,000 lbs. and 6,000 lbs., respectively). The Class C license is the standard "driver's license." With a Class C, you can transport up to 16 passengers. A commercial Class C license can contain endorsements that allow the driver to transport hazardous materials or more than 16 passengers.
Illustration on how to count axles. Class of truck as shown above is based on the truck's weight.
 | Truck with 2 axles |
 | Truck with 3 axles |
 | Combination of road vehicles with 3 axles (Truck with 2 axles and semi-trailer with 1 axle) |
 | Truck with 4 axles |
 | Combination of road vehicles with 4 axles (Truck with 2 axles and semi-trailer with 2 axles) |
 | Combination of road vehicles with 5 axles (Truck with 3 axles and semi-trailer with 2 axles) |
 | Combination of road vehicles with 5 axles (Truck with 2 axles, semi-trailer with 1 axle, 1 removable axle and semi-trailer with 1 axle) |
 | Combination of road vehicles with 6 or more axles (Truck with 3 axles and trailer with 3 or more axles) |
 | Combination of road vehicles with six or more axles (Truck with 3 axles and semi-trailer with more than three axles) |
3-axle vehicle
2-axle vehicle:
(CDL) Commercial Driver's License
Class A: Combination vehicle--tractor plus trailer--of 26,000 lb (11,790 kg) or more. Includes split (coupled) buses.
Class B: Single, straight vehicle of 26,000 lb (11,790 kg) or more (includes most buses including articulated buses; see articulated vehicles: any vehicle with a pivoting joint for greater turning radius). Also includes combination vehicles for commercial use weighing less than 26,000 lb GVW.
Articulated bus
Class C: Commercial vehicle that doesn't fit classes A or B, but is placarded for hazardous materials or is intended to carry more than 15 persons (excluding Georgia.) May include heavy-duty non-commercial vehicles with trailers capable of carrying over 16,000 lb, and all vehicles that can carry over 16,000 lb but not more than 25,999 lb.
Class C licenses are issued in most states in both commercial and non-commercial status. A non-commercial Class C license may not be used for hire. Most recreational vehicles that do not fall into the class D/E category, such as converted buses or full size (greater than 40 feet) campers require a non-commercial Class C license.
CDL ENDORSEMENTS:
According to Wikipedia, "Professional drivers are usually required to add endorsements to their CDL in order to drive certain types of vehicles that require additional training, such as those equipped with air brakes. CDL endorsements are also common among all states, and the training and testing requirements are regulated by the US Department of Transportation. Endorsements are as follows:
P: Passenger Transport (buses carrying 16 or more persons, vans for hire carrying 11 or more persons in California)
H: Hazardous Materials (requires a TSA background check as well as an extensive written exam. The driver must be a US Citizen or permanent lawful resident to obtain an H or X endorsement.)
M: Metal coil
N: Tank Vehicles (Required for carrying liquids in bulk.)
T: Double/Triple Trailers (Road trains) (Class A licenses only.)
X: Hazardous Materials and Tank Combination
L: Air Brakes
S: School Bus (In addition to a standard bus endorsement, more stringent TSA and CORI background checks are required.)
The Commercial Class B license allows you to operate vehicles up to a certain amount (for instance, 26,000 lbs. in California) and tow commercial trailers up to a certain amount (usually 10,000 lbs). Commercial Class B drivers can also operate non-commercial Class B vehicles and tow vehicles that Class C drivers can tow.
With a Commercial Class A license, you can operate all Class B and C vehicles and tow all commercial vehicles, regardless of weight. On the non-commercial side, a Class A license allows operation and towing of all vehicles and trailers except commercial vehicles, motorcycles and other vehicles that require additional endorsements.
Driving a motorcycle requires a Class M license. Depending on the state, M licenses may fall into more than one category. In California, for instance, an M1 license is required to operate standard motorcycles and an M2 license is needed for motorized bikes.
California Commercial Driver License Handbook California Driver License Classes
| You May Drive… | And You May Tow… | Examples… |
| With a Commercial Class A License: Any legal combination of vehicles, including vehicles under Class B and Class C. |
|    |
| With a Restricted Class A Fire Fighter License: Only Class A and Class B defined combination fire fighting vehicles and all vehicles listed under Class C. |
|    |
| With a Noncommercial Class A License: Any vehicles under Class C. |
livestock trailer exceeding 10,000 lbs. GVWR but not exceeding 15,000 lbs. GVWR if the vehicle is controlled and operated by a farmer, used to transport livestock to or from a farm, not used in commerce or contract carrier operations, and is used within 150 miles of the person's farm. |   |
With a Commercial Class B License:
|
|      |
| With a Restricted Class B Fire Fighter License: Only a Class B defined single fire fighting vehicle and all the vehicles listed under Class C. | ||
With a Noncommercial Class B License:
With a Commercial Class C License: Any Class C vehicle carrying hazardous materials which requires placards. The hazardous materials (HAZMAT) endorsement must be on the license. Drivers who transport hazardous wastes, as defined by VC §§353 and 15278, are also required to have the HAZMAT endorsement. |
|        |
| With a Class M1 License: Two-wheel motorcycle, motor-driven cycle, or motorized scooter. | NOTES:
|   |
| With a Class M2 License: Motorized bicycle, moped, any bicycle with an attached motor, or motorized scooter. | ||
