CDL Glossary
Commercial driver’s license terminology mixes federal regulatory language (FMCSA, ELDT, TSA) with state-specific licensing terms. This glossary defines the key terms you’ll encounter getting a CDL and looking up your state’s requirements.
B
C
CDL (Commercial Driver's License)
The license required to legally operate a commercial motor vehicle — broadly, one with a gross vehicle or combination weight rating of 26,001 lbs or more, one designed to carry 16 or more passengers including the driver, or one placarded for hazardous materials. States issue CDLs under a shared federal framework (49 CFR Part 383) that every state must meet or exceed, but each state sets its own fees and testing process.
CDL Class (Class A, B, C)
The three federally defined CDL vehicle classes: Class A (combination vehicles with a gross combination weight rating of 26,001 lbs or more), Class B (single vehicles at or above that same threshold), and Class C (smaller vehicles that either carry 16 or more passengers or transport hazardous materials). The class definitions are identical in every state.
See CDL classes in full→CLP (Commercial Learner's Permit)
A permit that lets a CDL applicant practice driving a commercial vehicle before taking the skills test. Getting one requires passing the CDL knowledge test first, and federal law sets a 14-day minimum holding period between CLP issuance and skills-test eligibility, which states may extend but not shorten.
D
DOT Medical Certificate
Also called a Medical Examiner's Certificate — proof, issued by an examiner on the FMCSA National Registry of Certified Medical Examiners, that a driver meets federal physical qualification standards. Most CDL holders operating in interstate commerce must hold a current one; it's valid for up to 24 months.
Full federal detail→Doubles/Triples Endorsement (T)
The endorsement required to pull two or three trailers connected together. It requires a knowledge test federally, and in practice is almost always paired with a Class A CDL, since a multi-trailer combination typically exceeds the Class B weight threshold on its own.
See all five endorsements→E
ELDT (Entry-Level Driver Training)
Federally mandated training, completed with a provider on the FMCSA Training Provider Registry, required before a first-time CDL applicant — or a first-time school bus, passenger, or hazmat endorsement applicant — can take the relevant test. In effect nationwide since February 7, 2022.
Full ELDT requirements→Endorsement
Additional authorization added to a base CDL to drive a specific vehicle type or carry specific cargo. Five exist federally — hazmat, tanker, doubles/triples, passenger, and school bus — each with its own knowledge and/or skills test requirement, layered on top of the base CDL class test.
See all five endorsements→F
FMCSA (Federal Motor Carrier Safety Administration)
The US Department of Transportation agency that sets the federal floor every state's CDL program must meet — vehicle class and endorsement definitions, ELDT, and medical certification standards among them. FMCSA doesn't issue CDLs itself; states do, under FMCSA's regulatory framework.
H
Hazmat Endorsement (H)
The endorsement required to drive a vehicle transporting hazardous materials in a quantity that requires placarding. It requires a knowledge test at the state level, plus a separate federal TSA security threat assessment — a background check distinct from, and in addition to, the state's own CDL testing process.
See all five endorsements→I
Interstate (Interstate Commerce)
Driving across state lines, or otherwise operating under federal commerce jurisdiction. Interstate CDL driving requires a minimum age of 21 and, for most drivers, a DOT medical certificate — a higher federal bar than intrastate-only driving.
Full federal detail→Intrastate
Driving entirely within one state. States set their own intrastate minimum age (commonly 18), below the federal 21-year floor that applies to interstate driving — an 18-to-20-year-old CDL holder can drive commercially, but only within their own state, and can't yet transport hazardous materials, drive a school bus, or cross state lines.
K
Knowledge Test
The written or computer-based exam covering CDL rules and, for endorsements, endorsement-specific content. It's required to get a CLP in the first place, and — per federal rule — for every one of the five CDL endorsements, though only two of the five (passenger and school bus) also require a skills test.
P
Passenger Endorsement (P)
The endorsement required to drive a vehicle designed to carry 16 or more passengers, including the driver. It requires both a knowledge and a skills test federally — one of only two endorsements (with school bus) that requires both.
See all five endorsements→R
Restriction
A limitation coded onto a CDL that narrows what it authorizes — for example, an automatic-transmission restriction for a driver who tested in a vehicle without a manual transmission, or an air-brake restriction for one who didn't test with air brakes. A restriction narrows an otherwise-valid CDL rather than adding to it, the opposite of an endorsement.
S
School Bus Endorsement (S)
The endorsement required to drive a commercial motor vehicle transporting students to or from school, or to or from a school-sponsored event. It requires both a knowledge and a skills test federally, and in most states also requires holding (or simultaneously applying for) the passenger (P) endorsement, since a school bus is itself a passenger-carrying vehicle.
See all five endorsements→Self-Certification
The process every CDL holder must complete with their state, declaring which of four FMCSA-defined operating categories they fall into: non-excepted interstate, excepted interstate, non-excepted intrastate, or excepted intrastate. Only the two "non-excepted" categories require the driver to maintain a DOT medical certificate. Which categories a given state actually offers can vary — see that state's page.
Skills Test (Road Test)
The behind-the-wheel exam — a vehicle inspection, basic vehicle control maneuvers, and an on-road driving segment — required for a CDL itself and, federally, for the passenger and school bus endorsements specifically. Some states let an approved third-party tester administer it; others require it be taken at a state licensing office.
T
Tanker / Tank Vehicle Endorsement (N)
The endorsement required to drive a vehicle transporting liquid or gaseous material in a tank (or tanks) with an individual rated capacity over 119 gallons and an aggregate rated capacity of 1,000 gallons or more. It requires a knowledge test federally.
See all five endorsements→Third-Party Tester
A person or organization — sometimes a private company, sometimes an employer — that a state has authorized to administer the CDL skills test on its behalf. Not every state runs a third-party testing program; where one exists, it's often faster to schedule than a state licensing office.
TSA HME (Hazardous Materials Endorsement Threat Assessment)
A federal, fingerprint-based background check TSA runs on anyone applying for, renewing, or transferring a hazmat endorsement — separate from, and in addition to, the state's own hazmat knowledge test. It's valid for five years; an applicant pre-enrolls online, then completes the process at a TSA enrollment center.
Full TSA process detail→