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Study guide

CDL Classes, Endorsements and Restrictions Explained

Updated

This guide sums up Section 1 of the CDL manual in plain words: when you need a commercial driver’s license, which class fits your vehicle, which endorsements and knowledge tests you need, and what the restriction codes on a license mean. It follows the Commercial Driver's License Manual (Version 07/20/2026 (form DMV 60A), Virginia DMV edition). The other state editions we checked say the same in this section. The manual describes the federal standard and does not cover every federal and state requirement. Your state may add rules of its own, so check with your state driver licensing agency too.

When do you need a CDL?

Under the federal standard, you need a CDL to drive any of these:

The GVWR is the loaded weight the manufacturer rates a single vehicle for. Some states count more vehicles as commercial, for example buses built for fewer than 16 passengers.

CDL classes: A, B and C

ClassVehicles it coversAlso lets you drive
Class A Combinations with a GCWR of 26,001 pounds or more, when the towed vehicle or vehicles have a GVWR of more than 10,000 pounds. Most are tractor-trailers or truck and trailer combinations. Class B and Class C vehicles
Class B Single vehicles with a GVWR of 26,001 pounds or more, including when they tow a vehicle of 10,000 pounds GVWR or less. This covers straight trucks and large buses, articulated buses included. Class C vehicles
Class C Single vehicles under 26,001 pounds GVWR, alone or towing a vehicle of 10,000 pounds GVWR or less, but only when they are designed to carry 16 or more people including the driver, or carry hazardous materials that need placards or a listed select agent or toxin. No other class

A bus can fall in Class A, B or C, depending on its weight rating and whether it is a combination vehicle.

The six CDL endorsements

An endorsement on your license shows you have the extra knowledge needed for a type of vehicle or cargo. Each one needs a passed knowledge test (X needs both the HazMat and the Tank Vehicles tests), and states may add endorsements of their own.

LetterEndorsementWho needs itPractice
H Hazardous Materials Drivers in any class who haul hazardous materials that must be placarded, or any amount of a listed select agent or toxin. You must also pass a TSA background check, which reviews criminal, immigration and FBI records. HazMat practice test
N Tank Vehicle Drivers of commercial vehicles designed to carry liquids or gases in tanks, permanently or temporarily attached, where each tank is rated for more than 119 gallons and all tanks together for 1,000 gallons or more. Applies in Classes A and B, and in Class C only when hauling hazardous materials. Tank Vehicles practice test
P Passenger Drivers of vehicles designed to carry 16 or more people, counting the driver, in any class. You must also pass the skills tests in a passenger vehicle. Passenger practice test
S School Bus School bus drivers in any class. You must also pass the skills tests in a school bus. School Bus practice test
T Double and Triple Trailers Class A drivers who want to pull double or triple trailers. Doubles/Triples practice test
X Hazardous Materials and Tank Vehicle combined Tank vehicle drivers who haul hazardous materials or waste in amounts that need placards. It shows you passed both tests. HazMat and Tank Vehicles

Endorsements on a learner’s permit (CLP)

Only three endorsements can be added to a Commercial Learner’s Permit: Passenger (P), School Bus (S) and Tank Vehicle (N). They come with limits. A CLP with the P or S endorsement also carries the P restriction (no passengers), and a CLP with the N endorsement carries the X restriction (empty tanks only). Both are explained below.

Which knowledge tests do you need?

You take one or more knowledge tests, depending on your license class and endorsements. Once you pass the ones you need, you can take the skills test when you are eligible. Each of our practice tests is written from the manual section listed here.

Knowledge testWho takes itManual section
General Knowledge Everyone who applies for a CDL. Sections 2 and 3
Air Brakes Drivers of vehicles with air brakes, including air over hydraulic brakes. Section 5
Combination Vehicles Drivers who want to drive combination vehicles. Section 6
Passenger Everyone applying to drive a bus. Section 4
HazMat Drivers who want to haul hazardous materials. A TSA background check is also required. Section 9
Tank Vehicles Drivers who want to haul liquids or gases in tanks of the size described in the Tank Vehicle (N) row above. Section 8
Doubles/Triples Drivers who want to pull double or triple trailers. Section 7
School Bus Drivers who want to drive a school bus. Section 10

Air brakes are not an endorsement. If you skip or fail the air brakes test, your license gets the L restriction, described below.

The CDL skills test has three parts taken in this order: vehicle inspection, basic vehicle control and on-road driving. You must pass each part before the next, in the type of vehicle you want to be licensed for. The manual also says that it does not replace a commercial vehicle training class or program.

CDL restriction codes

A restriction limits what you may drive, often because of the vehicle or equipment you used for the skills test. There are ten standard codes. N, P and X are also endorsement letters, but as restriction codes they mean something different.

CodeMeaningWhen it is added
ENo manual transmissionYou took the skills test in a vehicle with an automatic transmission. Any transmission that does not work fully by gear shift and clutch counts as automatic.
KIntrastate only You self-certified as non-excepted intrastate or excepted intrastate, so you may not drive a CMV in interstate commerce. States may also add it for other reasons.
LNo air brake equipped CMV You did not take or did not pass the air brakes knowledge test, or took the skills test in a vehicle without air brakes. It covers any type of air brakes, including systems that work only partly on air, such as air over hydraulic.
MNo Class A passenger vehicleYou took the passenger skills test in a passenger vehicle that needs a Class B CDL.
NNo Class A and B passenger vehicle You took the passenger skills test in a passenger vehicle that needs a Class C CDL.
ONo tractor-trailer CMV You took the Class A skills test in a combination joined by a pintle hook or another connection that is not a fifth wheel, or in a combination with a fifth wheel that is not a truck tractor and semi-trailer.
PNo passengers in CMV bus Your CLP has the P or S endorsement. With P you may not drive a CMV carrying passengers, and with S you may not drive a school bus with passengers. The only exceptions are test examiners, federal or state auditors and inspectors, other trainees and the CDL holder riding with you.
VMedical varianceThe state was told you were given a medical variance, which is noted on your driver record.
XNo cargo in CMV tank vehicle Your CLP has the N endorsement. You may drive only empty tank vehicles, and not one that held hazardous materials unless it has been purged of any residue.
ZNo full air brake equipped CMV You took the skills test in a vehicle with air over hydraulic brakes.

Start practicing

Everyone takes the General Knowledge test, so start with the General Knowledge practice test. See all CDL practice tests and our guide How to Study for the CDL Knowledge Tests.

Start with General Knowledge

Then add the tests for your license class and endorsements.

Start the General Knowledge test All CDL tests

Sources