CDL restrictions are letter codes printed on your commercial driver’s license that limit which vehicles you can operate or where you can operate them. You pick one up when you test in a vehicle missing a certain feature, when you miss a section of the knowledge test, or when your age or a medical condition narrows your driving authority. Most equipment restrictions can be removed without retaking the full CDL exam; federal rules let states give a modified skills test focused on the specific area you were restricted in.
How a Restriction Ends Up on Your License
Federal regulations set eight standard restriction codes that every state must use, and states may add their own codes on top as long as each one is explained on the license itself.1eCFR. 49 CFR 383.153 A code lands on your CDL in one of three ways: you took the skills test in a vehicle lacking a particular feature, you failed a specific section of the knowledge test, or a medical or age issue limits your operating authority. The code appears on the face of the license, so any inspector, officer, or carrier compliance reviewer can read it at a glance.
Equipment Restrictions
These are the codes most drivers deal with, because they follow directly from whichever vehicle you tested in.
L: No Air Brake Equipped CMV
If you fail the air brake section of the knowledge test (scoring below 80 percent) or take your skills test in a vehicle without air brakes, the state must place an L on your license.2eCFR. 49 CFR 383.95 The L bars you from driving any CMV with a braking system that operates fully or partially on the air brake principle. Because the vast majority of heavy trucks and buses use air brakes, this is one of the most limiting codes you can carry.3eCFR. 49 CFR Part 383 Subpart H – Tests
Z: No Full Air Brake Equipped CMV
The Z is a narrower version of the L. You get it when you take the skills test in a vehicle with air-over-hydraulic brakes, which use air pressure to assist a hydraulic system rather than running entirely on air.2eCFR. 49 CFR 383.95 With a Z, you can still drive air-over-hydraulic vehicles, but not any CMV with a braking system that operates fully on the air brake principle.
E: No Manual Transmission Equipped CMV
Testing in a truck with an automatic transmission gives you the E, which keeps you out of any CMV with a manual gearbox.1eCFR. 49 CFR 383.153 The E matters less than it used to. Many large carriers now run automatic fleets, so it won’t disqualify you from every big employer. Smaller carriers and specialty operations still run manuals, and the E narrows the pool of trucks you can legally drive.
O: No Tractor-Trailer CMV
Test for a Class A in a combination vehicle that uses a non-fifth-wheel connection (a pintle hook or ball hitch instead of a standard fifth wheel), and the O goes on your license.3eCFR. 49 CFR Part 383 Subpart H – Tests That blocks the classic tractor-trailer configuration. For over-the-road freight work, this restriction has to come off before you can start.
Where You Can Drive: The K Restriction
The K limits you to commercial driving inside the state that issued your CDL. The most common reason for a K is age. Federal rules require interstate CMV drivers to be at least 21.4eCFR. 49 CFR 391.11 – General Qualifications of Drivers Many states issue CDLs at 18 for intrastate work, and those drivers carry the K until they hit 21. A state-only medical waiver that doesn’t satisfy federal physical standards can also trigger it.
Passenger Class Restrictions: M and N
These codes affect drivers with a passenger endorsement. The M means “No Class A passenger vehicle” and applies when you hold a Class A CDL with the endorsement but tested in a Class B passenger vehicle; your passenger authority drops to Class B and C only.1eCFR. 49 CFR 383.153 The N works one step down, meaning “No Class A and B passenger vehicle,” which leaves you with Class C only. If you don’t carry a passenger endorsement, neither of these applies to you.
Medical Restrictions
The V code appears when FMCSA grants a variance from one or more federal physical qualification standards, such as a vision exemption, hearing exemption, or a Skill Performance Evaluation for a missing or impaired limb.1eCFR. 49 CFR 383.153 Drivers who hold a variance must carry the documentation while operating a CMV.5Federal Motor Carrier Safety Administration. Medical
Beyond the federal V, many states add their own medical codes for things like corrective lenses or hearing aids. A corrective-lenses code (often “B” in state systems) simply means you have to wear glasses or contacts while driving.
What Each Restriction Costs You in Hiring
Carriers check restrictions before making an offer, and the wrong code can end a hiring conversation. The L is the most damaging for over-the-road trucking, because nearly every heavy-duty tractor uses full air brakes. An L on your license means a carrier legally cannot put you in those trucks. The O is similarly disqualifying for freight work, since it bars tractor-trailers outright.
The E draws the most anxiety from new drivers but is the least career-limiting of the equipment codes. If you plan to stay with a large fleet that runs automatics, the E won’t hold you back much. If you want the flexibility to jump to a smaller carrier, an owner-operator running older equipment, or a specialty hauler, remove it.
How to Remove Each Equipment Restriction
You generally do not have to retake the full CDL skills test to drop a restriction. Federal rules let states administer a modified skills test focused on the specific area where you were restricted.3eCFR. 49 CFR Part 383 Subpart H – Tests The procedure differs by code.
Removing the L or Z
To drop the L, you need to pass the air brake knowledge test (at least 80 percent) and complete the air brake pre-trip inspection portion of the skills test in a vehicle equipped with air brakes.3eCFR. 49 CFR Part 383 Subpart H – Tests The Z follows the same pattern, except you test in a vehicle with a full air brake system rather than air-over-hydraulic. In both cases, the state can use a modified skills test focused on air brakes rather than the entire driving exam.
Removing the E
Show that you can safely operate a manual transmission CMV. The state gives a modified skills test in a manual-transmission vehicle. You do not have to repeat the written knowledge tests or the full three-part driving exam.3eCFR. 49 CFR Part 383 Subpart H – Tests Practicing with a manual truck before you schedule the retest, whether through a CDL program or time behind the wheel with a qualified driver, is worth the effort.
Removing the O
The O is the exception to the modified-test shortcut. To take it off, you have to retake all three parts of the skills test (pre-trip inspection, basic vehicle control, and on-road driving) in a representative tractor-trailer with a fifth-wheel coupling.3eCFR. 49 CFR Part 383 Subpart H – Tests That makes the O the most time-consuming code to clear.
The Practical Steps at the Licensing Agency
Whichever restriction you’re removing, the process at your state agency follows the same general path:
- Obtain or update your commercial learner’s permit if the current one doesn’t cover the vehicle type you need to test in. Federal rules require you to hold the CLP for at least 14 days before you can take a skills test.6eCFR. 49 CFR 383.25
- Schedule and pass the applicable test. For the L, Z, or E, that’s usually a modified skills test. For the O, it’s the full skills test. For air brake removal, you also pass the air brake knowledge test and pre-trip inspection.
- Get your CDL reissued. The state updates your record and issues a new document without the code. Reissue fees generally run from about $11 to $100 depending on the state.
Contact your local CDL testing office before you show up. A few states require you to visit a specific testing location rather than any DMV branch.
Restrictions You Can’t Simply Test Out Of
Not every code lifts by retesting. The K comes off automatically once the underlying condition no longer applies, which for most drivers means turning 21 and becoming eligible for interstate commerce.4eCFR. 49 CFR 391.11 – General Qualifications of Drivers If your K comes from a state-only medical waiver, you need a federal medical certificate that meets the full FMCSA standards to have it removed.
The V stays as long as you rely on the variance. If your condition improves to the point where you can pass the standard DOT physical without an exemption, submit updated medical documentation through your state licensing agency to have it removed. A corrective-lenses code comes off if an eye exam shows you now meet the vision standard without glasses or contacts, though that rarely happens in practice.
What Happens If You Drive Outside a Restriction
Operating a CMV in violation of a CDL restriction is treated as driving without the proper license for that vehicle. It can trigger an out-of-service order at a roadside inspection, which parks you on the spot. The violation goes on your driving record and can bring fines, points, or disqualification depending on the state. Carriers treat restriction violations seriously because they carry liability exposure. Getting caught in a full-air-brake truck with an L on your license is the kind of thing that ends the job, not just the trip.