If you've come across the term "43 endorsement" while researching commercial driver's licenses, you may have found it referenced in the context of air brakes — specifically, the removal of an air brake restriction rather than a traditional add-on endorsement. Understanding the distinction matters, because the 43 endorsement works differently than most people expect.
In the CDL system, endorsements are typically additions to a base license — they expand what a driver is authorized to operate. Common examples include the H endorsement (hazardous materials), T endorsement (double/triple trailers), and P endorsement (passenger vehicles).
The 43 endorsement, however, is used in some states to denote authorization to operate vehicles equipped with air brakes. In practice, this functions less like a traditional endorsement and more like the removal of a restriction. When a CDL applicant fails the air brakes portion of the knowledge test — or chooses not to take it — their license is issued with a restriction (typically coded as "L") that prohibits them from driving vehicles with full air brake systems.
Completing the air brakes knowledge component, and in many cases a skills test in an air brake-equipped vehicle, removes that restriction. Some states record this cleared status using the "43" code, while others simply remove the L restriction without adding any numeric endorsement code. The terminology and coding vary by state.
Air brake systems are standard on most heavy trucks, tractor-trailers, and many buses. They operate differently from hydraulic brakes found on passenger vehicles — they use compressed air to actuate braking, and improper use can lead to brake fade, trailer jackknifing, or delayed stopping distance.
Because of these differences, federal regulations under 49 CFR Part 383 require that CDL applicants demonstrate knowledge of air brake systems to operate air brake-equipped vehicles without restriction. This includes:
The air brakes knowledge test is part of the general CDL knowledge exam in most states, though some administer it as a separate section. Passing it — and completing a skills test in an air brake-equipped vehicle — is what qualifies a driver to operate those vehicles.
| Situation | Result |
|---|---|
| Fails or skips air brakes knowledge section | L restriction placed on CDL |
| Passes knowledge but tests in non-air brake vehicle | L restriction may still apply |
| Passes knowledge and tests in air brake vehicle | L restriction removed; some states apply 43 code |
| Holds 43 endorsement or equivalent clearance | Authorized to drive air brake-equipped CMVs |
The L restriction is one of the more consequential CDL restrictions in practice, because most Class A commercial vehicles — and many Class B vehicles — use air brakes. A driver with an L restriction is significantly limited in the types of jobs and vehicles they can take on professionally.
Several factors shape how the 43 endorsement — or its functional equivalent — is handled:
CDL class matters. Class A licenses cover combination vehicles over 26,001 lbs. with a towed unit over 10,000 lbs. Class B covers single vehicles over 26,001 lbs. The air brake restriction can apply to both, but the skills test vehicle requirements may differ by class.
State coding varies. Not all states use the "43" designation. Some use different numeric or alpha codes. Others simply note the absence of the L restriction without adding any endorsement code. Your state's CDL manual will define the specific codes used on your license.
Testing format differs. Some states include air brakes questions within the general CDL knowledge test. Others offer a standalone air brakes test section. The number of questions, passing scores, and retake policies vary by state.
Skills test vehicle requirements. To fully remove the air brake restriction, most states require that the CDL road skills test — including the pre-trip inspection, basic vehicle controls, and on-road test — be completed in a vehicle equipped with air brakes. Passing the written portion alone is generally not enough.
Existing CDL holders adding the clearance. Drivers who already hold a CDL with an L restriction may be able to remove it by passing the air brakes knowledge section and retesting in an air brake-equipped vehicle, without retaking their entire CDL exam. The process and fees for this vary by state.
The air brakes knowledge section typically covers:
Most state CDL manuals include a dedicated air brakes chapter. The federal FMCSA Commercial Driver's License Manual also contains a standardized air brakes section that reflects the minimum federal knowledge requirements — though states may add to it. ✅
Whether your state uses the "43" endorsement code, how the restriction removal is processed, what fees apply, how many attempts you're allowed on the knowledge section, and what vehicle classes trigger the requirement — all of these depend on where you're licensed. Federal standards set the floor; states administer the actual testing and documentation.
A driver in one state may see a "43" on their CDL. A driver in another state may simply have no L restriction listed. The underlying authorization is the same — but the paperwork looks different depending on where you got your license. 🗺️