What does the L restriction on a CDL mean?

It means you may not drive a commercial vehicle with air brakes. The state adds it if you fail the air brake part of the knowledge test or take the skills test in a truck without air brakes.

How do I remove the air brake restriction?

Pass the air brakes knowledge test and the skills test in a vehicle with air brakes. Your state licensing office tells you how to book the tests and what they cost.

How many questions can I miss on the air brakes test?

A passing score is at least 80 percent, so multiply the number of questions by 0.80 for the right answers you need. With 25 questions, that is 20 right and 5 missed. Check the count in your state manual.

Can I take the skills test in a truck without air brakes?

You can, but the rule then puts the air brake restriction on your license. Ask the testing site before test day what brake system the truck has.

What is the difference between air brakes and air over hydraulic?

Air over hydraulic brakes use air to work a hydraulic system. A skills test in that kind of truck can add a separate restriction from vehicles with brakes that work fully on the air brake principle.

How long do I wait to retest if I fail?

It depends on the state. Examples from state guides range from one day in Washington and North Dakota to 5 business days in Rhode Island, usually with a retest fee. Check your state manual.

CDL Air Brake Restriction: What It Means, How to Remove

The air brake restriction is a mark on your CDL that bars you from driving any commercial vehicle with air brakes. You remove it by passing the air brakes knowledge test and then the skills test in a truck that has air brakes. Below is how the restriction gets on a license, the steps to take it off, and a short checklist to keep it off in the first place.

Rules and fees differ by state, so use your state's CDL manual for the exact steps.

The restriction goes on when you fail the air brakes test or test in a truck without air brakes

The federal rule is short. If you fail the air brake part of the knowledge test, or take the skills test in a vehicle not equipped with air brakes, the state must mark your permit or license as restricted from operating a commercial vehicle with any type of air brakes. In this rule, "air brakes" means any braking system that works fully or partly on the air brake principle.

So there are two ways to get it:

You miss too many questions in the air brakes section of the written test.
You take the skills test in a truck that has no air brakes.

On a license, this shows up as the L code. The other codes are listed in CDL Restriction Codes: What E, L, Z, K and P Mean.

Why it matters: most heavy trucks and buses use air brakes

A trucking company's restriction guide notes that almost all vehicles over 26,000 pounds use air brakes. That is why an L restriction is limiting for anyone aiming at a Class A or Class B job. If your plan is to drive a heavy truck or a bus, treat the restriction as something to avoid, not something to fix later.

Take it off in two passes, in this order

To remove the restriction, you pass the knowledge test and the skills test in an air brake equipped vehicle. Follow this order:

Study the air brakes section of your state manual. Use the manual from your state, because question counts and details differ.
Pass the air brakes knowledge test. A passing knowledge test needs a score of at least 80 percent.
Ask the testing office what the skills test truck has. It must have air brakes.
Pass the skills test in that truck. It includes the pre-trip inspection with the three-part air brake check.
Ask the office to update your license. They tell you how and what it costs.

Worked example: say your state's air brakes test has 25 questions, as state practice guides describe it. 25 x 0.80 = 20 right answers needed, so you can miss 5. Use the same math with the count in your own manual: questions x 0.80 = right answers you need.

Learn the three-part air brake check once and use it twice

The skills test pre-trip includes an air brake check. One state guide lists an air leakage check, a low air warning device check, and an automatic spring brake engagement check. These are also on the air brakes knowledge test, so study them as one topic.

Your state manual gives the exact steps and psi numbers. To practice saying them in order, use Air Brakes Pre Trip Inspection Script: Say It Word for Word.

An air over hydraulic truck can add a different restriction

Not every truck with air in the system is a full air brake truck. If you take the skills test in a vehicle with air over hydraulic brakes, the rule has the state restrict you from vehicles with any braking system that works fully on the air brake principle. That is a separate restriction from the one above. Your manual explains how your state words it and how it comes off.

The fix is the same habit: ask before test day what brake system the truck has, and say you want a full air brake truck.

Pick your next move from this table

If this is you	Do this
You have not taken the air brakes test yet	Study the air brakes section first, then book the test, so the restriction never goes on
You failed the air brakes section	Look up your state's retest wait and fee, then study the questions you missed before you rebook
You have the restriction already	Pass the air brakes knowledge test, then book the skills test in a truck with air brakes
You are told the test truck is air over hydraulic	Ask for a full air brake truck, and check your manual for the second restriction
You are not sure what your license says	Read the restriction line on your permit or license and match it to your state manual

A failed test costs a wait and usually a fee

Retest rules depend on the state. Three examples from state guides:

State	After a fail
Washington	One day wait and a retest fee
North Dakota	At least one day wait and a retest fee
Rhode Island	5 business days and an extra fee

These are examples, not your state's rule. Look yours up before you book. The page Failed CDL Permit Test: Retake Waits by State lists waits for the written test.

Use this checklist to keep the restriction off your license

I studied the air brakes section of my state manual before I booked the knowledge test.
I know the three parts of the air brake check and can say them in order.
I asked the testing site what brake system the skills test truck has.
The truck has air brakes.
I looked up my state's retest wait and fee, just in case.

Three mistakes that cost you a wait and a fee

Skipping air brakes study because your first job might not use them. A restriction limits the jobs you can take, and it can close off most heavy trucks and buses.
Testing in a truck without air brakes to get it over with. The rule adds the restriction right there, and you have to test again in an air brake truck.
Not asking what brakes the test truck has. You find out too late, after the test is done.

Do this in the next ten minutes

Open your state CDL manual and find the air brakes section. Write down the number of questions on the air brakes test, then multiply it by 0.80 to get the right answers you need. Put that number on a sticky note, because it is your target.

Not sure you are ready for the air brakes test?

Take the free diagnostic first. It takes about 10 minutes, needs no account, and shows a predicted score and your weak spots, so you know what to study before you book. Take the free diagnostic.