What an air brakes endorsement is and why you might need it
An air brakes endorsement is an addition to your Class B commercial driver's license that shows you have been tested on how to operate vehicles with air brake systems. If you drive a bus, truck, or other commercial vehicle that uses air brakes instead of hydraulic brakes, most states require this endorsement before you can legally operate that vehicle for work.
You do not need the endorsement if your vehicle uses only hydraulic brakes. But if your employer assigns you to a vehicle with air brakes, or if you want to be able to drive any Class B commercial vehicle regardless of brake type, you will need to pass the air brakes test at your state's Department of Motor Vehicles (DMV) or equivalent licensing agency.
The endorsement itself costs money — the fee varies by state, typically between $5 and $15 — and requires you to pass a written test. Some states also require a hands-on air brake inspection before you can take the written test.
Key Takeaways
- You must pass a written test about air brake systems at your state's DMV, and some states also require a hands-on inspection before you can take the test.
- Study materials are usually free and available on your state DMV website, often as a PDF or online module covering brake components, operation, and safety checks.
- The written test typically has 25 to 40 questions and covers how air brakes work, pre-trip inspections, and emergency procedures.
- You can take the test at any DMV office that handles commercial driver's license services, and results are usually available when ready or within a few days.
- Once you pass, the endorsement is added to your existing Class B license and does not require renewal separate from your regular license renewal cycle.
What you need before you can test
Before you walk into the DMV to take the air brakes test, you need to have a valid Class B commercial driver's license already in hand. If you do not yet have your Class B, you will need to get that first — the air brakes endorsement is added to an existing license, not issued on its own.
You will also need to bring identification to the DMV. Bring your current driver's license, proof of residency (a utility bill or lease agreement works), and your Social Security number or card. Requirements vary slightly by state, so check your state DMV website before you go.
Some states require a pre-trip air brake inspection before you can sit for the written test. This means a DMV examiner or certified instructor watches you perform a walk-around inspection of a vehicle with air brakes, checking things like brake lines, air tanks, and warning lights. If your state requires this, the DMV website will tell you where and when these inspections are offered.
How to study for the air brakes test
Your state DMV publishes a study guide for the air brakes test, almost always for free. Go to your state's DMV website and search for "air brakes endorsement study guide" or "Class B air brakes test." Most states offer the guide as a downloadable PDF or as an online module you can read on the website itself.
The study guide covers the same topics the test will ask about: how air brake systems work, the parts of an air brake system and what each does, how to inspect air brakes before driving, how to use air brakes safely while driving, and what to do if the air brake system fails. Read through the guide at least once, then go back and focus on the sections that feel least familiar.
Some states also offer practice tests online. These are not the real test, but they follow the same format and cover the same material, so taking one or two practice tests can help you know what to expect and where you still have gaps in your knowledge.
Taking the written test at the DMV
When you are ready, go to your local DMV office that handles commercial driver's license testing. Call ahead or check the website to confirm that office offers air brakes endorsement tests — not all DMV locations do. You may need to make an appointment, or you may be able to walk in; this varies by state and by location.
Bring your Class B license, your identification, and any documents your state requires. The test itself is usually 25 to 40 multiple-choice questions, and you typically have 30 to 60 minutes to complete it. The passing score is usually 80 percent, though this varies by state.
The test is administered on a computer at most DMV offices, though some still use paper tests. You will see your score when ready or within a few days. If you pass, the endorsement is added to your license on the spot or mailed to you within one to two weeks, depending on your state's process.
What happens if you do not pass the first time
If you do not pass, you can retake the test. Most states allow you to retake it the same day or within a few days, though a few require you to wait a week before trying again. Check your state's rules when you get your test results.
Before you retake the test, go back to the study guide and focus on the topics you found hardest. If your state offers practice tests, take another one and pay close attention to which questions you get wrong. Many people pass on the second attempt after spending a few more hours with the study material.
How the endorsement appears on your license and when it expires
Once you pass the test, the air brakes endorsement is printed on your Class B license as a code or notation — the exact format depends on your state. You do not get a separate card or document; it is part of your regular commercial driver's license.
The endorsement does not have its own expiration date. It stays valid as long as your Class B license is valid. When your Class B license expires and you renew it, the air brakes endorsement renews with it automatically — you do not have to retake the test or pay an additional fee at renewal time.
If your Class B license is suspended or revoked, the endorsement is suspended or revoked along with it. If you let your license expire without renewing it, you will lose the endorsement and will have to pass the test again if you want it back.
Frequently Asked Questions
Do I have to take a hands-on air brake inspection before the written test?
It depends on your state. Some states require a pre-trip inspection performed in front of a DMV examiner before you can sit for the written test. Others do not. Check your state DMV website or call your local office to find out whether your state requires it and where you can schedule one if it does.
Can I take the air brakes test online from home?
No. The written test must be taken in person at a DMV office. Some states offer online study materials and practice tests, but the actual endorsement test is administered at a DMV location. If your state requires a hands-on inspection, that must also be done in person.
How long does it take to get the endorsement after I pass the test?
If you pass the test, the endorsement is usually added to your license when ready or printed on a replacement license mailed to you within one to two weeks. Some states issue it the same day; others mail it. Ask the DMV staff when you take the test what the timeline is for your state.
What if I fail the air brakes test but my job requires the endorsement?
You can retake the test as soon as your state allows — usually within a few days. Study the material again before your second attempt. If you are struggling with the content, some employers or unions offer air brakes training classes that can help you understand the material better before you test again.
Does the air brakes endorsement cost extra when I renew my Class B license?
No. The endorsement renews automatically with your Class B license at no additional cost. You only pay the endorsement fee once, when you first pass the test. Renewal fees cover your entire license, including all endorsements.