What Class A and Class B licenses are, and which one you need

A Class A Commercial Driver's License (CDL) lets you drive the largest trucks and truck-trailer combinations on public roads. A Class B CDL lets you drive large single vehicles — like city buses, dump trucks, or cement mixers — but not tractor-trailers. The difference comes down to the weight of what you're pulling or driving.

Class A requires you to haul a trailer weighing 10,001 pounds or more, or tow any trailer behind a truck that weighs 26,001 pounds or more combined. Class B covers vehicles over 26,001 pounds that don't involve towing a heavy trailer — the weight is all in one unit. If you want to drive an 18-wheeler, you need Class A. If you want to drive a city bus or a large dump truck, Class B is what you're after.

Both require passing a written test on federal rules, a skills test with a vehicle, and a medical exam. Both also require you to be at least 18 years old (21 if you want to cross state lines). The Class A test is harder because the vehicle combinations are more complex to handle.

Key Takeaways

  • Class A CDLs are for tractor-trailers and any combination where the trailer weighs 10,001 pounds or more; Class B is for single large vehicles like buses or dump trucks.
  • You must pass a written knowledge test, a skills test with an actual vehicle, and a Department of Transportation medical exam for either license.
  • Class A requires more training and a harder skills test because you're controlling two connected units instead of one.
  • You can get a Class B first and upgrade to Class A later, though you'll need to pass the Class A skills test again.
  • Both licenses require you to renew every four years and maintain a clean driving record or face suspension.

The written test: what you study and how it differs between Class A and B

Both Class A and Class B require you to pass a written test on the Federal Motor Carrier Safety Regulations. You study the same core material: how to inspect your vehicle, how to load cargo safely, how to handle brakes and steering in emergencies, and what the hours-of-service rules are (how long you can drive before you must rest).

The Class A test goes deeper into combination vehicle dynamics — how a trailer behaves when you brake, how to back up with a trailer attached, and how weight distribution changes when you're towing. The Class B test focuses on the single vehicle you're operating, so the questions are about that vehicle's braking system, its blind spots, and how to handle it in traffic.

You can study using the CDL manual your state's Department of Motor Vehicles publishes, or through third-party study guides and apps. Most people spend two to four weeks studying before they feel ready. The written test is usually 50 questions, and you need to pass with a score of 80 percent or higher.

The skills test: backing, pre-trip inspection, and road driving

The skills test has three parts: a pre-trip vehicle inspection, a backing and maneuvering test, and a road test. You perform all three in the same vehicle you'll be licensed to drive — so if you're testing for Class A, you bring a tractor-trailer; if you're testing for Class B, you bring a dump truck or bus.

The pre-trip inspection means you walk around the vehicle and point out safety features — lights, brakes, tires, mirrors, coupling devices (on a Class A rig). You have to know what you're looking for and be able to explain why it matters. An examiner watches and listens.

The backing test is where most people struggle. For Class A, you back a tractor-trailer into tight spaces — a dock, a 90-degree alley, a parallel parking spot. For Class B, you back a large single vehicle into similar spaces. You're not allowed to hit cones or curbs, and you can only pull forward a set number of times before you fail.

The road test lasts 30 to 45 minutes. You drive in city traffic, on highways, and sometimes in bad weather or at night, depending on when you test. The examiner watches how you handle turns, lane changes, merging, and emergency stops. For Class A, they're also watching how you manage the trailer — how you position it, how you account for its swing on turns.

Medical certification and what disqualifies you

Before you can get either license, you must pass a Department of Transportation (DOT) medical exam. A certified medical examiner — usually a doctor, nurse practitioner, or physician assistant — checks your vision, hearing, blood pressure, and overall health. They also review your medical history for conditions that could make you unsafe to drive a large vehicle.

Conditions that can disqualify you include uncontrolled high blood pressure, diabetes that requires insulin (though some states have exceptions), heart disease, sleep apnea, and certain neurological conditions. Vision must be at least 20/40 in each eye, corrected or uncorrected, and you need a field of vision of at least 70 degrees in each eye. If you're colorblind, you can still get a CDL, but you may have restrictions.

If you have a condition that might disqualify you, you can still get a medical certificate — you may just need documentation from your doctor showing the condition is controlled. The examiner fills out a Medical Examiner's Certificate, which is valid for two years. You'll need to renew it before it expires or your CDL becomes invalid.

Getting your permit before the skills test

Most states require you to hold a Commercial Learner's Permit (CLP) before you can take the skills test. You get the CLP by passing the written test and the medical exam. Once you have it, you can practice driving the vehicle with a licensed CDL holder in the passenger seat.

The CLP is usually valid for 180 days to one year, depending on your state. During that time, you practice backing, pre-trip inspections, and road driving. Some states require a minimum number of hours behind the wheel before you can test; others just require that you hold the permit for a certain amount of time. Check your state's rules.

You cannot use a CLP to haul cargo or passengers for pay. It's practice only. Once you pass the skills test, you get your full CDL and can work when ready.

Endorsements and restrictions that go on your license

Your CDL can come with endorsements — special permissions to haul certain cargo or operate certain vehicles. The most common are Hazmat (hazardous materials), Tanker (liquid cargo in a tank), and Passenger (for buses). Each endorsement requires an additional written test and, for Hazmat, a background check.

You can also have restrictions on your license. A common one is air brake restriction — if you fail the air brake portion of the skills test, you can only drive vehicles with hydraulic brakes. You can remove this restriction later by passing the air brake test. Another is automatic transmission only, which means you tested in an automatic truck and can only drive automatics until you pass the test again in a manual.

If you get a Class B first and later want to upgrade to Class A, you don't need to retake the written test — you only take the Class A skills test. Your license will be upgraded once you pass.

Renewal, medical recertification, and keeping your license valid

A CDL is valid for four years from the date you receive it. Before it expires, you must renew it at your state's Department of Motor Vehicles. You'll need to pass a new medical exam and pay a renewal fee (usually $50 to $150, depending on your state).

If your medical certificate expires before your CDL does, your license becomes invalid until you get a new medical certificate. You cannot drive commercially without a current one. Some states allow you to renew your medical certificate online or by mail; others require an in-person visit to a certified examiner.

If you get a traffic violation, an accident, or a failed inspection while driving commercially, points go on your record. Accumulating too many points can lead to suspension or disqualification. The rules vary by state, but generally, three serious violations in three years can result in a one-year disqualification.

Frequently Asked Questions

Can I get a Class B license and upgrade to Class A later?

Yes. You can test for Class B first, work with that license, and then test for Class A whenever you're ready. You'll need to pass the Class A skills test, but you won't retake the written test. Your license will be upgraded once you pass.

What happens if I fail the skills test?

You can retake it. Most states let you retake it within a certain window — usually 14 days to 60 days after a failure. You'll pay a retest fee, which is usually $50 to $100. You keep your CLP while you practice and prepare to test again.

Do I need a Class A or Class B to drive a school bus?

You need a Class B CDL with a Passenger endorsement. School buses are single vehicles over 26,001 pounds, so they fall under Class B. The Passenger endorsement requires an additional written test and a background check.

What if I have a medical condition that might disqualify me?

Talk to your doctor first, then contact a certified medical examiner. Many conditions can be managed with documentation or treatment plans. The examiner will tell you whether you can get a certificate and what restrictions or conditions might explore.

How long does it take to get a CDL from start to finish?

Most people take two to four months. That includes studying for the written test (two to four weeks), holding a CLP and practicing (one to three months), and then testing. If you fail the skills test, add another month or two to practice and retake it.