Skip to main content
Hero background

Learn more about Commercial Drivers Licenses

What is a CDL?

A CDL is a driver's license needed to operate heavy, large, or hazardous material vehicles in US. There are different types of commercial motor vehicles(CMVs) whose drivers must obtain and possess a valid commercial driver's license such as semi-trucks, tractor-trailers, commuter buses, and dump trucks.

According to these vehicles' gross weight ratings, the licenses also vary, which means you must be sure of the type of equipment you are seeking to operate before applying for a CDL. Generally, these three CDL classes will dictate the type of CMV you are allowed to drive: Class A, Class B, and Class C CDLs.

How do you obtain a CDL?

The first step toward obtaining a valid CDL is earning a commercial learner's permit (CLP). Issued by your state, a CLP allows you to practice driving a CMV before earning a CDL.

The minimum age to obtain a CDL may vary from state to state but generally falls between 18 and 21 years. To begin the application, head to your local DMV office.

There, you'll be made aware of the federal guidelines as well as state requirements that must be satisfied. You must also pass a state-specific written knowledge exam and driving skills test.


What is the base requirement for a CDL application?

If you want to drive commercially, you must first take and pass a written General Knowledge Test. This test involves about 50 multiple choice questions and is compulsory for all aspiring CMV drivers. The test runs for an hour and you must score at least 80% or get 40 of the 50 questions correct.

The test generally covers driver communication, pre-trip inspection, dangers of drunk driving, and other general trucking knowledge. To be eligible for this test, you must be at least 21 years old, provide identity information, verify your social security number, and provide a complete medical examination report.

Why must you obtain a CDL?

Since 1992, it has been a requirement in the United States to obtain a commercial driver's license to earn the right to drive certain commercial motor vehicles. To earn the CDL, the Federal Motor Carrier Safety Administration (FMCSA) has outlined the standards to be followed by all the states when testing and licensing CDL holders.

According to the set standards, a state can only issue CDLs to CMV drivers after passing the knowledge and skills tests issued by the particular state. The test must resonate with the vehicle type the driver intends to operate.

Whether operating intrastate, interstate, or foreign commerce, commercial drivers must acquire a valid CDL in line with applicable commercial vehicle classification. Your CDL will attract a restriction when you undertake your skills test in a vehicle without the critical equipment found in that particular type of CMV. To avoid this kind of career jeopardy, you should only take a skills test for the specific CMV you are seeking to operate.

What are the CMV license classifications?

States issue CDLs to CMV drivers based on these broad classifications:

  • Class A CDL

    • This license class is required to drive any combination of vehicles with a gross combination weight equal to or greater than 26,001 pounds. This includes a towed vehicle or vehicles with a gross weight greater than 10,000 pounds.

    • Some of the vehicles you may drive with this license include 18-wheelers, trucks combined with trailers, tanker trucks, flatbeds, and animal carriers.


  • Class B CDL

    • Class B CDL is needed to operate any single vehicle with a gross vehicle weight or gross vehicle weight rating greater than or equal to 26,001 pounds or any single vehicle towing a cargo unit with a gross vehicle weight not exceeding 10,000 pounds.

    • CMVs qualifying for this license class includes box trucks, straight trucks, school buses, city buses, as well as segmented buses.


  • Class C CDL

    • This is a requirement for drivers operating any combination of or single vehicles that do not satisfy the definition of Class A or Class B vehicles but are either designed to ferry hazardous material or 16 or more passengers.

    • Examples of such vehicles are placarded HazMat vehicles, buses, double and triple trailers, as well as tanker trucks.

It is imperative to note that driving some of the vehicles listed above may require proper endorsements over and above possessing the CDL. What's more, if you hold a Class A CDL, you may be allowed to drive some Class B and Class C vehicles with the proper endorsements.

What are CDL endorsements?

To qualify as a driver for specialized CMVs like tankers, buses, or vehicles ferrying hazardous material, you are required to apply for the appropriate endorsements to be stamped on your CDL. Such endorsements open you up to additional job opportunities by affording you a competitive edge.

As great as that may sound, getting your hands on some of these endorsements may prove to be an uphill climb because of the extra skills tests and background checks needed. Luckily for you, it is now easier to maneuver the written tests because of the availability of different CDL practice tests that help you climb the endorsement ladder faster.

The most common federal CDL endorsements include these 6. However, there may be additional endorsements based on your state of operation.

1. Hazardous material endorsement (H)

The H endorsement or HazMat endorsement is needed when operating a CMV ferrying hazardous material. It is commonly applicable for tanker and truck drivers working for petroleum, environmental services, and transportation companies. Most such positions may require a proper endorsement before being hired.

This is one of the most difficult endorsements to earn because of the stringent background checks and security clearance involved from the Department of Homeland Security. The process may entail taking fingerprints, an immigration check, and an intelligence-related check. It is also very expensive and extremely time-consuming spanning 3 whole months.

To obtain this endorsement, you must also pass a written knowledge test. This makes it important to start your HazMat practice test as soon as you can. The most common elements tested here are identification of hazardous material or waste shipments, safe loading of shipments, proper placarding, and safe shipment transportation.

2. Passenger endorsement (P)

To be authorized to operate a vehicle that transports 16 or more passengers including the driver, you must earn the P endorsement. So, if you have plans of becoming a limousine, taxi, bus, or airport shuttle driver someday, you will need this endorsement on your CDL.

You must pass a written knowledge test coupled with a road skills test to complete the endorsement process. As such, it is advisable that you begin your practice test early. Some of the skills tested for this endorsement are proper traveler loading and unloading procedures, emergency response procedures, and proper braking procedures.

3. School bus endorsement (S)

The S endorsement is a requirement for anyone wishing to drive a school bus loaded with passengers or heading to or from school-related events. It is earned only after obtaining the P endorsement. To successfully earn one, you must pass a written knowledge test and road skills test. A background check is also mandatory here.

Taking a practice test for this endorsement helps the driver understand their vehicle, emergency procedures, and the needful state laws. Mechanics who may find themselves driving such buses in the course of their work are exempt from this endorsement. Before seeking the S endorsement, find out from your employer if it's a requirement because the definition of 'school bus' may differ from state to state.

4. Tank vehicle endorsement (N)

Also known as N endorsement, this endorsement allows you to operate tank vehicles ferrying gaseous or liquid hazardous material. To obtain the endorsement, you will need to take a written knowledge test. This means that you need to get acquainted through a tank driver practice test as soon as you can.

5. Double or Triple trailer endorsement (T)

It is also commonly called T endorsement and is mandated for truck drivers driving vehicles towing either a double or triple trailer. Without this endorsement, a truck driver is likely to face severe fines or even license withdrawal. To receive the T endorsement, you will have to take a written knowledge test. As such, you need to start your T endorsement practice test as early as you can.

6. Tank plus HazMat vehicles endorsement (X)

The last endorsement category is the X endorsement that involves receiving a combination endorsement for both hazardous material and tank vehicles. For this endorsement to materialize, you will have to take a written knowledge test. Be sure to review available resources to know what a practice test for the combination looks like.

What are CDL restrictions?

Essentially, a CDL restriction limits the type of commercial vehicles and equipment you can legally operate. That doesn't sound so good for your driving career, does it? As such, you should minimize or completely avoid having a restriction on your CDL.

Nonetheless, you can't avoid what you don't know, and that's precisely why this next section is important. It talks about the most common CDL restrictions and how they can affect your commercial driving career.

What are the commonest CDL restrictions?

There are 8 popular CDL restrictions applicable in all states. However, some states have additional restrictions over and above the issued federal regulations. Therefore, it is only wise to check with your specific state first. Only ensure the additional items are clearly and fully explained on the license document.

1. L Restriction (No full air brake)

When placed on your commercial driver's license, this restriction bars you from operating a vehicle with a full air brake system. This may be occasioned by:

  • Failing the Air Brakes Knowledge Test
  • Improperly identifying the air brake system components
  • Failure to conduct a proper air brake system check
  • Taking the skills test in a vehicle without a full air brake system

To remove this restriction on your CDL, you will have to pass a written test for air brake systems, basic skills, and road tests in a commercial vehicle with a partial or full air brake system, as well as the pre-trip inspection.

2. M Restriction (Passenger vehicle or school bus only)

This restriction is issued when a driver possessing a Class A CDL obtains their passenger or school bus endorsement in a Class B vehicle. When placed on your CDL, the M restriction means that you can only drive Class B and Class C passenger vehicles or school buses.

3. Z Restriction (No full air brake)

This restriction, just like the L restriction, bars a driver from operating a commercial vehicle fitted with a full air brake system. This arises if you take your skills test in a vehicle with a hydraulic brake system or partial air brake system.

To remove the restriction from your CDL, you must take your driving tests in a CMV equipped with a full air brake system.

4. O Restriction (No semi-trailer)

With this restriction on your CDL, you cannot drive any Class A CMV with a fifth-wheel connection. This may result from taking a skills test in a Class A vehicle with a non-fifth wheel connection or pintle hook.

Removing this restriction demands taking your skills test in a truck trailer or semi-trailer.

5. N Restriction (Class C passenger vehicle or school bus only)

When you hold a Class B commercial driver's license yet obtain your passenger or school bus endorsement in a Class C vehicle, you automatically earn an N restriction from your state. This restriction indicates that you are only allowed to drive Class C commuter vehicles or school buses.

6. V Restriction (Medical variance)

Upon completion of your Department of Transportation physical exam, the Federal Motor Carrier Safety Administration may issue you with a medical waiver for health conditions like diabetes, seizures, hearing, or sight problems.

Any of such conditions will be marked as 'V' indicating a medical variance on your CDL. This variance must reflect both on your CDL and the commercial driver's license information system (CDLIS) driving record.

7. E Restriction (No manual transmission)

You will be issued with this restriction if you take your skills test in a commercial vehicle with an automatic transmission. This automatically disqualifies you from operating commercial vehicles with a manual transmission.

The only way to remove this restriction on your CDL is by completing your skills test in a manual transmission vehicle. If you take your driving tests in an automatic transmission vehicle, your chances of working for a company with such vehicles diminishes almost instantly because there are hardly any.

8. K Restriction (Intrastate only)

This restriction allows you to operate your CMV only within the state that issued your CDL. That automatically prohibits you from interstate driving. Avoiding this restriction as much as possible is the only way of keeping your interstate movement freedom.

How do you remove your CDL restriction?

Removing your CDL restriction is not that hard but will definitely cost you some extra time and money. This, therefore, calls for more inclination toward prevention rather than cure. The best you can do to prevent a restriction is to do it right the first time. This means that you only take your basic skills test and road driving test in a commercial vehicle that you intend to drive upon earning your CDL.

The steps involved in getting the restriction removed include retaking a written knowledge test, retaking the skills test, and parting with a stipulated fee. That said, states may differ on the procedure, which means that you must find out the specifics.

Remember that having a restriction on your CDL may limit your driving options as well as your career opportunities. Before it gets to that, do everything in your power to avoid getting one.

The takeaway

If you plan on operating a Class A commercial vehicle, such as a semi-trailer or tractor-trailer someday, the one restriction you should avoid the most is the manual transmission restriction. This particular restriction can be detrimental to your career prospects and availability as a commercial driver.

Even though automatic transmissions are quickly gaining traction in the trucking world, the most popular transmission with a vast majority of employers is the manual one. To avoid getting passed over for driving jobs requiring an operator with manual transmission experience, avoid getting this restriction on your CDL by taking your skills test in a manual transmission commercial vehicle.

Armed with that knowledge along with reliable, proven, and practical CDL practice tests, go ahead and obtain your CDL or restriction removal. Best of luck and drive safely!