How to Get a Double Trailer Endorsement on Your Commercial License

What a double trailer endorsement is and why you need it

A double trailer endorsement (sometimes called a doubles endorsement or twin trailers endorsement) is a notation on your Class B commercial driver's license that permits you to operate a truck towing two trailers at once. Without it, your license restricts you to towing one trailer only, even if your truck and training would allow it.

This endorsement is required by law in every state. If you drive doubles without the endorsement, you risk a citation, fines, and suspension of your commercial driving privileges. The endorsement itself costs between $10 and $50 depending on your state, and the process typically takes a few weeks from start to finish.

You need this endorsement if your job involves hauling doubles — common in long-haul trucking, livestock transport, and some regional delivery routes. If you only ever tow one trailer, you do not need it.

Key Takeaways

You must pass a written knowledge test specific to doubles operation before your state will issue the endorsement.
Most states require you to pass a skills test (backing, coupling, and uncoupling two trailers) either before or at the same time as the written test.
You will need your current Class B commercial license, proof of residency, and sometimes a medical certificate, depending on your state.
The entire process — from studying to receiving your updated license — usually takes two to four weeks.

The written knowledge test for doubles

Every state requires a written test covering doubles-specific operation. The test focuses on coupling and uncoupling procedures, weight distribution, braking differences, and handling characteristics unique to towing two trailers. Questions typically cover how doubles behave on curves, what happens when the tractor jackknifes, and how to inspect both trailers before departure.

The test length and passing score vary by state. Most states use 30 to 50 questions and require a score of 70 to 80 percent to pass. You can usually take the test at your state's Department of Motor Vehicles office or an approved testing location.

Study materials are free or low-cost. Your state's DMV website publishes a doubles manual or handbook that covers all tested topics. Some states also offer online practice tests. You should plan to study for one to two weeks before taking the test, depending on your familiarity with doubles operation.

The skills test and vehicle requirements

Most states require a practical skills test in addition to the written test. You will need to demonstrate that you can safely couple and uncouple two trailers, perform a pre-trip inspection on both units, and execute specific driving maneuvers — typically backing in a straight line and backing into a 90-degree angle.

For the skills test, you must provide a vehicle that meets the state's specifications. This means a Class B truck capable of towing doubles, with two trailers that are properly registered and insured. The vehicle must pass a pre-test inspection covering brakes, lights, coupling devices, and tire condition. If your vehicle fails inspection, you cannot test that day.

Some states allow you to take the skills test before the written test; others require the written test first. A few states allow you to take both on the same day. Check your state's DMV website to confirm the order and whether both tests must happen within a certain timeframe of each other.

Documents and fees you will need

Bring your current Class B commercial driver's license and proof of residency (utility bill, lease, or mortgage statement dated within 60 days). Some states also require a current medical certificate — the same one you use for your Class B license — so verify this before you schedule your test.

The endorsement fee ranges from $10 to $50 depending on your state and whether you are renewing your license at the same time. Some states charge a flat fee for the endorsement; others charge per year of validity. If you are renewing your Class B license and adding the endorsement simultaneously, you may pay a combined fee rather than two separate ones.

Payment methods vary by location. Most DMV offices accept cash, check, debit card, and credit card. A few states accept payment online before you visit in person. Check your state's website to confirm what forms of payment are accepted at your local office.

How to schedule your test and what to expect on test day

Contact your state's DMV office or visit its website to schedule both the written and skills tests. Some states allow online scheduling; others require a phone call or in-person visit. Scheduling can take anywhere from a few days to several weeks depending on how busy your local office is and whether you need to coordinate a time when you have access to a doubles-equipped vehicle.

On test day, arrive 15 minutes early with all required documents. For the written test, you will sit at a computer or paper test station for 30 to 60 minutes. For the skills test, plan for 45 minutes to an hour. The examiner will watch you couple and uncouple the trailers, perform your pre-trip inspection, and execute the required driving maneuvers. You do not need to pass both tests on the same day, but most states require you to pass the written test before attempting the skills test.

If you fail either test, you can retake it. Retake policies vary — some states allow you to test again when ready, while others require you to wait a few days or pay another fee. Ask the examiner about the retake policy before you leave.

After you pass: receiving your updated license

Once you pass both tests, the DMV will issue you an updated Class B commercial license with the doubles endorsement noted on it. In most states, this happens on the spot or within a few business days. Some states mail the license to you; others allow you to pick it up at the office.

Your new license will show the doubles endorsement code (usually "T" or "2" depending on your state) in the endorsements section. This is the document you need to carry when operating doubles. Driving doubles without this endorsement visible on your license is a violation, even if you have passed the test.

The endorsement is valid for the same period as your Class B license — typically four to eight years depending on your state. When you renew your Class B license, the endorsement renews automatically unless you request its removal.

What to do if you fail the test

Failing either the written or skills test is not permanent. You can retake the test after a waiting period that varies by state — typically three to seven days. You do not lose your Class B license if you fail the doubles test; the endorsement straightforward is not added.

If you fail the written test, review the study materials again and focus on the topics you missed. The DMV can often tell you which sections of the test you struggled with. If you fail the skills test, practice the specific maneuvers that caused the failure — backing, coupling, or uncoupling — with someone experienced in doubles operation before you retake it.

You will need to pay the test fee again for each retake. Some states waive the fee for a retake within a certain window; others charge the full fee each time. Confirm your state's retake policy when you schedule your first test.

Frequently Asked Questions

Can I take the doubles test if my Class B license is expired?

No. Your Class B commercial license must be valid and current to test for the doubles endorsement. If your license is expired, renew it first at your DMV office, then schedule the doubles test. Renewal typically takes one to two weeks.

Do I need a medical certificate to get the doubles endorsement?

It depends on your state. Most states require the same medical certificate you use for your Class B license. If your medical certificate is expired, you will need to renew it before testing. Check your state's DMV website or call your local office to confirm whether a current medical certificate is required.

What if I do not own a doubles-equipped truck?

You can borrow one for the skills test, but it must be properly registered and insured in someone's name. The vehicle must pass the pre-test inspection. Some commercial driving schools rent doubles-equipped trucks for testing purposes — contact schools in your area to ask about rental options and pricing.

How long does the doubles endorsement stay on my license?

Can I lose my doubles endorsement after I get it?

Yes. If you are convicted of certain traffic violations or safety violations while operating doubles, your state can suspend or revoke the endorsement. You can also request removal of the endorsement yourself if you no longer need it. If it is suspended, you may be able to retake the test to restore it after a waiting period.

This guide is for general information only and is not medical, financial, legal, or other professional advice. For decisions specific to your situation, consult a qualified professional. See our Editorial Policy.