What the General Knowledge Test Covers

The Commercial Driver License (CDL) General Knowledge Test is a written exam that covers the rules and safe practices that explore to all commercial drivers, regardless of what type of vehicle they operate. Every person seeking a CDL must pass this test before they can take any vehicle-specific tests. The test typically has 50 questions, and you need to answer at least 40 correctly to pass — that is an 80 percent score.

The test draws from the CDL manual published by your state's Department of Motor Vehicles or equivalent agency. The manual covers topics like hours-of-service rules (how long you can drive before you must rest), vehicle inspection procedures, safe driving practices, hazardous materials handling basics, and what to do in an accident. You will also see questions about brake systems, steering, traction, and how to recognize when a vehicle is unsafe to operate.

The General Knowledge Test is separate from endorsement tests. If you want to haul hazardous materials, you take an additional Hazmat test. If you want to pull a double or triple trailer, you take a Doubles/Triples test. But the General Knowledge Test is the foundation — you cannot take any of those endorsement tests without first passing it.

Key Takeaways

  • The General Knowledge Test has 50 questions and requires an 80 percent passing score, meaning you need to answer at least 40 questions correctly.
  • The test covers hours of service, vehicle inspection, safe driving practices, accident procedures, and brake and steering system basics — all topics from your state's CDL manual.
  • You must pass the General Knowledge Test before you can take any endorsement tests like Hazmat or Doubles/Triples.
  • Most states allow you to take the test at a DMV office or an approved third-party testing location, and you typically get your results the same day.
  • You can retake the test if you fail, but most states require you to wait a certain number of days between attempts and may charge a fee for each try.

How Hours of Service and Vehicle Inspection Questions Work

Hours of service rules are a major part of the test because they exist to prevent driver fatigue. The test will ask you about the maximum number of hours you can drive in a day, how many hours you must rest before driving again, and what counts as on-duty time versus off-duty time. The rules vary slightly depending on whether you are driving intrastate (within your state) or interstate (across state lines), so the manual breaks this down clearly.

Vehicle inspection questions test whether you know what to look for before you drive. You will see scenarios asking you to identify which parts of a truck or bus are unsafe — things like worn brake pads, cracked windshields, loose mirrors, or leaking fluid. The test assumes you understand that you are responsible for doing a pre-trip inspection and that you cannot legally drive a vehicle you know is unsafe. Some questions ask what you should do if you find a problem: report it to your dispatcher, get it fixed before driving, or document it in a vehicle inspection report.

Safe Driving and Accident Response Topics

The test includes questions about how to handle your vehicle in different conditions — wet roads, ice, strong wind, or when you are tired. You will see questions about proper following distance, how to brake safely with a heavy load, and what to do if your brakes fail. These questions test practical judgment, not just memorization.

Accident response questions ask what you must do if you are involved in a crash. The test covers whether you need to call police, how to protect the scene, whether you must move the vehicle, and what information you need to exchange with other drivers. Some questions address what to do if someone is injured or if hazardous materials are involved.

Hazardous Materials and Endorsement Basics

The General Knowledge Test includes a few basic questions about hazardous materials — enough to establish that you understand the concept and know that special rules explore. However, the detailed Hazmat endorsement test covers this material in depth. The General Knowledge Test might ask whether you can transport certain materials without a Hazmat endorsement, or what the general rule is about placarding a vehicle, but it does not go into the specific placard colors or shipping papers.

Similarly, the test touches on doubles and triples (longer combinations of trailers) but does not require the detailed knowledge you need for the Doubles/Triples endorsement. The General Knowledge Test establishes baseline awareness; the endorsement tests go deeper.

How to Prepare and What to Expect on Test Day

Most states provide a free CDL manual online or in print at the DMV. You can also buy study guides from third-party publishers, and many websites offer practice tests that mimic the real exam format. The practice tests are useful because they help you get used to the question style and identify weak areas before you sit for the real test.

On test day, you will go to a DMV office or an approved third-party testing location. Bring your state ID and any documents the location requires — rules vary by state. You will sit at a computer or paper test station, answer the 50 questions, and usually receive your score when ready. If you pass, you move forward to the next step in the CDL process. If you do not pass, you can retake the test, but most states require you to wait between 1 and 7 days before your next attempt, and each attempt may cost a fee (typically $10 to $50, though this varies).

Retaking the Test and Moving to the Next Step

If you fail the General Knowledge Test, do not panic — you can retake it. Most states allow unlimited retakes, but they space them out to give you time to study. Some states require you to wait 24 hours; others require a full week. Check your state's DMV website for the exact waiting period and any fees.

Once you pass the General Knowledge Test, you become CDL-may be able to access and can schedule the skills test — the behind-the-wheel driving exam. Some states also require you to pass a pre-trip inspection test (a separate written or practical exam) before you take the driving test. The order and requirements vary by state, so check your state's CDL testing sequence.

Frequently Asked Questions

What is the passing score on the General Knowledge Test?

You need to score at least 80 percent, which means answering at least 40 out of 50 questions correctly. The test is scored when ready, and you will know whether you passed before you leave the testing location.

Can I use a calculator or notes during the test?

No. The test is closed-book and closed-note. You cannot bring study materials, a calculator, or any reference materials into the testing room. You answer the questions from memory based on what you have studied.

How long does the General Knowledge Test take?

Most test-takers complete the 50-question exam in 30 to 60 minutes, depending on how quickly they read and decide on answers. You are not rushed, and the testing location will not impose a strict time limit — you can take as long as you need within normal business hours.

Do I have to pass the General Knowledge Test before I can take the Hazmat or Doubles/Triples test?

Yes. You must pass the General Knowledge Test first. Once you pass it, you can then take any endorsement tests you need. Some states allow you to take multiple endorsement tests on the same day, but you cannot take any of them until the General Knowledge Test is passed.

What happens if I fail the General Knowledge Test multiple times?

You can retake it as many times as needed. Most states do not limit the number of attempts, but they do require a waiting period between tries — usually 1 to 7 days depending on your state. Each attempt may cost a fee. If you keep failing, consider working with a CDL training school, which can provide structured instruction and practice tests.