Preparing for your Commercial Driver’s License (CDL) permit test requires knowing exactly what to expect when you sit down at the testing station. The number of questions, passing scores, and specific endorsements you need vary depending on the license class you pursue and the type of commercial vehicle you plan to operate.
Understanding the test structure helps you focus your study time and build the confidence needed to earn your CDL permit on the first attempt. This guide explains how many questions appear on each section, what scores you need to pass, and how endorsements affect your total test length.
How many questions are on the CDL permit test?
The CDL permit test typically includes 50 questions for the General Knowledge section, which all applicants must pass. If you need endorsements for air brakes, combination vehicles, or specialized cargo, you’ll take additional sections with 20 to 30 questions each, depending on your state and the endorsements required for your intended commercial driving work.
Understanding the General Knowledge Test
Every CDL applicant must pass the General Knowledge test before obtaining a commercial learner’s permit. This core exam covers vehicle inspection, basic control, safe driving practices, and federal motor carrier regulations that apply to all commercial vehicles.
The General Knowledge section contains 50 multiple-choice questions in most states. You must answer at least 40 questions correctly to achieve the required 80 percent passing score, though some states may require higher scores or have slightly different question counts.
The test draws from a pool of questions based on your state’s CDL manual, which itself follows the Federal Motor Carrier Safety Administration guidelines. Questions cover topics including pre-trip inspections, hazard perception, safe following distances, speed management, night driving, emergency procedures, and cargo securement fundamentals.
You cannot skip the General Knowledge test regardless of which CDL class you pursue. Class A, Class B, and Class C CDL applicants all take this same foundational exam before moving to endorsement tests.
Air Brakes Endorsement Questions
If you plan to drive any commercial vehicle equipped with air brakes, you must pass the Air Brakes knowledge test. Most modern Class A trucks and many Class B vehicles use air brake systems, making this endorsement essential for the majority of commercial drivers.
The Air Brakes test typically includes 25 questions, and you must answer at least 20 correctly to pass with the required 80 percent score. Questions focus on air brake system components, proper inspection procedures, low-pressure warnings, emergency stopping, brake lag, and the differences between air brakes and hydraulic systems.
Failing to take or pass the air brakes test results in a restriction on your CDL that prohibits operating vehicles with air brakes. This restriction severely limits employment opportunities, as most tractor-trailers, dump trucks, and commercial buses rely on air brake technology.
Combination Vehicles Endorsement
Class A CDL applicants who will operate tractor-trailers, truck-trailer combinations, or other articulated vehicles must pass the Combination Vehicles test. This endorsement confirms you understand the unique challenges of driving vehicles with detachable trailers.
The Combination Vehicles section contains 20 questions in most states. You need to answer at least 16 questions correctly to achieve the 80 percent passing threshold.
Topics covered include coupling and uncoupling procedures, fifth-wheel inspection, trailer brake systems, anti-lock braking systems on trailers, weight distribution, off-tracking, trailer swing during turns, and preventing trailer skids or jackknifing. The test ensures you understand how pulling weight affects acceleration, braking distance, stability, and maneuverability.
Additional Endorsement Tests
Depending on the type of commercial driving work you pursue, you may need one or more specialized endorsements beyond the core requirements. Each endorsement requires a separate knowledge test with its own question count and passing standards.
Passenger Endorsement
The Passenger (P) endorsement is required for drivers operating buses or other vehicles designed to carry 16 or more passengers, including the driver. The test includes 20 questions covering passenger safety, emergency exits, proper use of mirrors with passengers aboard, rider rules, standee line requirements, prohibited practices, baggage and cargo handling, and special safety considerations for school bus operations.
You must answer at least 16 questions correctly to pass. If you plan to drive a school bus specifically, you’ll also need to pass a separate School Bus endorsement test with an additional 20 questions focusing on loading and unloading procedures, railroad crossings, and student safety protocols.
Tank Vehicle Endorsement
Drivers hauling liquids or gases in tanks with an individual capacity of 1,000 gallons or more need the Tank Vehicle (N) endorsement. This test contains 20 questions about liquid surge, proper baffling, high center of gravity concerns, retest requirements, tank-specific inspection points, and outage requirements for different cargo types.
The passing score requires at least 16 correct answers. Many drivers who haul fuel, milk, chemicals, or other bulk liquids need this endorsement in addition to a Hazardous Materials endorsement if the cargo is regulated as hazmat.
Hazardous Materials Endorsement
The Hazardous Materials (H) endorsement requires both a knowledge test and a Transportation Security Administration background check. The knowledge portion includes 30 questions covering placarding requirements, shipping papers, emergency response procedures, loading and unloading regulations, and communication rules specific to hazmat transportation.
You must answer at least 24 questions correctly to pass. This endorsement involves additional costs for fingerprinting and background screening, and it must be renewed every five years with retesting to maintain current knowledge of federal hazmat regulations.
Doubles and Triples Endorsement
The Doubles/Triples (T) endorsement allows you to pull two or three trailers in states where such configurations are legal. The test contains 20 questions about coupling multiple trailers, inspecting converter dollies, managing longer stopping distances, understanding off-tracking with multiple trailer units, and preventing trailer instability.
You need 16 correct answers to pass. This endorsement is common among drivers hauling freight for less-than-truckload carriers and certain specialized operations, though some companies and routes prohibit multiple-trailer configurations regardless of driver endorsement.
Total Question Count for Your CDL Permit
The total number of questions you face depends on your license class and intended driving work. A Class A driver hauling general freight in a standard tractor-trailer takes three tests: General Knowledge (50 questions), Air Brakes (25 questions), and Combination Vehicles (20 questions), for a total of 95 questions.
A Class B driver operating a straight truck with air brakes takes General Knowledge and Air Brakes, totaling 75 questions. Add the Passenger endorsement for a bus driver, and the total reaches 95 questions across three separate tests.
Drivers pursuing multiple endorsements can face well over 100 questions. For example, a tanker-endorsement driver hauling hazardous materials in a combination vehicle with air brakes would take General Knowledge, Air Brakes, Combination Vehicles, Tank Vehicle, and Hazardous Materials tests for a combined total of 145 questions.
Each endorsement test is scored separately, and you must pass every required section to obtain your permit with the endorsements you need. Failing one endorsement test does not invalidate other passing scores in most states, but you cannot get that endorsement until you retake and pass the failed section.
State Variations in CDL Testing
While federal standards establish minimum requirements for CDL knowledge testing, individual states administer the exams and may include additional questions or slightly different formats. Some states add questions about state-specific regulations, local traffic laws, or regional driving conditions.
A few states require more than 50 questions on the General Knowledge test or set passing scores higher than 80 percent. Others may combine certain endorsement topics or use computerized adaptive testing that adjusts question difficulty based on your answers.
Verify the exact question counts and passing scores with your state’s Department of Motor Vehicles, Department of Transportation, or licensing agency before you schedule your test. State CDL manuals, available free online or at licensing offices, provide current test specifications and study materials tailored to your state’s requirements.
Test Format and Time Limits
Most states administer CDL knowledge tests on computers at licensing offices or approved third-party testing centers. The computerized format presents one question at a time, allows you to review and change answers before submitting each section, and provides immediate pass-fail results when you finish.
Time limits vary by state but typically allow two to three hours for all required sections combined. The computer system usually tracks time per section rather than for the entire session, giving you adequate time to read each question carefully without feeling rushed.
Some states still offer paper tests, particularly in rural areas or during computer system outages. Paper tests follow the same content and scoring standards but may take longer to grade, delaying your results by a few days instead of providing immediate feedback.
Retaking Failed Sections
If you fail one or more sections of the CDL permit test, most states allow retesting after a waiting period that ranges from one day to one week. Some states limit the number of attempts within a certain timeframe or charge a retest fee for each additional attempt.
You only need to retake the sections you failed, not the entire battery of tests. Passing scores on individual sections remain valid for a set period, typically 30 to 180 days depending on state rules, giving you time to study and retake failed endorsements without repeating tests you already passed.
Check your state’s retesting policies including waiting periods, attempt limits, fee schedules, and score validity periods before scheduling your first test. Understanding these rules helps you plan study time and avoid delays in obtaining your commercial learner’s permit.
Studying for the CDL Knowledge Tests
Thorough preparation significantly improves your chances of passing all required sections on the first attempt. Start by obtaining your state’s current CDL manual, which contains all the information covered on the tests and often includes sample questions.
Focus your study on one section at a time rather than trying to memorize the entire manual at once. Read each chapter carefully, take notes on key concepts, and use practice tests to identify weak areas that need additional review.
Many states offer free online practice tests that mirror the actual exam format and question style. Third-party study guides, apps, and online courses are also available, but ensure they’re updated for current federal regulations and your specific state’s requirements.
Allow several weeks of consistent study before scheduling your test, especially if you’re pursuing multiple endorsements. Cramming the night before rarely produces passing scores on CDL exams, which test understanding of safety principles and regulations rather than simple memorization.
After Passing the Written Tests
Once you pass all required knowledge tests, you receive a commercial learner’s permit (CLP) that allows you to practice driving a commercial vehicle under supervision. The CLP requires you to drive with a qualified CDL holder in the front seat and prohibits hauling certain cargo or passengers during the practice period.
Most states require you to hold the CLP for at least 14 days before taking the skills test, though some mandate longer waiting periods. Use this practice time to master pre-trip inspections, basic vehicle control exercises, and on-road driving skills that will be evaluated during the CDL skills exam.
The passing knowledge test scores are the first step in earning your full CDL. The skills test, which includes a pre-trip inspection, basic maneuvers, and a road test, determines whether you can safely operate a commercial vehicle and qualify for an unrestricted license.
Preparing for Success
Knowing that you’ll face 50 General Knowledge questions plus 20 to 30 questions for each required endorsement lets you plan realistic study sessions and build the knowledge base needed for commercial driving. Take the preparation seriously, study the official materials, and schedule your test only when practice exams consistently show passing scores.
Your CDL permit is the foundation for a commercial driving career, and the knowledge you gain while studying protects you, your cargo, and other road users throughout your driving life. Approach the testing process with focus and patience, and verify all current requirements with your state licensing agency to ensure you’re fully prepared on test day.