CDL Test Guide: Knowledge Exams, Endorsements, and How to Prepare

A Commercial Driver's License (CDL) is required to operate large or specialized commercial motor vehicles in the United States. Before the skills (driving) test, applicants must pass one or more written knowledge tests based on the CDL manual, which is built on the Federal Motor Carrier Safety Administration (FMCSA) standards and each state's specific rules.

All applicants take a general knowledge test, and additional tests are required depending on the class of license and any endorsements sought.

CDLs come in classes (A, B, and C) based on the weight and type of vehicle. Beyond the general knowledge test, endorsements authorize specific operations and each require their own knowledge test, including: Tanker (N), Passenger (P), School Bus (S), Doubles/Triples (T), Hazardous Materials (H), and combinations. There are also restrictions and, for some endorsements such as Hazmat, additional federal background-check requirements.

Decide which class and endorsements your target job requires, because that determines exactly which knowledge tests you must pass.

CDL knowledge tests are multiple-choice and administered by your state licensing agency. A passing score is commonly 80%, though the exact passing threshold, number of questions, and procedures are set by each state and can vary. The Hazmat endorsement additionally requires a Transportation Security Administration background check.

Confirm the current passing score, number of questions, and fees with your state's licensing agency before you test.

Start with your state's official CDL manual, which is the source of the test questions, and study the sections that apply to your class and endorsements. Focus on safety-critical topics — pre-trip inspection, safe driving practices, air brakes (if applicable), and the specific hazards of each endorsement (such as liquid surge for tankers or the danger zones around a school bus).

Then drill practice questions for each test you need to pass. Working endorsement-specific practice questions with explanations helps you learn the reasoning, not just memorize answers, which matters because the real test rephrases concepts.

Bring the identification and documentation your state requires. Read each question carefully — CDL questions often hinge on a specific safety rule or procedure. If your state lets you take multiple endorsement tests in one visit, make sure you have studied each one. Take your time; accuracy matters more than speed on a knowledge test.