Short answer
Most states use 50 questions; federal rules require at least 30 and a score of 80%.
CDL Knowledge Tests
- General Knowledge (all applicants)
- Air Brakes
- Combination Vehicles (Class A)
- Endorsements: Hazardous Materials (H), Tank (N), Doubles/Triples (T), Passenger (P), School Bus (S)
Since 2022, first-time Class A and B applicants must also complete federal Entry-Level Driver Training (ELDT) before the skills test (and before the hazmat knowledge test).
USA CDL Exam: Quick Facts
- Passing
- 80% on each knowledge test
- General Knowledge
- Usually 50 questions
- Required
- DOT medical certificate
- Skills test
- Inspection, basic control, road
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