Federal CDL Study Guide
A plain-English summary of the federal Commercial Driver License rules, applicable in every U.S. state. For state-specific differences (ages, fees, retake rules), pick your state from the state list.
Practice tests by category
Federal references
Frequently asked questions
What does the federal CDL knowledge test cover?
The General Knowledge test covers vehicle inspection, driving safely, transporting cargo safely, and CDL-specific traffic rules. Class A applicants also take Combination Vehicles. Anyone with air brakes takes Air Brakes.
Is the same CDL manual used in every state?
No — every state publishes its own CDL manual that adopts the federal FMCSA model and adds state-specific rules (ages, fees, retake policy). Read your state's manual on its DMV/DOT website.
How long does CDL preparation usually take?
Most applicants spend 2-6 weeks studying, then attend an Entry-Level Driver Training (ELDT) program. ELDT minimum hours vary by class and endorsement.