Introduction
The CDL exam is really a series of tests: a written knowledge test for your Commercial Learner's Permit (CLP), endorsement knowledge tests, a pre-trip inspection, basic control skills, and a road test. Everything you'll be tested on comes from the Federal Motor Carrier Safety Regulations (FMCSA) and your state's CDL manual. This guide walks through every major topic in the order most people study.
CDL Classes (A, B, C)
Class A covers combination vehicles over 26,001 lbs where the towed unit is over 10,000 lbs — most tractor-trailers. Class B is for single vehicles over 26,001 lbs (straight trucks, most buses). Class C is smaller vehicles used to carry 16+ passengers or placarded HazMat.
General Knowledge
Every CDL applicant takes the General Knowledge test: vehicle inspection, basic control, shifting, backing, seeing, communicating, space management, night driving, extreme weather, hazards, skid recovery, accident procedures, and cargo basics.
Air Brakes
Required for any CDL vehicle equipped with air brakes. Covers how the system works, dual air systems, spring parking brakes, the seven-step brake check, low-air warning, static leakage test, and applied leakage test.
Combination Vehicles
Required for Class A: coupling and uncoupling, off-tracking, rollover prevention, trailer brake operation, and inspecting the fifth wheel, kingpin, and landing gear.
Passenger (P) Endorsement
For any vehicle designed to carry 16 or more people (including the driver). Covers pre-trip for passenger buses, standee lines, prohibited practices, emergency exits, and railroad crossings.
School Bus (S) Endorsement
Adds school-bus-specific rules on top of P: student loading and unloading, danger zones, using flashing lights and the stop arm, railroad crossings, and post-trip child checks. Requires ELDT before taking the skills test.
HazMat (H) Endorsement
Required to haul placarded hazardous materials. Covers the hazardous materials table, shipping papers, placarding, loading and unloading, driving and parking rules, emergency response, and TSA background check. Requires ELDT theory.
Hours of Service
The federal driving-time rules: 11-hour driving limit, 14-hour on-duty window, 30-minute break, 60/70-hour weekly limit, the 34-hour restart, the short-haul exception, sleeper berth splits, and adverse driving conditions.
ELDT (Entry-Level Driver Training)
Since Feb 7, 2022, new CDL applicants must complete FMCSA-approved theory and behind-the-wheel training before the skills test. CDLTest360's ELDT Theory practice covers all 30+ required topics.
Pre-Trip Inspection
The skills-test walkaround. Examiners want to hear specific phrases for every component: engine compartment, front suspension, brakes, tires, coupling, trailer, and in-cab. Our trainer walks you through it component by component.
Medical Card (DOT Physical)
Interstate CDL drivers need a current Medical Examiner's Certificate from a certified examiner on the National Registry. Intrastate rules vary by state. The card is typically good for up to 24 months.
State CDL Requirements
Every state issues CDLs under the same federal minimums but adds its own manual, fees, road-test scheduling, and endorsement quirks. Pick your state to practice from that state's manual.
FAQs
- How long does it take to study for the CDL?
- Most drivers need 2–4 weeks of consistent study to be ready for the CDL written (knowledge) test. Reading the FMCSA-based study guides here, then drilling practice tests until you can consistently score 90% or better, is the fastest path.
- What's the passing score on the CDL written test?
- 80% on every knowledge test — General Knowledge, Air Brakes, Combination Vehicles, and each endorsement. CDLTest360's exam mode uses the same 80% threshold.
- Do I need ELDT before my CDL road test?
- Yes. As of February 2022, Entry-Level Driver Training (theory + behind-the-wheel) from a provider on FMCSA's Training Provider Registry is required before upgrading from a CLP to a CDL, or before adding a Passenger, School Bus, or HazMat endorsement.
- Are CDL rules different in each state?
- The knowledge test itself is based on the same FMCSA regulations everywhere in the U.S. States add their own manuals with local rules — parking, chains, weight enforcement — which is why CDLTest360 also publishes state-specific practice tests.
Ready to test yourself?
You've read the rules. Now prove it with a realistic DMV-style practice test.