What's on the CDL General Knowledge Test? Complete Topic Breakdown (2026)
By Penn Mahana | Published 2026-08-05
The CDL General Knowledge test is the gateway to every commercial driver's license in the United States. It's 50 multiple-choice questions drawn from your state's CDL Manual. You need 40 correct answers (80%) to pass. Most states give you 60 minutes.
Disclaimer: This guide is for educational purposes only. CDL requirements, fees, and regulations are set by the FMCSA and individual state DMVs. Always verify current requirements with your state DMV and consult official FMCSA resources for the most up-to-date information.
But "50 questions from the manual" doesn't tell you what to study. This guide breaks down every topic area, what to expect, and how to prepare — so you walk into the DMV knowing exactly what you're facing.
Table of Contents
The 9 Topic Areas
The CDL knowledge test system covers nine distinct topic areas. Not every driver takes every test — which tests you take depends on the class of CDL and endorsements you're pursuing.
1. General Knowledge — ~20 of 50 Questions
This is the core section every CDL applicant must pass. It covers the fundamentals of safe commercial vehicle operation:
- Vehicle Inspection: Pre-trip, en-route, and post-trip inspection procedures. What to check, why it matters, and how to document findings.
- Basic Control of Your Vehicle: Accelerating, steering, stopping, and backing safely. Mirror adjustment and blind spot management.
- Shifting Gears: When and how to shift up and down. Double-clutching, engine speed management, and avoiding transmission damage.
- Seeing and Communicating: Seeing ahead and to the sides, using mirrors, signaling intentions, and communicating with other drivers.
- Speed Management: Stopping distances, speed on curves and downgrades, speed in traffic and adverse conditions.
- Space Management: Following distance, space to the sides, space overhead, and space for turns.
- Hazard Awareness: Identifying hazards, emergency maneuvers, and avoiding collisions.
- Skid Control and Recovery: Causes of skids, skid types, and recovery techniques.
- Railroad Crossings: When to stop, how to cross safely, and what to do if you're stuck.
2. Air Brakes — 25 Questions
Required if you want to operate vehicles with air brake systems. Passing this test removes the L restriction from your CDL.
- Air brake system components and their functions
- Air compressor, governor, and air storage tanks
- Dual air brake systems
- Air brake inspection procedures
- Air pressure buildup and loss rates
- Emergency and parking brake systems
- Brake fade and brake failure procedures
3. Combination Vehicles — 20 Questions
Required for Class A CDL. Covers the unique challenges of combination vehicles (tractor-trailers).
- Coupling and uncoupling procedures
- Tractor-trailer stability and rollover risks
- Trailer skids and jackknife prevention
- Fifth wheel inspection and operation
- Gladhand connections and air/electrical lines
- Trailer brake systems
4. Transporting Cargo — ~12 Questions
Covers cargo safety for all CDL classes.
- Weight and balance principles
- Cargo securement requirements
- Special cargo types (liquid, bulk, oversized)
- Loading and unloading safety
- Weight distribution and axle weight limits
5. Transporting Passengers — 20 Questions
Required for the Passenger (P) endorsement.
- Pre-trip inspection for passenger vehicles
- Loading and unloading passengers safely
- Emergency exits and evacuation procedures
- Passenger safety briefings
- Prohibited practices (drugs, alcohol, distractions)
- Railroad crossing procedures for buses
6. School Buses — 25 Questions
Required for the School Bus (S) endorsement.
- Danger zones and student safety around the bus
- Loading and unloading procedures
- Railroad crossing procedures for school buses
- Emergency evacuation drills
- Student management and discipline
- Mirror adjustment for maximum visibility
7. Hazardous Materials — 30 Questions
Required for the Hazmat (H) endorsement. Also requires a TSA security threat assessment.
- Hazard classes and divisions
- Hazardous materials table and shipping papers
- Placarding requirements
- Loading and unloading hazmat
- Emergency response procedures
- Security requirements and route restrictions
- Tank vehicle hazmat considerations
8. Tank Vehicles — 20 Questions
Required for the Tanker (N) endorsement.
- Liquid surge and its effects on vehicle stability
- Tank vehicle types and baffling
- Weight distribution in tank vehicles
- Loading and unloading procedures
- Emergency procedures for tank vehicles
9. Doubles and Triples — 20 Questions
Required for the Doubles/Triples (T) endorsement.
- Coupling and uncoupling multiple trailers
- Converter dolly inspection and operation
- Stability and handling of multi-trailer combinations
- Backing restrictions (you can't back doubles)
- Special air brake considerations for doubles/triples
Topic Deep Dive: General Knowledge Section
The General Knowledge section is the one every CDL applicant faces. Here's what to study for each sub-topic.
Vehicle Inspection
What to study: The CDL Manual's pre-trip inspection checklist. Know the seven-step inspection method: engine compartment, cab check, lights and reflectors, walk-around inspection, and brake tests.
Key numbers: Air brake warning activates below 60 psi. Air compressor cuts out at 120-135 psi. Minimum tread depth: 4/32" on front tires, 2/32" on others.
Common test questions: "What should you check during a pre-trip inspection?" "When should you perform an en-route inspection?"
Basic Control and Shifting
What to study: Starting, accelerating, steering techniques, and stopping. Downshifting before downgrades. Double-clutching procedure.
Key concepts: Downshift before entering a downgrade — never during. Use engine braking to control speed on long downgrades. Keep the engine RPM in the operating range.
Common test questions: "When should you downshift?" "What is the proper way to hold the steering wheel?"
Speed and Space Management
What to study: Stopping distances at various speeds, following distance rules, and space cushion management.
Key numbers:
- Stopping distance at 55 mph (loaded tractor-trailer): ~400+ feet (perception + reaction + braking)
- Minimum following distance: 1 second per 10 feet of vehicle length (at speeds under 40 mph), add 1 second above 40 mph
- 4-second following distance is the standard minimum for ideal conditions
Common test questions: "What is the total stopping distance at 55 mph?" "How much space should you keep in front of your vehicle?"
Hazard Awareness and Emergencies
What to study: Types of hazards, emergency maneuvers, and accident procedures.
Key concepts: Evasive steering is often safer than emergency braking. If a tire fails, hold the steering wheel firmly and avoid braking until the vehicle slows. For brake failure, downshift and use the emergency brake gradually.
Common test questions: "What should you do if a tire blows out?" "How should you handle a brake failure on a downgrade?"
Railroad Crossings
What to study: When to stop, how to cross, and what to do if stuck.
Key rules: Stop 15-50 feet from the nearest rail. Buses and hazmat vehicles must stop at all railroad crossings. If you're stuck on the tracks, get out and call the emergency number posted at the crossing.
Common test questions: "How far from the nearest rail should you stop?" "Which vehicles must stop at all railroad crossings?"
How the Test Is Structured
Format: Multiple choice, typically with 4 answer options per question. Most states use computer-based testing at DMV offices or authorized third-party testing centers.
Question types:
- Factual recall: "What is the maximum legal blood alcohol concentration for a CDL holder operating a CMV?" (0.04%)
- Procedure: "What is the first step in the pre-trip inspection?" (Engine compartment check)
- Scenario: "You're driving a tanker and the liquid begins to surge. What should you do?" (Reduce speed gradually)
- Safety judgment: "You're approaching a railroad crossing with a bus. What must you do?" (Stop and look both ways)
No trick questions. The CDL test is designed to verify you know the material — not to trick you. If an answer seems obvious from the manual, it's probably correct.
State variations: While the core test is based on the FMCSA Model CDL Manual, states may add questions about state-specific laws, weight limits, or procedures. Always study your state's CDL Manual.
Study Resources
The CDL Manual (Free)
Your state's CDL Manual is the primary source for every test question. Get it from your state DMV website or office. Read it cover to cover at least once. The manual is typically 150-250 pages — dense but not difficult.
CDL Practice Tests
Practice tests are the most effective study tool. They help you:
- Identify weak areas before test day
- Get comfortable with the question format
- Build confidence through repetition
- Learn from detailed answer explanations
ELDT Theory Training
Since February 2022, all first-time CDL applicants must complete FMCSA-registered Entry-Level Driver Training. The theory portion covers the same material as the General Knowledge test — completing ELDT theory training is excellent test preparation.
Explore ELDT CoursesStudy Groups and Forums
Online communities like TruckersReport and Reddit's r/Truckers can provide study tips, practice questions, and moral support. Just verify any advice against the official CDL Manual.
Test-Taking Strategy
- 1
Read every question twice.
The CDL test isn't timed tightly — you have plenty of time. Misreading a question is the most common cause of wrong answers.
- 2
Eliminate obviously wrong answers first.
Most questions have 1-2 answers that are clearly incorrect. Narrow the field, then choose from the remaining options.
- 3
Watch for absolutes.
Words like "always," "never," and "must" are often correct in CDL test questions because safety rules are absolute. But not always — read carefully.
- 4
Flag and return.
If you're unsure, flag the question and come back. Sometimes a later question will jog your memory.
- 5
Trust your study.
If you've read the manual and taken practice tests, your first instinct is usually correct. Don't overthink.
- 6
Use all your time.
If you finish early, review your answers. Look for questions you may have misread.
State-by-State Differences
While the General Knowledge test is standardized at 50 questions nationwide, some states have variations:
| Variation | States |
|---|---|
| Additional state-specific questions | New York, California, Texas, Florida |
| Different passing score (higher than 80%) | None (all states use 80%) |
| Oral testing available | Most states (by request) |
| Language options beyond English | Varies — check with your state DMV |
| Third-party testing allowed | Most states |
| Online knowledge testing | Limited — check with your state |
Always confirm requirements with your state DMV before scheduling your test.
Frequently Asked Questions
What topics are on the CDL General Knowledge test?
The General Knowledge test covers three main areas from the CDL Manual: Driving Safely (vehicle inspection, basic control, speed and space management, hazard awareness, emergencies, skid control, railroad crossings), Transporting Cargo Safely (weight and balance, cargo securement, special cargo), and Air Brakes (if applicable). The test draws 50 questions from these sections.
How many questions are on each section?
The FMCSA doesn't publish exact question counts per section, but Driving Safely typically accounts for 60-70% of questions (30-35), with the remainder split between cargo handling and vehicle systems. Air Brakes is a separate 25-question test.
Is the CDL General Knowledge test hard?
It's challenging if you don't study, manageable if you do. The pass rate for first-time test takers who've read the manual and taken practice tests is high. The most common reason for failure is walking in unprepared. The material isn't conceptually difficult — it's about knowing the rules, procedures, and safety standards.
Can I take the CDL knowledge test in Spanish?
Many states offer the CDL knowledge test in Spanish and other languages. However, federal law requires CDL holders to be able to read and speak English sufficiently to communicate with the public, understand highway signs, respond to official inquiries, and make entries on reports and records. Check with your state DMV for available languages.
How long should I study for the CDL General Knowledge test?
Most people need 1-2 weeks of consistent study. Read the CDL Manual (8-12 hours), take practice tests (4-6 hours), and review weak areas (2-4 hours). If you're studying part-time, budget 2-3 weeks.
What happens after I pass the General Knowledge test?
You receive your Commercial Learner's Permit (CLP). You must hold the CLP for at least 14 days before taking the CDL skills test. During this time, you must complete ELDT training if you're a first-time applicant. You can drive with a CLP as long as a qualified CDL holder is in the passenger seat.
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