CDL General Knowledge Test Guide: FMCSA 49 CFR 383 Pass Score, CLP Rules, Classes and Endorsements
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The CDL general knowledge test is the first step to a commercial driver's licence. Your state gives it under FMCSA's federal standards in 49 CFR Part 383. This guide covers the 80 percent pass mark, how the test is built, CLP rules, Class A, B and C, endorsements and restrictions, entry-level driver training, the offenses that can cost you your CDL, and a two-week study plan. Every rule is quoted from the eCFR.
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CDL General Knowledge Test at a Glance
| Item | Federal Rule (49 CFR) |
|---|---|
| Who gives the test | Your state licensing agency, using the FMCSA pre-approved question pool |
| Pass score | At least 80 percent on each knowledge test (383.135) |
| Answer choices | Three per question (383.133) |
| Number of questions | Set by your state's FMCSA-approved test design |
| Retakes | Allowed. The state must give a different version of the test. |
| Language | The knowledge test may be in a foreign language, with no interpreter |
| CLP minimum age | 18 (383.71) |
| Interstate driving age | 21 (391.11) |
| Fee | Set by your state |
The primary source is 49 CFR Part 383 on the eCFR. Your state CDL manual is what you study from, and it follows the same federal standard.
Who Needs a CDL: FMCSA Class A, B and C
Under 383.91, a CDL is required for three vehicle groups:
- Class A (combination): a GCWR of 26,001 pounds or more, where the towed unit's GVWR is more than 10,000 pounds.
- Class B (heavy straight): a single vehicle with a GVWR of 26,001 pounds or more, or one towing no more than 10,000 pounds GVWR.
- Class C (small vehicle): neither A nor B, but designed to carry 16 or more passengers including the driver, or used to carry placarded hazardous materials.
A Class A holder may also drive B and C vehicles, and a Class B holder may drive C, as long as they hold the needed endorsements. The skills-test vehicle is judged on its weight rating, not its actual weight on the day.
How the CDL General Knowledge Test Is Built
States don't write their own questions. Under 383.133(b), they must use the FMCSA pre-approved question pool. Each test version must fall within a set difficulty range and include a set number of questions from each knowledge area. Twenty-five percent of the questions must be new compared with the previous version. Repeated questions move to a different position, and their three answer choices are shuffled. That is why memorising an answer key fails. You need to understand the material.
The test covers the 20 general knowledge areas in 383.111(a):
- safe operations rules and the vehicle's control systems
- basic control, shifting and backing
- visual search and communication
- speed and space management
- night driving and extreme conditions
- hazard perception, emergency maneuvers and skid control
- cargo and how it affects vehicle control
- vehicle inspections and hazardous materials basics
- mountain driving, and fatigue and awareness
Air brakes add 7 areas, and combination vehicles add 3.
CDL Pass Score and Retakes
You must score at least 80 percent on each knowledge test. Two results matter beyond pass or fail. If you fail the air brakes portion and are still issued a CLP or CDL, it carries an air brake restriction (code L). If you fail the combination vehicles portion, you cannot be issued a Group A CLP or CDL at all. When you retake a failed test, the state must give you a different version. Retest waiting periods and fees are set by the state.
Commercial Learner's Permit (CLP) Rules
| CLP Rule | Requirement |
|---|---|
| Minimum age | 18, with proof of age |
| Before issue | Pass the general knowledge test, and list every state where you were licensed in the last 10 years |
| Supervision | A properly licensed CDL holder must sit in the front seat next to you. On a bus, they sit directly behind you or in the first row. |
| Endorsements allowed | Only P, S and N |
| Hazmat | A CLP holder may never drive with placarded hazmat |
| Skills test wait | Not in the first 14 days after the CLP is first issued |
| Validity | No more than one year from first issue before you retake the knowledge tests |
Entry-Level Driver Training (ELDT)
Since February 7, 2022, 49 CFR 380.609 requires training from a provider on FMCSA's Training Provider Registry in these cases:
- before your first Class A or B skills test, or an upgrade to A or B,
- before your first passenger (P) or school bus (S) skills test, and
- before your first hazmat (H) knowledge test.
The general knowledge test itself can be taken before ELDT, so many drivers get their CLP first.
CDL Endorsements and Restrictions
| Code | Meaning | Tests |
|---|---|---|
| T | Double/triple trailers | Knowledge |
| P | Passenger | Knowledge and skills |
| N | Tank vehicle | Knowledge |
| H | Hazardous materials | Knowledge (plus TSA approval) |
| X | Tank plus hazmat | Both tests |
| S | School bus | Knowledge and skills (P first) |
Restrictions come from what you test in. L means no air brakes. Z means no full air brakes, from testing with air-over-hydraulic brakes. E means no manual transmission, from testing in an automatic. Testing a Class A combination with a pintle hook instead of a fifth wheel brings a tractor-trailer restriction. Removing that one means retaking all three skills tests.
The CDL Skills Test That Follows
After the knowledge test and the 14-day wait, the skills test runs in a fixed order: pre-trip inspection, then basic vehicle control, then the on-road drive. If you fail one segment, you cannot continue. Segments you passed count only during your first CLP, so if the CLP is renewed, you redo all three. No interpreter is allowed, and the test is conducted in English. Breaking traffic laws or causing an accident is an automatic fail.
Rules Tested From Parts 391, 392 and 395
- Hours of service (395.3): 10 hours off before driving, 11 hours of driving within a 14-hour window, and a 30-minute break after 8 hours of driving. The weekly limit is 60 hours in 7 days or 70 in 8, and it restarts after 34 or more hours off.
- Alcohol (392.5): no alcohol within 4 hours before duty. A violation puts you out of service for 24 hours.
- Phones (392.80, 392.82): no texting and no hand-held phone use while driving, even when stopped in traffic, except to contact emergency services.
- Warning devices (392.22): hazard flashers on at once, and triangles placed within 10 minutes. On a two-way road they go about 10 ft from the truck on the traffic side, plus 100 ft ahead and 100 ft behind.
- Railroad crossings (392.10): buses and certain hazmat vehicles stop between 15 and 50 feet from the tracks, and never shift gears while crossing.
- Driver qualification (391.11): 21 for interstate driving, and enough English to talk with the public and read signs. Medical certification is required at least every 24 months.
Offenses That Can Disqualify You
The tables in 383.51 are frequently tested:
- Major offenses: a first DUI, refusing an alcohol test, leaving the scene of an accident, or a felony using the vehicle means 1 year. That rises to 3 years if you were hauling placarded hazmat. A second offense is a lifetime disqualification.
- The 0.04 limit: an alcohol concentration of 0.04 or more in a CMV is a major offense.
- Serious violations: speeding 15 mph or more over the limit, following too closely, or texting. Two within 3 years means 60 days; three means 120 days.
- Your own car counts: convictions in a personal vehicle are counted too.
Is the CDL General Knowledge Test Hard?
It is fair, but the 80 percent bar is higher than many car tests, and the three-choice format leaves little room for guessing. FMCSA publishes no national pass rate. People most often fail on numbers they never memorised: the weight thresholds, warning-device distances, hours-of-service limits and disqualification periods. Questions on speed, space and skid control also catch people out if they rely on car habits.
State Differences
Each state issues the CDL and runs the tests, but under 383.133 every state draws from the same FMCSA question pool and uses the same 80 percent pass mark. Fees, appointment systems, the number of questions, retest waiting periods and intrastate age rules are set by the state. Use your state's CDL manual alongside this guide.
2-Week CDL Knowledge Test Study Plan
- Days 1 to 3: Learn the classes, CLP rules and endorsements. Memorise the 26,001/10,000/16-passenger thresholds.
- Days 4 to 6: Work through the 20 knowledge areas in your state manual, focusing on speed, space, night and mountain driving, and skids.
- Days 7 to 8: Study hours of service, alcohol, phones, warning devices and railroad crossings.
- Days 9 to 10: Learn the disqualification tables and notification deadlines.
- Days 11 to 12: Study the air brakes and combination sections if you need them.
- Days 13 to 14: Take our CDL General Knowledge Practice Test and a timed CDL General Knowledge Full Mock Exam, aiming well above 80 percent.
How Our CDL Questions Are Built
All 161 questions come from the eCFR text of 49 CFR Parts 380, 383, 391, 392 and 395, and each answer quotes the sentence it rests on. They are not copies of a state test, and they do not replace your state manual's driving-technique chapters. For other transport and safety exams, see our Forklift Certification Exam Guide: OSHA 1910.178 Training, Evaluation and the Rules Your Forklift Test Covers.
Frequently Asked Questions
What score do I need to pass the CDL general knowledge test?
80 percent on each knowledge test. 49 CFR 383.135(a)(1) says you must correctly answer at least 80 percent of the questions. The air brakes and combination vehicles tests use the same 80 percent mark.
How many questions are on the CDL general knowledge test?
Your state sets the exact number. Federal rules require each state to build its tests from the FMCSA pre-approved question pool, with a set number of questions drawn from each knowledge area. Check your state CDL manual for the count.
How much does the CDL permit test cost?
FMCSA sets no fee. Your state licensing agency charges its own fees for the CLP, the knowledge tests, the skills test and the licence, so check your state DMV.
Is the CDL knowledge test open book?
No. It is a proctored state test, and when you retake a failed test the state must give you a different version.
What happens if I fail the CDL knowledge test?
You can retake it, and the state must use a different version of the test. Waiting periods and retest fees are set by your state.
Can I take the CDL test in another language?
The knowledge test may be given in a foreign language, but no interpreter may be used. The skills test must be done in English, with no interpreter.
How old do I need to be?
18 for a CLP, and you can drive within your state from 18 where state law allows. To drive a CMV across state lines, 391.11 requires you to be at least 21.
How long after getting my CLP can I take the skills test?
Not in the first 14 days after the CLP is first issued. A CLP is valid for no more than one year before you must retake the knowledge tests.
Do I need CDL school before testing?
Yes, if you are a first-time Class A or B applicant, or upgrading to one. Since February 7, 2022 you must complete entry-level driver training from a provider on FMCSA's Training Provider Registry before your first Class A or B skills test. The same applies before a first passenger or school bus skills test, or a first hazmat knowledge test.
Which CDL tests should I take with the general knowledge test?
Air brakes if your vehicle has them, since failing it puts an L restriction on your licence. Add combination vehicles for Class A, plus any endorsements you need: tank (N), passenger (P) or school bus (S) can go on a CLP.
TradeExamHub is independent and not affiliated with FMCSA or any state DMV. Always confirm fees and procedures with your state licensing agency.