Two manuals are live.
Your state picks.

General Knowledge is the one test every CDL applicant takes, whatever the class and whatever the endorsements. It comes out of the CDL manual, the passing score is 80 percent and that part is federal, and a surprising amount of what is taught about it online is simply out of date. This page covers which licence you need and why the two weight ratings decide it, what every endorsement and restriction letter means, the learner permit and the training you must now complete before the skills test, what takes a licence away, and the two hours-of-service clocks that run at different rates.

Read this part

This is study material, not the test and not the manual. The CDL knowledge tests are written by AAMVA from the CDL manual your own state publishes, and that manual is the authority — get the current one from your state licensing agency and read it. Federal rules set the floor; your state can and does add to them, and a few states test material that is theirs alone. Nothing here is legal advice.

ON THIS PAGE

What the General Knowledge test actually is Which CDL manual your state is using Which class of licence, and how the numbers decide it Endorsements and restrictions, by their letters The learner permit, and the training you now have to have first What takes your licence away Hours of service: the two clocks Phones, texting and what counts as a serious violation

START HERE

What the General Knowledge test actually is

General Knowledge is one specific test, and every CDL applicant takes it regardless of class or endorsement. It is drawn from the CDL manual — Section 1 and Section 2 for everyone, plus Section 3 if you will haul cargo, which in practice is everyone in a truck. Air Brakes and Combination Vehicles are separate tests from separate sections, and this set does not cover them.

The passing score is federal and it is not negotiable: 49 CFR 383.135 requires an applicant to answer at least 80 percent of the questions on each knowledge test correctly. Most states set General Knowledge at 50 questions, which makes 40 the pass and 10 the most you can miss, but the number of questions is a state choice and the 80 percent is not.

Failing the air brake section has a permanent consequence

Under 49 CFR 383.95, an applicant who fails the air brake component of the knowledge test, or who takes the skills test in a vehicle without air brakes, gets an L restriction on the licence: no air-brake-equipped commercial vehicle. That rules out most of the trucks worth driving. Removing it takes more than a retake of the written test: under 383.135(b)(7) you must pass the air brake knowledge test and perform the air brake portion of the pre-trip inspection and the skills test in a vehicle that has air brakes. It is the single most common self-inflicted limitation on a new CDL.

Test	Manual sections	Who takes it
General Knowledge	Section 1, Section 2, and Section 3 for cargo	Every CDL applicant, every class
Air Brakes	Section 5	Anyone who does not want the L restriction
Combination Vehicles	Section 6	Class A applicants
Doubles and Triples (T)	Section 7	Knowledge test only
Tank Vehicle (N)	Section 8	Knowledge test only
Hazardous Materials (H)	Section 9	Knowledge test, plus a TSA security threat assessment
Passenger (P)	Section 4	Knowledge and a skills test
School Bus (S)	Section 10	Knowledge and a skills test

TWO MANUALS ARE LIVE

Which CDL manual your state is using

AAMVA has modernized the CDL test system, and the modernized CDL manual carries a 2025 copyright. The old 2005 CDL Test System manual is still in use in a great many states. AAMVA is explicit that jurisdictions may offer the modernized version, the current version, or both, and there is no federal mandate to switch. The result is a real patchwork rather than a rollout: Massachusetts transitioned in October 2023, Texas through 2024, Georgia went statewide in June 2026, and other states have not moved at all.

What actually changed, and what did not

Section numbering	Unchanged. Both manuals run 1 to 13 with the same section titles: Introduction, Driving Safely, Transporting Cargo Safely, and so on. If a study guide tells you to read Section 2, that instruction survives the change.	no effect on you
General Knowledge content	Substantially the same physics and the same numbers. The modernized manual adds material on entry-level driver training, human trafficking awareness, distracted driving and the medical certification framework, and rewrites a good deal of the prose.	read the newer one if you have it
The vehicle inspection test	This is the real change. The modernized inspection has fewer items, focused on critical safety items, with the reasoning for each one given in the manual rather than left to be memorised.	skills test only
The basic control skills test	Reduced to four exercises — forward stop, straight-line backing, forward offset tracking, and reverse offset backing, which merges the old parallel park and alley dock, and the course fits in a smaller footprint. The widely repeated claim that each manoeuvre begins where the last one ended is not stated by AAMVA or by any state source we could find.	skills test only
The road test	Unchanged.	no effect on you

For the General Knowledge test specifically, the two manuals are close enough that studying either will get you through. Everything on these pages is drawn from material common to both, or is federal regulation, which does not vary by manual at all. Where the skills test is concerned the difference is real, and you need to know which version your state gives before you practise.

49 CFR 383.91

Which class of licence, and how the numbers decide it

The class is decided by two weight ratings and, failing those, by what you are carrying. It is not decided by what the vehicle looks like, and that is where people go wrong: Class A is not a synonym for "tractor-trailer".

The test as 49 CFR 383.91 actually writes it. Ratings, not actual weights — GVWR and GCWR are what the manufacturer says the vehicle is rated for, so an empty truck is in the same class as a loaded one.

Class A — any combination with a gross combination weight rating of 26,001 lb or more, provided the towed unit or units are rated over 10,000 lb. Both halves of that must be true. A Class A also lets you drive Class B and Class C vehicles, subject to your endorsements.
Class B — any single vehicle with a GVWR of 26,001 lb or more, or such a vehicle towing something rated 10,000 lb or less. A Class B also covers Class C.
Class C — anything that is not A or B but is either designed to transport 16 or more people including the driver, or is used to carry hazardous materials as 383.5 defines them — a quantity requiring placards, or any quantity at all of a select agent or toxin listed in 42 CFR part 73.
Rating, not load. GVWR and GCWR are manufacturer ratings. Running a 33,000 lb GVWR truck empty does not make it a Class C vehicle, and loading a 20,000 lb GVWR truck to 27,000 lb makes it overweight, not a Class B.

The case that catches people

A tractor rated 30,000 lb GVWR pulling a trailer rated 9,000 lb GVWR is a Class B combination, because the towed unit is not over 10,000 lb. It looks like a tractor-trailer from fifty feet away and it is not a Class A vehicle. Note which rating Class B is keyed to: 383.91(a)(2) says "any single vehicle with a GVWR of 26,001 pounds or more, or any such vehicle towing a vehicle not in excess of 10,000 pounds GVWR" — the power unit's GVWR, not its GCWR. The trap runs the other way too: a 24,000 lb GVWR straight truck pulling a 12,000 lb GVWR trailer has a GCWR over 26,001 lb and a towed unit over 10,000, so it is Class A.

49 CFR 383.153

Endorsements and restrictions, by their letters

The letters are standardised federally, so they mean the same thing in every state. An endorsement adds something you may do; a restriction takes something away. Both are printed on the licence.

Code	Endorsement	What it takes
T	Double and triple trailers	Knowledge test only
P	Passenger	Knowledge test and a skills test
N	Tank vehicle	Knowledge test only
H	Hazardous materials	Knowledge test, plus a TSA security threat assessment and fingerprinting
X	Tank vehicle and hazardous materials combined	The requirements for both N and H
S	School bus	Knowledge test and a skills test

Code	Restriction	What triggers it
L	No air-brake-equipped commercial vehicle	Failing the air brake knowledge component, or taking the skills test in a vehicle with no air brakes
Z	No full-air-brake-equipped commercial vehicle	Taking the skills test in a vehicle with air-over-hydraulic brakes
E	No manual transmission commercial vehicle	Taking the skills test in a vehicle with an automatic transmission
O	No tractor-trailer commercial vehicle	Taking the Class A skills test in a combination coupled by a pintle hook or other non-fifth-wheel connection
M	No Class A passenger vehicle	Taking the passenger skills test in a passenger vehicle requiring a Class B CDL
N	No Class A and B passenger vehicle	Taking the passenger skills test in a passenger vehicle requiring a Class C CDL
K	Intrastate only	Not meeting the federal interstate requirements, usually age or medical
V	Medical variance	A medical variance recorded on the CDLIS driver record
P	No passengers in a commercial bus — learner permit only	Held automatically by any CLP holder with a passenger endorsement
X	No cargo in a commercial tank vehicle — learner permit only	Held automatically by any CLP holder with a tank endorsement

Two letters do double duty

N as an endorsement is the tank vehicle endorsement; N as a restriction means no Class A and B passenger vehicle. X as an endorsement is tank plus hazardous materials; X as a learner permit restriction means no cargo in a tank vehicle. Each pair is unrelated, they appear in different fields on the document, and a question that gives you the bare letter without saying which field it is in has two answers.

49 CFR 383.25 AND PART 380

The learner permit, and the training you now have to have first

1

Entry-Level Driver Training, since 7 February 2022.

Before you can take the skills test for a Class A or Class B CDL for the first time, upgrade from B to A, or get a passenger, school bus or hazardous materials endorsement, you must complete training from a provider listed on the FMCSA Training Provider Registry, and the provider must report your completion to FMCSA. This is federal and it applies everywhere. It is theory plus behind-the-wheel training with no minimum hours, but the theory portion must be passed at 80 percent.
2

Pass the knowledge tests and get a commercial learner permit.

The CLP is issued on the general knowledge test and any endorsement knowledge tests you want on it. Only three endorsements may appear on a CLP at all: P, S and N, and each carries conditions.
3

Hold it for at least 14 days.

49 CFR 383.25: a CLP holder is not eligible to take the CDL skills test in the first 14 days after initial issuance. There is no way to shorten this and no state may waive it.
4

Take the skills test within the permit's life.

The CLP must be valid for no more than one year from the date of initial issuance without the holder having to retake the knowledge tests. A state may issue for a shorter period and renew, so long as the total does not run past one year from first issue.

The 180-day figure is a ceiling your state may still be using

The CLP used to be valid for 180 days with one 180-day renewal. Since a rule effective 19 February 2019 the federal ceiling has been one year from initial issuance — but that gave states an option, not a mandate, so your own state may still issue a 180-day permit. A great deal of study material states 180 days as though it were still the federal rule, and a great deal more states one year as though every state had taken the option. Check what your own permit says. The 14-day wait is the part that does not vary.

You are never alone in the vehicle. A CLP holder must be accompanied by a CDL holder with the proper class and endorsements, who must be seated in the front passenger seat, or in a passenger vehicle directly behind or in the first row behind the driver, and who must supervise and observe at all times.
P and S on a CLP carry no passengers. No passengers at all other than federal or state auditors and inspectors, test examiners, other trainees, and the accompanying CDL holder.
N on a CLP means empty. A CLP holder with a tank endorsement may only operate an empty tank vehicle, and may not operate any tank that has previously contained hazardous materials unless it has been purged of all residue.
No other endorsements on a CLP. H in particular cannot be held on a permit.

49 CFR 383.51

What takes your licence away

The disqualification tables are federal and the periods are minimums, so a state may be harsher but not more lenient. Note what is in the first table: it applies to conduct in a commercial vehicle and, for most of the offences, to the same conduct in your own car.

Offence	First conviction	Second
Driving under the influence of alcohol or a controlled substance; alcohol concentration of 0.04 or more; refusing a required test; leaving the scene; using a vehicle to commit a felony; driving a CMV with a revoked, suspended or cancelled CDL; causing a fatality through negligent operation	1 year, or 3 years if the vehicle was placarded for hazardous materials	Lifetime
Using a commercial vehicle in the commission of a felony involving controlled substances, or a felony involving human trafficking	Lifetime, with no ten-year reinstatement	—
Two serious traffic violations in three years — excessive speeding at 15 mph or more over the limit, reckless driving, improper or erratic lane changes, following too closely, a violation connected with a fatal accident, driving without the right CDL or CLP, texting, or using a hand-held phone	60 days at the second	120 days at the third
Railroad-highway grade crossing violations	60 days	120 days at the second and 1 year at the third, each within a three-year period
Violating an out-of-service order, non-hazardous	180 days to 1 year	2 to 5 years at the second within ten years
Violating an out-of-service order while placarded for hazardous materials or in a vehicle designed for 16 or more passengers	180 days to 2 years	3 to 5 years at the second within ten years

Two numbers, and the lower one still stops you

0.04 is the alcohol concentration at which operating a commercial vehicle is illegal and a disqualifying offence — half the limit for a private car in every state. But it is not the only threshold: any detectable amount of alcohol below 0.04 puts you out of service for 24 hours. And refusing the test is treated exactly like failing it, at a full year for a first offence. There is no version of this where declining to blow helps you.

49 CFR 395.3

Hours of service: the two clocks

These are the property-carrying limits. Passenger-carrying drivers work to a different set of numbers, and this is not the place to learn those. Everything below assumes you have first had 10 consecutive hours off duty, which is what starts the day.

One day drawn on one axis. The 11-hour driving limit counts driving time only, so it pauses; the 14-hour window counts elapsed time from coming on duty, so it does not. Running out of window with driving hours left is the normal outcome, not an unusual one.

11-hour driving limit. A maximum of 11 hours of driving after 10 consecutive hours off duty.
14-hour window. You may not drive after the 14th consecutive hour following coming on duty. Ordinary off-duty time inside the window does not extend it. The one exception is the split sleeper berth at 49 CFR 395.1(g)(1): two rest periods, neither shorter than 2 consecutive hours, one of them at least 7 consecutive hours in the sleeper berth, totalling at least 10 — and the qualifying sleeper period is excluded from the window.
30-minute break. Driving is not permitted if more than 8 cumulative hours of driving time have passed without at least a consecutive 30-minute interruption. The interruption may be off duty, sleeper berth, or on duty not driving — so thirty minutes spent doing paperwork counts, and it is eight hours of driving, not eight hours on duty.
60 hours in 7 days, or 70 in 8. Which one applies depends on whether the carrier operates vehicles every day of the week.
34-hour restart. A period of 34 or more consecutive hours off duty restarts the 7- or 8-day count.

The break rule changed and the old version is still taught

Until the hours-of-service final rule took effect on 29 September 2020, the trigger was eight hours of elapsed time since the end of the last qualifying break, and the break itself had to be off duty or in the sleeper berth. It is now eight hours of driving time, and on-duty-not-driving time satisfies it. That is a meaningful difference for a driver who spends a long morning loading, and material written before that date will teach you the wrong rule.

49 CFR 392.80 AND 392.82

Phones, texting and what counts as a serious violation

DO

Use a hands-free phone that is within immediate reach and can be operated with a single button push — that wording is in 49 CFR 390.5, not in 392.82 itself.
Mount the phone so you can reach it without leaning out of a seated, belted driving position.
Pull off the road and stop where it is safe if you need to do anything more than that.
Treat a hand-held call as what the regulation treats it as: a serious traffic violation that counts toward the 60-day and 120-day disqualifications.

DO NOT

Hold a mobile phone to conduct a voice communication while driving.
Dial by pressing more than a single button.
Reach for a phone in a way that requires leaving a seated, belted position.
Send or read a text message while driving — this includes emailing, instant messaging and accessing a web page.
Assume the truck being stopped at a light makes it legal. The rules apply while the vehicle is on a highway, including temporarily stationary because of traffic.

These are not ordinary tickets

Texting and hand-held phone use are both listed as serious traffic violations in 49 CFR 383.51 Table 2. Two of those in three years is a 60-day disqualification and three is 120 days, and the count is across any combination of serious violations, not two of the same kind. They also carry civil penalties for the driver and for a carrier that allows the practice.

Two manuals are live.Your state picks.