State DMVs (FMCSA rules, AAMVA CDL Manual)

Commercial Driver's License (CDL) Knowledge Tests: General Knowledge, Air Brakes and Combination Vehicles

The three written tests between you and a Class A learner's permit — General Knowledge, Air Brakes and Combination Vehicles — in one practice bank built on the CDL manual every state uses.

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QuestionsTypically General Knowledge 50 · Air Brakes 25 · Combination Vehicles 20 (counts vary by state)

Passing80% on each test, scored separately (49 CFR 383.135)

Who takes whichGeneral Knowledge for every class · Air Brakes for vehicles with air brakes · Combination Vehicles for Class A

TimeMost states don't set a strict limit per test. Allow 1 to 1½ hours for all three

WhereAt your state DMV or driver licensing office, usually on a computer. Some states also use approved third-party testers

FeeSet by your state. Some states charge nothing for the knowledge tests, others charge per test or per permit

After you passCLP valid up to 1 year. Hold it 14 days before the skills test, and complete ELDT first if it's your first Class A or B

About the exam

Before you can get a commercial learner's permit (CLP) and train behind the wheel, you have to pass your state's CDL knowledge tests. Every applicant takes General Knowledge. You add Air Brakes if your truck or bus has air brakes, and Combination Vehicles for a Class A tractor-trailer. Federal rules (49 CFR Part 383) set what the tests cover, and nearly every state builds its CDL manual and question pool on the AAMVA model CDL Manual.

Each test is scored separately, and you need at least 80% on each one. General Knowledge typically has 50 questions, Air Brakes 25 and Combination Vehicles 20, though counts vary a little by state. If you skip or fail Air Brakes, your license gets an air brake restriction. Once you pass, you hold the CLP at least 14 days before the skills test, and first-time Class A or B applicants must also finish Entry-Level Driver Training (ELDT) with a provider on FMCSA's Training Provider Registry.

Our practice follows the manual section by section. General Knowledge covers inspection, basic control, space and speed management, hazards and weather, emergencies and skids, cargo, and the rules that cost drivers their CDL. Air Brakes covers the system parts, the 7-step air brake check and braking technique. Combination Vehicles covers coupling, trailer air lines and rollover. Every answer is explained in plain language, and you can drill one test at a time or take all three back to back.

How we track your progress

Every blueprint domain moves through five levels as you study:

Not startedNo questions answered in this domain yet.
Getting startedFirst questions answered — not enough yet to judge.
DevelopingAt least 5 answered and 50% or better on your recent questions.
ProficientAt least 15 answered and 70% or better on your recent questions.
Exam readyAt least 25 answered, 80% or better recently, and holding up on hard questions.

The exam blueprint

AAMVA model CDL Manual (2005 CDL Test System as republished in state CDL manuals; 2022 modernized skills-test option) · 49 CFR Part 383 — General Knowledge (typically 50), Air Brakes (25) and Combination Vehicles (20), each scored separately with 80% to pass. Domain weights are QuizMe estimates based on typical question counts. Tap a domain to see its topics.

1 Vehicle Inspection about 8% (est.) of the exam

Why and when to inspect: pre-trip, en route and post-tripSeven-step pre-trip inspection methodTires, wheels and rims (tread depth, damage)Brakes, steering and suspension defectsLights, reflectors and emergency equipmentEngine compartment and fluid checksCoupling devices and cargo securement checksOut-of-service defects and the inspection report

24 practice questions in this domain so far

2 Basic Control, Shifting and Backing about 5% (est.) of the exam

Accelerating smoothly and avoiding rollbackSteering with both hands and turningStopping smoothlyBacking safely: helpers, GOAL and the driver sideShifting gears and double clutchingRetarders and engine brakingAutomatic and automated manual transmissions

15 practice questions in this domain so far

3 Seeing, Communicating, Space and Speed Management about 11% (est.) of the exam

Looking ahead 12 to 15 seconds and scanningMirror use and blind spotsSignaling, horn use and communicating intentFollowing distance: 1 second per 10 feet of lengthSpace ahead, behind, to the sides, overhead and belowSpace for turns and crossing trafficStopping distance: perception, reaction and brakingSpeed for road surface, curves, sight distance and trafficDistracted driving and phone use

30 practice questions in this domain so far

4 Hazards, Night, Weather, Railroad and Mountain Driving about 11% (est.) of the exam

Recognizing hazardous roadway conditionsSpotting hazardous road users and aggressive driversNight driving: headlights, glare and fatigueFog and reduced visibilityWinter driving, black ice and slippery roadsHydroplaning and wet brakesHot weather: tires, engine and bleeding tarRailroad-highway crossingsMountain driving: gear selection, brake fade, escape rampsWork zones

30 practice questions in this domain so far

5 Emergencies, Skid Control and Crash Procedures about 7% (est.) of the exam

Emergency steering vs. stoppingLeaving the road safelyControlled and stab brakingAntilock braking systems (ABS)Skid causes and skid recoveryBrake failure and tire blowoutsCrash scene: protect the area, warning devices, reportVehicle fires: causes, extinguishers and fire classes

21 practice questions in this domain so far

6 Cargo Safety about 4% (est.) of the exam

Inspecting cargo: first 50 miles, then every 3 hours or 150 milesWeight terms: GVWR, GCWR, axle weight, tire loadBalancing weight and center of gravityBlocking, bracing and tiedownsCovering cargo and sealed or containerized loadsDry bulk, hanging meat, livestock and oversized loads

12 practice questions in this domain so far

7 Alcohol, Drugs, Fatigue and CDL Rules about 6% (est.) of the exam

CDL classes, endorsements and restrictionsAlcohol, drugs and other substancesBlood alcohol limits and implied consentDisqualifications and serious traffic violationsFatigue, illness and staying alertNotifying employers and the state of convictionsDrug & Alcohol Clearinghouse and CDL downgrades

18 practice questions in this domain so far

8 Air Brakes about 26% (est.) of the exam

Compressor, governor and air storage tanksTank drains, alcohol evaporator and safety valveBrake pedal, foundation brakes and slack adjustersSupply pressure gauges and low air pressure warningSpring brakes and parking brake controlsDual air brake systemsInspecting air brakes and the 7-step air brake checkLeakage rates and pressure build-upAir brake lag and stopping distanceBraking on downgrades and low air pressure

75 practice questions in this domain so far

9 Combination Vehicles about 21% (est.) of the exam

Rollover risk and steering gentlyCrack-the-whip effect and offtracking in turnsBraking early and trailer skidsTrailer air: emergency and service lines, glad handsTractor protection valve and trailer air supply controlTrailer hand valve and trailer air tanksCoupling tractor-semitrailersUncoupling and landing gearInspecting a combination vehicle and fifth wheel

60 practice questions in this domain so far

What you get when you access this exam

Free with your QuizMe account.

Questions built on the CDL manual

Every question is original, written to the AAMVA-based manual your state uses, and tagged to one of 9 areas across General Knowledge, Air Brakes and Combination Vehicles.

Hints that teach the rule

Reveal the manual rule behind a question when you're stuck: following-distance math, air pressure numbers, the coupling sequence. Every answer comes with a plain-language explanation.

Adaptive practice

Questions steer toward your weakest areas, weighted by how much each test counts, and get harder as you get stronger.

Timed practice tests

Take all three tests back to back (95 questions) with a pacing indicator, a full review and a percent score against the 80% pass mark.

Flashcards, case simulations and guides

100 flashcards, 6 unfolding driving cases where every decision changes what happens next, and interactive illustrated guides to the air brake system and coupling.

Progress for every area

Each area moves from Not started to Getting started, Developing, Proficient and Exam ready, so you know exactly what to study next.

Test at home or at a center

CDL knowledge tests are given by your state's driver licensing agency, not booked with a national testing company. Check your state's CDL page for documents, fees and whether you need an appointment.

At your state DMV or licensing office

Bring what your state asks for: usually your current driver's license, proof of identity and residency, and your DOT medical examiner's certificate or medical self-certification.
Most offices give the tests on a computer, one test at a time. Take General Knowledge plus Air Brakes and Combination if your vehicle needs them.
Results usually appear as soon as you finish each test. Pass every test you need and you can be issued a commercial learner's permit (CLP).
Phones, notes and study materials aren't allowed while you test.

Before you go

Download your state's CDL manual. It's free, and it's what the questions come from.
Ask which language options your state offers. Some states now give CDL knowledge tests only in English.
Plan your training: first-time Class A or B drivers must finish ELDT with a provider on FMCSA's Training Provider Registry before the skills test.
Fail a test? Most states let you retest after a short wait, sometimes with a fee. Check your state's retest rules.

Exam-day game plan

How to walk in ready — and how to pace 95 questions in 95 minutes (General 50 + Air Brakes 25 + Combination 20; the real tests are taken separately).

Pacing checkpoints

Hit these and you finish with time to revisit your flagged questions. Our timed practice exams run at this same pace.

24questions0:24

48questions0:48

71questions1:11

95questions1:35

The week before

Read your state's CDL manual, Sections 1–3, 5 and 6, once all the way through, then drill the sections where you're weakest.
Memorize the air brake numbers: governor cut-in about 100 and cut-out about 125 psi, 85 to 100 psi in 45 seconds, low-air warning before 60 psi, spring brakes at 20–45 psi, leakage limits.
Walk through the coupling and uncoupling steps in order until you can say them without notes.
Take one full timed practice run 3–5 days out, then shorter sets.

Test day

Bring every document your state lists. A missing medical certificate or proof of residency is the most common reason people get turned away.
Get there early. Lines at licensing offices can be long, and some close testing before the office closes.
Eat something and go easy on caffeine.

During the tests

Read every choice. DMV questions often have two answers that sound right, and the manual wording decides it.
Watch for EXCEPT, NOT and FIRST.
When in doubt, choose the safest, most conservative action: slow down, leave more space, stop and check.
Remember each test is scored on its own. Do well on General and you can still miss Air Brakes.

Keep your head

A few nerves sharpen focus. If you freeze, take three slow breaths and reread the question.
You need 40 of 50 on General Knowledge, 20 of 25 on Air Brakes and 16 of 20 on Combination, so a few misses won't sink you.
If you miss one test, you usually retake only that test.

Keeping your CDL

CDL renewal periods and fees are set by your state, usually every 4 to 8 years. Most states don't make you retake the knowledge tests to renew.
Keep your DOT medical certificate current, usually up to 24 months, and file it with your state. If it lapses, your state can downgrade your CDL.
A drug or alcohol violation that puts you in 'prohibited' status in FMCSA's Clearinghouse removes your commercial privileges until you finish the return-to-duty process.
Adding an endorsement later, such as Hazmat, Tank or Doubles/Triples, means passing that endorsement's knowledge test.

Official sources and further reading

FMCSA — Commercial Driver's License Program ↗Federal CDL requirements, classes and endorsements, with links to state licensing agencies.
FMCSA — Entry-Level Driver Training (ELDT) ↗Who needs ELDT and how it fits before the skills test.
FMCSA Training Provider Registry ↗Find a registered ELDT provider and check your training record.
FMCSA Drug & Alcohol Clearinghouse ↗Driver registration, violations, and the return-to-duty process.
49 CFR 383.135 — Passing knowledge and skills tests ↗The federal 80% passing rule and the air brake restriction.

Ready to start?

285 questions and scenarios across the blueprint — and growing.

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QuizMe and thinQtank Learning are not affiliated with or endorsed by any state DMV or driver licensing agency, FMCSA or AAMVA. All questions are original and written to the AAMVA-based CDL manual, but states add their own rules and question pools, so always study your state's CDL manual and confirm requirements with your state before you test.