CDL · General Knowledge
CDL General Knowledge: The 50-Question Exam Every Trucker Fails at Least Once
2026-07-28 · UniPrep2Go Blog
Before you can add HazMat, drive a school bus, or pull a tanker, you must pass the CDL General Knowledge test. It is the gatekeeper for every commercial driver in America — Class A, B, and C. The format sounds simple: 50 multiple-choice questions, 60 minutes, 80% to pass. Roughly half of first-timers fail because they confuse this exam with endorsements, study the wrong manual chapters, or walk in thinking “I have driven for 20 years — how hard can it be?” This guide covers topics, state wrinkles, and the hard line between General Knowledge and the endorsement tests that come after.
Clear the gate with the free CDL General Knowledge readiness check — timed practice on inspection, space management, and emergencies. Then join the Anki waitlist to drill weak spots before you pay the DMV fee.
The Format (Federal Baseline, State Variation)
FMCSA sets the minimum standard; each state DMV adds its own layer. Federal baseline:
Federal baseline
| Detail | Specification |
|---|---|
| Questions | 50 multiple-choice |
| Time limit | 60 minutes (most states) |
| Passing score | 40 correct (80%) |
| Delivery | Computer-based at DMV or third-party centre |
| Languages | English and Spanish in most states; some add Russian, Serbian-Croatian |
| Open book? | No — no notes, phones, or alpha-keypad calculators |
- Texas: pass a separate 25-question Texas Commercial Rules test before the 50-question General Knowledge — scored separately
- New Jersey: ~$125 Examination Test Receipt covers knowledge tests; fail → wait 7 days and pay again
- Washington: knowledge tests valid ~180 days; CLP renewal windows can extend another 180 days
What Is Actually on the Test
General Knowledge covers the first ~6–7 chapters of your state CDL manual. It does not include endorsements. Studying air brakes, combination vehicles, or HazMat for this sitting wastes time — those are separate exams.
Core topics
| Topic | What the test asks |
|---|---|
| Vehicle inspection | Pre-trip items, brake check, defect reporting |
| Basic vehicle control | Shifting, backing, turning radius, clearances |
| Space management | Following distance, stopping distance, overhead clearance |
| Speed management | Curves, grades, weather, cargo shift |
| Night driving | Glare, fatigue, lighting |
| Extreme weather | Hydroplaning, high winds, fog, ice |
| Emergency procedures | Brake failure, tire blowout, fires, accidents |
| Hazard perception | Road conditions, other drivers, animals |
| Railroad crossings | Stopping distance, passive vs active crossings |
| Cargo securement | Weight distribution, tie-downs, inspection |
| Alcohol and drugs | BAC limits, disqualification, random testing |
| Fatigue / HOS | Basic hours-of-service concepts |
Air brakes trap: not on General Knowledge — separate ~25-question endorsement. Skip it and your CDL gets an L restriction (no air brakes). Most modern CMV fleets use air brakes, so most applicants take both — separate fees, separate passes.
The Math You Actually Need
- Stopping distance = perception + reaction + braking distance
- Following distance: ~1 second per 10 feet of vehicle length under 40 mph; add 1 second per extra 10 mph
- Bridge formulas: gross weight limits by axle spacing
- Cargo weight: total − empty = cargo
Example: 60-foot truck at 50 mph → 6 seconds (length) + 1 second (extra 10 mph over 40) = 7 seconds minimum following time. No calculus — formulas cold, then apply.
The Difference Between General Knowledge and Endorsements
Knowledge tests at a glance
| Test | Questions | Who needs it | Separate fee? |
|---|---|---|---|
| General Knowledge | 50 | Everyone | Yes |
| Air Brakes | 25 | Most drivers (avoid L restriction) | Yes |
| Combination Vehicles | 20 | Class A only | Yes |
| HazMat | 30 | HazMat haulers | Yes + TSA background |
| Tank Vehicles | 20 | Tanker drivers | Yes |
| Doubles/Triples | 20 | Doubles/triples | Yes |
| Passenger | 20 | Bus drivers | Yes |
| School Bus | 20 | School bus drivers | Yes |
Class A combo: General Knowledge + Air Brakes + Combination = 50 + 25 + 20 = 95 questions. Some states allow one sitting; others split appointments. Confirm with your DMV.
Study Strategy: The Two-Step Method
- Read your official state CDL manual once — exam wording comes from it, not random prep books
- Full 50-question timed mocks until bored — not 10-question snack quizzes
- First mock (diagnostic): ~60–70% is normal
- After review: ~75–80%
- Confidence check: 85%+ before you book
Do not schedule the DMV until you hit 85% on a timed mock with questions you have not memorised by rote.
FAQ
How many questions are on the CDL General Knowledge test?
50 multiple-choice questions. You need 40 correct (80%) to pass.
What score do I need to pass the CDL General Knowledge exam?
80% — 40 out of 50 correct answers.
How long is the CDL General Knowledge test?
Most states allow about 60 minutes. Some have no hard clock — still plan for an hour.
Is the CDL General Knowledge test the same in every state?
Federal content is standardised, but states add local items. Texas requires a separate Commercial Rules test first. Always use your state’s CDL manual.
Are air brakes on the General Knowledge test?
No. Air brakes have a separate ~25-question endorsement. Skip it and you get an L restriction — no air-brake vehicles.
How much does the CDL General Knowledge test cost?
Varies by state (CLP, knowledge receipt, skills fees differ). Check your DMV fee schedule.
Can I retake the CDL General Knowledge test if I fail?
Yes. Most states require a wait of 24 hours to 7 days. You usually pay again unless retakes are bundled.
What languages is the CDL General Knowledge test available in?
English and Spanish in most states; some offer additional languages. Federal rules still require enough English to read signs and talk with officials.
Do I need to pass General Knowledge before endorsement tests?
Yes. General Knowledge is the prerequisite for endorsements and the skills test.
How long is a CDL permit valid after passing the knowledge tests?
About 180 days in most states. Some allow a one-time renewal for another 180 days if you renew in time.
Bottom Line
CDL General Knowledge is reading comprehension about commercial safety with a timer — not an IQ test. Failures skip the manual and trust “common sense.” Trucks are not cars: longer stops, bigger blinds, worse consequences. Read the state manual, take full 50-question timed mocks, clear 80%. Endorsements come later — only after this gate.
Clear the gate with the free CDL General Knowledge readiness check — timed practice on inspection, space management, and emergencies. Then join the Anki waitlist to drill weak spots before you pay the DMV fee.
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