General Knowledge Practice Test
The core commercial driving test every CDL applicant takes, whatever the class. Vehicle control, inspection, cargo, hours of service, and emergency handling.
This is a core knowledge test — every CDL applicant takes it, whatever the class.
Do you need this test?
Required for Class A, Class B. Everyone takes the general knowledge test as well.
Practice now
Study the material, not just the questions
Start with general knowledge, safety, and emergency judgment.
Open the CDL Foundations moduleThe other tests you'll need
- Air Brakes — 25 questions · 80% to pass
- Combination Vehicles — 20 questions · 80% to pass
- Hazardous Materials — 30 questions · 80% to pass
- Tank Vehicles — 20 questions · 80% to pass
- Doubles and Triples — 20 questions · 80% to pass
- Passenger Transport — 20 questions · 80% to pass
- School Bus — 20 questions · 80% to pass
- LCV Doubles — 30 questions · 80% to pass
- LCV Triples — 30 questions · 80% to pass
See every CDL knowledge test →
More CDL guides
See every CDL knowledge test and guide →
Sample General Knowledge questions
What is the maximum BAC allowed for CDL holders operating a commercial vehicle?
- A. 0.04%
- B. 0.08%
- C. 0.02%
- D. 0.00%
Show answer
A. 0.04% — CDL holders face a stricter 0.04% BAC limit because commercial vehicles are heavier and harder to stop, making impairment far more dangerous. Even at 0.04% a driver can be charged with DUI regardless of how they feel.
Universal rule · checked against 49 CFR § 392.5 — Alcohol prohibition and 0.04 BAC standard for drivers on duty · verified 2026-05-17
What are the three emergency equipment items required on commercial vehicles?
- A. Fire extinguisher, spare fuses, warning triangles
- B. First aid kit, flares, flashlight
- C. Jack, tire iron, jumper cables
- D. Tow strap, shovel, ice scraper
Show answer
A. Fire extinguisher, spare fuses, warning triangles — Federal law requires all commercial motor vehicles to carry a fire extinguisher of the correct type and rating, a set of three reflective warning triangles, and spare electrical fuses — missing any item is an out-of-service violation.
Universal rule · checked against 49 CFR § 393.95 — Emergency equipment on commercial motor vehicles · verified 2026-05-17
How often should you check your mirrors while driving a commercial vehicle?
- A. Every 30 seconds
- B. Every minute
- C. Every 5-8 seconds
- D. Only when changing lanes
Show answer
C. Every 5-8 seconds — Check mirrors every 5-8 seconds to maintain awareness of your surroundings and traffic conditions.
Universal rule · checked against FMCSA Commercial Driver License Manual — Section 2: Driving Safely · verified 2026-05-17
Which of these is most important for safe driving?
- A. Proper cargo securement
- B. Having a radio
- C. Wearing sunglasses
- D. Having snacks
Show answer
A. Proper cargo securement — Proper cargo securement helps keep the vehicle stable and prevents cargo from shifting, falling, or creating a roadway hazard.
Universal rule · checked against FMCSA Commercial Driver License Manual — Section 3: Transporting Cargo Safely · verified 2026-05-17
During a pre-trip inspection, engine oil level should be checked:
- A. Before every trip
- B. Only if the low oil warning comes on
- C. Once a week
- D. Only in hot weather
Show answer
A. Before every trip — Check engine oil level (along with coolant, power steering, washer fluid) during every pre-trip inspection.
Universal rule · checked against FMCSA Commercial Driver License Manual — Section 11: Vehicle Inspection Test · verified 2026-05-17
Frequently asked questions
How many questions are on the General Knowledge test?
50 multiple-choice questions, and you need 80% correct — so you can miss 10. The federal standard is consistent across nearly every state.
Is this General Knowledge practice test free?
Yes. Every practice test here and everything in the DMV Prep app is free — no ads, no paywall, no account.
Where do these questions come from?
The FMCSA Commercial Driver's License Manual and 49 CFR. Every question carries its citation, which you can open from the answer explanation.
