Every CDL applicant takes the general knowledge test, whatever the class. The questions come from the federal CDL driver manual that each state's test is built on. Rules and fees change, so treat this guide as a starting point and confirm everything on the official site before you go.
Passing score
Federal rules set the minimum passing score at 80 percent. The number of questions can differ by state, so ask your licensing agency how many questions you will see.
What the test covers
- Vehicle inspection: what to check before a trip, and why.
- Controlling the vehicle: steering, braking, speed on curves and backing.
- Seeing and communicating: scanning ahead, mirrors, signals and the horn.
- Hazards and emergencies: skids, brake failure, fires and escape ramps.
- Night, weather and mountains: fog, ice, long downgrades and driving when tired.
- Cargo and weight: balance, tie-downs and weight limits.
- Alcohol, drugs and licensing: the 0.04 limit for commercial drivers and the rules that can disqualify you.
A study plan that works
- Read one section of the manual, then take the matching practice test.
- Read the explanation for every missed question, not only the right answer.
- Repeat the topic until you score above 90 percent.
- Finish with a mixed test so you practice switching between topics.
Numbers worth memorizing
- 0.04 percent: the alcohol limit for a commercial driver in a commercial vehicle.
- 4 hours: the wait between drinking and driving a commercial vehicle.
- 14 days: the minimum time to hold a CLP before the skills test.
- 50 miles: when to first check your cargo, then every 150 miles or 3 hours.
The test likes the safe answer. If one choice says to slow down or stop and another says to speed up or keep going, the safe choice is usually right.