FirstTryEn españolCDL permit test study guide
The CDL General Knowledge test is written from the Commercial Driver's License Manual (AAMVA CDL Driver's Manual, Modernized Testing System, Version: March 2025 (Virginia DMV print DMV 60A, 07/20/2026)). Federal rules require at least 80 percent on every CDL knowledge test. Many states give 50 General Knowledge questions (40 right to pass), but the count varies by state and license class, so check with yours. FirstTry's practice test gives 50 questions with 40 right to pass (the federal rule).
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What the test covers
FirstTry's CDL bank has 150 General Knowledge questions written from the manual (Classes A, B and C). The biggest topics:
- Vehicle inspection: 13 questions
- Cargo: 13 questions
- Speed: 10 questions
- Licensing: 10 questions
- Disqualification: 8 questions
- Emergencies: 8 questions
- Communicating: 7 questions
- Accidents and fires: 7 questions
- Basic control: 7 questions
- Night driving: 7 questions
Numbers to know
- Braking distance grows much faster than speed. Going from 20 to 40 mph makes it 4 times longer, and impact force rises the same way. handbook section
- At 55 mph, perception takes about 142 feet and braking about 216 feet; with reaction distance added, the total is at least 419 feet. handbook section
- Wet roads can double your stopping distance. Slowing by about one-third, for example from 55 to about 35 mph, helps you stop in a similar distance. handbook section
- A 12-ounce beer, a 5-ounce glass of wine, and 1 1/2 ounces of 80-proof liquor all hold about the same alcohol. It is the alcohol that impairs you, not the type of drink. handbook section
- Without a stop line, vehicles that must stop do so at least 15 feet, and no more than 50 feet, from the nearest rail. handbook section
- Once you are safe, look for the emergency phone number on the signal housing or signpost and call it or 911, giving the crossing's DOT number if posted. handbook section
- Turn on your four-way flashers right away and set out your warning devices within 10 minutes. handbook section
- For CMV drivers the limit is 0.04%. If you drive a CMV, you are considered to have consented to alcohol testing. handbook section
- Front tires need at least 4/32 inch of tread in every major groove, and all other tires need at least 2/32 inch. No fabric should show through. handbook section
- With air brakes, pressure should climb from 50 to 90 psi within 3 minutes. Know your vehicle's governor cut-out pressure. handbook section
- Alcohol, drug, or felony violations in your personal vehicle that cost you that privilege also cost you your CDL for 1 year. handbook section
- Low beams reach about 250 feet and high beams about 350 to 500 feet. Drive slowly enough to stop within the range of your lights. handbook section
Sample questions
Speed
In fog or heavy rain, how fast should you drive?
- Slowly enough that you could stop in the distance you can see
- Fast enough to get out of the bad weather quickly
- At the posted speed limit
Show the answer
Slowly enough that you could stop in the distance you can see. When fog, rain, or darkness cuts how far you can see, slow down so you can still stop in that distance. Low beams show less than high beams.
From the handbook: Section 2 Driving Safely, 2.6.4 Speed and Distance Ahead (manual p. 2-15, PDF p. 33)
Alcohol and drugs
As your blood alcohol rises, which abilities does alcohol affect first?
- Muscle strength
- Hearing and smell
- Judgment and self-control
Show the answer
Judgment and self-control. Because judgment goes first, drinkers often can't tell they are getting drunk, yet good judgment and self-control are essential for safe driving.
From the handbook: Section 2 Driving Safely, 2.22.1 Alcohol and Driving (Alcohol and the Brain) (manual p. 2-41, PDF p. 59)