CDL General Knowledge Practice Test
Fifteen original practice questions on the safe-driving basics every CDL applicant is tested on. Each answer comes with a short explanation.
Pick an answer for each question. You’ll see right away if it’s correct and why.
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Answer: C. 5 seconds Below 40 mph, keep at least one second for every 10 feet of vehicle length. A 50-foot truck needs 5 seconds.
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Answer: A. 5 seconds One second per 10 feet gives 4 seconds, and above 40 mph you add one more second, for 5 seconds.
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Answer: B. 12 to 15 seconds The manual says to look 12 to 15 seconds ahead. At highway speed that is roughly a quarter mile, enough time to react to changes.
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Answer: C. It becomes about four times longer Braking distance grows with the square of speed. Going from 20 to 40 mph makes the braking distance and the impact about four times greater.
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Answer: D. By about one-third Wet roads can double stopping distance, so slow down by about one-third, for example from 55 to about 35 mph. Packed snow calls for half or more.
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Answer: B. 30 mph if there is a lot of water With enough standing water, tires can lose contact with the road at around 30 mph. Low tire pressure and worn tread make it more likely.
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Answer: A. Hold the wheel firmly and stay off the brake until the truck slows A failed front tire can twist the wheel out of your hands, and braking can cause loss of control. Keep a firm grip, let the truck slow, then brake gently and pull off.
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Answer: D. Stop braking so the wheels can roll again Locked wheels have less traction than rolling wheels. Release the brake, steer quickly where you want to go, then countersteer as the truck straightens.
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Answer: C. You can almost always steer around it faster than you can stop Turning to miss an obstacle usually takes less time than stopping. Top-heavy vehicles and multiple trailers can still roll over, so steer with care.
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Answer: B. One about 10 feet back on the traffic side, one about 100 feet behind and one about 100 feet ahead On a two-way road, 49 CFR 392.22 calls for one device about 10 feet from the truck on the traffic side, and one about 100 feet away in each direction.
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Answer: A. Within 10 feet of the rear on the traffic side, plus 100 feet and 200 feet back toward approaching traffic On divided or one-way roads all three go toward approaching traffic: one within 10 feet of the rear, one at 100 feet and one at 200 feet.
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Answer: D. As soon as possible, and within 10 minutes 49 CFR 392.22 requires the devices as soon as possible and in any event within 10 minutes. Turn on the hazard flashers right away until they are out.
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Answer: C. An empty truck has less traction Brakes, tires and suspension on heavy vehicles work best fully loaded. Empty, the wheels have less traction, so they lock more easily and stopping takes longer.
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Answer: B. On bridges Bridges freeze before the rest of the road. Shaded areas also stay icy long after open areas melt.
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Answer: D. Leave the air in; pressure rises with heat and will drop as it cools Air pressure goes up with temperature. Letting air out leaves the tire underinflated once it cools. If a tire is too hot to touch, stay stopped until it cools.
About this test
The general knowledge test is the written exam every CDL applicant takes, no matter which class (A, B or C) they want. It covers vehicle inspection, basic control, speed and space management, hazards, emergencies, skids and cargo basics. Federal rules (49 CFR 383.135) require a score of at least 80 percent on each knowledge test. The number of questions is set by each state, so check with your DMV.
These are practice questions, not the official test. They are written from the model CDL manual used by most states and from the federal rules, but your state's CDL manual is what the real test is built from. Read it section by section, and use this quiz to find the topics you need to review.
More CDL practice tests
- New York State Commercial Driver's Manual (CDL-10), Section 2: Driving Safely
- 49 CFR 392.22: Emergency signals; stopped commercial motor vehicles (eCFR)
- 49 CFR 383.135: Passing knowledge and skills tests (eCFR)
- 49 CFR 383.133: Test methods (eCFR)
This page is general information, not legal or tax advice. Rules change; confirm with FMCSA, the IRS or your state before you file.
Questions carriers ask
What score do I need to pass the CDL knowledge test?
Federal rules require at least 80 percent correct on each CDL knowledge test (49 CFR 383.135). Your state may have its own number of questions, but the 80 percent standard applies everywhere.
Can I take the CDL written test in Spanish?
Federal rules allow knowledge tests to be given in a foreign language as long as no interpreter is used (49 CFR 383.133). Whether a Spanish version is offered depends on your state, so ask your DMV. The skills test must be done in English.
Is this the same as the real general knowledge test?
No. These are original practice questions based on the model CDL manual and the FMCSRs. The real test uses an approved question pool, so study your state's CDL manual and use this quiz to check your understanding.