Ohio General Knowledge practice test
50 questions · 80% to pass · Required for every CDL applicant.
How to use this practice test
Read each question, click an answer, and the correct choice is highlighted with a short explanation referencing the underlying CDL Manual concept. Your live score appears at the top of the page. Refresh to reset.
This test runs entirely in your browser. Nothing is uploaded; no account is required. Pages refresh to a new randomized cut from the bank.
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1. You must use low beams within how many feet of an oncoming vehicle?
Explanation. Switch to low beams within 500 feet of an oncoming vehicle to avoid blinding the other driver.
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2. You should NOT drive when taking which of these?
Explanation. Drowsiness-causing medications, even legal ones, can disqualify you from driving.
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3. When taking the CDL knowledge exam, what does the term "perception distance" mean?
Explanation. Perception distance is the distance traveled while your brain identifies a hazard, typically about 1.5 seconds at highway speed. (Reinforcement variant — same underlying CDL Manual concept.)
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4. When taking the CDL knowledge exam, you should NOT drive when taking which of these?
Explanation. Drowsiness-causing medications, even legal ones, can disqualify you from driving. (Reinforcement variant — same underlying CDL Manual concept.)
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5. When operating a CMV in interstate commerce, when checking your vehicle, the engine should be off and the wheels chocked because:
Explanation. Chocking wheels and shutting down the engine prevents the vehicle from rolling away while you are underneath or alongside it. (Reinforcement variant — same underlying CDL Manual concept.)
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6. Most state DMV CDL handbooks state that you should signal continuously when turning because:
Explanation. Continuous signaling keeps other drivers informed and prevents the signal from cancelling before the turn is complete. (Reinforcement variant — same underlying CDL Manual concept.)
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7. You should check your mirrors:
Explanation. Frequent mirror checks (every 5-8 seconds) are part of safe scanning.
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8. During a pre-trip inspection, texting while driving a CMV is:
Explanation. Texting is banned for all CMV drivers under federal law. (Reinforcement variant — same underlying CDL Manual concept.)
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9. According to the FMCSA CDL Manual, when you double your speed, your stopping distance:
Explanation. Stopping distance increases roughly with the square of speed, so doubling speed nearly quadruples the distance. (Reinforcement variant — same underlying CDL Manual concept.)
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10. In real-world commercial driving, you should NOT drive when taking which of these?
Explanation. Drowsiness-causing medications, even legal ones, can disqualify you from driving. (Reinforcement variant — same underlying CDL Manual concept.)
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11. Convex (curved) mirrors:
Explanation. Convex mirrors widen the view but make objects appear smaller and farther away than they actually are.
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12. Experienced commercial drivers know that you should check your mirrors:
Explanation. Frequent mirror checks (every 5-8 seconds) are part of safe scanning. (Reinforcement variant — same underlying CDL Manual concept.)
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13. Most state DMV CDL handbooks state that when approaching a railroad crossing, you should:
Explanation. Always slow, look, listen, and prepare to stop. A full stop is required only for buses, hazmat, and certain placarded vehicles. (Reinforcement variant — same underlying CDL Manual concept.)
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14. Most state DMV CDL handbooks state that when merging onto a highway, you should:
Explanation. Match traffic speed and yield; stopping is dangerous and can cause rear-end collisions. (Reinforcement variant — same underlying CDL Manual concept.)
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15. During a pre-trip inspection, what is the standard color of a placard for a Class 2 (gases) hazardous material?
Explanation. Class 2 placards are red for flammable gas, green for non-flammable, and yellow/white for poison/oxygen subdivisions. (Reinforcement variant — same underlying CDL Manual concept.)
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16. During a pre-trip inspection, the most common cause of serious skids is:
Explanation. Driving too fast for road and weather conditions is the leading cause of skids. (Reinforcement variant — same underlying CDL Manual concept.)
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17. A driver may use a hand-held mobile phone while driving a CMV:
Explanation. Federal rules prohibit hand-held mobile phone use by CMV drivers except in emergencies.
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18. When operating a CMV in interstate commerce, a vehicle is most likely to roll over when:
Explanation. High center of gravity plus sudden steering or braking is the recipe for rollovers. (Reinforcement variant — same underlying CDL Manual concept.)
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19. Experienced commercial drivers know that which of these is NOT a sign of a tired driver?
Explanation. A "second wind" is a brief, deceptive boost. All of the others, including the second wind, are warning signs of fatigue. (Reinforcement variant — same underlying CDL Manual concept.)
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20. Experienced commercial drivers know that aggressive driving by other motorists is best handled by:
Explanation. The safest response is to disengage and report when safe; never engage an aggressive driver. (Reinforcement variant — same underlying CDL Manual concept.)
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21. Experienced commercial drivers know that a driver loses their CDL for life if convicted of:
Explanation. Using a CMV to commit a controlled-substance felony is grounds for a lifetime CDL disqualification. (Reinforcement variant — same underlying CDL Manual concept.)
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22. During a pre-trip inspection, most pre-trip inspections begin with which step?
Explanation. The CDL Manual lists "review last inspection report" as the first step in the seven-step pre-trip inspection. (Reinforcement variant — same underlying CDL Manual concept.)
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23. Most state DMV CDL handbooks state that when driving in fog, you should:
Explanation. High beams reflect off fog and reduce vision; low beams and slower speed are correct. (Reinforcement variant — same underlying CDL Manual concept.)
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24. When taking the CDL knowledge exam, when driving down a long, steep grade, you should:
Explanation. Always select a low gear before descending so engine compression helps hold speed and brakes do not overheat. (Reinforcement variant — same underlying CDL Manual concept.)
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25. During a pre-trip inspection, stab braking is used:
Explanation. Stab braking is an emergency technique for non-ABS vehicles: brake hard until wheels lock, release, brake again. (Reinforcement variant — same underlying CDL Manual concept.)
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26. Black ice is dangerous because:
Explanation. Black ice is a thin layer of ice clear enough that the road below shows through, making it look merely wet.
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27. According to the FMCSA CDL Manual, the best way to recover from a drive-wheel skid is to:
Explanation. Releasing the accelerator and disengaging the clutch removes power from the drive wheels so they can regain traction. (Reinforcement variant — same underlying CDL Manual concept.)
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28. In real-world commercial driving, brake fade is caused by:
Explanation. Brakes lose effectiveness when overheated; this is why low gears are essential on grades. (Reinforcement variant — same underlying CDL Manual concept.)
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29. When operating a CMV in interstate commerce, cargo should be inspected:
Explanation. You must inspect cargo within the first 50 miles, then every 150 miles or 3 hours, whichever is sooner. (Reinforcement variant — same underlying CDL Manual concept.)
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30. The 14-hour rule means a driver may not drive after the:
Explanation. After 14 consecutive hours on duty following 10 hours off, no further driving is allowed even if some of those 14 hours were not driving.
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31. In real-world commercial driving, when making a right turn in a large vehicle, you should:
Explanation. Stay in the right lane and watch the trailer; swinging left first invites a same-direction driver to squeeze in on your right. (Reinforcement variant — same underlying CDL Manual concept.)
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32. During a pre-trip inspection, a vehicle is most likely to roll over when:
Explanation. High center of gravity plus sudden steering or braking is the recipe for rollovers. (Reinforcement variant — same underlying CDL Manual concept.)
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33. Per federal regulations, which of these is NOT a sign of a tired driver?
Explanation. A "second wind" is a brief, deceptive boost. All of the others, including the second wind, are warning signs of fatigue. (Reinforcement variant — same underlying CDL Manual concept.)
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34. Per federal regulations, the 14-hour rule means a driver may not drive after the:
Explanation. After 14 consecutive hours on duty following 10 hours off, no further driving is allowed even if some of those 14 hours were not driving. (Reinforcement variant — same underlying CDL Manual concept.)
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35. Most state DMV CDL handbooks state that a driver loses their CDL for life if convicted of:
Explanation. Using a CMV to commit a controlled-substance felony is grounds for a lifetime CDL disqualification. (Reinforcement variant — same underlying CDL Manual concept.)
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36. According to the FMCSA CDL Manual, a retarder helps the driver by:
Explanation. Retarders slow the vehicle without using service brakes, reducing brake wear and overheating risk. (Reinforcement variant — same underlying CDL Manual concept.)
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37. A vehicle is most likely to roll over when:
Explanation. High center of gravity plus sudden steering or braking is the recipe for rollovers.
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38. A driver who is convicted of DUI in any vehicle while holding a CDL faces:
Explanation. A first DUI conviction in any vehicle disqualifies a CDL for at least one year.
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39. A safe following distance for a 40-foot vehicle at 50 mph is at least:
Explanation. Use 1 second per 10 feet of vehicle length under 40 mph, plus 1 extra second above 40 mph: 4 + 1 = 5 seconds for a 40-foot truck at 50 mph.
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40. When taking the CDL knowledge exam, cargo should be inspected:
Explanation. You must inspect cargo within the first 50 miles, then every 150 miles or 3 hours, whichever is sooner. (Reinforcement variant — same underlying CDL Manual concept.)
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41. When taking the CDL knowledge exam, when checking your vehicle, the engine should be off and the wheels chocked because:
Explanation. Chocking wheels and shutting down the engine prevents the vehicle from rolling away while you are underneath or alongside it. (Reinforcement variant — same underlying CDL Manual concept.)
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42. Experienced commercial drivers know that when merging onto a highway, you should:
Explanation. Match traffic speed and yield; stopping is dangerous and can cause rear-end collisions. (Reinforcement variant — same underlying CDL Manual concept.)
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43. When driving at night, you should adjust your speed so you can stop within:
Explanation. You must be able to stop within the distance you can see, which at night is the range of your low or high beam headlights.
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44. In real-world commercial driving, controlled braking means:
Explanation. Controlled braking is firm pressure that does not lock the wheels, allowing you to continue steering. (Reinforcement variant — same underlying CDL Manual concept.)
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45. Experienced commercial drivers know that what is the standard color of a placard for a Class 2 (gases) hazardous material?
Explanation. Class 2 placards are red for flammable gas, green for non-flammable, and yellow/white for poison/oxygen subdivisions. (Reinforcement variant — same underlying CDL Manual concept.)
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46. Stab braking is used:
Explanation. Stab braking is an emergency technique for non-ABS vehicles: brake hard until wheels lock, release, brake again.
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47. According to the FMCSA CDL Manual, drivers must complete a written post-trip inspection report when:
Explanation. Federal rules require a report whenever defects are found, and many carriers require one for every trip. (Reinforcement variant — same underlying CDL Manual concept.)
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48. What does the term "perception distance" mean?
Explanation. Perception distance is the distance traveled while your brain identifies a hazard, typically about 1.5 seconds at highway speed.
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49. During a pre-trip inspection, a driver loses their CDL for life if convicted of:
Explanation. Using a CMV to commit a controlled-substance felony is grounds for a lifetime CDL disqualification. (Reinforcement variant — same underlying CDL Manual concept.)
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50. When operating a CMV in interstate commerce, most pre-trip inspections begin with which step?
Explanation. The CDL Manual lists "review last inspection report" as the first step in the seven-step pre-trip inspection. (Reinforcement variant — same underlying CDL Manual concept.)
About the General Knowledge exam
The General Knowledge exam is required for every Class A, B, and C CDL applicant. It covers vehicle inspection, basic control, shifting, backing, communicating with other drivers, distracted driving, fatigue, hazard perception, emergency maneuvers, skid control, accident procedures, hazardous materials awareness, and federal hours-of-service rules.
This Ohio-specific edition uses the same federal source material every U.S. state adopts. The Ohio BMV administers the actual exam at its service centers. Bring your CDL handbook for any last-minute reference; it’s free at every Ohio BMV office.
Once you’re consistently scoring above 90% on this practice set, you’re well above the 80% required to pass the official Ohio exam. Drill the questions you miss most often, then take the test cold once a day for a week leading up to your appointment.
Tips that actually work
- Read every answer choice before clicking. CDL questions are famous for "best answer" wording where two choices look right.
- Don’t memorize question text — learn the underlying rule. The DMV reshuffles wording constantly.
- Keep a list of the questions you miss. Re-drill them in isolation until you can’t miss them.
- Practice in short, frequent sessions. Two 20-minute sessions per day beats one two-hour cram.
What happens after I pass?
Passing the knowledge test earns you a Commercial Learner’s Permit (CLP). You must hold the CLP for at least 14 days before you can take the road skills test, and you must drive with a CDL-holding instructor in the cab during that period. Once you pass the road skills test, your CDL is issued.