South Dakota 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. 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.
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2. 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.
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3. 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.
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4. The most common cause of serious skids is:
Explanation. Driving too fast for road and weather conditions is the leading cause of skids.
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5. 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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6. When driving in fog, you should:
Explanation. High beams reflect off fog and reduce vision; low beams and slower speed are correct.
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7. Experienced commercial drivers know that 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. (Reinforcement variant — same underlying CDL Manual concept.)
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8. Total stopping distance equals:
Explanation. Total stopping distance is perception + reaction + braking distance combined.
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9. 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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10. 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.
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11. According to the FMCSA CDL Manual, 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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12. 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.
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13. 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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14. 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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15. When checking lights during the pre-trip, you should turn the key on and:
Explanation. Have someone else watch, or turn lights on and off and walk around to verify each lamp is working.
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16. 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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17. When backing a commercial vehicle, you should:
Explanation. Backing toward the driver side gives the driver a direct line of sight, which is much safer than blind-side backing.
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18. 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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19. Carbon monoxide poisoning may be a hazard if:
Explanation. A cracked exhaust manifold or rusted-through pipe can leak CO into the cab, causing drowsiness or death.
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20. 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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21. The eye-lead time recommended for highway driving is at least:
Explanation. Look 12-15 seconds ahead so you can identify hazards in time to react smoothly.
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22. 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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23. Experienced commercial drivers know that empty trucks need:
Explanation. Empty trucks have less traction and brakes designed for the loaded weight, so they can actually take longer to stop and lock up more easily. (Reinforcement variant — same underlying CDL Manual concept.)
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24. Per federal regulations, you should warm up the engine before driving because:
Explanation. Allowing the engine to warm circulates oil and reduces wear before load is applied. (Reinforcement variant — same underlying CDL Manual concept.)
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25. You should warm up the engine before driving because:
Explanation. Allowing the engine to warm circulates oil and reduces wear before load is applied.
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26. 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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27. You should signal a lane change for at least:
Explanation. Signal early and continuously enough for surrounding traffic to see your intent.
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28. Per federal regulations, 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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29. According to the FMCSA CDL Manual, 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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30. In real-world commercial driving, hours-of-service property-carrying drivers may drive a maximum of how many hours after 10 consecutive hours off duty?
Explanation. The federal HOS rule allows up to 11 hours of driving after 10 consecutive hours off duty. (Reinforcement variant — same underlying CDL Manual concept.)
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31. Hydroplaning is most likely when:
Explanation. Hydroplaning can occur at speeds as low as 30 mph if there is enough water and the tires cannot channel it away.
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32. 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.
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33. Experienced commercial drivers know that when backing a commercial vehicle, you should:
Explanation. Backing toward the driver side gives the driver a direct line of sight, which is much safer than blind-side backing. (Reinforcement variant — same underlying CDL Manual concept.)
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34. Experienced commercial drivers know that a driver placing reflective triangles after a breakdown on a divided highway should place them at:
Explanation. On a one-way or divided road, place triangles at 10, 100, and 200 feet toward approaching traffic. (Reinforcement variant — same underlying CDL Manual concept.)
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35. Per federal regulations, a driver placing reflective triangles after a breakdown on a divided highway should place them at:
Explanation. On a one-way or divided road, place triangles at 10, 100, and 200 feet toward approaching traffic. (Reinforcement variant — same underlying CDL Manual concept.)
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36. 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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37. Empty trucks need:
Explanation. Empty trucks have less traction and brakes designed for the loaded weight, so they can actually take longer to stop and lock up more easily.
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38. According to the FMCSA CDL Manual, 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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39. You should check your mirrors:
Explanation. Frequent mirror checks (every 5-8 seconds) are part of safe scanning.
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40. Retarders should usually be turned off when:
Explanation. On slick surfaces a retarder can cause drive wheels to skid; turn it off in those conditions.
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41. 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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42. When operating a CMV in interstate commerce, when driving in the mountains, gravity will:
Explanation. Going downhill, gravity adds to your speed and the distance needed to stop. (Reinforcement variant — same underlying CDL Manual concept.)
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43. 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.
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44. Which is the best way to handle a tire failure?
Explanation. Hard braking after a tire failure can cause loss of control. Hold the wheel firmly, ease off the throttle, and brake gently after slowing.
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45. During a pre-trip inspection, empty trucks need:
Explanation. Empty trucks have less traction and brakes designed for the loaded weight, so they can actually take longer to stop and lock up more easily. (Reinforcement variant — same underlying CDL Manual concept.)
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46. When taking the CDL knowledge exam, you should warm up the engine before driving because:
Explanation. Allowing the engine to warm circulates oil and reduces wear before load is applied. (Reinforcement variant — same underlying CDL Manual concept.)
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47. In real-world commercial driving, total stopping distance equals:
Explanation. Total stopping distance is perception + reaction + braking distance combined. (Reinforcement variant — same underlying CDL Manual concept.)
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48. 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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49. When operating a CMV in interstate commerce, 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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50. 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.)
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 South Dakota-specific edition uses the same federal source material every U.S. state adopts. The South Dakota DPS administers the actual exam at its service centers. Bring your CDL handbook for any last-minute reference; it’s free at every South Dakota DPS office.
Once you’re consistently scoring above 90% on this practice set, you’re well above the 80% required to pass the official South Dakota 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.