Massachusetts 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. 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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2. 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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3. When taking the CDL knowledge exam, convex (curved) mirrors:
Explanation. Convex mirrors widen the view but make objects appear smaller and farther away than they actually are. (Reinforcement variant — same underlying CDL Manual concept.)
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4. 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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5. 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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6. 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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7. When taking the CDL knowledge exam, 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. (Reinforcement variant — same underlying CDL Manual concept.)
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8. When operating a CMV in interstate commerce, 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. (Reinforcement variant — same underlying CDL Manual concept.)
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9. 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.
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10. 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.
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11. 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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12. 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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13. 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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14. 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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15. 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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16. 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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17. Per federal regulations, 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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18. A retarder helps the driver by:
Explanation. Retarders slow the vehicle without using service brakes, reducing brake wear and overheating risk.
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19. Per federal regulations, convex (curved) mirrors:
Explanation. Convex mirrors widen the view but make objects appear smaller and farther away than they actually are. (Reinforcement variant — same underlying CDL Manual concept.)
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20. During a pre-trip inspection, communicating presence with the horn is appropriate when:
Explanation. Use the horn only to warn others of your presence when there is a real risk they have not seen you. (Reinforcement variant — same underlying CDL Manual concept.)
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21. Most state DMV CDL handbooks state that 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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22. 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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23. 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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24. Per federal regulations, 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. (Reinforcement variant — same underlying CDL Manual concept.)
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25. 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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26. 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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27. According to the FMCSA CDL Manual, 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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28. Per federal regulations, 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. 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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30. 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.
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31. When taking the CDL knowledge exam, cargo securement standards require tiedowns capable of supporting at least:
Explanation. The aggregate working load limit of all tiedowns must equal at least one-half the weight of the cargo. (Reinforcement variant — same underlying CDL Manual concept.)
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32. During a pre-trip inspection, 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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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. In real-world commercial driving, 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. (Reinforcement variant — same underlying CDL Manual concept.)
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35. In real-world commercial driving, 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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36. 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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37. When taking the CDL knowledge exam, 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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38. During a pre-trip inspection, 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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39. Per federal regulations, 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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40. Experienced commercial drivers know that communicating presence with the horn is appropriate when:
Explanation. Use the horn only to warn others of your presence when there is a real risk they have not seen you. (Reinforcement variant — same underlying CDL Manual concept.)
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41. 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.
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42. Per federal regulations, 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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43. 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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44. 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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45. Per federal regulations, you should signal a lane change for at least:
Explanation. Signal early and continuously enough for surrounding traffic to see your intent. (Reinforcement variant — same underlying CDL Manual concept.)
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46. During a pre-trip inspection, 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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47. 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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48. You should check your mirrors:
Explanation. Frequent mirror checks (every 5-8 seconds) are part of safe scanning.
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49. When taking the CDL knowledge exam, 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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50. 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.
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 Massachusetts-specific edition uses the same federal source material every U.S. state adopts. The Massachusetts RMV administers the actual exam at its service centers. Bring your CDL handbook for any last-minute reference; it’s free at every Massachusetts RMV office.
Once you’re consistently scoring above 90% on this practice set, you’re well above the 80% required to pass the official Massachusetts 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.