Mississippi DPS CDL General Knowledge Practice Test 3
Test 3 of 5. Pick an answer for each question to see if it is right and why; your score appears at the end. You need 40 correct answers to pass, the same ratio as the real Mississippi test.
- Questions50
- Correct to pass40
- Passing score80%
- Minimum age18 years
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1. Which items belong to the trailer part of the walkaround inspection?
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Answer D: Landing gear, doors, tires, wheels, lights, reflectors, frame and cargo securement
The trailer has its own running gear, lighting, structure and load, and all of it is the responsibility of the driver pulling it.
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2. What is the maximum total height allowed for a vehicle, loaded or unloaded, in Mississippi?
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Answer C: 13 feet 6 inches
Mississippi caps total vehicle height at thirteen and one-half feet, and a driver or owner exceeding twelve and one-half feet is liable for damage caused by the excess height.
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3. What does a front-end header board on a van or flatbed protect against?
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Answer A: Cargo moving forward toward the cab in a crash or hard stop
The header board, often called a headache rack, blocks forward movement of the load toward the driver.
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4. You are stopped in traffic on a steep upgrade behind another truck. How much space should you leave in front?
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Answer A: Enough that you can pull away without rolling back into the vehicle behind you
Room ahead lets you get moving smoothly on a grade instead of having to hold the vehicle perfectly still or roll back toward the traffic behind.
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5. What should a driver assume about the height posted at a bridge or an overpass?
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Answer B: That it may be wrong, because repaving or packed snow can leave less clearance than the sign shows
Resurfacing and packed snow raise the road under the structure, so the real clearance can be lower than the posted figure.
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6. Most rollovers of loaded trucks on exit and entrance ramps happen for which reason?
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Answer B: The ramp was taken faster than the load could tolerate
A posted ramp speed is set for cars, and a loaded trailer with a high center of gravity can roll at a speed a car would take easily.
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7. What is generally the safest speed in dense but freely moving highway traffic?
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Answer D: The speed of the traffic around you, up to the posted limit
Crashes rise with the difference between your speed and the traffic around you, so moving with the flow within the legal limit is safest.
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8. What does the working load limit stamped on a chain or strap describe?
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Answer B: The maximum load the device is rated to hold in normal use
The working load limit is the rated safe capacity for everyday use, deliberately set well below the force that would break the device.
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9. Why does the manual insist on a firm grip with both hands on opposite sides of the steering wheel?
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Answer A: A hard bump can pull the wheel out of a loose grip
Hitting a curb or a deep pothole can jerk the wheel violently, and only a firm two-handed grip keeps the vehicle under control when that happens.
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10. What are you checking when you pull the engine oil dipstick during the pre-trip?
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Answer A: That the oil level is within the safe operating range marked on the stick
The dipstick shows whether there is enough oil to lubricate and cool the engine, and a level outside the safe range must be corrected before driving.
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11. A car is following you far too closely. What is the safest response?
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Answer A: Open up more space ahead so you can slow gradually, avoid sudden changes, and do not speed up
Extra room in front lets you slow smoothly instead of braking hard, which is exactly what the driver behind cannot cope with.
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12. Why does a load need to be balanced from side to side?
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Answer B: Because a heavy side raises the rollover risk and can overload the tires and springs on that side
An uneven load tips the balance of the vehicle in curves and pushes the tires and suspension on the loaded side past their rating.
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13. Which set of emergency equipment must be carried on a commercial motor vehicle?
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Answer D: A fire extinguisher, spare electrical fuses unless the vehicle has circuit breakers, and warning devices
The required kit is a properly charged and rated fire extinguisher, spare fuses when the vehicle uses them, and warning devices for a stopped vehicle.
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14. As a long vehicle goes around a corner, how do the rear wheels travel compared with the front wheels?
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Answer A: They follow a tighter path, closer to the inside of the turn
The rear wheels off-track toward the inside of the turn, and the longer the vehicle the bigger the difference, which is why the front must swing wide enough to keep the rear off the curb.
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15. The only way into a customer yard forces you to back toward the right, or blind, side of the vehicle. What should you do?
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Answer D: Use a helper and get out to check the path more often than you normally would
Blind side backing is allowed but far riskier, so it calls for a spotter you can see and for repeated checks of the path on foot.
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16. How does a driver measure following distance in seconds?
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Answer A: Wait for the vehicle ahead to pass a fixed roadside object, then count the seconds until the front of your vehicle reaches the same object
Counting from the moment the vehicle ahead passes a landmark until you reach it turns a gap you cannot judge in feet into a number of seconds.
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17. A tire may be regrooved only when what is true?
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Answer B: It carries a marking from the manufacturer showing that it is regroovable
Only casings built with extra rubber under the tread and marked regroovable by the manufacturer may be cut, because others would be grooved into the belts.
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18. Your brakes have failed and you decide to use the parking brake to slow down. Why should you hold the release button or lever while doing so?
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Answer D: So you can release the brake at once if the wheels lock and the vehicle starts to skid
The parking brake can lock the wheels; keeping your hand on the release lets you let go the moment a skid starts and regain control.
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19. Apart from the legal duty, what is the main practical reason for a thorough pre-trip inspection?
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Answer A: It finds problems that could cause a breakdown or a crash before the vehicle is on the road
A defect found in the yard is an inconvenience, while the same defect found at highway speed can be a crash, so the inspection is where problems are cheapest to fix.
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20. You are stopped in a line of traffic behind a car. How much space should you leave in front of you?
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Answer C: Enough to see where the rear tires of that car meet the road
That amount of space lets you pull around the vehicle ahead if it stalls and absorbs some of the shock if you are struck from behind.
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21. Which set of maneuvers makes up the basic control skills part of the commercial driving test?
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Answer D: Straight line backing, offset backing, parallel parking and alley docking
The basic control skills test is carried out off the road and consists of low speed exercises such as straight line backing, offset backing, parallel parking and the alley dock.
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22. Which of these vehicles requires a Mississippi Class D light commercial license?
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Answer D: A limousine carrying no more than fifteen passengers for hire
Mississippi requires the Class D license for commercial work such as a taxicab or limousine carrying no more than fifteen passengers. A pick-up truck is expressly excluded unless it carries placarded hazardous materials.
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23. A doctor prescribes you a medicine that can cause drowsiness. What should you do?
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Answer A: Tell the doctor what you drive and not drive while affected
Both prescription and over the counter medicines can make a driver unsafe, so the medical professional must know the job and the driver must stay out of the seat while affected.
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24. You are pulling away from a curb in a 65 foot combination. Besides traffic, what must you watch?
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Answer B: The trailer wheels, which stay close to the curb and can strike it or an object on it
Because of off-tracking, the rear wheels follow a tighter path than the front, so they stay near the curb while the cab is already out in the lane.
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25. After coupling, where should the fifth wheel release handle be?
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Answer A: In the locked position with the safety latch in place
The handle must be pushed in and latched, because a handle left out means the jaws can open and release the trailer while you are driving.
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26. Why must a bent, cracked or badly seated lock ring be reported?
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Answer D: It can come off under pressure and let the tire and rim separate violently
The lock ring holds the assembly together against the full pressure of the tire, so a damaged ring can release with enough force to kill.
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27. How should a commercial driver treat the speed posted for a curve?
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Answer B: As a limit set for cars in good conditions, so a heavy or tall load calls for a lower speed
Posted curve speeds are based on passenger vehicles in good conditions, and a tall or heavy load can roll over well below that speed.
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28. You need to check your route on a navigation device. What is the correct approach?
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Answer D: Set it before the trip or after you have parked
Route programming is planning work, and it belongs to the time before the wheels turn or after the vehicle is safely parked off the roadway.
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29. Which vehicles are most likely to get hung up on a raised railroad crossing?
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Answer A: Low-slung units such as car carriers and lowboys
Vehicles with low ground clearance or a long wheelbase can bottom out on a humped crossing and become stuck on the tracks.
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30. You are unsure whether your vehicle will fit through a narrow gate. What should you do?
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Answer A: Stop, get out and look, and take another route if the space is not clearly enough
Clearance is never guessed at from the seat; you look at it on foot and go round rather than trying a gap that may be too tight.
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31. An unblocked crate 4 feet long and weighing 1,500 pounds needs at least how many tiedowns?
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Answer A: Two
A short article that weighs more than 1,100 pounds requires at least two tiedowns even though it is under 5 feet long.
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32. You have finished a lane change in a vehicle whose turn signal does not cancel by itself. What must you do?
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Answer D: Turn the signal off yourself
A signal left running tells other drivers you are about to move again, and they may act on that false information.
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33. With the tractor coupled to the trailer, what should you see between the upper and lower fifth wheel plates?
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Answer A: No space at all between the two plates
Any daylight between the plates means the trailer is not properly seated on the fifth wheel and the coupling can come apart under load.
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34. What is the maximum total outside width of a vehicle, including its load, on Mississippi highways?
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Answer B: 8 feet 6 inches
Mississippi limits total outside width, load included, to eight and one-half feet, while a farm tractor may reach ten feet.
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35. Which situations call for a mirror check in a commercial vehicle?
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Answer A: Every lane change, turn, merge and tight maneuver
Mirrors must be checked regularly and always before, during and after any movement that changes the path of the vehicle.
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36. Why is cargo often covered with a tarp?
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Answer C: To protect people from spilled cargo and to protect the cargo from weather
A cover keeps material from blowing or spilling onto the road and shields the load from rain and sun; it does not replace securement.
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37. What is the correct way to make a right turn in a long vehicle?
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Answer D: Keep the rear of the vehicle close to the curb and swing wide only as you complete the turn
Swinging left before a right turn invites another driver to move into the gap on your right, so any extra width is taken as the turn is finished.
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38. Why should both outside mirrors be checked over and over while backing?
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Answer B: Each mirror covers only part of the path and neither covers the blind spots, so people and objects can appear without warning
Working both mirrors in turn is the only way to follow the whole path of a vehicle you cannot see behind.
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39. An unblocked article is 15 feet long. What is the minimum number of tiedowns?
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Answer B: Three
Two tiedowns cover the first 10 feet and one more is added for each further 10 feet or any part of it, so 15 feet needs three.
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40. Besides being uncomfortable, what can a series of hard, jerky brake applications do to a loaded combination?
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Answer A: Shift the load and push the trailer out of line behind the tractor
Sudden, uneven braking can move cargo forward and upset the alignment of a trailer, which is why stops should be made smoothly.
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41. You find a defect during the pre-trip inspection. What must happen before the vehicle is driven?
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Answer C: It must be repaired, or the vehicle must not be driven
Writing a defect down does not make the vehicle safe; a defect that affects safe operation has to be corrected before the trip starts.
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42. A car that passed you on the right slows and stays alongside your trailer. What is the best response?
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Answer D: Ease off the accelerator so the car can move clear
A vehicle sitting beside a trailer is in a blind area and has nowhere to go if you need the lane, so the safest fix is to let it get ahead or behind.
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43. An automatic transmission is left in its normal drive position as the vehicle rolls down a long grade. What does it tend to do?
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Answer A: Shift up as road speed rises, so engine braking falls away
An automatic left in drive keeps upshifting as speed builds, which is the opposite of what you want on a grade; that is why the driver must select a low range.
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44. Cargo carried inside the cab must never do which of these?
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Answer C: Block the driver view, restrict arm or leg movement, or block an emergency exit
Anything inside the cab must leave the driver a clear view, free movement of the arms and legs, and an unobstructed way out of the vehicle.
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45. What should you check about the tire valve stems during the walkaround?
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Answer D: That the stems are not cut, cracked or leaking and the caps are in place
A split stem or a missing cap lets air escape or lets dirt into the valve, and either one can flatten a tire between stops.
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46. You are the first to arrive at a crash. What is the correct order of actions?
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Answer C: Protect the area, notify the authorities, care for the injured
Preventing a second crash comes first, because an unprotected scene puts the injured and the helpers in more danger than the original collision.
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47. An enforcement officer inspects your vehicle at the roadside and attaches an out-of-service sticker. What may you do?
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Answer C: Nothing until the defect is repaired; the vehicle may not be driven
An out-of-service order means the vehicle is unsafe, and no schedule, load or destination allows it to be driven before the defect is corrected.
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48. Part of your load stands high enough to hide a rear lamp or a reflector. What must be done?
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Answer B: The load must be moved or extra lamps fitted so the required lights can be seen
Required lamps and reflectors must remain visible; if the cargo blocks them, the load is rearranged or additional lamps are fitted so the vehicle can still be seen.
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49. What is the correct order for a basic double clutch upshift?
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Answer B: Release the accelerator and push the clutch, shift to neutral, release the clutch, let engine speed drop, push the clutch again and shift to the higher gear
Double clutching passes through neutral with the clutch released so engine speed can drop to match the next gear before it is engaged.
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50. Loading heavy freight on top of lighter freight has what effect on the vehicle?
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Answer B: It raises the center of gravity and makes a rollover more likely
A high center of gravity lets the vehicle tip more easily in curves or during a sudden swerve.