South Dakota DPS CDL General Knowledge Practice Test 8
- Questions50
- Correct to pass40
- Passing score80%
- Minimum age18 years
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1. You are told a posted bridge ahead has a weight limit lower than your gross weight. What must you do?
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Answer C: Take a route that avoids it, because a posted limit is a legal limit
A posted structure limit must be obeyed exactly as any other weight limit, so a heavier vehicle has to be routed around it.
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2. You are not certain that your loaded vehicle will clear a low overpass. What should you do?
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Answer A: Take another route rather than risk it
There is no safe way to guess at a clearance, and striking a bridge endangers everyone on and under it, so the only correct choice is a different route.
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3. The engine oil pressure gauge falls toward zero while you are driving. What should you do?
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Answer C: Stop as soon as it is safe to do so and shut the engine down
Loss of oil pressure destroys an engine in a very short time, so the correct response is to stop and shut down rather than to drive on.
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4. Which brake lining condition must be reported?
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Answer C: Linings that are worn thin, loose, cracked or soaked with oil or grease
Linings must have enough material left and must be securely attached and clean, because a thin, loose or contaminated lining cannot deliver its share of braking.
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5. Which road users are hardest to see at night?
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Answer C: Pedestrians and cyclists in dark clothing
People on foot or on a bicycle carry no lights of their own in many cases, so they appear only when the headlights reach them.
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6. Where should a trailer be dropped, and what else does the driver do before pulling out from under it?
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Answer C: On solid level ground, with the trailer wheels chocked if it may roll
A dropped trailer must sit on ground that will carry the landing gear without sinking, and chocks stop it rolling once the tractor and its air supply are gone.
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7. Why should a large vehicle be accelerated smoothly and gradually?
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Answer A: Rough acceleration can damage the drivetrain and, on a combination, the coupling
Jerky throttle inputs put shock loads through the driveline and the coupling, which causes mechanical damage over time.
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8. Why does the commercial driver manual tell you to look far down the road instead of only at the vehicle ahead?
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Answer D: So you can adjust smoothly instead of braking hard at the last moment
A heavy vehicle cannot react quickly, so early information lets you slow gradually rather than make a sudden stop or swerve.
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9. How long is a South Dakota commercial driver disqualified after a first conviction for violating an out-of-service order?
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Answer A: 180 days
A first out-of-service order violation carries a 180-day CDL disqualification, longer than the periods used for serious traffic violations.
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10. When should a lower gear be selected for a long downgrade?
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Answer D: Before you start down the hill
The gear is chosen at the top, while speed is still low, because a heavy vehicle already rolling fast may not go into a lower gear at all.
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11. 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.
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12. 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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13. Under the federal hours of service rules, when must a property-carrying driver take a 30 minute break?
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Answer C: After 8 cumulative hours of driving time
Driving is not allowed after 8 cumulative hours of driving time without at least a 30 consecutive minute interruption of driving.
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14. How is the fluid level in an automatic transmission usually checked?
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Answer A: With the engine running, following the procedure in the operator manual
Most automatic transmissions are designed to be checked with the engine running, and the operator manual gives the exact conditions for that vehicle.
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15. Which of these South Dakota vehicles must stop at every railroad grade crossing, regardless of whether a warning signal is active?
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Answer B: A school bus carrying passengers
State law requires school buses carrying passengers, along with vehicles for hire and vehicles carrying explosives or flammable cargo, to stop at every grade crossing.
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16. Does the federal texting ban apply to a company dispatching device mounted in the cab?
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Answer B: Yes, entering or reading text on it while driving is banned
The rule is written around the act of reading or entering text on any electronic device, not around who owns the device.
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17. You must drive well below the speed of surrounding traffic, for example when climbing a steep grade with a heavy load. What should you do?
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Answer B: Turn on the four-way flashers to warn following traffic, where state law allows it
Flashers warn faster traffic that a slow-moving vehicle is ahead, which helps prevent rear-end crashes; some states restrict their use while moving, so check the local rule.
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18. What information does an inspection decal on a commercial vehicle carry?
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Answer B: The date of the inspection, where the inspection report is kept, and information identifying the vehicle
The decal shows when the inspection was done, the name and address of the entity that holds the inspection report, and which vehicle it belongs to, so an officer can confirm the inspection at a glance.
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19. Which windshield condition should be reported during the inspection?
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Answer B: Cracks or dirt that get in the way of your view of the road
The windshield must give a clear view; damage or grime in the driver line of sight is a safety defect.
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20. What is the correct way to make a normal stop?
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Answer A: Push the brake pedal down gradually and bring the vehicle to a smooth stop
Steady, progressive pedal pressure keeps the vehicle stable and lets the driver behind you react to a predictable slowdown.
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21. A roadside test shows a commercial driver has measurable alcohol in the system but below 0.04. What happens?
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Answer C: The driver is placed out of service for 24 hours
Any measurable alcohol while on duty results in an immediate 24 hour out of service order, even when the concentration is under the 0.04 limit.
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22. During the walkaround you find the reflective conspicuity tape along the trailer caked with road grime. What should you do?
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Answer B: Clean it, because dirty reflective material cannot make the trailer visible at night
Reflective sheeting only works if light can reach it and bounce back, so a dirty strip leaves the trailer effectively unmarked to approaching traffic.
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23. Why is a leaking exhaust system on a commercial vehicle dangerous to the driver?
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Answer B: It can let carbon monoxide reach the cab, where it can poison the occupants
Exhaust gas contains carbon monoxide, which has no smell and dulls the driver judgment long before it becomes obvious that anything is wrong.
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24. What tells you that an air suspension bag has a problem?
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Answer B: The bag is leaking or damaged, or the vehicle sits unevenly on that side
An air bag that leaks or is cut lets that corner of the vehicle settle, which throws the load onto the other suspension parts and changes the ride height.
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25. 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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26. Before starting a trip, what must the driver confirm about the weight of the loaded vehicle?
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Answer A: That it is within the legal gross and axle limits for the route being driven
Overweight vehicles brake poorly, damage tires and suspension components, and can be put out of service at a scale, so weight is checked before the wheels turn.
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27. What must be checked about the cargo doors and any tarpaulin before a trip?
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Answer B: That the doors are closed and latched and that any tarp is tied down securely
An unlatched door or a loose tarp can swing open or tear free at speed, spilling cargo or blocking the view of the traffic behind you.
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28. Where are regrooved, recapped or retreaded tires not allowed on a truck or truck tractor?
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Answer C: On the front steering wheels
Regrooved and retreaded tires are prohibited on the front wheels of a truck or truck tractor because a steering tire blowout is extremely difficult to manage.
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29. What does it mean to overdrive your headlights at night?
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Answer D: Driving so fast that you cannot stop within the distance lit by your headlights
You must be able to stop inside the distance you can see; at night that distance is limited by the headlights, so speed must be lowered to match.
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30. Where should a driver expect fog to form first?
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Answer D: In low ground, near water and in valleys
Cool moist air settles in low places, so fog patches appear in hollows, river valleys and near lakes before they appear anywhere else.
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31. What is the purpose of an escape ramp on a mountain grade?
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Answer C: To stop a runaway vehicle without injuring the driver
Escape ramps use soft material or a steep upgrade to bring a vehicle with failed brakes to a controlled stop.
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32. 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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33. A driver snores heavily, stops breathing briefly during the night and is tired all day despite long hours in bed. What should be suspected?
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Answer B: Sleep apnea
Sleep apnea repeatedly interrupts breathing during sleep, so the driver never gets true rest and stays dangerously drowsy during the day.
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34. Which winter preparation matters most for keeping the road in view?
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Answer D: Working wipers, washer fluid and a working defroster
Slush and road spray coat the windshield within minutes in winter, so wipers, washer fluid and the defroster are what keep any view at all.
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35. When traction is poor, such as on packed snow, how should you speed up?
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Answer C: Very gradually, so the drive wheels do not spin
Gentle throttle keeps the drive wheels from breaking traction, because spinning wheels give up both grip and directional control.
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36. You have stopped and a pedestrian is waiting to cross in front of your truck. Why should you not wave the person across?
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Answer C: Another driver may not stop, and your wave sends the person into danger
You cannot control what drivers in the other lanes will do, so you should not invite a pedestrian into a lane you do not command.
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37. Why must exhaust components be checked for contact with other parts of the vehicle?
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Answer B: Hot exhaust parts touching fuel lines, tires or wiring can start a fire
Exhaust pipes run hot enough to ignite fuel and melt insulation, so they must be kept clear of the fuel system, the tires and the electrical harness.
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38. Your windshield washer reservoir is empty and rain and road spray are expected. What should you do?
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Answer D: Fill it before the trip, because you need the washers to keep the windshield clear
Wipers alone smear the film of oil and grit thrown up by traffic, so the washers are part of keeping a usable view of the road.
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39. What are you looking for on the brake drums during the walkaround?
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Answer B: Cracks, dents and any oil or grease that has reached the friction surface
A cracked or badly scored drum can break apart under braking heat, and oil or grease on the friction surface destroys the braking effort at that wheel.
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40. 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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41. Why must you never coast down a hill in neutral or with the clutch pushed in?
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Answer C: You lose the braking effect of the engine and your brakes may overheat and fail
Engine braking is what keeps a heavy vehicle in check on a grade; coasting throws it away and leaves the service brakes to do all the work until they overheat.
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42. Within what distance should high beams be lowered at night?
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Answer D: Within about 500 feet of an oncoming vehicle and within about 500 feet of a vehicle you are following
High beams blind other drivers at close range, so they are lowered at roughly the same distance whether the other vehicle is coming toward you or is ahead of you.
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43. 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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44. 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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45. Which lamp must make the rear registration plate legible after dark?
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Answer C: A white lamp that lights the plate
A white license plate lamp is required so the plate can be read at night, and a burned out one is a defect like any other lamp.
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46. How often must every commercial motor vehicle receive a periodic inspection?
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Answer C: At least once every twelve months
Federal rules require each commercial motor vehicle to pass a periodic inspection at least once in every twelve month period.
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47. 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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48. You stop to check the load. Which set of things are you looking at?
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Answer C: Tight tiedowns, cargo that has not moved, secure doors and tarps still fastened
A cargo check covers the load and everything holding it: whether it has shifted, whether the devices are still tight, and whether doors and covers are still closed and fastened.
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49. The brake pedal goes to the floor in a vehicle with hydraulic brakes. What can you do to build some braking pressure?
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Answer B: Pump the brake pedal rapidly, which may bring back enough pressure to slow the vehicle
Pumping can restore some hydraulic pressure; along with downshifting and the parking brake it is one of the ways to stop when the pedal fails.
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50. What does South Dakota law require of the vehicles that must stop at railroad crossings, regarding how they cross the tracks afterward?
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Answer C: They must cross in a gear that avoids the need to shift gears while on the tracks
After stopping, these vehicles must cross using a gear that will not require a gear change while traversing the tracks.