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South Dakota Combination Vehicles CDL Practice Test

Below are 25 exam-style questions for the South Dakota Combination Vehicles CDL knowledge test, modeled on the FMCSA-aligned content used by the South Dakota Driver Licensing Program. Try to answer each question on your own before reading the answer key directly under it. The questions and answer choices are shuffled deterministically per state and endorsement, so the order will stay the same on repeat visits — that lets you genuinely measure your improvement.

Heads up: this is a study tool, not a graded exam. Cover the answer with your hand or a sheet of paper for an honest practice run, then re-read the explanations for any questions you missed. Aim for 22 out of 25 or better, three times in a row, before scheduling the real exam.
Question 1 of 25
You should inspect a combination vehicle for:
  • A Loose or missing fifth-wheel mounting bolts
  • B All of the above
  • C Misalignment between tractor and trailer
  • D Cracks in the kingpin
Correct answer: B
All three are pre-trip combination-vehicle items.
Question 2 of 25
Why should you not jackknife to get out of a tight spot?
  • A It is fine if you are careful
  • B It is illegal in some states
  • C It is the standard procedure
  • D It can damage the cab and the trailer (cab corner crush)
Correct answer: D
Bending the tractor too sharply against the trailer can cause body damage and disconnect the lines.
Question 3 of 25
A heavy combination vehicle in a curve is most likely to:
  • A Roll over before sliding
  • B Stop suddenly
  • C Spin out
  • D Lose engine power
Correct answer: A
Loaded trailers reach the rollover threshold before they slide. Slow before the curve.
Question 4 of 25
Glad hands are:
  • A Manual transmission shifters
  • B Brake adjustment levers
  • C Coupling devices for connecting tractor air lines to the trailer
  • D Electrical connectors
Correct answer: C
Glad hands have rubber seals and a metal coupler that joins the tractor and trailer air lines.
Question 5 of 25
Trailer air supply valves on tractors are typically:
  • A Triangular, green, marked SERVICE
  • B Octagonal, red, marked TRAILER AIR SUPPLY
  • C Square, white, marked CHARGE
  • D Round, blue, marked TRACTOR
Correct answer: B
The trailer air-supply valve is the red, octagonal knob — a federal standard.
Question 6 of 25
The proper test of a good fifth-wheel coupling is:
  • A Listen for a click
  • B Look at the locking jaws only
  • C Honk the horn
  • D Tug the trailer with the trailer parking brakes set
Correct answer: D
After coupling and locking, gently pull forward against the locked trailer brakes to confirm engagement.
Question 7 of 25
The proper sequence for uncoupling is generally:
  • A No specific order is required
  • B Pull tractor away first, then disconnect lines
  • C Release fifth wheel first, then connect lines
  • D Lower landing gear, disconnect lines, release fifth wheel, pull tractor away
Correct answer: D
Lower the landing gear, chock the wheels, disconnect air and electrical lines and stow them, release the fifth wheel, then slowly pull the tractor forward.
Question 8 of 25
When the trailer begins to skid, you should:
  • A Apply the trailer hand valve harder
  • B Accelerate
  • C Disconnect the air supply
  • D Release the brakes to allow the trailer wheels to roll again, then steer
Correct answer: D
Releasing the brakes lets the wheels rotate again so the trailer can recover its tracking.
Question 9 of 25
Which is true about combination braking?
  • A ABS prevents jackknife in all cases
  • B Drive wheels never lock
  • C Trailer wheels lock more often than drive wheels in panic stops
  • D Brake balance is irrelevant
Correct answer: C
Empty trailer wheels lock easily and contribute to jackknife and trailer-swing risks.
Question 10 of 25
After connecting the air lines, before pulling the tractor away, you must:
  • A Drive away immediately
  • B Pump the brakes 10 times
  • C Drain the wet tank
  • D Charge the trailer brakes by setting the trailer air supply control
Correct answer: D
After connecting, charge the trailer system and verify brake operation.
Question 11 of 25
Trailer parking brakes are released:
  • A By pushing in the red trailer-air-supply valve
  • B By pulling out the red trailer-air-supply valve
  • C By the trailer hand valve
  • D By setting the red trailer-air-supply valve
Correct answer: A
Pushing in the red knob charges the trailer brakes and releases the spring brakes.
Question 12 of 25
Sharp turns at low speed will cause:
  • A No off-tracking
  • B Off-tracking — the trailer wheels follow a tighter arc than the tractor
  • C Brake fade
  • D Wheel damage
Correct answer: B
Off-tracking always happens; sharper turns make it worse.
Question 13 of 25
When you cross a railroad track in a combination vehicle, the safest practice is:
  • A Honk and accelerate
  • B Shift in the middle of the track
  • C Cross in a low gear without shifting
  • D Stop on the tracks if traffic ahead slows
Correct answer: C
Cross in a low gear without shifting; never stop on the tracks; never shift in the middle.
Question 14 of 25
The trailer landing gear (dolly legs) should be:
  • A Fully raised before driving
  • B Lowered to the ground while driving
  • C Disconnected before driving
  • D Always halfway extended
Correct answer: A
Landing gear must be fully raised and the crank handle secured before moving the trailer.
Question 15 of 25
A "trailer skid" usually starts because:
  • A The tractor brakes lock up
  • B The trailer brakes lock up
  • C The fifth wheel breaks
  • D A wheel bearing fails
Correct answer: B
Locking the trailer brakes is the most common cause of a trailer skid (jackknife).
Question 16 of 25
When coupling a tractor to a semitrailer, the trailer should be at:
  • A A height where the tractor will lift the trailer slightly when backing under
  • B Maximum legal height
  • C A height that requires the tractor to drop down to fit
  • D Whatever height it happens to be
Correct answer: A
The trailer should be slightly lower than the fifth wheel so backing in lifts the trailer.
Question 17 of 25
The "emergency" line (supply line) on a tractor-trailer:
  • A Carries electrical signals
  • B Drains the wet tank
  • C Operates the parking brake only
  • D Sends supply air to the trailer reservoirs and controls the trailer emergency brakes
Correct answer: D
Loss of pressure on the emergency line causes the trailer's emergency brake to apply automatically.
Question 18 of 25
When you make a wide right turn, you should:
  • A Stop traffic by signaling left
  • B Turn from the left lane
  • C Use the shoulder
  • D Stay in the right lane and swing the front of the tractor wide enough to clear the curb without inviting cars to pass on the right
Correct answer: D
Use only as much room as needed and keep the right side blocked to following vehicles.
Question 19 of 25
Which of the following can damage a fifth wheel?
  • A All of the above
  • B Coupling with the trailer too high
  • C Backing too fast
  • D Failure to grease
Correct answer: A
All three: high trailer skips the jaws, fast backing impacts hardware, and lack of lubrication accelerates wear.
Question 20 of 25
If you are pulling two trailers, the heavier trailer should be:
  • A Loaded last
  • B First (closest to the tractor)
  • C Either position is fine
  • D Last
Correct answer: B
Heavier trailer first reduces the rear-trailer crack-the-whip effect.
Question 21 of 25
The trailer hand valve operates:
  • A The parking brake
  • B The tractor service brakes only
  • C Both tractor and trailer brakes simultaneously
  • D The trailer service brakes only
Correct answer: D
The hand valve applies only the trailer service brakes. It is for testing — not for parking or routine use.
Question 22 of 25
When you drive a combination vehicle, watch for:
  • A Reduced visibility along the trailer
  • B Off-tracking on right turns
  • C Trailer sway in crosswinds
  • D All of the above
Correct answer: D
All three are routine combination-vehicle considerations.
Question 23 of 25
Combination vehicles are usually harder to drive than single CMVs because:
  • A They take more skill to back, couple, and uncouple
  • B They are heavier and longer
  • C They have a higher rollover risk
  • D All of the above
Correct answer: D
All three factors apply. The Combination Vehicles section of the federal manual emphasizes the higher skill needed.
Question 24 of 25
Brake-system pressure should be checked:
  • A Only at the destination
  • B Before, during, and after coupling
  • C Only at the start of the day
  • D Every 3 hours
Correct answer: B
Pressure changes during coupling indicate connection problems early.
Question 25 of 25
Which is true about coupling order to a trailer?
  • A Connect any line first; order doesn't matter
  • B Connect electrical first, then air
  • C Connect air emergency line first, then service line, then electrical (or per company policy) — verify with brake check
  • D Connect only air; electrical is optional
Correct answer: C
Specific orders vary by carrier, but the principle is to charge the trailer brakes before moving and to verify with a brake check.

Study tips for the South Dakota Combination Vehicles exam

The Combination Vehicles portion of the South Dakota CDL exam is graded out of the bank of questions the South Dakota Driver Licensing Program draws from each year. While the exact bank is not published, every question is sourced from the Combination Vehicles chapter of the South Dakota CDL handbook, which itself is derived from the FMCSA Model Commercial Driver's License Manual. That means studying our practice tests, reading the corresponding handbook chapter, and re-reading the parts you got wrong is genuinely the most efficient route to a first-time pass.

Most successful applicants follow a simple cycle: take the practice test cold, write down every question you missed, open the matching chapter of the official South Dakota handbook, re-read the section that contains the right answer, then re-take the practice test 24 to 48 hours later. The 24-hour delay matters — sleep is when your brain commits new information to long-term memory, and CDL knowledge questions reward that kind of consolidated learning rather than cramming.

Pay particular attention to questions that include qualifier words like always, never, only, primary, or most. CDL test writers love to flip the right answer with a single qualifier. When two answer choices look almost identical, pay attention to the verb (is it must, should, or may?) and to any numbers (14 days, 100 air miles, 8 hours, 70/8 split). On endorsement tests in particular, watch for trick framing where a true statement about a different endorsement is offered as the "correct" answer to a question that is actually about Combination Vehicles.

Test-day logistics matter too. Bring photo ID, your Social Security card or birth certificate, your medical examiner's certificate (DOT card), and proof of state residency if you haven't already submitted those documents. The South Dakota Driver Licensing Program will not let you sit for the knowledge exam without your documentation, and most offices charge an additional fee for re-attempts. Arrive early — the wait at most CDL testing offices runs 30 to 60 minutes — and silence your phone before the exam begins.

Finally, keep your General Knowledge fundamentals sharp even when you're focused on the Combination Vehicles exam. Many states administer multiple knowledge tests in a single sitting, and questions on weight definitions (GVWR, GCWR, GAWR), stopping distance, and the pre-trip inspection routine show up across endorsements. If you're unsure on the basics, sit a fresh South Dakota General Knowledge practice test before scheduling the real exam.

Next steps

Missed more than four questions? Re-read the Combination Vehicles study guide and the matching chapter in the official South Dakota CDL handbook. Then come back and re-take the test. Once you can score 22 of 25 or higher on three runs in a row, you're in good shape to schedule the real exam at your local South Dakota Driver Licensing Program office.

Already comfortable with this endorsement? Drill another: SD General Knowledge · SD Air Brakes · SD Hazardous Materials · SD Passenger · SD School Bus · SD Tank Vehicle · SD Doubles / Triples

New to the CDL process in South Dakota? Read How to apply for a CDL in South Dakota for the document checklist and step-by-step timeline.