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VT · GK (Class A) Endorsement

Vermont Combination Vehicles CDL Practice Test

Below are 25 exam-style questions for the Vermont Combination Vehicles CDL knowledge test, modeled on the FMCSA-aligned content used by the Vermont Department of Motor Vehicles. 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
Which of the following can damage a fifth wheel?
  • A Failure to grease
  • B Backing too fast
  • C Coupling with the trailer too high
  • D All of the above
Correct answer: D
All three: high trailer skips the jaws, fast backing impacts hardware, and lack of lubrication accelerates wear.
Question 2 of 25
The "emergency" line (supply line) on a tractor-trailer:
  • A Sends supply air to the trailer reservoirs and controls the trailer emergency brakes
  • B Drains the wet tank
  • C Carries electrical signals
  • D Operates the parking brake only
Correct answer: A
Loss of pressure on the emergency line causes the trailer's emergency brake to apply automatically.
Question 3 of 25
A worn or damaged fifth wheel can cause:
  • A Engine damage
  • B Tire wear only
  • C The trailer to come uncoupled
  • D Rust on the cab
Correct answer: C
Worn locking jaws or a cracked structure can fail and release the trailer in motion.
Question 4 of 25
A combination vehicle with empty trailers:
  • A May actually take longer to stop because brakes are designed for the loaded weight
  • B Stops in the same distance
  • C Stops only with parking brake
  • D Stops faster than when loaded
Correct answer: A
Empty trailers can lock up easily and skid, which counterintuitively increases stopping distance.
Question 5 of 25
Brake-system pressure should be checked:
  • A Only at the destination
  • B Before, during, and after coupling
  • C Every 3 hours
  • D Only at the start of the day
Correct answer: B
Pressure changes during coupling indicate connection problems early.
Question 6 of 25
A skid is most likely to result in a jackknife if:
  • A The trailer wheels lock briefly
  • B The brakes are released gently
  • C The drive wheels lock and the trailer pushes the tractor sideways
  • D You are driving slowly
Correct answer: C
Drive-wheel lockup is the classic jackknife cause.
Question 7 of 25
When uncoupling, after the tractor is clear, you should:
  • A Connect the lines back to the tractor
  • B Move the tractor far away immediately without checking
  • C Disable the trailer parking brake
  • D Check that the trailer is stable on its landing gear
Correct answer: D
Verify the trailer is sitting solidly before leaving the area.
Question 8 of 25
A heavy combination vehicle in a curve is most likely to:
  • A Roll over before sliding
  • B Spin out
  • C Lose engine power
  • D Stop suddenly
Correct answer: A
Loaded trailers reach the rollover threshold before they slide. Slow before the curve.
Question 9 of 25
Glad hands are:
  • A Electrical connectors
  • B Manual transmission shifters
  • C Brake adjustment levers
  • D Coupling devices for connecting tractor air lines to the trailer
Correct answer: D
Glad hands have rubber seals and a metal coupler that joins the tractor and trailer air lines.
Question 10 of 25
The proper sequence for uncoupling is generally:
  • A Release fifth wheel first, then connect lines
  • B Pull tractor away first, then disconnect lines
  • C Lower landing gear, disconnect lines, release fifth wheel, pull tractor away
  • D No specific order is required
Correct answer: C
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 11 of 25
Which is true about coupling order to a trailer?
  • A Connect only air; electrical is optional
  • B Connect air emergency line first, then service line, then electrical (or per company policy) — verify with brake check
  • C Connect electrical first, then air
  • D Connect any line first; order doesn't matter
Correct answer: B
Specific orders vary by carrier, but the principle is to charge the trailer brakes before moving and to verify with a brake check.
Question 12 of 25
When the trailer begins to skid, you should:
  • A Disconnect the air supply
  • B Release the brakes to allow the trailer wheels to roll again, then steer
  • C Accelerate
  • D Apply the trailer hand valve harder
Correct answer: B
Releasing the brakes lets the wheels rotate again so the trailer can recover its tracking.
Question 13 of 25
A "trailer skid" usually starts because:
  • A The tractor brakes lock up
  • B The fifth wheel breaks
  • C The trailer brakes lock up
  • D A wheel bearing fails
Correct answer: C
Locking the trailer brakes is the most common cause of a trailer skid (jackknife).
Question 14 of 25
Combination vehicles are usually harder to drive than single CMVs because:
  • A All of the above
  • B They have a higher rollover risk
  • C They are heavier and longer
  • D They take more skill to back, couple, and uncouple
Correct answer: A
All three factors apply. The Combination Vehicles section of the federal manual emphasizes the higher skill needed.
Question 15 of 25
Before pulling the kingpin release lever to uncouple, you must:
  • A Honk the horn
  • B Lower the trailer landing gear and chock the trailer wheels
  • C Disconnect the electrical line first
  • D Drain the air tanks
Correct answer: B
Always lower the landing gear and chock the trailer so it cannot move once you pull out from under it.
Question 16 of 25
If you are pulling two trailers, the heavier trailer should be:
  • A Last
  • B Loaded last
  • C First (closest to the tractor)
  • D Either position is fine
Correct answer: C
Heavier trailer first reduces the rear-trailer crack-the-whip effect.
Question 17 of 25
Most tire problems on a combination vehicle:
  • A Need a mechanic to find
  • B Show up only at high speed
  • C Are caused by low fuel
  • D Can be detected during pre-trip inspection by visual and pressure checks
Correct answer: D
Visual and pressure checks catch most problems before they become roadside failures.
Question 18 of 25
The proper test of a good fifth-wheel coupling is:
  • A Tug the trailer with the trailer parking brakes set
  • B Honk the horn
  • C Look at the locking jaws only
  • D Listen for a click
Correct answer: A
After coupling and locking, gently pull forward against the locked trailer brakes to confirm engagement.
Question 19 of 25
After coupling, the locking jaws should:
  • A Be open
  • B Be loose
  • C Be missing
  • D Be closed around the shank of the kingpin (not on the head)
Correct answer: D
Visual check: jaws around the shank, not the head. A flashlight helps.
Question 20 of 25
When backing a tractor-trailer, you should:
  • A Back without using mirrors
  • B Always back to the right
  • C Back as fast as practical
  • D Back to the left whenever possible because you can see better
Correct answer: D
Backing to the driver's side gives the best view of the trailer. Always GOAL — Get Out And Look — before and during.
Question 21 of 25
When you cross a railroad track in a combination vehicle, the safest practice is:
  • A Cross in a low gear without shifting
  • B Honk and accelerate
  • C Stop on the tracks if traffic ahead slows
  • D Shift in the middle of the track
Correct answer: A
Cross in a low gear without shifting; never stop on the tracks; never shift in the middle.
Question 22 of 25
When coupling a tractor to a semitrailer, the trailer should be at:
  • A Whatever height it happens to be
  • B A height where the tractor will lift the trailer slightly when backing under
  • C A height that requires the tractor to drop down to fit
  • D Maximum legal height
Correct answer: B
The trailer should be slightly lower than the fifth wheel so backing in lifts the trailer.
Question 23 of 25
The seven-pin connector on a tractor-trailer carries:
  • A Electrical power for trailer lights and ABS
  • B Air for the brakes
  • C Hydraulic fluid
  • D Fuel
Correct answer: A
The seven-pin (or older five-pin) is electrical, supplying lights, brake-light signal, and ABS.
Question 24 of 25
When inspecting the air lines between tractor and trailer, look for:
  • A Loose lug nuts only
  • B Engine oil leaks
  • C Cargo placement
  • D Cuts, abrasions, and worn seals
Correct answer: D
Air-line condition is a typical roadside inspection focus on combinations.
Question 25 of 25
When the trailer brakes are operating but pulling weakly, this can indicate:
  • A Engine wear
  • B Air leakage in the supply line, low pressure, or a brake-balance issue
  • C Cargo placement
  • D Driver fatigue
Correct answer: B
Weak trailer brakes are usually an air-system problem and require diagnosis before continuing.

Study tips for the Vermont Combination Vehicles exam

The Combination Vehicles portion of the Vermont CDL exam is graded out of the bank of questions the Vermont Department of Motor Vehicles draws from each year. While the exact bank is not published, every question is sourced from the Combination Vehicles chapter of the Vermont 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 Vermont 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 Vermont Department of Motor Vehicles 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 Vermont 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 Vermont 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 Vermont Department of Motor Vehicles office.

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

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