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New Jersey Combination Vehicles CDL Practice Test

Below are 25 exam-style questions for the New Jersey Combination Vehicles CDL knowledge test, modeled on the FMCSA-aligned content used by the New Jersey Motor Vehicle Commission. 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
If you cross the air lines (service to emergency and vice versa) when coupling:
  • A You will notice immediately because trailer brakes will not work properly
  • B The horn will sound
  • C The trailer brakes will be locked on
  • D Nothing will happen
Correct answer: A
Crossed glad hands often produce no air flow to brake chambers and incorrect brake operation; you should notice on the brake test.
Question 2 of 25
Most rear-end collisions caused by combination vehicles result from:
  • A Engine failure
  • B Cargo movement
  • C Worn out tires
  • D Driving too fast for conditions and/or too closely
Correct answer: D
Speed and following distance dominate the causes. Increase cushion and slow down.
Question 3 of 25
When you turn a combination vehicle right at an intersection, you should:
  • A Stop in the middle of the turn
  • B Swing left then right
  • C Swing wide to the right first to avoid hitting the curb
  • D Keep the cab close to the curb and swing the front out so following cars cannot squeeze beside you on the right
Correct answer: D
Hugging the right side of the turn lane prevents another vehicle from squeezing in next to you and getting clipped by the trailer.
Question 4 of 25
A tractor jackknife happens when:
  • A The drive wheels lose traction and the tractor begins to slide
  • B The tractor parking brake fails
  • C The fifth wheel disengages
  • D The trailer is too heavy
Correct answer: A
A drive-wheel skid causes the tractor to swing into the trailer at an angle.
Question 5 of 25
When coupling a tractor to a semitrailer, the trailer should be at:
  • A A height that requires the tractor to drop down to fit
  • B A height where the tractor will lift the trailer slightly when backing under
  • C Maximum legal height
  • D Whatever height it happens to be
Correct answer: B
The trailer should be slightly lower than the fifth wheel so backing in lifts the trailer.
Question 6 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 7 of 25
A heavy combination vehicle in a curve is most likely to:
  • A Roll over before sliding
  • B Lose engine power
  • C Spin out
  • D Stop suddenly
Correct answer: A
Loaded trailers reach the rollover threshold before they slide. Slow before the curve.
Question 8 of 25
A safe combination-vehicle following distance is at least:
  • A No specific rule
  • B One second per 10 feet of vehicle length below 40 mph, plus one extra second above 40 mph
  • C Two car lengths
  • D A vehicle length
Correct answer: B
A 60-ft combination needs at least 6 seconds under 40 mph, 7 seconds above 40 mph.
Question 9 of 25
When backing a trailer, small steering inputs cause:
  • A Large trailer angle changes; small inputs are key
  • B No effect
  • C Small trailer movement
  • D Loss of brake pressure
Correct answer: A
Trailer responds aggressively to small wheel inputs in reverse — back slowly and correct quickly.
Question 10 of 25
The proper test of a good fifth-wheel coupling is:
  • A Listen for a click
  • B Honk the horn
  • C Tug the trailer with the trailer parking brakes set
  • D Look at the locking jaws only
Correct answer: C
After coupling and locking, gently pull forward against the locked trailer brakes to confirm engagement.
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 setting the red trailer-air-supply valve
  • D By the trailer hand valve
Correct answer: A
Pushing in the red knob charges the trailer brakes and releases the spring brakes.
Question 12 of 25
Which is true about coupling order to a trailer?
  • A Connect only air; electrical is optional
  • 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 any line first; order doesn't matter
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.
Question 13 of 25
After connecting the air lines, before pulling the tractor away, you must:
  • A Drive away immediately
  • B Drain the wet tank
  • C Charge the trailer brakes by setting the trailer air supply control
  • D Pump the brakes 10 times
Correct answer: C
After connecting, charge the trailer system and verify brake operation.
Question 14 of 25
Trailer ABS uses:
  • A Hydraulic brakes
  • B Hand valves
  • C A separate compressor
  • D Sensors at each wheel that release brake pressure when wheel lockup is detected
Correct answer: D
Wheel-speed sensors trigger valves to release pressure when lockup is detected.
Question 15 of 25
When uncoupling, after the tractor is clear, you should:
  • A Disable the trailer parking brake
  • B Move the tractor far away immediately without checking
  • C Connect the lines back to the tractor
  • 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 16 of 25
During a brake check before moving, you should look for:
  • A Engine knocking
  • B Steering wander only
  • C Pulling, sticking, or unusual feel as you apply the brakes
  • D Smoke from the cab
Correct answer: C
Low-speed brake test identifies pulling, sticking, or weakness so you don't discover it on the highway.
Question 17 of 25
The trailer hand valve operates:
  • A The tractor service brakes only
  • B The parking brake
  • 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 18 of 25
The trailer hand valve should NOT be used to:
  • A Both for parking and to prevent jackknife
  • B Test the trailer brakes
  • C Hold the vehicle when parking
  • D Apply trailer brakes momentarily
Correct answer: A
Don't use it to park (it can leak off) or to prevent a jackknife (it locks the trailer wheels and worsens the skid).
Question 19 of 25
A skid is most likely to result in a jackknife if:
  • A The brakes are released gently
  • B You are driving slowly
  • C The drive wheels lock and the trailer pushes the tractor sideways
  • D The trailer wheels lock briefly
Correct answer: C
Drive-wheel lockup is the classic jackknife cause.
Question 20 of 25
You should inspect a combination vehicle for:
  • A Cracks in the kingpin
  • B All of the above
  • C Loose or missing fifth-wheel mounting bolts
  • D Misalignment between tractor and trailer
Correct answer: B
All three are pre-trip combination-vehicle items.
Question 21 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 can damage the cab and the trailer (cab corner crush)
  • D It is the standard procedure
Correct answer: C
Bending the tractor too sharply against the trailer can cause body damage and disconnect the lines.
Question 22 of 25
If you are pulling two trailers, the heavier trailer should be:
  • A Last
  • B First (closest to the tractor)
  • C Either position is fine
  • D Loaded last
Correct answer: B
Heavier trailer first reduces the rear-trailer crack-the-whip effect.
Question 23 of 25
The trailer landing gear (dolly legs) should be:
  • A Always halfway extended
  • B Lowered to the ground while driving
  • C Disconnected before driving
  • D Fully raised before driving
Correct answer: D
Landing gear must be fully raised and the crank handle secured before moving the trailer.
Question 24 of 25
When the trailer brakes are operating but pulling weakly, this can indicate:
  • A Cargo placement
  • B Engine wear
  • C Driver fatigue
  • D Air leakage in the supply line, low pressure, or a brake-balance issue
Correct answer: D
Weak trailer brakes are usually an air-system problem and require diagnosis before continuing.
Question 25 of 25
When you uncouple a trailer with cargo on it, you should:
  • A Use blocks instead
  • B Lower the landing gear all the way until firmly on the ground, then a few extra cranks
  • C Leave the gear up
  • D Raise the gear partway
Correct answer: B
Make sure the gear takes the full weight before pulling out from under.

Study tips for the New Jersey Combination Vehicles exam

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

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

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