25 realistic Combination Vehicles practice questions for Maryland CDL applicants. Required for: Class A CDL (tractor-trailer combinations). Official test: 20 questions, 16 correct to pass.
Question 1 of 25 · Inspection
When should you check trailer brakes during operation?
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A.
First few miles after coupling
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B.
Every fuel stop
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C.
Just at the end of the trip
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D.
Never during the trip
Correct answer: A.
Test trailer brakes early in the trip to make sure they are functioning correctly.
Question 2 of 25 · Skids
Tractor jackknife occurs when:
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A.
Drive wheels lose traction and skid
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B.
The trailer wheels lock
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C.
The trailer slides forward
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D.
Steering wheels lock
Correct answer: A.
Drive wheels skidding cause tractor jackknife; trailer wheels skidding cause trailer jackknife.
Question 3 of 25 · Operation
Which of these is most important when driving with a trailer?
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A.
Use the engine retarder constantly
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B.
Use proper braking and signaling
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C.
Drive at maximum speed limits
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D.
Skip pre-trip checks if running late
Correct answer: B.
Proper braking and clear signaling are essential to safe combination driving.
Question 4 of 25 · Cargo
Why is securement of cargo essential?
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A.
To prevent the load from shifting
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B.
To prevent injury to others
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C.
To prevent damage to the vehicle
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D.
All of the above
Correct answer: D.
Securement protects the load, prevents shifts that affect handling, and protects others.
Question 5 of 25 · Coupling
When coupling, what should you do after the fifth wheel locks onto the kingpin?
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A.
Pull the tractor forward gently to make sure the kingpin is locked
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B.
Disconnect the air lines
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C.
Drive away immediately
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D.
Release the trailer parking brake first
Correct answer: A.
Tug-test by gently pulling forward with the trailer brakes set to confirm the lock.
Question 6 of 25 · Inspection
When inspecting your trailer's wheels, what should you look for?
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A.
Loose or missing nuts
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B.
Cracked or broken wheel rims
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C.
Bent or broken studs
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D.
All of the above
Correct answer: D.
Inspect for loose nuts, cracks, bent studs, and other defects on every pre-trip.
Question 7 of 25 · Coupling
You should NEVER:
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A.
Back under a trailer at an angle
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B.
Inspect the fifth wheel
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C.
Use the parking brake
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D.
Tug-test the kingpin
Correct answer: A.
Backing at an angle can damage the kingpin or push the trailer sideways.
Question 8 of 25 · Inspection
Which is true about gladhand seals?
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A.
They should be replaced if cracked or damaged
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B.
They never need replacement
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C.
They are the same as electrical connections
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D.
They are always made of metal
Correct answer: A.
Replace damaged or worn rubber seals to keep air from leaking at the gladhands.
Question 9 of 25 · Coupling
Which is true about pulling away after coupling?
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A.
Test that the kingpin is locked by gently pulling forward against the trailer brakes
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B.
Pull away as quickly as possible
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C.
Lower the landing gear before pulling away
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D.
Disconnect the air lines first
Correct answer: A.
A pull-test confirms the kingpin is locked before driving away.
Question 10 of 25 · Coupling
What is the proper position for the fifth wheel?
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A.
Tilted down toward the rear of the tractor with jaws open
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B.
Pointed straight up
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C.
Locked and ready
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D.
Removed for inspection
Correct answer: A.
Before coupling, the fifth wheel should tilt down toward the rear with the jaws open.
Question 11 of 25 · CDL Rules
Which is true about long combination vehicles (LCVs)?
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A.
They are easier to maneuver in tight spaces
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B.
They require additional driver training and special permits
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C.
They handle the same as single trailers
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D.
They never require special routes
Correct answer: B.
LCVs need extra training, certifications, and often follow restricted routes.
Question 12 of 25 · Vehicle Dynamics
Off-tracking is most pronounced in:
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A.
Single vehicles
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B.
Long combinations and curves
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C.
Empty trailers
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D.
Vehicles with disc brakes
Correct answer: B.
Longer wheelbases and tighter curves cause greater off-tracking.
Question 13 of 25 · Mountain Driving
When should you use lower gears?
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A.
On steep upgrades and downgrades
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B.
In flat terrain
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C.
In stop-and-go traffic only
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D.
Never in a combination vehicle
Correct answer: A.
Use lower gears on grades to maintain torque and engine braking.
Question 14 of 25 · Vehicle Dynamics
Why should you avoid sudden steering and braking with combinations?
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A.
It wears tires faster
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B.
It can cause jackknife or rollover
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C.
It uses more fuel
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D.
It scares passengers
Correct answer: B.
Sudden inputs can break traction and lead to jackknifing or rollovers.
Question 15 of 25 · Speed Management
What is the most common cause of fatal crashes for combination vehicles?
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A.
Loss of control due to speed too fast for conditions
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B.
Engine failure
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C.
Tire blowouts
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D.
Mechanical defects only
Correct answer: A.
Driving too fast for conditions is the leading cause of serious crashes.
Question 16 of 25 · Skids
What can cause a trailer skid in a combination vehicle?
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A.
Locked trailer wheels and over-application of brakes
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B.
Light loads on the trailer
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C.
Tight steering at low speed
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D.
High pressure in steering tires
Correct answer: A.
Locked trailer wheels cause trailer skid; reduce brake pressure to recover.
Question 17 of 25 · Inspection
You should inspect the rear of the trailer for:
-
A.
Cracked or missing lights
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B.
Lights and reflectors are clean and operational
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C.
Mud flap condition
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D.
All of the above
Correct answer: D.
Check lights, reflectors, mud flaps, and license plate during pre-trip.
Question 18 of 25 · Cargo
How do you know the trailer is properly loaded?
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A.
Cargo is centered, balanced, and properly secured
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B.
Cargo extends beyond the trailer ends
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C.
Cargo is stacked unevenly
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D.
Cargo is on top of the cab
Correct answer: A.
Centered, balanced, and secured loads handle predictably.
Question 19 of 25 · Skids
What is the result of a "trailer jackknife"?
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A.
Trailer continues straight ahead
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B.
Trailer swings out and tractor pivots
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C.
Trailer comes to a quick safe stop
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D.
Trailer disengages
Correct answer: B.
In a trailer jackknife, the trailer swings out, often into adjacent lanes.
Question 20 of 25 · Coupling
What is the kingpin?
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A.
A pin in the engine
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B.
A vertical pin on the front of the trailer that locks into the fifth wheel
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C.
A part of the air brake system
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D.
A type of warning device
Correct answer: B.
The kingpin slides into the fifth wheel jaws to lock the trailer to the tractor.
Question 21 of 25 · Coupling
What are landing gear used for?
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A.
Supporting the front of the trailer when uncoupled
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B.
Steering the trailer
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C.
Powering the trailer brakes
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D.
Lighting the trailer
Correct answer: A.
Landing gear holds up the trailer when it is not connected to a tractor.
Question 22 of 25 · Vehicle Dynamics
Which of these is true about the front trailer of a doubles or triples?
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A.
It is less likely to overturn
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B.
It is more stable
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C.
It is more likely to overturn than the rear trailer
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D.
It does not need brakes
Correct answer: A.
The front trailer in a combination is generally more stable than the rear trailer.
Question 23 of 25 · Combination Air
Trailer hand valve is used to:
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A.
Test trailer brakes
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B.
Park the trailer
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C.
Bypass the foot valve
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D.
Drain trailer tanks
Correct answer: A.
Use the trailer hand valve only for testing — not for parking or normal stops.
Question 24 of 25 · Vehicle Dynamics
What is "off-tracking"?
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A.
When the rear wheels follow a different path than the front wheels
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B.
When the trailer slides off the road
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C.
When the trailer is improperly loaded
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D.
A type of fifth wheel
Correct answer: A.
In turns, rear wheels travel a smaller arc than the front, causing off-tracking.
Question 25 of 25 · Skids
What should you do to recover from a trailer skid?
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A.
Apply more brake pressure
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B.
Release the brakes to allow trailer wheels to roll again
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C.
Steer hard right
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D.
Accelerate forward
Correct answer: B.
Release brakes to let trailer wheels roll, then steer to recover direction.
About the Combination Vehicles Test
The Combination Vehicles test covers driving combination vehicles safely, combination vehicle air brakes, antilock brake systems, coupling and uncoupling, and inspecting a combination vehicle. Combination vehicles are usually heavier, longer, and require more driving skill than single commercial vehicles. They are also more likely to roll over and jackknife.
The Maryland Motor Vehicle Administration administers this knowledge test as part of its commercial driver license program. To earn the Combination Vehicles on your Maryland CDL, you need to score at least 16 out of 20 on the official version.
Topics covered on this practice test
- Coupling: 6 questions
- Inspection: 4 questions
- Skids: 4 questions
- Vehicle Dynamics: 4 questions
- Cargo: 2 questions
- Operation: 1 question
- CDL Rules: 1 question
- Mountain Driving: 1 question
- Speed Management: 1 question
- Combination Air: 1 question
How to use this practice test
- Read each question carefully. CDL questions are written precisely — small wording differences matter.
- Click "Show Answers & Explanations" only after answering every question. Don't peek mid-test.
- Read the explanation for every question, even ones you got right. The reasoning is more important than the answer.
- Repeat the test until you score 100%. The questions are deterministic per state, so you can track your improvement over multiple sessions.
- Move on to the other endorsement tests for Maryland until you're ready for the official exam.
Tips specific to the Combination Vehicles test
Combination Vehicles questions cover off-tracking, jackknifing, coupling and uncoupling, the fifth wheel, kingpin, glad hands, landing gear, and the special air-brake considerations for tractor-trailer combinations. Expect detailed step-by-step coupling questions.