25 realistic Combination Vehicles practice questions for Ohio CDL applicants. Required for: Class A CDL (tractor-trailer combinations). Official test: 20 questions, 16 correct to pass.
Question 1 of 25 · Skids
How can drivers avoid jackknifing?
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A.
Brake gently and look ahead
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B.
Adjust speed for road and weather
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C.
Use ABS where equipped
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D.
All of the above
Correct answer: D.
Smooth braking, appropriate speed, and ABS all reduce jackknife risk.
Question 2 of 25 · Coupling
What should you do before connecting air lines?
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A.
Clean the rubber seals on the glad hands
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B.
Lubricate them with oil
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C.
Replace the seals every trip
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D.
Heat them up
Correct answer: A.
Clean glad hand seals before connecting to ensure a good air seal.
Question 3 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 4 of 25 · Combination Air
Trailer brakes are required to be:
-
A.
Adjusted properly and matched to tractor brakes
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B.
Stronger than tractor brakes
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C.
Disengaged on level roads
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D.
Off when empty
Correct answer: A.
Trailer brakes must be in proper adjustment and balance with tractor brakes.
Question 5 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 6 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 7 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 8 of 25 · Combination Air
When the trailer breaks away or loses air pressure, the trailer brakes should:
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A.
Release
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B.
Apply automatically
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C.
Vibrate
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D.
Disengage
Correct answer: B.
A loss of air should automatically apply the trailer brakes via the emergency system.
Question 9 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 10 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 11 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 12 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 13 of 25 · Coupling
When uncoupling, you should:
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A.
Lower the landing gear before pulling the kingpin release
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B.
Lift the trailer with the fifth wheel
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C.
Release the parking brake
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D.
Rev the engine
Correct answer: A.
Lower the landing gear so the trailer is supported before disconnecting the kingpin.
Question 14 of 25 · Vehicle Dynamics
When you turn suddenly with a high center of gravity, the trailer can:
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A.
Roll over
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B.
Stop more quickly
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C.
Track better
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D.
Reduce fuel use
Correct answer: A.
High centers of gravity make trailers prone to rollover during sharp turns.
Question 15 of 25 · Bobtail
What happens if you bobtail (no trailer) and brake hard?
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A.
You stop more quickly than loaded
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B.
Drive wheels can lock and skid because there is little weight on them
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C.
Vehicle handles like a loaded truck
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D.
No special concerns
Correct answer: B.
Bobtailing leaves little weight on drive axles, increasing skid risk under hard braking.
Question 16 of 25 · Coupling
How can you keep a stiff coupling system from causing problems?
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A.
Lubricate the fifth wheel
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B.
Avoid backing under fast
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C.
Inspect mounting bolts
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D.
All of the above
Correct answer: D.
Lubricate, back slowly, and inspect mounting bolts to keep the coupling working safely.
Question 17 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 18 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 19 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.
Question 20 of 25 · Following Distance
What is "rear-end collision" risk for combination vehicles?
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A.
It is reduced when carrying long cargo
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B.
They have a higher risk because of long stopping distances and rear blind spots
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C.
They have no greater risk
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D.
Only for empty rigs
Correct answer: B.
Long stopping distance and rear blind spots increase rear-end collision risk.
Question 21 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 22 of 25 · Skids
What is "tractor jackknife"?
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A.
Tractor drive wheels skid and the trailer pushes the tractor sideways
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B.
Trailer wheels skid
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C.
Steering wheels skid
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D.
Engine fails
Correct answer: A.
When drive wheels skid, the trailer can push the tractor sideways into a jackknife.
Question 23 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 24 of 25 · Combination Air
What should the tractor protection valve do?
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A.
Keep tractor air supply if trailer breaks away or develops a major leak
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B.
Set the trailer parking brake on a hill
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C.
Apply trailer brakes during a normal stop
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D.
Disconnect the trailer
Correct answer: A.
It protects the tractor air supply by closing if a major air loss occurs.
Question 25 of 25 · Coupling
When you finish coupling, the air lines should be:
-
A.
Connected to the proper glad hands and supported off the catwalk and the deck plate
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B.
Coiled tightly on top of the trailer
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C.
Loose so they can move freely
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D.
Disconnected
Correct answer: A.
Air lines must be connected and supported off the deck so they don't snag or wear.
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 Ohio Bureau of Motor Vehicles administers this knowledge test as part of its commercial driver license program. To earn the Combination Vehicles on your Ohio CDL, you need to score at least 16 out of 20 on the official version.
Topics covered on this practice test
- Coupling: 9 questions
- Combination Air: 4 questions
- Skids: 3 questions
- Vehicle Dynamics: 2 questions
- Mountain Driving: 1 question
- CDL Rules: 1 question
- Inspection: 1 question
- Bobtail: 1 question
- Cargo: 1 question
- Operation: 1 question
- Following Distance: 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 Ohio 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.