25 realistic Combination Vehicles practice questions for Kansas CDL applicants. Required for: Class A CDL (tractor-trailer combinations). Official test: 20 questions, 16 correct to pass.
Question 1 of 25 · Combination Air
Trailer hand valve is used to:
-
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 2 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 3 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 4 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 5 of 25 · Following Distance
How can you reduce risk of rear-end collisions?
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A.
Maintain safe following distances and watch for slowing traffic
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B.
Drive at the speed limit always
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C.
Use mirrors only at night
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D.
Avoid signaling
Correct answer: A.
Use safe following distances and watch ahead so you have time to slow down.
Question 6 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 7 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 8 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.
Question 9 of 25 · Emergency Equipment
What are some common causes of vehicle fires?
-
A.
Under-inflated tires and electrical short circuits
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B.
Improper use of flares
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C.
Cargo that catches fire from spilled fuel
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D.
All of the above
Correct answer: D.
All of these can cause vehicle fires. Pre-trip and en-route inspections reduce risk.
Question 10 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 11 of 25 · Skids
How can you correct a tractor jackknife?
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A.
Apply the brakes harder
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B.
Steer in the direction of the skid and accelerate gently
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C.
Stop steering input
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D.
Release the brakes and counter-steer
Correct answer: D.
Release the brakes to regain traction; counter-steer carefully to recover.
Question 12 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 13 of 25 · Backing
Which is correct about backing a tractor-trailer?
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A.
Steer in the same direction you want the trailer to go
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B.
Steer in the opposite direction you want the trailer to go
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C.
Use the throttle to back
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D.
Back as fast as possible
Correct answer: B.
When backing, turn the steering wheel opposite to the direction you want the trailer to move.
Question 14 of 25 · Inspection
What is the proper way to test the parking brakes after coupling?
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A.
Apply trailer parking brake and try to gently pull forward
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B.
Drive at normal speed
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C.
Apply foot brake repeatedly
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D.
Disconnect glad hands
Correct answer: A.
A gentle pull forward with parking brakes set confirms holding power.
Question 15 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 16 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 17 of 25 · Vehicle Dynamics
What's the safest way to handle a tight turn with a long combination?
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A.
Take it wide using both lanes if necessary
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B.
Drive as fast as possible to maintain momentum
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C.
Use the trailer hand valve
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D.
Make a tight turn
Correct answer: A.
Take wider turns to avoid hitting curbs or other vehicles due to off-tracking.
Question 18 of 25 · Inspection
When checking the trailer air supply, you should:
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A.
Charge the trailer with air, then disconnect the supply hose to test trailer emergency brakes
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B.
Pump the brakes
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C.
Disconnect the trailer power cord
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D.
Open the trailer service line manually
Correct answer: A.
Disconnecting the supply line tests that the trailer emergency brakes apply automatically.
Question 19 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 20 of 25 · Inspection
Air leaks during pre-trip can be detected by:
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A.
Listening for hissing
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B.
Watching the air gauges drop
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C.
Visually inspecting hoses and fittings
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D.
All of the above
Correct answer: D.
Use multiple methods — listening, watching gauges, and visual inspection — to detect leaks.
Question 21 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 22 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 23 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 24 of 25 · Coupling
What is the fifth wheel?
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A.
A spare wheel
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B.
A coupling device that connects the tractor to the trailer
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C.
A device on the trailer to support cargo
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D.
A type of axle
Correct answer: B.
The fifth wheel is the round, plate-shaped coupling that connects the tractor to the trailer.
Question 25 of 25 · Inspection
You should inspect the rear of the trailer for:
-
A.
Cracked or missing lights
-
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.
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 Kansas Department of Revenue — Division of Vehicles administers this knowledge test as part of its commercial driver license program. To earn the Combination Vehicles on your Kansas CDL, you need to score at least 16 out of 20 on the official version.
Topics covered on this practice test
- Coupling: 5 questions
- Inspection: 5 questions
- Skids: 4 questions
- Combination Air: 3 questions
- Vehicle Dynamics: 2 questions
- Following Distance: 1 question
- Emergency Equipment: 1 question
- Cargo: 1 question
- Backing: 1 question
- Bobtail: 1 question
- Operation: 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 Kansas 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.