25 realistic Combination Vehicles practice questions for Tennessee CDL applicants. Required for: Class A CDL (tractor-trailer combinations). Official test: 20 questions, 16 correct to pass.
Question 1 of 25 · Coupling
You should NEVER:
-
A.
Back under a trailer at an angle
-
B.
Inspect the fifth wheel
-
C.
Use the parking brake
-
D.
Tug-test the kingpin
Correct answer: A.
Backing at an angle can damage the kingpin or push the trailer sideways.
Question 2 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
-
C.
Mud flap condition
-
D.
All of the above
Correct answer: D.
Check lights, reflectors, mud flaps, and license plate during pre-trip.
Question 3 of 25 · Vehicle Dynamics
Empty trucks have what kind of stopping distance compared to fully loaded ones?
-
A.
Shorter
-
B.
Same
-
C.
Longer
-
D.
Half
Correct answer: C.
Empty rigs have less traction on drive axles and require greater stopping distance.
Question 4 of 25 · Coupling
What is the fifth wheel?
-
A.
A spare wheel
-
B.
A coupling device that connects the tractor to the trailer
-
C.
A device on the trailer to support cargo
-
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 5 of 25 · Emergency Equipment
What are some common causes of vehicle fires?
-
A.
Under-inflated tires and electrical short circuits
-
B.
Improper use of flares
-
C.
Cargo that catches fire from spilled fuel
-
D.
All of the above
Correct answer: D.
All of these can cause vehicle fires. Pre-trip and en-route inspections reduce risk.
Question 6 of 25 · Skids
How can drivers avoid jackknifing?
-
A.
Brake gently and look ahead
-
B.
Adjust speed for road and weather
-
C.
Use ABS where equipped
-
D.
All of the above
Correct answer: D.
Smooth braking, appropriate speed, and ABS all reduce jackknife risk.
Question 7 of 25 · CDL Rules
Which is true about long combination vehicles (LCVs)?
-
A.
They are easier to maneuver in tight spaces
-
B.
They require additional driver training and special permits
-
C.
They handle the same as single trailers
-
D.
They never require special routes
Correct answer: B.
LCVs need extra training, certifications, and often follow restricted routes.
Question 8 of 25 · Backing
Which is correct about backing a tractor-trailer?
-
A.
Steer in the same direction you want the trailer to go
-
B.
Steer in the opposite direction you want the trailer to go
-
C.
Use the throttle to back
-
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 9 of 25 · Skids
How can you correct a tractor jackknife?
-
A.
Apply the brakes harder
-
B.
Steer in the direction of the skid and accelerate gently
-
C.
Stop steering input
-
D.
Release the brakes and counter-steer
Correct answer: D.
Release the brakes to regain traction; counter-steer carefully to recover.
Question 10 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
-
B.
Coiled tightly on top of the trailer
-
C.
Loose so they can move freely
-
D.
Disconnected
Correct answer: A.
Air lines must be connected and supported off the deck so they don't snag or wear.
Question 11 of 25 · Cargo
What can cause a high center of gravity?
-
A.
Loading cargo too low
-
B.
Loading cargo too high or unevenly
-
C.
Driving too slowly
-
D.
Empty trailers
Correct answer: B.
Stacking cargo too high or loading unevenly raises the center of gravity and rollover risk.
Question 12 of 25 · Coupling
When uncoupling, what is the final step?
-
A.
Lower the landing gear and disconnect electrical cord and air lines
-
B.
Drive forward immediately
-
C.
Set the parking brake on the tractor only
-
D.
Engage the trailer brakes only
Correct answer: A.
After raising the fifth wheel jaws and pulling forward, disconnect lines and lower landing gear.
Question 13 of 25 · Cargo
Why is securement of cargo essential?
-
A.
To prevent the load from shifting
-
B.
To prevent injury to others
-
C.
To prevent damage to the vehicle
-
D.
All of the above
Correct answer: D.
Securement protects the load, prevents shifts that affect handling, and protects others.
Question 14 of 25 · Coupling
What are landing gear used for?
-
A.
Supporting the front of the trailer when uncoupled
-
B.
Steering the trailer
-
C.
Powering the trailer brakes
-
D.
Lighting the trailer
Correct answer: A.
Landing gear holds up the trailer when it is not connected to a tractor.
Question 15 of 25 · Vehicle Dynamics
Which of these is true about driving combination vehicles?
-
A.
They are easier to handle than single vehicles
-
B.
They are more likely to roll over and jackknife
-
C.
They use less fuel per mile
-
D.
They need fewer mirrors
Correct answer: B.
Combination vehicles require more skill and are more prone to rollovers and jackknives.
Question 16 of 25 · Bobtail
What happens if you bobtail (no trailer) and brake hard?
-
A.
You stop more quickly than loaded
-
B.
Drive wheels can lock and skid because there is little weight on them
-
C.
Vehicle handles like a loaded truck
-
D.
No special concerns
Correct answer: B.
Bobtailing leaves little weight on drive axles, increasing skid risk under hard braking.
Question 17 of 25 · Skids
What is the result of a "trailer jackknife"?
-
A.
Trailer continues straight ahead
-
B.
Trailer swings out and tractor pivots
-
C.
Trailer comes to a quick safe stop
-
D.
Trailer disengages
Correct answer: B.
In a trailer jackknife, the trailer swings out, often into adjacent lanes.
Question 18 of 25 · Coupling
What should you do before connecting air lines?
-
A.
Clean the rubber seals on the glad hands
-
B.
Lubricate them with oil
-
C.
Replace the seals every trip
-
D.
Heat them up
Correct answer: A.
Clean glad hand seals before connecting to ensure a good air seal.
Question 19 of 25 · Vehicle Dynamics
What's the safest way to handle a tight turn with a long combination?
-
A.
Take it wide using both lanes if necessary
-
B.
Drive as fast as possible to maintain momentum
-
C.
Use the trailer hand valve
-
D.
Make a tight turn
Correct answer: A.
Take wider turns to avoid hitting curbs or other vehicles due to off-tracking.
Question 20 of 25 · Following Distance
What is "rear-end collision" risk for combination vehicles?
-
A.
It is reduced when carrying long cargo
-
B.
They have a higher risk because of long stopping distances and rear blind spots
-
C.
They have no greater risk
-
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
When uncoupling, you should:
-
A.
Lower the landing gear before pulling the kingpin release
-
B.
Lift the trailer with the fifth wheel
-
C.
Release the parking brake
-
D.
Rev the engine
Correct answer: A.
Lower the landing gear so the trailer is supported before disconnecting the kingpin.
Question 22 of 25 · Inspection
When should you check trailer brakes during operation?
-
A.
First few miles after coupling
-
B.
Every fuel stop
-
C.
Just at the end of the trip
-
D.
Never during the trip
Correct answer: A.
Test trailer brakes early in the trip to make sure they are functioning correctly.
Question 23 of 25 · Skids
Which is the most common cause of trailer skid?
-
A.
Driving too fast for conditions
-
B.
Locking the rear trailer wheels by overbraking
-
C.
Worn brake shoes
-
D.
Too much trailer weight
Correct answer: B.
Trailer skids most often occur when rear trailer wheels lock during braking.
Question 24 of 25 · Combination Air
Trailer brakes are required to be:
-
A.
Adjusted properly and matched to tractor brakes
-
B.
Stronger than tractor brakes
-
C.
Disengaged on level roads
-
D.
Off when empty
Correct answer: A.
Trailer brakes must be in proper adjustment and balance with tractor brakes.
Question 25 of 25 · Coupling
What does a "low coupling" condition look like?
-
A.
Trailer is too high above the fifth wheel
-
B.
Trailer is at the right height
-
C.
Trailer is too low and tractor frame can hit the trailer
-
D.
Trailer is angled to the right
Correct answer: C.
A trailer too low can damage the tractor frame as it slides under it.
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 Tennessee Department of Safety — Driver Services administers this knowledge test as part of its commercial driver license program. To earn the Combination Vehicles on your Tennessee CDL, you need to score at least 16 out of 20 on the official version.
Topics covered on this practice test
- Coupling: 8 questions
- Skids: 4 questions
- Vehicle Dynamics: 3 questions
- Inspection: 2 questions
- Cargo: 2 questions
- Emergency Equipment: 1 question
- CDL Rules: 1 question
- Backing: 1 question
- Bobtail: 1 question
- Following Distance: 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 Tennessee 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.