100+ Free CDL Combination Vehicles Practice Questions

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Question 1

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FMCSA cargo securement rules require tie-downs to be sized based on:

The aggregate working load limit equal to at least half the cargo weight

Trailer length

Speed of travel

Number of axles

to track

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Key Facts: CDL Combination Vehicles Exam

80%

Passing Score

49 CFR 383.135

~20

Questions

FMCSA Model CDL Manual

Class A

CDL Required

49 CFR 383.91

26,001 lb

GCWR Threshold

49 CFR 383.5

Red / Blue

Emergency / Service Glad-Hands

FMCSA

$10-25

Test Fee

State DMV

The CDL Combination Vehicles Knowledge Test requires an 80% passing score on approximately 20 multiple-choice questions. The test covers off-tracking and wide turns, jackknife prevention, the full coupling and uncoupling procedure, fifth wheel and kingpin components, glad-hand connections (red emergency, blue service), the trailer air supply control, and combination pre-trip inspection. Passing this test is mandatory for the Class A CDL.

Sample CDL Combination Vehicles Practice Questions

Try these sample questions to test your CDL Combination Vehicles exam readiness. Each question includes a detailed explanation. Start the interactive quiz above for the full 100+ question experience with AI tutoring.

1What is a combination vehicle?

A.A straight truck with cargo loaded in the bed

B.A truck or tractor pulling one or more trailers

C.Any commercial vehicle with a GVWR over 10,000 lb

D.A vehicle with both gasoline and diesel engines

Explanation: A combination vehicle is a truck or tractor pulling one or more trailers. Common examples include the tractor-semi-trailer, doubles (tractor with two trailers), and triples (tractor with three trailers). A straight truck has no separate trailer and is not a combination vehicle.

2Which of the following is the most common combination vehicle on U.S. highways?

A.Tractor with a full trailer

B.Tractor-semi-trailer

C.Tractor pulling three trailers

D.Straight truck with a converter dolly

Explanation: The tractor-semi-trailer is the most common combination vehicle on U.S. highways. It consists of a tractor with a fifth wheel and a semi-trailer whose front end rests on the fifth wheel and is secured by the kingpin.

3What does GCWR stand for?

A.Gross Cargo Weight Rating

B.Gross Combination Weight Rating

C.General Combined Weight Reference

D.Government Commercial Weight Regulation

Explanation: GCWR is the Gross Combination Weight Rating — the total weight of the tractor plus trailer(s) plus cargo, fuel, and driver. A Class A CDL is required when GCWR is 26,001 lb or more and the towed unit has a GVWR over 10,000 lb.

4A Class A CDL is required when the combination has a GCWR of at least 26,001 lb AND the towed unit has a GVWR over:

A.5,000 lb

B.8,000 lb

C.10,000 lb

D.12,000 lb

Explanation: A Class A CDL is required for combinations with a GCWR of 26,001 lb or more provided the towed unit (trailer) has a GVWR over 10,000 lb. Below that threshold a Class B may apply.

5What is off-tracking?

A.The trailer drifting sideways on a wet road

B.The rear wheels of the trailer following a tighter path than the tractor's front wheels in a turn

C.Loss of tire traction during heavy braking

D.The vehicle leaving its travel lane on a curve

Explanation: Off-tracking is the phenomenon where the rear wheels of the trailer follow a shorter, tighter path than the tractor's steer axle through a turn. Drivers must compensate by swinging wider so the trailer's rear wheels clear curbs and other objects.

6You are making a right turn in a tractor-semi-trailer at a city intersection. Because of off-tracking, you should:

A.Turn the wheel as soon as the cab clears the curb

B.Drive farther into the intersection so the trailer's rear wheels clear the curb

C.Make the turn as tightly as possible to stay in your lane

D.Slow down and use the trailer hand valve to stabilize

Explanation: Because the trailer's rear wheels track inside the tractor's path, you must drive farther into the intersection before turning so the trailer's rear wheels do not climb the curb or strike pedestrians and signs. Watch for overhead clearance and keep an eye on the right mirror.

7When making a left turn in a combination vehicle, you should:

A.Make the tightest left turn possible to clear faster

B.Start in the right-most lane available

C.Watch for vehicles passing on your left in the lane next to you

D.Use the trailer hand valve halfway through the turn

Explanation: When turning left in a combination vehicle, watch for vehicles or motorcycles that may try to pass on your left in the adjacent lane. Stay in the right turn lane long enough so other drivers do not mistakenly try to squeeze past on your left side.

8Compared to a straight truck, a combination vehicle's steering response is:

A.Faster and more direct

B.Delayed and requires smaller, earlier corrections

C.Identical

D.Only affected by trailer length, not response time

Explanation: In a combination vehicle the trailer effectively pushes the tractor in turns, so steering response is delayed. Drivers must make smaller, earlier corrections. Over-steering can produce a trailer swing or jackknife.

9What is a jackknife?

A.A loose connection between the kingpin and fifth wheel

B.The tractor and trailer fold against each other at the coupling

C.A type of converter dolly used with doubles

D.A skid in which all four trailer tires lose traction simultaneously

Explanation: A jackknife occurs when the tractor and trailer fold against each other at the coupling, usually because the tractor's drive wheels lock under braking on slick pavement, causing the trailer to push the rear of the tractor sideways.

10If you start to feel the trailer skidding and swinging out behind you, what is the correct response?

A.Apply the trailer hand valve to slow the trailer

B.Steer in the same direction as the trailer is swinging

C.Get off the brakes so the trailer wheels can roll and the trailer can return inline

D.Use the parking brake to lock the trailer in place

Explanation: A trailer skid is almost always caused by locked trailer brakes. The cure is to release the brakes so the wheels can roll again, which lets the trailer return inline. Continuing to brake — or applying only the trailer hand valve — makes it worse.

About the CDL Combination Vehicles Exam

The CDL Combination Vehicles Knowledge Test is required for all Class A CDL applicants who will operate combination vehicles such as tractor-semi-trailers. The test covers driving combinations safely, coupling and uncoupling procedures, fifth wheel and kingpin operation, air brake systems for trailers, and pre-trip inspection under FMCSA Model CDL Manual Section 6 and 49 CFR 383.

Questions

20 scored questions

Time Limit

60 minutes

Passing Score

80%

Exam Fee

$10-25 (State DMV / FMCSA)

CDL Combination Vehicles Exam Content Outline

30%

Driving Combination Vehicles Safely

Off-tracking and wide turns, steering response, lane changes, increased braking distance, jackknife prevention, trailer skid recovery, and rollover risk

30%

Coupling and Uncoupling

Fifth wheel inspection, kingpin lock and locking jaws, tug test, air line and electrical connections, landing gear, and safe uncoupling sequence

20%

Air Brake Systems for Combinations

Red emergency and blue service glad-hands, trailer air supply knob, trolley/hand valve, tractor protection valve, ABS, and trailer brake test

20%

Combination Vehicle Inspection

Coupling area inspection, fifth wheel mounting, kingpin condition, landing gear, trailer lights and brakes, suspension, and cargo securement

How to Pass the CDL Combination Vehicles Exam

What You Need to Know

Passing score: 80%
Exam length: 20 questions
Time limit: 60 minutes
Exam fee: $10-25

Keys to Passing

Complete 500+ practice questions
Score 80%+ consistently before scheduling
Focus on highest-weighted sections
Use our AI tutor for tough concepts

CDL Combination Vehicles Study Tips from Top Performers

1Memorize the coupling sequence in order: inspect fifth wheel, line up, back under, tug test, visual inspection, connect air and electrical, raise landing gear

2Remember glad-hand colors: red = emergency (supply), blue = service — crossing them means brakes will not work correctly

3Know that the red 8-sided 'Trailer Air Supply' knob is pushed IN to supply air to the trailer and pulled OUT to apply trailer emergency brakes

4When backing a trailer, steering wheel input is OPPOSITE of forward steering — turn wheel right to swing the trailer left

5Drive far into the intersection before turning right so the trailer's rear wheels clear the curb (off-tracking)

6If a trailer skid begins, release the brakes immediately — locked trailer brakes are the cause, not the cure

Frequently Asked Questions

How many questions are on the CDL Combination Vehicles knowledge test?

The CDL Combination Vehicles knowledge test typically has 20 multiple-choice questions (exact count varies by state). You need 80% (16 out of 20) to pass. The test focuses on driving combinations safely, coupling and uncoupling, air brake systems for trailers, and combination pre-trip inspection.

What is off-tracking and why does it matter?

Off-tracking is the phenomenon where the rear wheels of a trailer follow a shorter, tighter path than the tractor's steer axle during a turn. The longer the wheelbase, the more pronounced the effect. To compensate, drivers of combination vehicles must turn wider — driving farther into an intersection before turning right so the trailer's rear wheels clear the curb, and watching for vehicles or pedestrians in the path of the swinging trailer.

What color are the trailer air lines and what do they do?

The emergency (supply) line uses a red glad-hand and charges the trailer's air reservoir while releasing the trailer's spring brakes. The service line uses a blue glad-hand and transmits service brake applications from the tractor to the trailer. The red 8-sided 'Trailer Air Supply' knob on the dash is pushed in to supply air to the trailer; pulling it out applies the trailer's emergency brakes.

What is a jackknife and how do I prevent it?

A jackknife occurs when the tractor and trailer fold against each other at the coupling, usually because the drive wheels lock under hard braking on slick pavement. Prevent it with controlled braking, smooth steering, lower speeds in poor conditions, and proper following distance. If you feel the trailer start to swing, get off the brakes immediately so the wheels can roll and the trailer can return inline. ABS helps maintain steering control during emergency stops.

What is the tug test in coupling?

After backing under the trailer and locking the fifth wheel, set the trailer parking brakes and gently pull the tractor forward in low gear with the trailer brakes engaged. If the coupling is secure, the tractor will not move. The tug test verifies the kingpin is properly locked in the fifth wheel jaws. Always follow the tug test with a visual inspection of the locked jaws and ensure there is no gap between the trailer apron and the fifth wheel.

When should I use the trailer hand valve (trolley valve)?

The trailer hand valve, also called the trolley valve, applies only the trailer's service brakes. It should be used sparingly — primarily for testing trailer brakes. Never use the trailer hand valve as a parking brake or as your primary braking method while driving, because applying only the trailer brakes can cause the trailer to swing out and jackknife, especially on slippery roads.