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CDL Combination Vehicles practice test

Needed for a Class A license: a tractor-trailer or other vehicle that tows a heavy trailer.

Examlane has 129 Combination Vehicles questions in 6 chapters. The usual test has 20 questions and needs 80% to pass. Some states set a different length: see the state table.

Practice Combination Vehicles

Chapters

Manual sectionChapterQuestions
6.0Combination vehicles1
6.1Driving combinations30
6.2Combination air brakes34
6.3Trailer ABS9
6.4Coupling and uncoupling43
6.5Inspecting a combination12

Chapter pages: Coupling and uncoupling.

Ten free questions

Open a question to see the answer and why.

  1. 1. Which of these is a combination vehicle?
    1. A straight truck with no trailer
    2. A straight truck pulling a trailer
    3. A bus carrying passengers
    4. A single-unit dump truck

    Answer: B. A straight truck pulling a trailer

    A combination vehicle is a power unit pulling one or more trailers, and a straight truck with a trailer is one of the common types.

    Based on: CDL manual, Section 6.0 (Georgia edition of the national model manual, read 2026-10-24). Question in our own words.

  2. 2. How do the knowledge and skill needed by combination vehicle drivers compare with those needed by single-vehicle drivers?
    1. Drivers need less, because the trailer simply follows the tractor
    2. Drivers need the same, because the controls are alike
    3. Drivers need more, because the rigs are heavier and longer
    4. Drivers need less, because the brakes are stronger

    Answer: C. Drivers need more, because the rigs are heavier and longer

    Combination vehicles tend to be heavier and longer, so driving one demands more skill and knowledge than driving a single vehicle.

    Based on: CDL manual, Section 6.1 (Georgia edition of the national model manual, read 2026-10-24). Question in our own words.

  3. 3. What does the braking system of a combination vehicle have besides the air brake parts used on a single vehicle?
    1. A second air compressor mounted on the trailer
    2. Parts that control the trailer brakes
    3. A hydraulic system that replaces the tractor's air brakes
    4. A separate steering system for the trailer

    Answer: B. Parts that control the trailer brakes

    A combination vehicle adds parts that control the trailer brakes to the usual air brake parts.

    Based on: CDL manual, Section 6.2 (Georgia edition of the national model manual, read 2026-10-24). Question in our own words.

  4. 4. Which manufacture date starts the ABS requirement for trailers and converter dollies?
    1. March 1, 1988
    2. March 1, 1993
    3. March 1, 1998
    4. March 1, 2003

    Answer: C. March 1, 1998

    Any trailer or converter dolly made from March 1, 1998 onward must have ABS.

    Based on: CDL manual, Section 6.3.1 (Georgia edition of the national model manual, read 2026-10-24). Question in our own words.

  5. 5. Before coupling a tractor-semitrailer, how should the fifth wheel be tilted?
    1. Tilted down toward the front of the tractor
    2. Level with the top of the tractor frame rails
    3. Tilted down toward the tractor's rear
    4. Tilted to one side

    Answer: C. Tilted down toward the tractor's rear

    Before you back under the trailer, the fifth wheel should be tilted down toward the rear of the tractor.

    Based on: CDL manual, Section 6.4.1 (Georgia edition of the national model manual, read 2026-10-24). Question in our own words.

  6. 6. How many steps are in the inspection procedure used for a combination vehicle?
    1. Five
    2. Seven
    3. Nine
    4. Eleven

    Answer: B. Seven

    A combination vehicle is inspected with the same seven-step procedure used for other vehicles, plus some extra checks.

    Based on: CDL manual, Section 6.5 (Georgia edition of the national model manual, read 2026-10-24). Question in our own words.

  7. 7. What is responsible for over half of the crash fatalities among truck drivers?
    1. Truck rollovers
    2. Trailer jackknifes
    3. Brake failures
    4. Cargo fires

    Answer: A. Truck rollovers

    Over half of crash fatalities among truck drivers come from rollovers.

    Based on: CDL manual, Section 6.1.1 (Georgia edition of the national model manual, read 2026-10-24). Question in our own words.

  8. 8. For which job should you use the trailer hand valve?
    1. Slowing the rig on a long downgrade
    2. Holding the rig in place while parked
    3. Testing the trailer brakes
    4. Straightening a trailer that is starting to skid

    Answer: C. Testing the trailer brakes

    The hand valve is only for testing the trailer brakes because using it while driving can make the trailer skid.

    Based on: CDL manual, Section 6.2.1 (Georgia edition of the national model manual, read 2026-10-24). Question in our own words.

  9. 9. On which side of a trailer will you find the ABS malfunction lamp?
    1. The right side
    2. The left side
    3. The roof
    4. Underneath, near the landing gear

    Answer: B. The left side

    Trailers carry the yellow ABS malfunction lamp on the left side.

    Based on: CDL manual, Section 6.3.1 (Georgia edition of the national model manual, read 2026-10-24). Question in our own words.

  10. 10. What problem can a fifth wheel plate that is not greased cause?
    1. Steering problems from friction between the units
    2. Trailer air lines coming apart
    3. The kingpin snapping off inside the jaws
    4. Loss of air pressure in the trailer tanks and lines

    Answer: A. Steering problems from friction between the units

    Without grease, friction builds up between the tractor and trailer and can cause steering problems.

    Based on: CDL manual, Section 6.4.1 (Georgia edition of the national model manual, read 2026-10-24). Question in our own words.

This is practice for the knowledge test. It is not Entry-Level Driver Training and does not count toward any federal training requirement.