Combination Vehicles Practice Test
Drivers seeking a Class A CDL must pass the Combination Vehicles test, which focuses on the safe operation of tractor-trailers and other combination vehicles. The exam covers coupling and uncoupling, the fifth wheel and kingpin, sliding tandems and the trailer landing gear, glad hands and pigtails, the tractor protection valve, anti-jackknife and anti-rollover techniques, off-tracking on turns, and inspection of every coupling component. The questions on this site are seeded directly from the AAMVA CDL Manual chapter on combination vehicles.
How to use this practice bank
Read each question carefully before checking the answer. Most CDL questions are not designed to trick you, but they do test whether you know the specific rule — not just what feels safe. After reading the explanation, try to restate the rule in your own words; if you can, you've internalized it. If you can't, look up the corresponding chapter of your state's CDL handbook before moving on.
Pass scores vary slightly by state, but most jurisdictions require at least 80% correct on each knowledge exam. With 45 questions in this bank you have substantially more practice material than any single sitting of the real exam, which typically contains 20 to 50 questions per endorsement.
All 45 questions in this bank
- #1Empty trucks have a longer stopping distance than fully loaded trucks because:
- #2What is the most common cause of fire in commercial vehicles?
- #3When coupling a tractor to a trailer, the trailer height should be:
- #4After backing under the trailer, you should test the connection by:
- #5Why should you charge the trailer air brake system before connecting?
- #6Off-tracking causes:
- #7A converter dolly is used to:
- #8When uncoupling a loaded trailer, you should set the trailer landing gear:
- #9Before uncoupling, you should:
- #10The kingpin of a semitrailer should be:
- #11Glad hands are:
- #12The proper procedure when coupling glad hands is to:
- #13The fifth wheel locking lever is in the locked position only when:
- #14A high coupling on the fifth wheel is when:
- #15When inspecting the coupling, you should check that:
- #16Front-end header boards (or headache racks):
- #17Cargo inspections during a trip should be made:
- #18Drivers may overload a vehicle when:
- #19Cargo that can shift or fall must be:
- #20You are driving a 40-foot vehicle at 35 mph. The minimum safe following distance is about:
- #21The center of gravity of a load should be:
- #22The amount of weight on the steering axle is important because:
- #23Tiedowns must have a working load limit (WLL) totaling at least:
- #24Dunnage is used to:
- #25A driver pulling doubles or triples should:
- #26The crack-the-whip effect refers to:
- #27A converter dolly's parking brake:
- #28Why should you not back up with a trailer dolly attached but no rear trailer?
- #29When driving doubles or triples, you should:
- #30Anti-lock braking systems (ABS) on trailers built since March 1998:
- #31The trailer ABS warning lamp is normally located:
- #32When making turns with a tractor-trailer, you should:
- #33When two air lines are crossed at the glad hands:
- #34When the tractor protection valve is in the emergency position, what happens?
- #35The trailer air supply control (red 8-sided knob) is used to:
- #36When you should test that the air brakes work properly between tractor and trailer:
- #37A driver checks for excessive wear on the fifth wheel by:
- #38When parking a trailer with no tractor attached, always:
- #39Which is the proper sequence for shutting down a tractor after parking?
- #40A vehicle with a high center of gravity can roll over at speeds:
- #41What is the minimum tread depth for the steering tires of a heavy truck?
- #42Hydroplaning is more likely to occur:
- #43When you suspect hydroplaning, the safest action is to:
- #44A controlled braking technique is when:
- #45A jackknife occurs when:
About the Combination Vehicles exam
The Combination Vehicles knowledge test is a multiple-choice exam administered at every state CDL testing site. The questions on this page are seeded from the AAMVA Commercial Driver License Manual — the same source that state agencies use when writing their official questions — and from the corresponding sections of Title 49 of the Code of Federal Regulations. Real test questions are randomly selected from a much larger pool, so practice covers the rules and concepts rather than the wording of any one item.
The most efficient way to study is to work through this bank twice. The first pass identifies the rules you do not yet know; the second pass confirms recall. Drivers who have studied for years rarely miss a question, but newcomers should expect to need a week or more of repeated reading and quizzing before sitting the real exam. Combine this site with your state's printed CDL handbook for the most complete preparation.