Kentucky Combination Vehicles CDL Practice Test
Below are 25 exam-style questions for the Kentucky Combination Vehicles CDL knowledge test, modeled on the FMCSA-aligned content used by the Kentucky Transportation Cabinet. Try to answer each question on your own before reading the answer key directly under it. The questions and answer choices are shuffled deterministically per state and endorsement, so the order will stay the same on repeat visits — that lets you genuinely measure your improvement.
- A A wheel bearing fails
- B The tractor brakes lock up
- C The trailer brakes lock up
- D The fifth wheel breaks
- A Tied with rope
- B Released and visible after coupling
- C Locked and the safety latch in place after coupling
- D Removed before driving
- A Only at the destination
- B Before, during, and after coupling
- C Only at the start of the day
- D Every 3 hours
- A Hold the vehicle when parking
- B Test the trailer brakes
- C Apply trailer brakes momentarily
- D Both for parking and to prevent jackknife
- A Drain the wet tank
- B Drive away immediately
- C Charge the trailer brakes by setting the trailer air supply control
- D Pump the brakes 10 times
- A A vehicle length
- B No specific rule
- C Two car lengths
- D One second per 10 feet of vehicle length below 40 mph, plus one extra second above 40 mph
- A A separate compressor
- B Hand valves
- C Sensors at each wheel that release brake pressure when wheel lockup is detected
- D Hydraulic brakes
- A Can be detected during pre-trip inspection by visual and pressure checks
- B Need a mechanic to find
- C Show up only at high speed
- D Are caused by low fuel
- A Leave the engine running with the brakes off
- B Set both tractor and trailer parking brakes
- C Use the trailer hand valve
- D Set only the tractor parking brake
- A Carries electrical signals
- B Drains the wet tank
- C Sends supply air to the trailer reservoirs and controls the trailer emergency brakes
- D Operates the parking brake only
- A Keep the cab close to the curb and swing the front out so following cars cannot squeeze beside you on the right
- B Swing wide to the right first to avoid hitting the curb
- C Swing left then right
- D Stop in the middle of the turn
- A Loose or missing fifth-wheel mounting bolts
- B Cracks in the kingpin
- C All of the above
- D Misalignment between tractor and trailer
- A Use only mirrors
- B Back at full speed
- C Have the dispatcher in the cab
- D GOAL — Get Out And Look — and walk around the trailer first
- A It can damage the cab and the trailer (cab corner crush)
- B It is fine if you are careful
- C It is the standard procedure
- D It is illegal in some states
- A It is shorter than a straight truck
- B Its tires are wider
- C It uses air brakes
- D Its center of gravity is high
- A Either position is fine
- B Loaded last
- C Last
- D First (closest to the tractor)
- A Drain the air tanks
- B Disconnect the electrical line first
- C Lower the trailer landing gear and chock the trailer wheels
- D Honk the horn
- A Brake adjustment levers
- B Coupling devices for connecting tractor air lines to the trailer
- C Electrical connectors
- D Manual transmission shifters
- A Asking a mechanic
- B Pressing the pedal once at startup
- C Listening to the brake light
- D Performing the seven-step air-brake check before each trip
- A Stop traffic by signaling left
- B Stay in the right lane and swing the front of the tractor wide enough to clear the curb without inviting cars to pass on the right
- C Turn from the left lane
- D Use the shoulder
- A Maximum legal height
- B Whatever height it happens to be
- C A height that requires the tractor to drop down to fit
- D A height where the tractor will lift the trailer slightly when backing under
- A Sliding sideways
- B Loss of traction
- C The trailer wheels follow a tighter arc than the tractor wheels in a turn
- D Driving off the road
- A Honk and accelerate
- B Stop on the tracks if traffic ahead slows
- C Cross in a low gear without shifting
- D Shift in the middle of the track
- A The parking brake
- B Both tractor and trailer brakes simultaneously
- C The tractor service brakes only
- D The trailer service brakes only
- A By pushing in the red trailer-air-supply valve
- B By the trailer hand valve
- C By pulling out the red trailer-air-supply valve
- D By setting the red trailer-air-supply valve
Study tips for the Kentucky Combination Vehicles exam
The Combination Vehicles portion of the Kentucky CDL exam is graded out of the bank of questions the Kentucky Transportation Cabinet draws from each year. While the exact bank is not published, every question is sourced from the Combination Vehicles chapter of the Kentucky CDL handbook, which itself is derived from the FMCSA Model Commercial Driver's License Manual. That means studying our practice tests, reading the corresponding handbook chapter, and re-reading the parts you got wrong is genuinely the most efficient route to a first-time pass.
Most successful applicants follow a simple cycle: take the practice test cold, write down every question you missed, open the matching chapter of the official Kentucky handbook, re-read the section that contains the right answer, then re-take the practice test 24 to 48 hours later. The 24-hour delay matters — sleep is when your brain commits new information to long-term memory, and CDL knowledge questions reward that kind of consolidated learning rather than cramming.
Pay particular attention to questions that include qualifier words like always, never, only, primary, or most. CDL test writers love to flip the right answer with a single qualifier. When two answer choices look almost identical, pay attention to the verb (is it must, should, or may?) and to any numbers (14 days, 100 air miles, 8 hours, 70/8 split). On endorsement tests in particular, watch for trick framing where a true statement about a different endorsement is offered as the "correct" answer to a question that is actually about Combination Vehicles.
Test-day logistics matter too. Bring photo ID, your Social Security card or birth certificate, your medical examiner's certificate (DOT card), and proof of state residency if you haven't already submitted those documents. The Kentucky Transportation Cabinet will not let you sit for the knowledge exam without your documentation, and most offices charge an additional fee for re-attempts. Arrive early — the wait at most CDL testing offices runs 30 to 60 minutes — and silence your phone before the exam begins.
Finally, keep your General Knowledge fundamentals sharp even when you're focused on the Combination Vehicles exam. Many states administer multiple knowledge tests in a single sitting, and questions on weight definitions (GVWR, GCWR, GAWR), stopping distance, and the pre-trip inspection routine show up across endorsements. If you're unsure on the basics, sit a fresh Kentucky General Knowledge practice test before scheduling the real exam.
Next steps
Missed more than four questions? Re-read the Combination Vehicles study guide and the matching chapter in the official Kentucky CDL handbook. Then come back and re-take the test. Once you can score 22 of 25 or higher on three runs in a row, you're in good shape to schedule the real exam at your local Kentucky Transportation Cabinet office.
Already comfortable with this endorsement? Drill another: KY General Knowledge · KY Air Brakes · KY Hazardous Materials · KY Passenger · KY School Bus · KY Tank Vehicle · KY Doubles / Triples
New to the CDL process in Kentucky? Read How to apply for a CDL in Kentucky for the document checklist and step-by-step timeline.