Oregon Combination Vehicles CDL Practice Test
Below are 25 exam-style questions for the Oregon Combination Vehicles CDL knowledge test, modeled on the FMCSA-aligned content used by the Oregon Driver and Motor Vehicle Services. 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 By pushing in the red trailer-air-supply valve
- B By the trailer hand valve
- C By setting the red trailer-air-supply valve
- D By pulling out the red trailer-air-supply valve
- A Lower the landing gear all the way until firmly on the ground, then a few extra cranks
- B Use blocks instead
- C Leave the gear up
- D Raise the gear partway
- A Nothing will happen
- B The horn will sound
- C The trailer brakes will be locked on
- D You will notice immediately because trailer brakes will not work properly
- A Loaded last
- B Last
- C Either position is fine
- D First (closest to the tractor)
- A The fifth wheel disengages
- B The drive wheels lose traction and the tractor begins to slide
- C The tractor parking brake fails
- D The trailer is too heavy
- A The parking brake
- B Both tractor and trailer brakes simultaneously
- C The tractor service brakes only
- D The trailer service brakes only
- A Released and visible after coupling
- B Removed before driving
- C Locked and the safety latch in place after coupling
- D Tied with rope
- 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 Engine failure
- B Driving too fast for conditions and/or too closely
- C Worn out tires
- D Cargo movement
- A Lower the trailer landing gear and chock the trailer wheels
- B Drain the air tanks
- C Honk the horn
- D Disconnect the electrical line first
- A A height that requires the tractor to drop down to fit
- B Whatever height it happens to be
- C Maximum legal height
- D A height where the tractor will lift the trailer slightly when backing under
- A A wheel bearing fails
- B The tractor brakes lock up
- C The fifth wheel breaks
- D The trailer brakes lock up
- A Pull tractor away first, then disconnect lines
- B Lower landing gear, disconnect lines, release fifth wheel, pull tractor away
- C Release fifth wheel first, then connect lines
- D No specific order is required
- A All of the above
- B Loose or missing fifth-wheel mounting bolts
- C Misalignment between tractor and trailer
- D Cracks in the kingpin
- A The fuel mileage
- B Lane positioning at intersections
- C Cargo placement
- D The trailer following the same path as the tractor in a straight line
- A Apply trailer brakes momentarily
- B Test the trailer brakes
- C Both for parking and to prevent jackknife
- D Hold the vehicle when parking
- A Back without using mirrors
- B Back to the left whenever possible because you can see better
- C Always back to the right
- D Back as fast as practical
- A No specific rule
- B Two car lengths
- C A vehicle length
- D One second per 10 feet of vehicle length below 40 mph, plus one extra second above 40 mph
- A Hydraulic fluid
- B Electrical power for trailer lights and ABS
- C Fuel
- D Air for the brakes
- A The drive wheels lock and the trailer pushes the tractor sideways
- B You are driving slowly
- C The trailer wheels lock briefly
- D The brakes are released gently
- A Lose engine power
- B Spin out
- C Stop suddenly
- D Roll over before sliding
- A May actually take longer to stop because brakes are designed for the loaded weight
- B Stops faster than when loaded
- C Stops only with parking brake
- D Stops in the same distance
- A A separate compressor
- B Hydraulic brakes
- C Hand valves
- D Sensors at each wheel that release brake pressure when wheel lockup is detected
- A Drain the wet tank
- B Pump the brakes 10 times
- C Drive away immediately
- D Charge the trailer brakes by setting the trailer air supply control
- A Failure to grease
- B Backing too fast
- C All of the above
- D Coupling with the trailer too high
Study tips for the Oregon Combination Vehicles exam
The Combination Vehicles portion of the Oregon CDL exam is graded out of the bank of questions the Oregon Driver and Motor Vehicle Services draws from each year. While the exact bank is not published, every question is sourced from the Combination Vehicles chapter of the Oregon 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 Oregon 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 Oregon Driver and Motor Vehicle Services 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 Oregon 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 Oregon 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 Oregon Driver and Motor Vehicle Services office.
Already comfortable with this endorsement? Drill another: OR General Knowledge · OR Air Brakes · OR Hazardous Materials · OR Passenger · OR School Bus · OR Tank Vehicle · OR Doubles / Triples
New to the CDL process in Oregon? Read How to apply for a CDL in Oregon for the document checklist and step-by-step timeline.