Washington Combination Vehicles CDL Practice Test
Below are 25 exam-style questions for the Washington Combination Vehicles CDL knowledge test, modeled on the FMCSA-aligned content used by the Washington State Department of Licensing. 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 Small trailer movement
- B Large trailer angle changes; small inputs are key
- C Loss of brake pressure
- D No effect
- A Air for the brakes
- B Hydraulic fluid
- C Fuel
- D Electrical power for trailer lights and ABS
- A Connect electrical first, then air
- B Connect air emergency line first, then service line, then electrical (or per company policy) — verify with brake check
- C Connect only air; electrical is optional
- D Connect any line first; order doesn't matter
- A All of the above
- B Loose or missing fifth-wheel mounting bolts
- C Cracks in the kingpin
- D Misalignment between tractor and trailer
- A Leave the gear up
- B Raise the gear partway
- C Lower the landing gear all the way until firmly on the ground, then a few extra cranks
- D Use blocks instead
- A Are normal until the lining is gone
- B Make the truck quieter
- C Should be replaced when worn beyond manufacturer specs
- D Only need attention every 5 years
- A A vehicle length
- B No specific rule
- C One second per 10 feet of vehicle length below 40 mph, plus one extra second above 40 mph
- D Two car lengths
- A Turn from the left lane
- 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 Use the shoulder
- D Stop traffic by signaling left
- A Sensors at each wheel that release brake pressure when wheel lockup is detected
- B Hydraulic brakes
- C Hand valves
- D A separate compressor
- A They are heavier and longer
- B All of the above
- C They take more skill to back, couple, and uncouple
- D They have a higher rollover risk
- A Pulling, sticking, or unusual feel as you apply the brakes
- B Steering wander only
- C Engine knocking
- D Smoke from the cab
- A Wheel damage
- B Off-tracking — the trailer wheels follow a tighter arc than the tractor
- C Brake fade
- D No off-tracking
- A Back as fast as practical
- B Always back to the right
- C Back to the left whenever possible because you can see better
- D Back without using mirrors
- A Lowered to the ground while driving
- B Fully raised before driving
- C Always halfway extended
- D Disconnected before driving
- A Cuts, abrasions, and worn seals
- B Loose lug nuts only
- C Cargo placement
- D Engine oil leaks
- A Triangular, green, marked SERVICE
- B Square, white, marked CHARGE
- C Octagonal, red, marked TRAILER AIR SUPPLY
- D Round, blue, marked TRACTOR
- A Worn out tires
- B Engine failure
- C Driving too fast for conditions and/or too closely
- D Cargo movement
- A Lane positioning at intersections
- B The fuel mileage
- C Cargo placement
- D The trailer following the same path as the tractor in a straight line
- A Back at full speed
- B Have the dispatcher in the cab
- C Use only mirrors
- D GOAL — Get Out And Look — and walk around the trailer first
- A Both tractor and trailer brakes simultaneously
- B The tractor service brakes only
- C The parking brake
- D The trailer service brakes only
- A By the trailer hand valve
- B By setting the red trailer-air-supply valve
- C By pushing in the red trailer-air-supply valve
- D By pulling out the red trailer-air-supply valve
- A Connect the lines back to the tractor
- B Disable the trailer parking brake
- C Move the tractor far away immediately without checking
- D Check that the trailer is stable on its landing gear
- A Brake balance is irrelevant
- B Drive wheels never lock
- C Trailer wheels lock more often than drive wheels in panic stops
- D ABS prevents jackknife in all cases
- A Sliding sideways
- B The trailer wheels follow a tighter arc than the tractor wheels in a turn
- C Driving off the road
- D Loss of traction
- A Leave the engine running with the brakes off
- B Use the trailer hand valve
- C Set both tractor and trailer parking brakes
- D Set only the tractor parking brake
Study tips for the Washington Combination Vehicles exam
The Combination Vehicles portion of the Washington CDL exam is graded out of the bank of questions the Washington State Department of Licensing draws from each year. While the exact bank is not published, every question is sourced from the Combination Vehicles chapter of the Washington 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 Washington 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 Washington State Department of Licensing 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 Washington 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 Washington 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 Washington State Department of Licensing office.
Already comfortable with this endorsement? Drill another: WA General Knowledge · WA Air Brakes · WA Hazardous Materials · WA Passenger · WA School Bus · WA Tank Vehicle · WA Doubles / Triples
New to the CDL process in Washington? Read How to apply for a CDL in Washington for the document checklist and step-by-step timeline.