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WA · GK (Class A) Endorsement

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.

Heads up: this is a study tool, not a graded exam. Cover the answer with your hand or a sheet of paper for an honest practice run, then re-read the explanations for any questions you missed. Aim for 22 out of 25 or better, three times in a row, before scheduling the real exam.
Question 1 of 25
When backing a trailer, small steering inputs cause:
  • A Small trailer movement
  • B Large trailer angle changes; small inputs are key
  • C Loss of brake pressure
  • D No effect
Correct answer: B
Trailer responds aggressively to small wheel inputs in reverse — back slowly and correct quickly.
Question 2 of 25
The seven-pin connector on a tractor-trailer carries:
  • A Air for the brakes
  • B Hydraulic fluid
  • C Fuel
  • D Electrical power for trailer lights and ABS
Correct answer: D
The seven-pin (or older five-pin) is electrical, supplying lights, brake-light signal, and ABS.
Question 3 of 25
Which is true about coupling order to a trailer?
  • 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
Correct answer: B
Specific orders vary by carrier, but the principle is to charge the trailer brakes before moving and to verify with a brake check.
Question 4 of 25
You should inspect a combination vehicle for:
  • A All of the above
  • B Loose or missing fifth-wheel mounting bolts
  • C Cracks in the kingpin
  • D Misalignment between tractor and trailer
Correct answer: A
All three are pre-trip combination-vehicle items.
Question 5 of 25
When you uncouple a trailer with cargo on it, you should:
  • 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
Correct answer: C
Make sure the gear takes the full weight before pulling out from under.
Question 6 of 25
Trailer wheels with worn brake linings:
  • 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
Correct answer: C
Worn linings are an out-of-service item; replace per manufacturer/federal limits.
Question 7 of 25
A safe combination-vehicle following distance is at least:
  • 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
Correct answer: C
A 60-ft combination needs at least 6 seconds under 40 mph, 7 seconds above 40 mph.
Question 8 of 25
When you make a wide right turn, you should:
  • 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
Correct answer: B
Use only as much room as needed and keep the right side blocked to following vehicles.
Question 9 of 25
Trailer ABS uses:
  • A Sensors at each wheel that release brake pressure when wheel lockup is detected
  • B Hydraulic brakes
  • C Hand valves
  • D A separate compressor
Correct answer: A
Wheel-speed sensors trigger valves to release pressure when lockup is detected.
Question 10 of 25
Combination vehicles are usually harder to drive than single CMVs because:
  • 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
Correct answer: B
All three factors apply. The Combination Vehicles section of the federal manual emphasizes the higher skill needed.
Question 11 of 25
During a brake check before moving, you should look for:
  • A Pulling, sticking, or unusual feel as you apply the brakes
  • B Steering wander only
  • C Engine knocking
  • D Smoke from the cab
Correct answer: A
Low-speed brake test identifies pulling, sticking, or weakness so you don't discover it on the highway.
Question 12 of 25
Sharp turns at low speed will cause:
  • A Wheel damage
  • B Off-tracking — the trailer wheels follow a tighter arc than the tractor
  • C Brake fade
  • D No off-tracking
Correct answer: B
Off-tracking always happens; sharper turns make it worse.
Question 13 of 25
When backing a tractor-trailer, you should:
  • 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
Correct answer: C
Backing to the driver's side gives the best view of the trailer. Always GOAL — Get Out And Look — before and during.
Question 14 of 25
The trailer landing gear (dolly legs) should be:
  • A Lowered to the ground while driving
  • B Fully raised before driving
  • C Always halfway extended
  • D Disconnected before driving
Correct answer: B
Landing gear must be fully raised and the crank handle secured before moving the trailer.
Question 15 of 25
When inspecting the air lines between tractor and trailer, look for:
  • A Cuts, abrasions, and worn seals
  • B Loose lug nuts only
  • C Cargo placement
  • D Engine oil leaks
Correct answer: A
Air-line condition is a typical roadside inspection focus on combinations.
Question 16 of 25
Trailer air supply valves on tractors are typically:
  • A Triangular, green, marked SERVICE
  • B Square, white, marked CHARGE
  • C Octagonal, red, marked TRAILER AIR SUPPLY
  • D Round, blue, marked TRACTOR
Correct answer: C
The trailer air-supply valve is the red, octagonal knob — a federal standard.
Question 17 of 25
Most rear-end collisions caused by combination vehicles result from:
  • A Worn out tires
  • B Engine failure
  • C Driving too fast for conditions and/or too closely
  • D Cargo movement
Correct answer: C
Speed and following distance dominate the causes. Increase cushion and slow down.
Question 18 of 25
Tracking refers to:
  • 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
Correct answer: D
Tracking is how well the trailer follows the tractor; misalignment can indicate suspension or tire problems.
Question 19 of 25
When backing into a dock, you should:
  • 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
Correct answer: D
A walk-around catches obstacles, people, and overhead clearance issues before you back.
Question 20 of 25
The trailer hand valve operates:
  • A Both tractor and trailer brakes simultaneously
  • B The tractor service brakes only
  • C The parking brake
  • D The trailer service brakes only
Correct answer: D
The hand valve applies only the trailer service brakes. It is for testing — not for parking or routine use.
Question 21 of 25
Trailer parking brakes are released:
  • 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
Correct answer: C
Pushing in the red knob charges the trailer brakes and releases the spring brakes.
Question 22 of 25
When uncoupling, after the tractor is clear, you should:
  • 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
Correct answer: D
Verify the trailer is sitting solidly before leaving the area.
Question 23 of 25
Which is true about combination braking?
  • 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
Correct answer: C
Empty trailer wheels lock easily and contribute to jackknife and trailer-swing risks.
Question 24 of 25
Off-tracking means:
  • 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
Correct answer: B
In a right turn, the trailer wheels cut the corner. To compensate, the tractor must swing wider.
Question 25 of 25
When parking a tractor-trailer, you should:
  • 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
Correct answer: C
For full parking, both parking brakes apply.

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.