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Washington combination-vehicle practice

Selected knowledge practice, not a complete licensing course or practical training.

Washington Combination Vehicles — Full question set

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Question 1 of 60
  1. 1. When planning a trailer load, which arrangement helps reduce rollover risk?
  2. 2. A loaded trailer leans noticeably to one side before departure. Why is this a warning?
  3. 3. What is the danger of a sudden lane change while pulling several trailers?
  4. 4. Which driving habit helps avoid a last-second swerve with a long combination?
  5. 5. You are driving a tractor without a semitrailer. What does the guide caution about this bobtail configuration?
  6. 6. Which trailer feature requires particular care at a raised railroad crossing?
  7. 7. After hard braking, what observation may give the earliest warning that a trailer is starting to skid?
  8. 8. A trailer has begun sliding because its wheels locked during braking. Why should you not use the trailer hand valve to straighten it?
  9. 9. In a slow, tight turn, the trailer's rear wheels pass inside the path of the tractor's front wheels. What is this called?
  10. 10. When several trailers make a slow, tight corner, which rear wheels generally cut farthest inside?
  11. 11. Why should a combination driver avoid swinging left before beginning a right turn?
  12. 12. From a straight tractor-semitrailer alignment, you want the trailer's rear to begin moving left while backing. Which initial steering action produces that movement?
  13. 13. While backing slowly, the trailer starts drifting right of the intended path. What steering correction does the guide describe?
  14. 14. When positioning a tractor-semitrailer for a backing maneuver, which path should you try to arrange first?
  15. 15. During a trailer backing maneuver, neither mirror gives you enough certainty about a nearby obstacle. What should you do?
  16. 16. What is the appropriate purpose of the trailer hand valve described in the guide?
  17. 17. During normal driving of an air-braked combination, which control applies the service brakes throughout the combination?
  18. 18. Why is the trailer hand valve unsuitable for holding a parked trailer without spring brakes?
  19. 19. A trailer air hose breaks or the trailer separates. What is the tractor protection valve intended to protect?
  20. 20. On a combination with the usual red, eight-sided trailer air-supply knob, what does pushing it in do?
  21. 21. What information does the trailer service air line carry?
  22. 22. Which two functions belong to the trailer emergency, or supply, air line?
  23. 23. When a service-line signal asks for trailer braking, where does the relay valve obtain the air it sends to the brake chambers?
  24. 24. A coupling setup uses conventional red and blue air-line identification. Which pairing is correct?
  25. 25. Before joining tractor and trailer glad hands, what should be checked and cleaned?
  26. 26. After coupling, a spring-braked trailer's brakes will not release when air is supplied. Which connection error should be checked?
  27. 27. An older trailer without spring brakes rolls freely after coupling. Does that prove its air lines are correctly connected?
  28. 28. Why should unused air hoses be attached to their provided dummy couplers?
  29. 29. A rig has more than one trailer. During normal operation, which air-line shut-off valves should be closed?
  30. 30. Why must a parked trailer without spring brakes be secured with wheel chocks?
  31. 31. Why might a major leak in a trailer service line become obvious only when you apply the brakes?
  32. 32. Where does the guide place the yellow ABS malfunction lamp on an ABS-equipped trailer?
  33. 33. What does ABS not justify when driving a tractor-trailer?
  34. 34. A combination has ABS only on the trailer. The tractor starts jackknifing during braking. What does the guide advise if it can be done safely?
  35. 35. Before using coupling instructions on an unfamiliar tractor-trailer, what must you establish?
  36. 36. The fifth wheel uses a design that requires lubrication. What belongs in its inspection?
  37. 37. Why should a tractor be directly in front of a semitrailer before backing under it?
  38. 38. A semitrailer is set too high before fifth-wheel coupling. What can happen?
  39. 39. In the guide's tractor-semitrailer sequence, how are the trailer brakes set before the tractor backs underneath to lock the kingpin?
  40. 40. A gentle pull test appears to show the trailer is attached. What must still be done before driving?
  41. 41. After coupling, you can see a gap between the trailer apron and the fifth-wheel skid plate. Is the connection ready for travel?
  42. 42. Where should conventional fifth-wheel locking jaws close around the kingpin?
  43. 43. Before traveling with a coupled semitrailer, what landing-gear condition should you confirm?
  44. 44. With the trailer's full weight on the tractor, which clearance needs checking?
  45. 45. Before uncoupling a semitrailer, what should you establish about the parking surface?
  46. 46. In the described uncoupling procedure, why is the tractor gently backed against the kingpin with the trailer brakes locked?
  47. 47. Before uncoupling, you are not sure whether the trailer has spring brakes. What does the guide require for wheel security?
  48. 48. For a loaded semitrailer, what is the aim of the few extra low-gear crank turns after the landing gear contacts firm ground?
  49. 49. When uncoupling, why should the disconnected electrical cable be supported with its plug pointing down?
  50. 50. During uncoupling, why stop with the tractor frame still under the trailer after the fifth wheel clears?
  51. 51. After the partial pull-out and securing the tractor, what should you check before pulling fully clear?
  52. 52. A pintle hook has a missing mounting bolt and visible movement at its bracket. How should this be treated?
  53. 53. What must be true of an equipped sliding fifth wheel's locking pins before travel?
  54. 54. The test vehicle uses a coupling system different from a fifth wheel or pintle hook. What does the supplement expect you to do?
  55. 55. Which finding on a pintle-hook trailer's drawbar ring or tongue requires attention?
  56. 56. For a non-fifth-wheel combination fitted with safety chains, what arrangement does the updated inspection supplement call for?
  57. 57. A trailer is fitted with a breakaway cable. What must be checked before departure?
  58. 58. A Washington ball-and-coupler trailer within the 10,000-pound-or-less scope of WAC 204-70 uses safety chains. May they be attached to its readily removable ball mount?
  59. 59. On a ball-and-coupler trailer covered by Washington's 10,000-pound-or-less towing rule, a safety-chain link is cracked. What is required?
  60. 60. For a Washington ball-and-coupler trailer within WAC 204-70's 10,000-pound-or-less scope, how must its tongue load on level ground compare with the hitch manufacturer's limit?
Review all 60 questions with answers

  1. When planning a trailer load, which arrangement helps reduce rollover risk?

    Correct answer: Keep the load low and centered across the trailer

    A lower, centered load reduces the tendency to tip. Load distribution does not remove the need to slow before curves.

    Source: Washington Commercial Driver Guide, N/10/20; section 6.1.1, physical PDF 89, printed 6-1. ↗

  2. A loaded trailer leans noticeably to one side before departure. Why is this a warning?

    Correct answer: An off-center load makes rollover more likely

    The guide warns against a load that makes the trailer lean. Correct load distribution and investigate the cause before driving.

    Source: Washington Commercial Driver Guide, N/10/20; section 6.1.1, physical PDF 89, printed 6-1. ↗

  3. What is the danger of a sudden lane change while pulling several trailers?

    Correct answer: The rearward whipping motion can overturn a trailer

    Abrupt steering can produce a crack-the-whip effect that grows toward the rear. This is a reason to steer smoothly, not a fixed rollover probability for every rig.

    Source: Washington Commercial Driver Guide, N/10/20; section 6.1.2, physical PDF 89, printed 6-1. ↗

  4. Which driving habit helps avoid a last-second swerve with a long combination?

    Correct answer: Look well ahead and leave room for gradual corrections

    A long view and adequate following space give time for controlled braking or gentle steering. Sudden corrections can destabilize a trailer.

    Source: Washington Commercial Driver Guide, N/10/20; section 6.1.2, physical PDF 89, printed 6-1. ↗

  5. You are driving a tractor without a semitrailer. What does the guide caution about this bobtail configuration?

    Correct answer: It can be difficult to stop smoothly, so allow ample space

    A bobtail tractor handles and brakes differently from a loaded combination. Do not assume that less total weight guarantees an easy, short stop.

    Source: Washington Commercial Driver Guide, N/10/20; section 6.1.3, physical PDF 89, printed 6-1. ↗

  6. Which trailer feature requires particular care at a raised railroad crossing?

    Correct answer: Low clearance under the trailer or its landing gear

    Low-slung equipment can hang up on a raised crossing. Assess clearance before entering rather than trying to power through a possible grounding point.

    Source: Washington Commercial Driver Guide, N/10/20; section 6.1.4, physical PDF 90, printed 6-2. ↗

  7. After hard braking, what observation may give the earliest warning that a trailer is starting to skid?

    Correct answer: Its position begins changing unexpectedly in the mirrors

    Check trailer alignment in the mirrors when braking hard. Waiting until it has swung far out of its lane makes recovery much harder.

    Source: Washington Commercial Driver Guide, N/10/20; section 6.1.5, physical PDF 90, printed 6-2. ↗

  8. A trailer has begun sliding because its wheels locked during braking. Why should you not use the trailer hand valve to straighten it?

    Correct answer: More trailer braking can keep the wheels sliding instead of restoring traction

    The guide says to release the braking that caused the trailer wheels to lock so they can regain traction. The trailer hand valve is not a device for pulling a skidding trailer straight.

    Source: Washington Commercial Driver Guide, N/10/20; section 6.1.5, physical PDF 91, printed 6-3. ↗

  9. In a slow, tight turn, the trailer's rear wheels pass inside the path of the tractor's front wheels. What is this called?

    Correct answer: Off-tracking

    Off-tracking means rear wheels follow a different, inner path around a corner. Plan the turn to keep those wheels clear of curbs and people.

    Source: Washington Commercial Driver Guide, N/10/20; section 6.1.6, physical PDF 91, printed 6-3. ↗

  10. When several trailers make a slow, tight corner, which rear wheels generally cut farthest inside?

    Correct answer: Those on the last trailer

    Each following unit adds to the off-tracking in this kind of turn. The last trailer needs attention even when the tractor has cleared the corner.

    Source: Washington Commercial Driver Guide, N/10/20; section 6.1.6, physical PDF 91, printed 6-3. ↗

  11. Why should a combination driver avoid swinging left before beginning a right turn?

    Correct answer: It can invite a vehicle into the space along the rig's right side

    An initial left swing can open a tempting gap on the right. Plan enough turning room without inviting another road user into the trailer's swept path.

    Source: Washington Commercial Driver Guide, N/10/20; section 6.1.6, physical PDF 91, printed 6-3. ↗

  12. From a straight tractor-semitrailer alignment, you want the trailer's rear to begin moving left while backing. Which initial steering action produces that movement?

    Correct answer: Turn the top of the steering wheel to the right

    To start a trailer backing turn, the steering input is opposite the desired direction of the trailer's rear. Follow and correct the trailer with subsequent small inputs under proper instruction.

    Source: Washington Commercial Driver Guide, N/10/20; section 6.1.7, physical PDF 91, printed 6-3. ↗

  13. While backing slowly, the trailer starts drifting right of the intended path. What steering correction does the guide describe?

    Correct answer: Turn the top of the steering wheel toward the right-hand drift

    The guide says to correct drift as soon as it develops by steering toward it. Back slowly and pull forward to reposition when necessary.

    Source: Washington Commercial Driver Guide, N/10/20; section 6.1.7, physical PDF 92, printed 6-4. ↗

  14. When positioning a tractor-semitrailer for a backing maneuver, which path should you try to arrange first?

    Correct answer: A straight backing path

    A straight path is preferred. When a curve is unavoidable, backing toward the driver's side improves visibility.

    Source: Washington Commercial Driver Guide, N/10/20; section 6.1.7, physical PDF 91, printed 6-3. ↗

  15. During a trailer backing maneuver, neither mirror gives you enough certainty about a nearby obstacle. What should you do?

    Correct answer: Stop, secure the vehicle and get out to check the path

    Mirrors are important, but uncertainty calls for stopping and rechecking the travel path and clearances. Do not continue backing into an area you cannot judge safely.

    Source: Washington Commercial Driver Guide, N/10/20; section 6.1.7, physical PDF 92, printed 6-4. ↗

  16. What is the appropriate purpose of the trailer hand valve described in the guide?

    Correct answer: Testing trailer-brake operation

    The hand valve applies trailer brakes alone and is used for testing. Using it for ordinary driving can cause a trailer skid.

    Source: Washington Commercial Driver Guide, N/10/20; section 6.2.1, physical PDF 92, printed 6-4. ↗

  17. During normal driving of an air-braked combination, which control applies the service brakes throughout the combination?

    Correct answer: The foot brake

    The foot brake sends the braking signal to the tractor and trailer service brakes. Trailer-only hand-valve application is not the normal driving method.

    Source: Washington Commercial Driver Guide, N/10/20; section 6.2.1, physical PDF 92, printed 6-4. ↗

  18. Why is the trailer hand valve unsuitable for holding a parked trailer without spring brakes?

    Correct answer: Stored air can leak away and release the brakes

    A hand-valve application depends on air remaining in the system. A trailer without spring parking brakes needs secure wheel chocking, not reliance on air that can leak away.

    Source: Washington Commercial Driver Guide, N/10/20; section 6.2.1, physical PDF 92, printed 6-4. ↗

  19. A trailer air hose breaks or the trailer separates. What is the tractor protection valve intended to protect?

    Correct answer: The tractor's remaining brake-air supply

    The protection valve closes off escaping air so a trailer failure does not drain the tractor's system. It must work correctly to perform that protective function.

    Source: Washington Commercial Driver Guide, N/10/20; section 6.2.2, physical PDF 93, printed 6-5. ↗

  20. On a combination with the usual red, eight-sided trailer air-supply knob, what does pushing it in do?

    Correct answer: Supplies air to the trailer system

    Pushing in supplies trailer air; pulling out shuts that supply off and commands emergency braking in the described system. Know the controls fitted to your actual vehicle.

    Source: Washington Commercial Driver Guide, N/10/20; section 6.2.3, physical PDF 93, printed 6-5. ↗

  21. What information does the trailer service air line carry?

    Correct answer: The requested braking application from the foot brake or hand valve

    Service-line pressure signals how strongly the trailer brakes should apply. It is a different role from the emergency/supply line charging the reservoirs.

    Source: Washington Commercial Driver Guide, N/10/20; section 6.2.4, physical PDF 93, printed 6-5. ↗

  22. Which two functions belong to the trailer emergency, or supply, air line?

    Correct answer: Charging trailer tanks and controlling emergency brake operation

    The supply line charges the trailer reservoirs. A loss of its pressure also triggers the trailer emergency-brake function in the system described.

    Source: Washington Commercial Driver Guide, N/10/20; section 6.2.4, physical PDF 93, printed 6-5. ↗

  23. When a service-line signal asks for trailer braking, where does the relay valve obtain the air it sends to the brake chambers?

    Correct answer: From the trailer's air reservoirs

    The service line supplies the command; the trailer reservoir supplies the braking air through the relay valve. This arrangement supports quicker application.

    Source: Washington Commercial Driver Guide, N/10/20; section 6.2.6, physical PDF 94, printed 6-6. ↗

  24. A coupling setup uses conventional red and blue air-line identification. Which pairing is correct?

    Correct answer: Blue for service and red for emergency/supply

    These colors help identify service and supply lines, but also check their labels and actual connections. Do not assume two lines are interchangeable.

    Source: Washington Commercial Driver Guide, N/10/20; section 6.2.5, physical PDF 93, printed 6-5. ↗

  25. Before joining tractor and trailer glad hands, what should be checked and cleaned?

    Correct answer: The couplers and their rubber sealing surfaces

    Clean, sound sealing surfaces help keep the connection airtight and prevent contamination from entering the brake-air system.

    Source: Washington Commercial Driver Guide, N/10/20; section 6.2.5, physical PDF 93, printed 6-5. ↗

  26. After coupling, a spring-braked trailer's brakes will not release when air is supplied. Which connection error should be checked?

    Correct answer: The service and emergency air lines may be crossed

    Crossed lines can send supply air into the service connection instead of charging the trailer tanks needed to release the spring brakes. Verify the connections and the complete brake check.

    Source: Washington Commercial Driver Guide, N/10/20; section 6.2.5, physical PDF 94, printed 6-6. ↗

  27. An older trailer without spring brakes rolls freely after coupling. Does that prove its air lines are correctly connected?

    Correct answer: No; crossed lines can still leave it rolling without working trailer brakes

    With no spring brakes and an empty reservoir, an older trailer may roll despite having no effective trailer braking. Test the brakes before driving.

    Source: Washington Commercial Driver Guide, N/10/20; section 6.2.5, physical PDF 94, printed 6-6. ↗

  28. Why should unused air hoses be attached to their provided dummy couplers?

    Correct answer: To keep dirt and moisture out of the lines

    Dummy couplers protect unused connections against contamination. They are not a substitute for working brake components.

    Source: Washington Commercial Driver Guide, N/10/20; section 6.2.5, physical PDF 94, printed 6-6. ↗

  29. A rig has more than one trailer. During normal operation, which air-line shut-off valves should be closed?

    Correct answer: Those at the back of the last trailer

    Intermediate valves stay open to supply following units. The valves at the very rear of the final trailer stay closed so air does not escape.

    Source: Washington Commercial Driver Guide, N/10/20; section 6.2.7, physical PDF 94, printed 6-6. ↗

  30. Why must a parked trailer without spring brakes be secured with wheel chocks?

    Correct answer: Its reservoir air can leak away until the brakes no longer hold

    Some older trailer emergency systems depend on stored air, which can eventually escape. Chocks prevent a rollaway when that air-dependent holding force is lost.

    Source: Washington Commercial Driver Guide, N/10/20; section 6.2.8, physical PDF 94, printed 6-6. ↗

  31. Why might a major leak in a trailer service line become obvious only when you apply the brakes?

    Correct answer: The service line is pressurized during a brake application

    A service-line leak may not show itself until braking sends air into that line. Air loss can then reduce system pressure rapidly.

    Source: Washington Commercial Driver Guide, N/10/20; section 6.2.8, physical PDF 94, printed 6-6. ↗

  32. Where does the guide place the yellow ABS malfunction lamp on an ABS-equipped trailer?

    Correct answer: On the left side, near a front or rear corner

    The guide identifies a left-side trailer lamp. Check the correct lamp and the system's specified startup behavior; a lamp is not proof that all equipment is fault-free.

    Source: Washington Commercial Driver Guide, N/10/20; section 6.3.1, physical PDF 95, printed 6-7. ↗

  33. What does ABS not justify when driving a tractor-trailer?

    Correct answer: Following closer or entering a curve faster

    ABS helps control wheel lockup but does not remove traction limits or rollover risk. Continue to leave space and choose a safe speed.

    Source: Washington Commercial Driver Guide, N/10/20; section 6.3.2, physical PDF 95, printed 6-7. ↗

  34. A combination has ABS only on the trailer. The tractor starts jackknifing during braking. What does the guide advise if it can be done safely?

    Correct answer: Ease off the brakes until tractor control returns

    Trailer ABS does not provide ABS control to the tractor. The guide calls for easing braking when safe to regain tractor control; equipment coverage matters.

    Source: Washington Commercial Driver Guide, N/10/20; section 6.3.1, physical PDF 95, printed 6-7. ↗

  35. Before using coupling instructions on an unfamiliar tractor-trailer, what must you establish?

    Correct answer: The correct procedure for that vehicle's coupling equipment

    Coupling systems and individual rigs differ. General knowledge supports, but does not replace, training and the manufacturer's equipment-specific procedure.

    Source: Washington Commercial Driver Guide, N/10/20; section 6.4, physical PDF 95, printed 6-7. ↗

  36. The fifth wheel uses a design that requires lubrication. What belongs in its inspection?

    Correct answer: Secure mounting, sound condition and the required lubrication

    The updated supplement checks the skid plate's mounting, cracks, breaks, excessive wear and lubrication where applicable. Some designs have different lubrication requirements.

    Source: Washington Commercial Driver Guide Supplement, September 9, 2022; 11M.6.1, Fifth Wheel Skid Plate, physical PDF 12, printed 11M-9. ↗

  37. Why should a tractor be directly in front of a semitrailer before backing under it?

    Correct answer: An angled approach can push the trailer sideways and damage its landing gear

    The guide warns against backing underneath at an angle. Correct initial alignment avoids side-loading the supported trailer.

    Source: Washington Commercial Driver Guide, N/10/20; section 6.4.1, step 3, physical PDF 96, printed 6-8. ↗

  38. A semitrailer is set too high before fifth-wheel coupling. What can happen?

    Correct answer: The kingpin may fail to couple correctly

    For the procedure described, the tractor should slightly raise the trailer as it backs under. Excessive trailer height can produce an unsafe or missed connection.

    Source: Washington Commercial Driver Guide, N/10/20; section 6.4.1, step 6, physical PDF 96, printed 6-8. ↗

  39. In the guide's tractor-semitrailer sequence, how are the trailer brakes set before the tractor backs underneath to lock the kingpin?

    Correct answer: The trailer brakes are locked

    The sequence locks the trailer brakes before slow backing in low reverse. Follow the complete procedure, including proper height, alignment and wheel security.

    Source: Washington Commercial Driver Guide, N/10/20; section 6.4.1, steps 9–10, physical PDF 96, printed 6-8. ↗

  40. A gentle pull test appears to show the trailer is attached. What must still be done before driving?

    Correct answer: Secure the vehicle and inspect that the coupling is correctly locked

    The guide follows the gentle pull test with a secured visual inspection. Resistance to a pull alone does not establish that the jaws and locking devices are correctly seated.

    Source: Washington Commercial Driver Guide, N/10/20; section 6.4.1, steps 11–13, physical PDF 96, printed 6-8. ↗

  41. After coupling, you can see a gap between the trailer apron and the fifth-wheel skid plate. Is the connection ready for travel?

    Correct answer: No; the trailer must sit flat with no gap

    The supplement requires the apron to lie flat on the skid plate. A gap can signal an incorrect connection and must be resolved before driving.

    Source: Washington Commercial Driver Guide Supplement, September 9, 2022; 11M.6.1, Kingpin, Apron & Gap, physical PDF 12, printed 11M-9. ↗

  42. Where should conventional fifth-wheel locking jaws close around the kingpin?

    Correct answer: Around its shank, not its lower head

    The guide's labeled kingpin diagram distinguishes the shank from the head. The jaws must be correctly engaged around the shank.

    Source: Washington Commercial Driver Guide, N/10/20; section 6.5.1, physical PDF 101, printed 6-13. ↗

  43. Before traveling with a coupled semitrailer, what landing-gear condition should you confirm?

    Correct answer: Fully raised, undamaged and with the crank handle secured

    The gear must be fully raised so it cannot catch road features, and the crank must not swing into traffic. Inspect the supports and pads for damage as well.

    Source: Washington Commercial Driver Guide Supplement, September 9, 2022; 11M.6.2, Landing Gear & Clearance, physical PDF 13, printed 11M-10. ↗

  44. With the trailer's full weight on the tractor, which clearance needs checking?

    Correct answer: Space between the tractor frame and landing gear during turns

    Check that the tractor frame cannot strike the landing gear and that tire-to-trailer clearance is adequate. The final loaded position matters.

    Source: Washington Commercial Driver Guide, N/10/20; section 6.4.1, step 15, physical PDF 97, printed 6-9. ↗

  45. Before uncoupling a semitrailer, what should you establish about the parking surface?

    Correct answer: It can support the trailer's weight on its landing gear

    The trailer's support load will transfer to the landing gear and ground. An unsuitable surface can allow the gear to sink or the trailer to fall.

    Source: Washington Commercial Driver Guide, N/10/20; section 6.4.2, step 1, physical PDF 97, printed 6-9. ↗

  46. In the described uncoupling procedure, why is the tractor gently backed against the kingpin with the trailer brakes locked?

    Correct answer: To ease pressure on the fifth-wheel locking jaws

    Easing the load on the jaws makes the release easier. This is a controlled part of the complete secured uncoupling sequence, not permission to ram the trailer.

    Source: Washington Commercial Driver Guide, N/10/20; section 6.4.2, step 2, physical PDF 97, printed 6-9. ↗

  47. Before uncoupling, you are not sure whether the trailer has spring brakes. What does the guide require for wheel security?

    Correct answer: Chock the trailer wheels

    If spring brakes are absent or their presence is uncertain, use chocks. Stored air can escape and release an air-dependent holding brake.

    Source: Washington Commercial Driver Guide, N/10/20; section 6.4.2, step 3, physical PDF 97, printed 6-9. ↗

  48. For a loaded semitrailer, what is the aim of the few extra low-gear crank turns after the landing gear contacts firm ground?

    Correct answer: Take some weight off the tractor without lifting the trailer off the fifth wheel

    The guide calls for relieving some tractor load, not lifting the trailer off the fifth wheel. Use the specified procedure for the actual landing gear.

    Source: Washington Commercial Driver Guide, N/10/20; section 6.4.2, step 4, physical PDF 97, printed 6-9. ↗

  49. When uncoupling, why should the disconnected electrical cable be supported with its plug pointing down?

    Correct answer: To help keep moisture out and prevent cable damage

    The guide calls for a downward-facing plug and properly supported lines. Protection against moisture and damage helps maintain a reliable future connection.

    Source: Washington Commercial Driver Guide, N/10/20; section 6.4.2, step 5, physical PDF 97, printed 6-9. ↗

  50. During uncoupling, why stop with the tractor frame still under the trailer after the fifth wheel clears?

    Correct answer: The frame can keep the trailer from falling far if its support fails

    The partial pull-out provides a safety margin if the landing gear sinks or collapses. Secure the tractor and inspect the supports before clearing the trailer completely.

    Source: Washington Commercial Driver Guide, N/10/20; section 6.4.2, step 7, physical PDF 97, printed 6-9. ↗

  51. After the partial pull-out and securing the tractor, what should you check before pulling fully clear?

    Correct answer: That the ground supports the trailer and the landing gear is sound

    The remaining steps include inspecting the trailer's support and landing gear before final movement. Do not leave a trailer resting on an unstable support.

    Source: Washington Commercial Driver Guide, N/10/20; section 6.4.2, steps 8–10, physical PDF 98, printed 6-10. ↗

  52. A pintle hook has a missing mounting bolt and visible movement at its bracket. How should this be treated?

    Correct answer: As an unsafe coupling defect that needs correction

    The updated inspection checks secure mounting and missing or loose parts. A sound ring does not compensate for a loose pintle-hook assembly.

    Source: Washington Commercial Driver Guide Supplement, September 9, 2022; 11M.6.1, Pintle Hook, physical PDF 12, printed 11M-9. ↗

  53. What must be true of an equipped sliding fifth wheel's locking pins before travel?

    Correct answer: They are undamaged and fully engaged

    The supplement specifically checks the sliding pins for damage and full engagement. The slide must not move unexpectedly under load.

    Source: Washington Commercial Driver Guide Supplement, September 9, 2022; 11M.6.1, Locking and Safety Devices, physical PDF 13, printed 11M-10. ↗

  54. The test vehicle uses a coupling system different from a fifth wheel or pintle hook. What does the supplement expect you to do?

    Correct answer: Explain how that system works and what you inspect

    The inspection is based on the equipment actually fitted. You must explain its operation and the safety-critical condition checks.

    Source: Washington Commercial Driver Guide Supplement, September 9, 2022; 11M.6.1, All Other Types of Combinations, physical PDF 12, printed 11M-9. ↗

  55. Which finding on a pintle-hook trailer's drawbar ring or tongue requires attention?

    Correct answer: A crack, broken weld or unsecured ring attachment

    The supplement calls for checking the ring, its attachment and the tongue for damage, wear and insecure parts. Their integrity is essential to retaining the trailer.

    Source: Washington Commercial Driver Guide Supplement, September 9, 2022; 11M.6.1, Trailer Drawbar Ring & Tongue, physical PDF 12, printed 11M-9. ↗

  56. For a non-fifth-wheel combination fitted with safety chains, what arrangement does the updated inspection supplement call for?

    Correct answer: Secure, crossed chains without kinks or excessive slack

    The supplement checks secure, crossed chains or cables with no kinks or excessive slack. Their attachment and capacity must also suit the actual equipment and applicable rules.

    Source: Washington Commercial Driver Guide Supplement, September 9, 2022; 11M.6.1, All Other Coupling Systems, physical PDF 13, printed 11M-10. ↗

  57. A trailer is fitted with a breakaway cable. What must be checked before departure?

    Correct answer: That the breakaway cable is engaged as required

    The supplement requires breakaway cables to be engaged. This safety connection does not replace the primary coupling or its locking devices.

    Source: Washington Commercial Driver Guide Supplement, September 9, 2022; 11M.6.1, All Other Coupling Systems, physical PDF 13, printed 11M-10. ↗

  58. A Washington ball-and-coupler trailer within the 10,000-pound-or-less scope of WAC 204-70 uses safety chains. May they be attached to its readily removable ball mount?

    Correct answer: No; that removable ball mount is not an allowed chain attachment

    Within this rule's scope, safety chains must not attach to the hitch ball or a readily removable ball mount, and their attachment must not share the ball or coupling fasteners.

    Source: Washington Administrative Code 204-70-070(2)(b), (4)(d); scope 204-70-020/-030; current text reviewed September 13, 2026. ↗

  59. On a ball-and-coupler trailer covered by Washington's 10,000-pound-or-less towing rule, a safety-chain link is cracked. What is required?

    Correct answer: Replace the defective chain immediately

    The rule requires immediate replacement of cut, cracked or excessively worn chain links and bars post-manufacture welding repairs. Do not rely on a repaired defective link.

    Source: Washington Administrative Code 204-70-070(3), (4)(c); scope 204-70-020/-030; current text reviewed September 13, 2026. ↗

  60. For a Washington ball-and-coupler trailer within WAC 204-70's 10,000-pound-or-less scope, how must its tongue load on level ground compare with the hitch manufacturer's limit?

    Correct answer: It must not exceed the recommended maximum tongue load

    The hitch's tongue-load limit is separate from the trailer's total weight. Other equipment does not authorize exceeding the manufacturer's hitch limit.

    Source: Washington Administrative Code 204-70-060(2); scope 204-70-030; current text reviewed September 13, 2026. ↗

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Question reference: wa-cdl-combo-001

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Washington combination-vehicle practice

60 questions on controlling and inspecting trucks with trailers. Every answer includes an explanation.

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Know the coupling on your vehicle

Study section 6 with the air-brake chapter. Inspection questions also use the updated skills supplement, which distinguishes fifth wheels, pintle hooks and other hitches. The three Washington towing-rule questions expressly identify the rule's lighter ball-and-coupler trailer scope; they are not universal fifth-wheel requirements.

Coupling procedures depend on the equipment. Practice questions do not replace supervised training or the manufacturer's instructions. This selection is not an official exam or complete preparation for every combination, endorsement or practical skill.

Combination-vehicle chapterUpdated coupling inspection