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. ↗
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. ↗
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. ↗
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. ↗
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. ↗
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. ↗
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. ↗
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. ↗
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. ↗
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. ↗
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. ↗
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. ↗
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. ↗
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. ↗
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. ↗
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. ↗
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. ↗
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. ↗
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. ↗
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. ↗
