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