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NY CDL Combination study materials
NY CDL Combination study resources

NY CDL Combination practice questions

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Question 1Combination vehicle inspection and coupling/uncoupling

Before backing a tractor-trailer under to couple, you should verify that the trailer kingpin is:

  1. raised so the trailer apron clears the fifth wheel
  2. locked open so the jaws close automatically
  3. greased and the trailer brakes are released
  4. aligned with the fifth wheel and the trailer is chocked Correct answer.

Explanation

Good coupling starts with the trailer sitting at roughly the right height and the kingpin lined up with the throat of the fifth wheel, with the trailer secured so it cannot roll when the tractor pushes against it. Checking alignment and chocking prevents the trailer from being pushed away or the kingpin striking the wrong part of the plate.

Question 2Combination vehicle inspection and coupling/uncoupling

After the fifth wheel jaws close on the kingpin, the next step in a proper coupling is to:

  1. raise the landing gear fully
  2. connect the air lines and electrical cord
  3. release the tractor parking brake and pull forward
  4. pull the tractor gently forward to test the lock Correct answer.

Explanation

A gentle pull test with the trailer brakes set confirms the jaws are locked around the kingpin before you commit to the road. If the trailer moves with the tractor, the coupling is not secure and you must stop and correct it.

Question 3Combination vehicle inspection and coupling/uncoupling

The purpose of the trailer air supply (emergency) line in a combination vehicle is to:

  1. supply air that releases the trailer spring brakes when charged Correct answer.
  2. power the trailer interior lights
  3. carry the service brake signal from the treadle valve
  4. drain moisture from the trailer air tanks

Explanation

The emergency or supply line charges the trailer system and holds the spring brakes off; if it loses pressure the trailer brakes apply automatically. The service line is the separate line that carries the brake application signal.

Question 4Combination vehicle inspection and coupling/uncoupling

You have coupled and connected the lines, and the trailer brakes will not release. Which condition best explains this?

  1. The trailer spring brakes are adjusted too loose
  2. The service line and supply line are crossed Correct answer.
  3. The landing gear is still on the ground
  4. The electrical cord is plugged in backwards

Explanation

If the service and emergency lines are swapped, the trailer never receives a steady supply charge and its spring brakes stay applied. Reconnecting the lines to their proper gladhands restores the supply and lets the brakes release.

Question 5Combination vehicle inspection and coupling/uncoupling

When uncoupling, you should lower the landing gear until the feet:

  1. are fully retracted to avoid damage
  2. lift the trailer slightly off the fifth wheel
  3. are just above the ground so the trailer settles on the tractor
  4. firmly contact the ground and the tractor is eased out from under Correct answer.

Explanation

Landing gear must be lowered to solid ground contact so the trailer is supported before the tractor is pulled out. That way the trailer weight transfers to the gear instead of dropping when the fifth wheel releases.

Question 6Combination vehicle inspection and coupling/uncoupling

Before pulling the tractor out from under a trailer during uncoupling, you must:

  1. release the trailer parking brakes
  2. disconnect the electrical cord only
  3. raise the trailer with the landing gear
  4. release the fifth wheel locking jaws Correct answer.

Explanation

The fifth wheel jaws must be released so the kingpin can slide free as the tractor moves forward. Pulling out with the jaws still locked damages the fifth wheel and can drag the trailer.

Question 7Combination vehicle inspection and coupling/uncoupling

Which component on a combination vehicle automatically applies the trailer brakes if the trailer separates from the tractor?

  1. The relay valve
  2. The slack adjusters
  3. The spring brake chambers Correct answer.
  4. The tractor protection valve

Explanation

Trailer spring brakes are held off by air pressure; if the supply line is broken in a separation, pressure is lost and the springs apply the brakes. This fail-safe design stops the trailer from rolling free.

Question 8Combination vehicle inspection and coupling/uncoupling

During a pre-trip inspection of a combination vehicle, you check that the fifth wheel jaws are:

  1. open and greased for the next coupling
  2. removed so the kingpin can be inspected
  3. locked in the released position
  4. closed around the kingpin with the release handle secured Correct answer.

Explanation

The jaws should be fully closed around the kingpin with the locking mechanism engaged and the release handle in its secured position. An open or unsecured handle can let the trailer separate in motion.

Question 9Combination vehicle inspection and coupling/uncoupling

While inspecting a coupled combination, you notice the trailer apron resting hard on the tractor frame rails. What is the most likely cause?

  1. The air lines are crossed
  2. The electrical cord is too short
  3. The landing gear is too high
  4. The trailer is too low for the tractor Correct answer.

Explanation

If the trailer rides too low, the apron or frame contacts the tractor instead of the fifth wheel carrying the load through the kingpin. The trailer height must be adjusted so the fifth wheel supports the trailer properly.

Question 10Combination vehicle inspection and coupling/uncoupling

When checking the coupling after backing under a trailer, the correct way to confirm the kingpin is locked is to:

  1. check the trailer lights come on
  2. listen for the engine to change tone
  3. gently tug forward with the trailer brakes applied, then secure the vehicle and visually inspect the locked jaws and release handle Correct answer.
  4. look at the release handle from the cab

Explanation

Verify the coupling with a gentle tug against the applied trailer brakes and a visual inspection of the jaws around the kingpin shank. With the vehicle secured, confirm that the release handle is seated in its locked position. Pulling the release handle can unlock the coupling.

Question 11Combination vehicle inspection and coupling/uncoupling

The tractor protection valve's main role in a combination vehicle is to:

  1. increase air pressure to the trailer brakes
  2. prevent the tractor's air supply from being lost through a trailer leak or break Correct answer.
  3. regulate the trailer ride height
  4. apply the trailer parking brake manually

Explanation

The tractor protection valve isolates the tractor air system if the trailer line loses pressure or separates, so the tractor retains enough air to stop. This fail-safe keeps the tractor from being drained by a trailer-side leak.

Question 12Combination vehicle inspection and coupling/uncoupling

You are uncoupling and have set the trailer brakes and lowered the landing gear. What should you do with the air lines before pulling out?

  1. Cap the gladhands and leave the lines hanging
  2. Leave them connected until the tractor is clear
  3. Disconnect the supply line only
  4. Disconnect both lines and secure them against damage Correct answer.

Explanation

Both the service and supply lines must be disconnected and stowed so they are not dragged or torn as the tractor pulls away. Hanging lines can catch on the landing gear or trailer frame.

Question 13Combination vehicle inspection and coupling/uncoupling

What is the purpose of the trailer hand valve (trolley valve) in a combination vehicle?

  1. To supply air to the landing gear
  2. To release the tractor protection valve
  3. To test the trailer brakes independently of the tractor Correct answer.
  4. To set the trailer spring brakes for parking

Explanation

The hand valve applies the trailer service brakes alone, which is useful for a brake test and for holding the trailer during coupling. It is not a parking brake and should not be used for parking.

Question 14Combination vehicle inspection and coupling/uncoupling

During the pre-trip inspection of a combination vehicle, you check the air line gladhands and find the rubber seals missing. The correct action is to:

  1. tape the gladhands and proceed
  2. replace the seals before coupling and driving Correct answer.
  3. leave the lines disconnected and drive
  4. connect them and continue because seals are optional

Explanation

Missing gladhand seals cause air leaks that can prevent the trailer brakes from releasing or drain the system. The seals must be replaced before coupling and driving.

Question 15Combination vehicle inspection and coupling/uncoupling

You have coupled to a loaded trailer and completed the pull test. Which check confirms the trailer is properly supported?

  1. The trailer apron is touching the tractor frame
  2. The landing gear is raised fully and the trailer weight rests on the fifth wheel Correct answer.
  3. The landing gear remains on the ground for extra support
  4. The trailer is high enough that the fifth wheel does not contact it

Explanation

Once coupling is confirmed, the landing gear is raised fully so the trailer load is carried by the fifth wheel and kingpin. Leaving the gear down or having the apron contact the frame indicates incorrect setup.

Question 16Combination vehicle inspection and coupling/uncoupling

When inspecting the coupling area, you notice the fifth wheel plate is cracked. What should you do?

  1. Weld the crack yourself before coupling
  2. Couple anyway and report it after the trip
  3. Place the trailer on the fifth wheel and drive slowly
  4. Do not couple; the vehicle is out of service until repaired Correct answer.

Explanation

A cracked fifth wheel plate is a structural defect that can fail under load and drop the trailer. The combination must be taken out of service until a qualified repair is made.

Question 17Combination vehicle inspection and coupling/uncoupling

During a pre-trip inspection, you find the trailer's spring brake chambers have broken mounting brackets. The correct action is to:

  1. wire the chambers in place and drive
  2. place the vehicle out of service until the brackets are repaired Correct answer.
  3. remove the broken chambers and drive without them
  4. adjust the slack adjusters to compensate

Explanation

Broken spring brake chamber mounts can let the chamber separate and disable the emergency and parking brakes. The defect makes the vehicle unsafe and it must be repaired before use.

Question 18Combination vehicle inspection and coupling/uncoupling

When backing under a trailer, you should stop when the fifth wheel:

  1. is still a foot short of the trailer
  2. is well under the trailer nose, just before the kingpin Correct answer.
  3. touches the landing gear
  4. has passed the kingpin by several inches

Explanation

Stopping with the fifth wheel just under the trailer nose lets you confirm alignment before the final push engages the kingpin. Backing too far past the kingpin can damage the trailer or fifth wheel.

Question 19Combination vehicle inspection and coupling/uncoupling

You are coupling in the dark and cannot clearly see whether the jaws have locked. The safest approach is to:

  1. assume the lock is good if the handle feels firm
  2. pull forward and see if the trailer follows
  3. rely on the sound of the jaws closing
  4. use a flashlight to inspect the jaws and handle directly Correct answer.

Explanation

A visual inspection with a light is the only reliable confirmation that the jaws are closed around the kingpin and the handle is secured. Sound and feel can be misleading, and a pull test alone does not prove the lock is correct.

Question 20Combination vehicle inspection and coupling/uncoupling

Which item on a combination vehicle pre-trip inspection specifically checks the trailer's emergency brake function?

  1. Measuring the trailer tire tread depth
  2. Checking the trailer marker lights
  3. Opening the supply line gladhand and listening for the trailer brakes to set Correct answer.
  4. Inspecting the landing gear crank

Explanation

Disconnecting the supply line simulates a break in the emergency line; the trailer spring brakes should apply automatically. This confirms the fail-safe emergency brake works.

Question 21Combination vehicle inspection and coupling/uncoupling

During uncoupling, the trailer starts to drop as the tractor pulls away. The most likely cause is that:

  1. the fifth wheel jaws were released
  2. the landing gear was not lowered to the ground Correct answer.
  3. the supply line was disconnected
  4. the trailer brakes were set

Explanation

If the landing gear was not lowered to solid ground contact, nothing supports the trailer once the fifth wheel releases and it drops. The gear must be down and bearing weight before the tractor is pulled out.

Question 22Combination vehicle inspection and coupling/uncoupling

When checking the air brake system on a combination vehicle, you should verify that the trailer brakes apply when you:

  1. release the parking brake
  2. press the foot pedal and observe the trailer brake chambers Correct answer.
  3. turn on the headlights
  4. raise the landing gear

Explanation

Applying the foot brake should send air through the service line and apply the trailer brakes; observing the chambers or having a helper watch confirms the service brakes work. This is part of the pre-trip brake check.

Question 23Combination vehicle inspection and coupling/uncoupling

Which statement about the trailer electrical cord during coupling is correct?

  1. It should be wrapped tightly around the air lines
  2. It should be connected before the air lines to test the lights
  3. It can be connected after the air lines and should have enough slack to turn without pulling Correct answer.
  4. It should be left disconnected while driving short distances

Explanation

The cord is connected after the air lines and must have enough slack to allow turns without pulling loose or breaking. Proper routing prevents damage and keeps trailer lights working.

Question 24Combination vehicle inspection and coupling/uncoupling

You are inspecting a coupled combination and notice the trailer's rear frame is much lower than normal on one side. Which condition best explains this?

  1. The trailer brakes are adjusted
  2. The electrical cord is too long
  3. A broken suspension spring or air bag on that side Correct answer.
  4. The gladhand seals are new

Explanation

A broken spring or air bag lets one side of the trailer sag, which is a structural defect that affects stability and braking. It must be repaired before the vehicle is driven.

Question 25Combination vehicle inspection and coupling/uncoupling

After coupling and connecting the lines, you notice the trailer brakes will not release even though the lines look correct. What should you do first?

  1. Check that the supply line is fully connected and the trailer air tanks are charged Correct answer.
  2. Drive slowly and let the brakes release on their own
  3. Disconnect the service line
  4. Adjust the slack adjusters

Explanation

The trailer spring brakes need a full supply charge to release, so a partially connected supply line or uncharged trailer tanks are the first things to check. If the supply is good and the brakes still will not release, the system needs repair.

Question 26Combination vehicle inspection and coupling/uncoupling

When you begin the coupling process, at what height should the trailer apron be relative to the fifth wheel before you back under it?

  1. As low as possible so the kingpin rides over the plate
  2. Exactly level with the top of the fifth wheel plate
  3. Well above the fifth wheel so the tractor passes under without contact
  4. Slightly below the fifth wheel so the plate lifts the trailer as you back under Correct answer.

Explanation

The trailer should be raised so the apron is just slightly below the fifth wheel, allowing the plate to lift and slide under the trailer as you reverse. If the trailer is too high, the kingpin can strike and damage the fifth wheel or the tractor frame.

Question 27Combination vehicle inspection and coupling/uncoupling

Which check confirms the trailer is properly supported after you have finished coupling and pulled the tractor forward slightly?

  1. The trailer has lifted off the landing gear and the gear is clear of the ground Correct answer.
  2. The trailer wheels are chocked
  3. The air lines are still disconnected
  4. The landing gear is still touching the ground

Explanation

After coupling and a gentle pull, the fifth wheel should be carrying the trailer's weight, which lifts the landing gear off the ground. Landing gear still bearing weight indicates the kingpin is not properly seated in the jaws.

Question 28Combination vehicle inspection and coupling/uncoupling

During a pre-trip inspection of a combination vehicle, you find the air line gladhand seals are cracked and flattened. What is the correct action?

  1. Replace the seals or have the defect repaired before driving Correct answer.
  2. Loosen the gladhands so the seals seat better
  3. Tape over the seals to keep them from leaking
  4. Ignore them because the couplers will still hold pressure

Explanation

Cracked or flattened gladhand seals leak air and can cause the trailer brakes to drag or fail to release. The seals must be replaced before the vehicle is operated, since a leak in the supply or service line is a safety defect.

Question 29Combination vehicle inspection and coupling/uncoupling

You are uncoupling and have already set the trailer parking brakes and lowered the landing gear. What is the next step before pulling the tractor forward?

  1. Open the trailer doors
  2. Release the trailer spring brakes
  3. Raise the landing gear again
  4. Disconnect the electrical cord and air lines from the trailer Correct answer.

Explanation

After the trailer brakes are set and the landing gear is down, you disconnect the electrical cord and the air lines so they are not stretched or torn as the tractor pulls away. Only then do you release the fifth wheel jaws and pull forward.

Question 30Combination vehicle inspection and coupling/uncoupling

While backing under a trailer, you stop when the fifth wheel touches the trailer apron. What should you do next?

  1. Chock the trailer wheels and disconnect the air lines
  2. Continue backing slowly until you hear the jaws lock, then tug forward Correct answer.
  3. Set the trailer brakes and lower the landing gear
  4. Get out and check the jaws before continuing to back

Explanation

When the fifth wheel contacts the apron, you continue backing slowly until the kingpin clicks into the jaws, then tug forward gently to confirm the lock. Stopping at first contact leaves the kingpin uncoupled.

Question 31Combination vehicle inspection and coupling/uncoupling

After coupling, you perform the pull test by tugging forward gently with the trailer brakes set. What result confirms a locked kingpin?

  1. The landing gear lifts off the ground
  2. The trailer rolls forward with the tractor
  3. The tractor moves forward and the trailer stays put Correct answer.
  4. The tractor stalls

Explanation

With the trailer brakes set, a gentle forward tug should move the tractor slightly while the trailer holds still, proving the jaws have locked the kingpin. If the trailer moves with the tractor, the kingpin is not locked and the coupling must be redone.

Question 32Combination vehicle inspection and coupling/uncoupling

You are inspecting a coupled combination and notice the trailer is not sitting level on the fifth wheel, with a visible gap at the rear of the plate. What is the most likely cause?

  1. The trailer brakes are adjusted too tight
  2. The fifth wheel is not fully seated under the trailer apron Correct answer.
  3. The gladhand seals are new
  4. The trailer is empty

Explanation

A gap between the fifth wheel and the trailer apron means the plate is not fully under the trailer, often because the trailer was too high or the jaws did not capture the kingpin correctly. You should not drive until the coupling is corrected.

Question 33Combination vehicle inspection and coupling/uncoupling

During the pre-trip inspection, how do you check that the trailer spring brakes apply and hold?

  1. Charge the trailer system, then release the tractor protection valve and listen for the trailer brakes to set Correct answer.
  2. Rev the engine and watch the trailer wheels spin
  3. Pull the trailer hand valve and release it quickly
  4. Disconnect the electrical cord and watch the lights

Explanation

With the trailer air system charged, closing the tractor protection valve (or otherwise interrupting the supply) should cause the trailer spring brakes to apply automatically. This confirms the emergency brake function works if the trailer separates.

Question 34Combination vehicle inspection and coupling/uncoupling

You are ready to couple to a trailer and the trailer is equipped with a front jack or dolly. Which precaution applies before you back under it?

  1. Remove the landing gear completely
  2. Disconnect the trailer brakes
  3. Raise the trailer so the apron is above the fifth wheel
  4. Make sure the trailer is chocked or held by its brakes so it cannot roll during coupling Correct answer.

Explanation

A trailer that is free to roll can move as the tractor contacts it, causing a misaligned or incomplete coupling. Chocking the wheels or confirming the parking brakes are set keeps the trailer stationary while you back under it.

Question 35Combination vehicle inspection and coupling/uncoupling

After coupling and connecting the air lines, the trailer brakes will not release even though the lines appear connected. What is the first thing to check?

  1. That the landing gear is fully raised
  2. That the fifth wheel is greased
  3. That the trailer lights are working
  4. That the gladhands are fully seated and the trailer supply valve is open Correct answer.

Explanation

Trailer brakes that stay applied usually mean the supply line is not delivering air, often because a gladhand is not fully seated or the trailer supply valve is closed. Confirm the connection and valve position before moving.

Question 36Combination vehicle inspection and coupling/uncoupling

You are inspecting the coupling area and notice the fifth wheel mounting bolts are loose. What is the correct action?

  1. Do not drive the vehicle until the mounting is repaired and torque checked Correct answer.
  2. Ignore them because the kingpin carries the load
  3. Drive only at low speed until the next stop
  4. Tighten them by hand and continue

Explanation

Loose fifth wheel mounting bolts can let the plate shift or separate from the tractor frame, which is a serious structural defect. The vehicle must be taken out of service until the mounting is properly repaired and torqued.

Question 37Combination vehicle inspection and coupling/uncoupling

During uncoupling, the trailer starts to drop as the tractor pulls away. Which cause is most consistent with this?

  1. The trailer brakes were set too firmly
  2. The landing gear was not lowered or was set too low before releasing the fifth wheel Correct answer.
  3. The gladhand seals were new
  4. The electrical cord was disconnected first

Explanation

If the landing gear was not lowered, or was lowered but not cranked down enough to contact the ground, the trailer has nothing to rest on once the fifth wheel releases. The gear must be firmly on the ground and supporting the trailer before you pull out.

Question 38Combination vehicle inspection and coupling/uncoupling

Before you release the fifth wheel jaws during uncoupling, why must the trailer brakes be set?

  1. So the trailer cannot roll once it is free of the tractor Correct answer.
  2. So the air lines will disconnect automatically
  3. So the tractor can be shut off
  4. So the landing gear will lower itself

Explanation

Once the jaws release, the trailer is no longer held by the tractor, so its own brakes must keep it from rolling. Setting the trailer parking brakes before releasing the fifth wheel prevents the trailer from moving or dropping unexpectedly.

Question 39Combination vehicle inspection and coupling/uncoupling

While inspecting a combination vehicle, you find the trailer's rear frame is much lower on one side. Which condition should you suspect?

  1. A loose electrical cord
  2. A broken or sagging suspension component on that side Correct answer.
  3. An overcharged air system
  4. A misadjusted tractor protection valve

Explanation

A trailer frame that is noticeably lower on one side usually points to a suspension problem such as a broken spring, shackle, or air bag on that side. This is a mechanical defect that must be repaired before the vehicle is driven.

Question 40Combination vehicle inspection and coupling/uncoupling

You have coupled, connected the lines, and charged the system, but the trailer brakes drag and the wheels feel hot after a short drive. Which inspection item is most relevant?

  1. The landing gear crank handle
  2. The trailer light bulbs
  3. The trailer supply line coupling and the tractor protection valve position Correct answer.
  4. The fifth wheel grease fitting

Explanation

Dragging trailer brakes often result from a restricted or closed supply line, such as a partially seated gladhand or a tractor protection valve not fully open, which prevents full release. Verify the supply coupling and valve position before continuing.

Question 41Driving combination vehicles: turning, tracking, and off-tracking

A tractor-trailer turns a corner. Which wheels follow the tightest path through the turn?

  1. The drive wheels of the tractor
  2. The front wheels of the tractor
  3. The trailer's front axle wheels
  4. The rear wheels of the trailer Correct answer.

Explanation

Off-tracking means the rear wheels of the trailer cut inside the path of the tractor's front wheels. The sharper the turn and the longer the wheelbase, the more the trailer's rear wheels track toward the inside of the curve. The driver must steer wide enough that the trailer's rear wheels clear curbs and other objects.

Question 42Driving combination vehicles: turning, tracking, and off-tracking

When making a right turn in a combination vehicle, when should you begin the turn?

  1. After the tractor's front wheels have cleared the curb line Correct answer.
  2. At the same point you would in a passenger car
  3. As soon as the front bumper reaches the corner
  4. Before entering the intersection to save space

Explanation

You must swing wide and delay the turn until the tractor's front wheels pass the curb or edge of the road. Starting the turn too early causes the trailer's rear wheels to run over the curb or into the corner. This is the practical remedy for rearward off-tracking on right turns.

Question 43Driving combination vehicles: turning, tracking, and off-tracking

Why does a longer wheelbase combination vehicle off-track more than a shorter one?

  1. The tires are wider on longer trailers
  2. The rear wheels cut a tighter arc relative to the front wheels Correct answer.
  3. The trailer brakes apply more force on curves
  4. The steering axle carries more weight

Explanation

Off-tracking increases with the distance between the tractor's front axle and the trailer's rear axle. The longer that distance, the more the rear of the combination cuts inside the front wheels' path. Drivers of long wheelbase rigs must swing wider and allow more clearance.

Question 44Driving combination vehicles: turning, tracking, and off-tracking

What is the primary danger of off-tracking when turning near a curb or fixed object?

  1. The steering wheel becomes harder to turn
  2. The trailer brakes lock automatically
  3. The trailer's rear wheels strike or run over the curb or object Correct answer.
  4. The tractor's front wheels lift off the pavement

Explanation

Because the trailer's rear wheels cut inside the tractor's path, they can hit curbs, poles, pedestrians, or parked vehicles on the inside of the turn. The driver must watch the trailer's rear wheels in the mirrors and leave enough room. This is the central hazard off-tracking creates.

Question 45Driving combination vehicles: turning, tracking, and off-tracking

When backing a tractor-trailer, which way should you turn the steering wheel to make the trailer go left?

  1. Hold the wheel straight and use the trailer brake
  2. Turn the wheel left, then immediately right
  3. Turn the wheel to the left
  4. Turn the wheel to the right Correct answer.

Explanation

When backing, the trailer pivots opposite to the steering input: turning the wheel right pushes the trailer's rear to the left. This reversed response is why backing a combination vehicle requires practice and small corrections. Use the mirrors and go slowly.

Question 46Driving combination vehicles: turning, tracking, and off-tracking

You are driving a combination vehicle and must turn left at an intersection with a tight inner corner. What is the safest approach?

  1. Turn sharply from the left lane to shorten the path
  2. Turn from the right lane and cut across the left lane
  3. Stay in the proper turn lane and move far enough into the intersection before turning slowly to allow for trailer offtracking Correct answer.
  4. Accelerate through the turn to keep the trailer straight

Explanation

On a left turn, the trailer's rear wheels track inside the tractor's path. Stay in the proper turn lane and move far enough into the intersection before turning so the trailer clears the inner corner. Keep the turn slow and watch the trailer in the mirrors.

Question 47Driving combination vehicles: turning, tracking, and off-tracking

Which mirror should you check to monitor the trailer's rear wheels during a turn?

  1. The left mirror only
  2. The hood mirror only
  3. The right and left flat mirrors showing the trailer's sides Correct answer.
  4. The sun visor mirror

Explanation

The flat side mirrors let you see the trailer's sides and rear wheels as you turn, so you can judge clearance from curbs and objects. Checking both sides is important because off-tracking can affect either side depending on turn direction. Hood and visor mirrors do not show the trailer's rear path.

Question 48Driving combination vehicles: turning, tracking, and off-tracking

What does 'swept path' refer to when describing a combination vehicle in a turn?

  1. The total width of roadway the vehicle occupies from outer front to inner rear Correct answer.
  2. The length of the trailer's landing gear
  3. The radius of the steering wheel
  4. The distance the trailer travels while braking

Explanation

The swept path is the full area the combination covers as it turns, from the outermost front corner to the innermost rear wheel. It is wider than the path of a single vehicle because of off-tracking. Drivers must ensure the entire swept path is clear of obstacles.

Question 49Driving combination vehicles: turning, tracking, and off-tracking

A driver turns a combination vehicle too sharply at low speed. What is the most likely result at the trailer's rear wheels?

  1. They swing wide into the outside lane
  2. They lift off the ground
  3. They lock and skid straight ahead
  4. They cut the corner and strike the inside curb Correct answer.

Explanation

Sharp low-speed turns maximize off-tracking, pulling the trailer's rear wheels toward the inside of the curve. That is why the rear wheels clip inside curbs and corners. The driver should widen the turn and delay steering until the front wheels clear.

Question 50Driving combination vehicles: turning, tracking, and off-tracking

How should you position a combination vehicle before making a wide right turn at a corner with a curb?

  1. Straddle the center line the entire approach
  2. Move as far left in your lane as legally possible before turning Correct answer.
  3. Hug the right curb to keep the trailer straight
  4. Stay centered and turn early

Explanation

Positioning left within your lane gives the trailer room to swing without hitting the right curb. You then turn only after the tractor's front wheels clear the curb line. Hugging the curb or turning early forces the trailer's rear wheels into it.