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CDL Test: Combination vehicles questions and answers

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Combination vehicles

63 questions

  1. #1

    Compared with an empty rig, a fully loaded rig is how much more likely to roll over in a crash?

    1. Twice as likely
    2. Five times as likely
    3. Ten times as likely
    4. Equally likely

    Answer: C. Fully loaded rigs are ten times more likely to roll over in a crash than empty rigs.

    Source: Pennsylvania CDL Manual (PUB 223), 6.1 Driving Combination Vehicles SafelyFully loaded rigs are ten times more likely to roll over in a crash than empty rigs.

  2. #2

    A rearward amplification of 2.0 means the rear trailer is:

    1. Twice as likely to turn over as the tractor
    2. Half as likely to turn over
    3. Twice as heavy as the tractor
    4. Allowed to go twice as fast

    Answer: A. Rearward amplification 2.0: the rear trailer is twice as likely to turn over as the tractor (the "crack-the-whip" effect).

    Source: Pennsylvania CDL Manual (PUB 223), 6.1 Driving Combination Vehicles Safelyrearward amplification of 2.0 in the chart means that the rear trailer is twice as likely to turn over as the tractor.

  3. #3

    For following distance, the manual says to leave at least:

    1. 1 second for each 20 feet of vehicle length
    2. 1 second for each 10 feet of vehicle length, plus 1 second over 40 mph
    3. 2 seconds total at any speed
    4. 1 second for each 10 mph of speed

    Answer: B. At least 1 second for each 10 feet of vehicle length, plus another second if going over 40 mph.

    Source: Pennsylvania CDL Manual (PUB 223), 6.1 Driving Combination Vehicles SafelyFollow far enough behind other vehicles (at least 1 second for each 10 feet of your vehicle length, plus another second if going over 40 mph).

  4. #4

    Large combination vehicles take longer to stop when they are:

    1. Fully loaded
    2. Half loaded
    3. Carrying liquids
    4. Empty

    Answer: D. Empty rigs take longer to stop than fully loaded ones; bobtail tractors need extra care too.

    Source: Pennsylvania CDL Manual (PUB 223), 6.1 Driving Combination Vehicles SafelyLarge combination vehicles take longer to stop when they are empty than when they are fully loaded.

  5. #5

    If your trailer starts to skid, you should:

    1. Release the service brakes to get traction back
    2. Apply the trailer hand brake to straighten the rig
    3. Accelerate hard
    4. Turn sharply toward the skid

    Answer: A. Release the brakes to regain traction; do not use the trailer hand brake to "straighten out the rig".

    Source: Pennsylvania CDL Manual (PUB 223), 6.1 Trailer Skidsdo not use the trailer hand brake (if you have one) to "straighten out the rig."

  6. #6

    If you cannot make a right turn without entering another lane, you should:

    1. Swing wide to the left before starting the turn
    2. Let the rear wheels run over the curb
    3. Turn wide as you complete the turn
    4. Back up and try again

    Answer: C. Turn wide as you complete the turn; steer the front wide enough so the rear does not run over the curb.

    Source: Pennsylvania CDL Manual (PUB 223), 6.1 Turn WideIf you cannot complete your turn without entering another traffic lane, turn wide as you complete the turn.

  7. #7

    The trailer hand valve (trolley valve) should be used:

    1. To park the trailer
    2. Only to test the trailer brakes
    3. To straighten out a skid
    4. For normal braking in traffic

    Answer: B. Use it only to test the trailer brakes; never for driving or parking, because air can leak out and release the brakes.

    Source: Pennsylvania CDL Manual (PUB 223), 6.2 Combination Vehicle Air Brakesthe trailer hand valve should be used only to test the trailer brakes.

  8. #8

    The tractor protection valve closes automatically when air pressure drops into which range?

    1. 60 to 80 psi
    2. 100 to 125 psi
    3. 5 to 10 psi
    4. 20 to 45 psi

    Answer: D. It closes automatically when air pressure is low, in the range of 20 to 45 psi.

    Source: Pennsylvania CDL Manual (PUB 223), 6.2 Tractor Protection Valvethe tractor protection valve will close automatically if air pressure is low (in the range of 20 to 45 psi).

  9. #9

    When connecting glad hands, you press the seals together with the couplers at what angle?

    1. 90 degrees
    2. 45 degrees
    3. 180 degrees
    4. 0 degrees (in line)

    Answer: A. Press the two seals together with the couplers at a 90-degree angle, after cleaning couplers and seals.

    Source: Pennsylvania CDL Manual (PUB 223), 6.2 Glad Handspress the two seals together with the couplers at a 90 degree angle to each other.

  10. #10

    How often should you drain the air tanks?

    1. Once a month
    2. Once a week
    3. Every day
    4. Only when the low-air warning comes on

    Answer: C. Each tank has a drain valve, and you should drain each tank every day.

    Source: Pennsylvania CDL Manual (PUB 223), 6.2 Trailer Air TanksEach tank has a drain valve on it and you should drain each tank every day.

  11. #11

    On a combination, the shut-off valves at the back of the LAST trailer must be:

    1. Open
    2. Closed
    3. Removed
    4. Half open

    Answer: B. All shut-off valves are open except those at the back of the last trailer, which must be closed.

    Source: Pennsylvania CDL Manual (PUB 223), 6.2 Shut-off ValvesYou must check that all shut-off valves are in the open position except the ones at the back of the last trailer, which must be closed.

  12. #12

    Trailers and converter dollies built on or after what date must have ABS?

    1. March 1, 1998
    2. January 1, 2005
    3. March 1, 1988
    4. January 1, 2010

    Answer: A. All trailers and converter dollies built on or after March 1, 1998, must have ABS; the yellow malfunction lamp is on the left side.

    Source: Pennsylvania CDL Manual (PUB 223), 6.3 Antilock Brake SystemsAll trailers and converter dollies built on or after march 1, 1998, are required to have ABS.

  13. #13

    If the ABS on your trailer malfunctions:

    1. You have no brakes on the trailer
    2. You must stop and call for a tow
    3. The trailer brakes lock up
    4. You still have regular brakes

    Answer: D. If ABS fails you still have regular brakes; ABS does not necessarily shorten stopping distance.

    Source: Pennsylvania CDL Manual (PUB 223), 6.3 Antilock Brake Systemsremember, if your ABS malfunctions, you still have regular brakes.

  14. #14

    When coupling, the trailer height should be:

    1. High enough that the fifth wheel passes under the apron without touching
    2. Low enough that the tractor raises it slightly when backed under
    3. Exactly level with the top of the tractor tires
    4. As low as the landing gear allows

    Answer: B. The trailer should be low enough that it is raised slightly by the tractor when backed under it.

    Source: Pennsylvania CDL Manual (PUB 223), 6.4 Coupling Tractor-semitrailersthe trailer should be low enough that it is raised slightly by the tractor when the tractor is backed under it.

  15. #15

    After backing under the trailer, how do you check that it is locked onto the tractor?

    1. Look at the landing gear
    2. Sound the horn and listen
    3. Pull forward gently with the trailer brakes still locked
    4. Drive around the block

    Answer: C. Pull the tractor gently forward while the trailer brakes are still locked (tug test).

    Source: Pennsylvania CDL Manual (PUB 223), 6.4 Coupling Tractor-semitrailersPull tractor gently forward while the trailer brakes are still locked to check that the trailer is locked onto the tractor.

  16. #16

    When you inspect the coupling, the locking jaws should be closed around:

    1. The shank of the kingpin
    2. The head of the kingpin
    3. The glide plate
    4. The apron

    Answer: A. Locking jaws around the shank, not the head, of the kingpin; no visible space between upper and lower fifth wheel.

    Source: Pennsylvania CDL Manual (PUB 223), 6.5 Inspecting a Combination VehicleLocking jaws around the shank, not the head of kingpin.

  17. #17

    Why should you never drive with the landing gear only part way up?

    1. It wastes fuel
    2. It overloads the fifth wheel
    3. It blocks the mirrors
    4. It may catch on railroad tracks or other things

    Answer: D. Landing gear left part way up may catch on railroad tracks or other things.

    Source: Pennsylvania CDL Manual (PUB 223), 6.4 Coupling Tractor-semitrailersnever drive with landing gear only part way up as it may catch on railroad tracks or other things.

  18. #18

    When uncoupling, why do you stop with the tractor frame still under the trailer?

    1. To keep the air lines connected
    2. So the trailer will not fall if the landing gear collapses or sinks
    3. To save the fifth-wheel grease
    4. To keep the lights working

    Answer: B. It prevents the trailer from falling to the ground if the landing gear collapses or sinks.

    Source: Pennsylvania CDL Manual (PUB 223), 6.4 Uncoupling Tractor-semitrailersStop with tractor frame under trailer (prevents trailer from falling to ground if landing gear should collapse or sink).

  19. #19

    To help prevent a rollover in a combination vehicle, you should keep the cargo:

    1. as close to the ground as possible
    2. concentrated over the drive axles
    3. stacked high so it is easy to secure
    4. toward the rear of the trailer

    Answer: A. Piling cargo up raises the center of gravity, so keeping cargo low helps prevent rollover.

    Source: North Dakota CDL Manual (AAMVA model), Section 6, p. 87keep the cargo as close to the ground as possible, and

  20. #20

    If the load is to one side so that it makes the trailer lean, then:

    1. the trailer will track more evenly in turns
    2. the trailer will be less likely to jackknife
    3. a rollover is more likely
    4. the center of gravity moves lower

    Answer: C. A load shifted to one side makes the trailer lean and makes a rollover more likely, so keep the load centered.

    Source: North Dakota CDL Manual (AAMVA model), Section 6, p. 87load is to one side so it makes a trailer lean, a rollover

  21. #21

    What rearward amplification does the manual give for triples?

    1. 2.0
    2. 2.5
    3. 3.0
    4. 3.5

    Answer: D. Triples have a rearward amplification of 3.5, so the last trailer can be rolled 3.5 times as easily as a five-axle tractor.

    Source: North Dakota CDL Manual (AAMVA model), Section 6, p. 87You can see that triples have a rearward amplification of 3.5.

  22. #22

    What is a “bobtail”?

    1. A tractor pulling an empty trailer
    2. A tractor without a semitrailer
    3. A trailer without a tractor
    4. A straight truck with a trailer

    Answer: B. Bobtail tractors are tractors without semitrailers.

    Source: North Dakota CDL Manual (AAMVA model), Section 6, p. 87(tractors without semitrailers)

  23. #23

    Compared with a tractor-semitrailer loaded to maximum gross weight, a bobtail tractor takes:

    1. less time to stop
    2. longer to stop
    3. the same time to stop
    4. less time to stop only on wet roads

    Answer: B. Tests show bobtails are hard to stop smoothly and take longer to stop than a fully loaded tractor-semitrailer.

    Source: North Dakota CDL Manual (AAMVA model), Section 6, p. 87It takes them longer to stop than a tractorsemitrailer

  24. #24

    Which trailers can get stuck on raised railroad-highway crossings?

    1. Low slung units such as a lowboy or car carrier
    2. Tall vans with a high center of gravity
    3. Tank trailers carrying liquids
    4. Empty flatbed trailers only

    Answer: A. Trailers with low underneath clearance, such as lowboys, car carriers, moving vans and possum-belly livestock trailers, can hang up on raised crossings.

    Source: North Dakota CDL Manual (AAMVA model), Section 6, p. 87Low slung units (lowboy, car carrier, moving van,

  25. #25

    If you get stuck on railroad tracks, you should first:

    1. try to rock the vehicle free
    2. stay in the cab and wait for help
    3. get out of the vehicle and away from the tracks
    4. set out reflective triangles on the tracks

    Answer: C. If you get stuck on the tracks, get out of the vehicle and away from the tracks, then call 911 or the emergency number posted at the crossing.

    Source: North Dakota CDL Manual (AAMVA model), Section 6, p. 87If for any reason you get stuck on the tracks, get out

  26. #26

    The wheels of a trailer locking up and the trailer swinging around is more likely when the trailer is:

    1. fully loaded
    2. carrying a liquid load
    3. carrying a centered load
    4. empty or lightly loaded

    Answer: D. A trailer skid and swing (trailer jackknife) is more likely when the trailer is empty or lightly loaded.

    Source: North Dakota CDL Manual (AAMVA model), Section 6, p. 88the trailer is empty or lightly loaded.

  27. #27

    What is the earliest and best way to recognize that your trailer has started to skid?

    1. Feeling the steering wheel pull
    2. Hearing the tires squeal
    3. Watching the speedometer drop
    4. Seeing it in your mirrors

    Answer: D. The earliest and best way to spot a trailer skid is to see it in your mirrors, so check them any time you brake hard.

    Source: North Dakota CDL Manual (AAMVA model), Section 6, p. 88The earliest and best way to recognize that the trailer has started to skid is by seeing

  28. #28

    What is offtracking?

    1. The trailer wheels locking up and sliding out of line when you brake hard in a curve
    2. The rear wheels following a different path than the front wheels when going around a corner
    3. The tractor drifting slowly out of its own lane on a long straight stretch of road
    4. The trailer swinging out sideways behind the tractor when backing into a dock

    Answer: B. When a vehicle goes around a corner, the rear wheels follow a different path than the front wheels; this is called offtracking.

    Source: North Dakota CDL Manual (AAMVA model), Section 6, p. 89follow a different path than the front wheels. This is

  29. #29

    On a vehicle with more than one trailer, which wheels will offtrack the most?

    1. The rear wheels of the last trailer
    2. The rear wheels of the tractor
    3. The front wheels of the first trailer
    4. The front wheels of the tractor

    Answer: A. If there is more than one trailer, the rear wheels of the last trailer offtrack the most.

    Source: North Dakota CDL Manual (AAMVA model), Section 6, p. 89trailer, the rear wheels of the last trailer will offtrack the

  30. #30

    When turning a combination vehicle, you should keep the rear of your vehicle close to the curb to:

    1. keep the trailer from swaying at higher speeds
    2. make the trailer wheels follow the tractor's path exactly
    3. stop other drivers from passing you on the right
    4. keep the tires from scuffing and wearing on the curb

    Answer: C. Keeping the rear of the vehicle close to the curb stops other drivers from passing you on the right.

    Source: North Dakota CDL Manual (AAMVA model), Section 6, p. 89to the curb. This will stop other drivers from passing

  31. #31

    When backing a trailer, compared with backing a car or straight truck, you turn the steering wheel:

    1. in the opposite direction
    2. in the same direction
    3. only a quarter turn
    4. only after the trailer stops

    Answer: A. When backing a trailer you turn the steering wheel in the opposite direction, and once the trailer starts to turn you turn the wheel the other way to follow it.

    Source: North Dakota CDL Manual (AAMVA model), Section 6, p. 89you turn the steering wheel in the opposite direction.

  32. #32

    If you must back a trailer on a curved path, you should back toward the:

    1. passenger side
    2. side with more space
    3. driver’s side so you can see
    4. side away from traffic

    Answer: C. If you must back on a curved path, back to the driver’s side so you can see.

    Source: North Dakota CDL Manual (AAMVA model), Section 6, p. 89must back on a curved path, back to the driver’s side

  33. #33

    When backing a trailer, as soon as you see the trailer drifting off the proper path, you should correct it by turning:

    1. the top of the steering wheel away from the drift
    2. the steering wheel gently back to center only
    3. the bottom of the steering wheel toward the drift
    4. the top of the steering wheel in the direction of the drift

    Answer: D. Correct drift immediately by turning the top of the steering wheel in the direction the trailer is drifting.

    Source: North Dakota CDL Manual (AAMVA model), Section 6, p. 89the top of the steering wheel in the direction of the drift.

  34. #34

    Before you begin backing with a trailer, you should look at your line of travel and:

    1. sound the horn twice
    2. get out and walk around the vehicle
    3. signal with your four-way flashers only
    4. shut off the engine and listen

    Answer: B. Before backing, look at your line of travel, get out and walk around the vehicle, and check clearance to the sides and overhead.

    Source: North Dakota CDL Manual (AAMVA model), Section 6, p. 89Get out and walk around the vehicle.

  35. #35

    Why should you never use the trailer hand valve for parking?

    1. It will overheat the trailer brake drums and cause the brakes to fade badly
    2. All the air might leak out, unlocking the brakes on trailers without spring brakes
    3. It will damage the relay valves and the trailer brake chambers beyond repair
    4. It will close the tractor protection valve and cut the air to the tractor brakes

    Answer: B. Never use the hand valve for parking because all the air might leak out, unlocking the brakes (in trailers that don’t have spring brakes).

    Source: North Dakota CDL Manual (AAMVA model), Section 6, p. 90Never use the hand valve for parking because all the

  36. #36

    If a trailer does not have spring brakes, what should you use to keep it from moving when parked?

    1. Wheel chocks
    2. The trailer hand valve
    3. The emergency line shut-off valve
    4. The service air line

    Answer: A. If the trailer does not have spring brakes, use wheel chocks to keep the trailer from moving.

    Source: North Dakota CDL Manual (AAMVA model), Section 6, p. 90spring brakes, use wheel chocks to keep the trailer

  37. #37

    The tractor protection valve keeps air in the tractor brake system if:

    1. the tractor brakes overheat on a long downgrade
    2. the engine is shut off and the parking brake is set
    3. the trailer breaks away or develops a bad leak
    4. the trailer is empty or only lightly loaded

    Answer: C. The tractor protection valve keeps air in the tractor or truck brake system should the trailer break away or develop a bad leak.

    Source: North Dakota CDL Manual (AAMVA model), Section 6, p. 90The tractor protection valve keeps air in the tractor

  38. #38

    When the tractor protection valve closes automatically, it also:

    1. applies the tractor spring brakes
    2. opens the service line to the trailer
    3. charges the trailer air tanks
    4. lets the air out of the trailer emergency line

    Answer: D. When it closes, it stops air from going out of the tractor and lets the air out of the trailer emergency line, so the trailer emergency brakes come on.

    Source: North Dakota CDL Manual (AAMVA model), Section 6, p. 90It also lets the air out of the trailer emergency line.

  39. #39

    On newer vehicles, the trailer air supply control is a:

    1. blue round knob
    2. yellow square knob
    3. green diamond-shaped knob
    4. red eight-sided knob

    Answer: D. The trailer air supply control on newer vehicles is a red eight-sided knob used to control the tractor protection valve.

    Source: North Dakota CDL Manual (AAMVA model), Section 6, p. 90The trailer air supply control on newer vehicles is a red

  40. #40

    Which trailer air line is also called the control line or signal line?

    1. The emergency line
    2. The service line
    3. The supply line
    4. The drain line

    Answer: B. The service line (also called the control line or signal line) carries air controlled by the foot brake or the trailer hand brake.

    Source: North Dakota CDL Manual (AAMVA model), Section 6, p. 90(also called the control line or signal line)

  41. #41

    Emergency air lines are often color coded:

    1. red
    2. blue
    3. yellow
    4. green

    Answer: A. Emergency (supply) lines are often coded red, and the service line is blue, to avoid mixing them up.

    Source: North Dakota CDL Manual (AAMVA model), Section 6, p. 90Emergency lines are often coded with the color red

  42. #42

    If you cross the air lines when connecting the glad hands, what happens?

    1. The trailer brakes lock up immediately
    2. The tractor protection valve cannot be opened
    3. Air will not be available to release the trailer spring brakes
    4. The trailer air tanks overfill

    Answer: C. Crossed lines send supply air to the service line instead of charging the trailer air tanks, so the trailer spring brakes will not release.

    Source: North Dakota CDL Manual (AAMVA model), Section 6, p. 91Air will not be available to release the trailer

  43. #43

    Before driving, how should you test the trailer brakes using the hand valve or the air supply control?

    1. Pull gently against them in a low gear
    2. Drive fast and brake hard
    3. Rev the engine in neutral
    4. Back up against them in reverse

    Answer: A. Always test the trailer brakes before driving, and pull gently against them in a low gear to make sure the brakes work.

    Source: North Dakota CDL Manual (AAMVA model), Section 6, p. 91them in a low gear to make sure the brakes work.

  44. #44

    Why should you use dummy couplers when the air lines are not connected to a trailer?

    1. To keep the air pressure from dropping in the tractor brake system
    2. To tell the service line apart from the emergency line on the tractor
    3. To prevent water and dirt from getting into the coupler and air lines
    4. To lock the tractor protection valve in the open position while parked

    Answer: C. Dummy couplers keep water and dirt out of the coupler and air lines, and it is very important to keep the air supply clean.

    Source: North Dakota CDL Manual (AAMVA model), Section 6, p. 91This will prevent water and dirt from getting into

  45. #45

    If your air tanks have automatic drains, you should:

    1. never open the manual drains
    2. open the drains only in freezing weather
    3. open them only if the gauge drops
    4. still open the drains to make sure

    Answer: D. Automatic drains keep most moisture out, but you should still open the drains to make sure.

    Source: North Dakota CDL Manual (AAMVA model), Section 6, p. 91you should still open the drains to make sure.

  46. #46

    Shut-off valves in the service and supply air lines are also called:

    1. glad hands
    2. relay valves
    3. trolley valves
    4. cut-out cocks

    Answer: D. Shut-off valves, also called cut-out cocks, are used in the service and supply lines at the back of trailers that tow other trailers.

    Source: North Dakota CDL Manual (AAMVA model), Section 6, p. 91Shut-off valves (also called cut-out cocks) are used in

  47. #47

    Converter dollies and trailers built before what year are not required to have spring brakes?

    1. 1965
    2. 1975
    3. 1985
    4. 1998

    Answer: B. Converter dollies and trailers built before 1975 are not required to have spring brakes.

    Source: North Dakota CDL Manual (AAMVA model), Section 6, p. 91However, converter dollies and trailers built before 1975 are not required to have spring

  48. #48

    On a trailer without spring brakes, once the emergency brakes come on, they will hold only as long as:

    1. there is air pressure in the trailer air tank
    2. the tractor engine is running
    3. the trailer hand valve is applied
    4. the tractor protection valve stays open

    Answer: A. The emergency brakes hold only as long as there is air pressure in the trailer air tank; eventually the air leaks away and there will be no brakes.

    Source: North Dakota CDL Manual (AAMVA model), Section 6, p. 91But the brakes will hold only as long as there is air

  49. #49

    An antilock braking system (ABS) only activates when:

    1. you brake at speeds over 40 mph
    2. the trailer is empty
    3. the wheels are about to lock up
    4. the parking brake is applied

    Answer: C. ABS is an addition to your normal brakes and only activates when wheels are about to lock up.

    Source: North Dakota CDL Manual (AAMVA model), Section 6, p. 92ABS only activates when wheels are about to lock up.

  50. #50

    Compared with a vehicle without ABS, ABS on a combination vehicle:

    1. does not necessarily shorten stopping distance but helps keep the vehicle under control
    2. always shortens the stopping distance by at least half on wet and dry roads
    3. lets you follow other vehicles more closely because you can stop in a shorter distance
    4. lets you drive faster in curves because the wheels can no longer lose traction

    Answer: A. ABS does not necessarily shorten stopping distance, but it helps you keep control during hard braking; it will not let you drive faster or follow more closely.

    Source: North Dakota CDL Manual (AAMVA model), Section 6, p. 92ABS does not necessarily shorten your stopping distance

  51. #51

    If only the trailer has ABS and you lose steering control or start a tractor jackknife, you should:

    1. apply the trailer hand valve
    2. brake harder
    3. turn the wheel sharply away from the skid
    4. let up on the brakes, if you can do so safely

    Answer: D. When only the trailer has ABS and you lose steering control or start a tractor jackknife, let up on the brakes (if you can safely do so) until you gain control.

    Source: North Dakota CDL Manual (AAMVA model), Section 6, p. 92tractor jackknife, let up on the brakes (if you can safely

  52. #52

    Failure to keep the fifth wheel plate lubricated could cause:

    1. tire blowouts
    2. steering problems
    3. a loss of air pressure
    4. trailer brake failure

    Answer: B. Failure to keep the fifth wheel plate lubricated could cause steering problems because of friction between the tractor and trailer.

    Source: North Dakota CDL Manual (AAMVA model), Section 6, p. 92could cause steering problems because of friction

  53. #53

    Before coupling, the fifth wheel safety unlocking handle should be in the:

    1. open position
    2. automatic lock position
    3. released position
    4. slide position

    Answer: B. To be ready for coupling, the fifth wheel should be tilted down toward the rear, jaws open, and the safety unlocking handle in the automatic lock position.

    Source: North Dakota CDL Manual (AAMVA model), Section 6, p. 93Safety unlocking handle in the automatic lock position.

  54. #54

    Why should you never back under a trailer at an angle?

    1. You might push the trailer sideways and break the landing gear
    2. You might bend the fifth wheel jaws and jam the release arm
    3. You might damage the air lines and the electrical cable between units
    4. You might release the trailer brakes and let the trailer roll away

    Answer: A. Never back under the trailer at an angle because you might push the trailer sideways and break the landing gear.

    Source: North Dakota CDL Manual (AAMVA model), Section 6, p. 93push the trailer sideways and break the landing gear.)

  55. #55

    When checking for crossed air lines, why do you shut the engine off?

    1. To build air pressure faster
    2. To prevent the tractor from moving
    3. So you can hear the brakes
    4. To close the tractor protection valve

    Answer: C. Shut the engine off so you can hear the trailer brakes being applied and released when you check for crossed air lines.

    Source: North Dakota CDL Manual (AAMVA model), Section 6, p. 93Shut engine off so you can hear the brakes.

  56. #56

    When you secure the vehicle to inspect the coupling, why should you take the key with you?

    1. So the fifth wheel stays locked while you inspect the air lines
    2. So the air pressure won't drop while you walk around the unit
    3. To reset the low air warning before you step out of the cab
    4. So someone else won’t move the truck while you are under it

    Answer: D. Shut off the engine and take the key with you so someone else won’t move the truck while you are under it.

    Source: North Dakota CDL Manual (AAMVA model), Section 6, p. 93Shut off engine and take key with you so someone

  57. #57

    After coupling, how much space should there be between the upper and lower fifth wheel?

    1. None
    2. About one inch
    3. About two inches
    4. Enough to see the kingpin

    Answer: A. There must be no space between the upper and lower fifth wheel; if there is space, something is wrong (the kingpin may be on top of the closed jaws).

    Source: North Dakota CDL Manual (AAMVA model), Section 6, p. 93Make sure there is no space between upper and

  58. #58

    When uncoupling, how should you hang the electrical cable?

    1. Coiled and resting on top of the fifth wheel plate
    2. Plugged into the dummy coupler to keep the plug clean
    3. With the plug down to prevent moisture from entering it
    4. Wrapped around the air lines to keep it off the ground

    Answer: C. Hang the electrical cable with the plug down to prevent moisture from entering it, and support the lines so they won’t be damaged.

    Source: North Dakota CDL Manual (AAMVA model), Section 6, p. 94Hang electrical cable with plug down to prevent moisture from entering it.

  59. #59

    When uncoupling, you should chock the trailer wheels if the trailer doesn’t have spring brakes or:

    1. if the trailer is empty
    2. if you are not sure
    3. if the trailer is loaded
    4. if the ground is level

    Answer: B. Chock the trailer wheels if the trailer doesn’t have spring brakes or if you’re not sure, because air could leak out and release the emergency brakes.

    Source: North Dakota CDL Manual (AAMVA model), Section 6, p. 94spring brakes or if you’re not sure.

  60. #60

    When uncoupling a loaded trailer, after the landing gear makes firm contact with the ground, you should:

    1. raise the trailer off the fifth wheel
    2. back the tractor away
    3. release the trailer brakes
    4. turn the crank in low gear a few extra turns

    Answer: D. After firm contact, turn the crank in low gear a few extra turns to lift some weight off the tractor (but do not lift the trailer off the fifth wheel).

    Source: North Dakota CDL Manual (AAMVA model), Section 6, p. 94turn crank in low gear a few

  61. #61

    When you unlock the fifth wheel, you should keep your legs and feet:

    1. clear of the rear tractor wheels
    2. on the trailer landing gear
    3. under the trailer apron
    4. behind the fifth wheel plate

    Answer: A. Keep legs and feet clear of the rear tractor wheels to avoid serious injury in case the vehicle moves.

    Source: North Dakota CDL Manual (AAMVA model), Section 6, p. 94Keep legs and feet clear of the rear tractor wheels to

  62. #62

    How many steps are in the inspection procedure the manual says to use for a combination vehicle?

    1. Five
    2. Seven
    3. Nine
    4. Twelve

    Answer: B. Use the seven-step inspection procedure described in Section 2 to inspect your combination vehicle.

    Source: North Dakota CDL Manual (AAMVA model), Section 6, p. 95Use the seven-step inspection procedure described in

  63. #63

    When you open the emergency line shut-off valve at the rear of the last trailer during the air-flow check, what should you hear?

    1. A hissing from the tractor protection valve
    2. Nothing, because the valve is dry
    3. Air escaping, showing the entire system is charged
    4. The trailer brakes locking

    Answer: C. You should hear air escaping, showing the entire system is charged; then close the emergency line valve.

    Source: North Dakota CDL Manual (AAMVA model), Section 6, p. 96You should hear air escaping,
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