CDL - Combination Vehicle Practice Test

A tractor with a(n) ________ trailer requires the shortest amount of stopping distance .
1. empty
2. fully loaded
3. lightly loaded

The air leakage rate for a combination vehicle ( engine off, brakes on) should not be more than _____ psi per minute .
1. 4
2. 6
3. 2

If you do not do the final air brake check for air leaks and fix them before driving,
1. you could lose your brakes while driving
2. your fuel usage will increase
3. tire pressure will drop

Which part of the kingpin should the locking jaws close around?

Glad hands are used to connect the ....
1. kingpin from the trailer to the locking jaws of the fifth wheel
2. electrical lines from the tractor to the trailer
3. service and emergency air lines from the truck or tractor to the trailer

Trucks roll over more easily when fully loaded and are
1. ten times more likely to roll over in a crash than empty rigs
2. five times more likely to roll over in a crash than empty rigs
3. two times more likely to roll over in a crash than empty rigs

In general, the higher your trucks center of gravity, the ...
1. easier it is to turn over
2. more stable it is when turning
3. easier it is to turn around corners

You are driving a combination vehicle when the trailer breaks away, pulling apart both air lines. You would expect the trailer brakes to come on and ...
1. the tractor to lose all air pressure
2. the tractor protection valve to close
3. the trailer supply valve to stay open

When you drive a set of doubles, which shut-off valve must be closed in the last trailer?
1. Middle section
2. front section
3. back section

The fifth wheel locking lever is not locked after the jaws close around the kingpin. This means that...
1. the parking lock is off and you may drive away
2. the trailer will not swivel on the fifth wheel
3. the coupling is not right and should be fixed before you drive the coupled unit

What gear should the tractor engine be in after you uncouple the trailer and are inspecting the trailer?
1. neutral
2. low reverse
3. high reverse

After you supply air to the trailer, make sure the air lines are not crossed and the trailer brakes are working. This is done by ..
1. lifting the brake pedal
2. applying and releasing the trailer brakes and listening for brake sounds
3. turning on the parking brake from the cab

If the brakes did not release when you pushed the trailer air supply valve, you should ...
1. cross the air lines,
2. check the air line connections
3. check the electrical cables

You have a major leak in the service line, and you apply the brakes. Service air pressure will escape and cause the
1. trailer tank pressure to be lost
2. trailer emergency brakes to come on
3. tractor spring brakes to lock on

You are uncoupling a trailer. After you shut off the trailer air supply and lock the trailer brakes, you should
1. immediately apply your tractor parking brakes
2. begin to lower the trailer landing gear
3. back up gently and ease pressure on the fifth wheel locking jaws

When should you use the hand valve to park a combination vehicle?
1. To park at loading docks
2. To park on a grade
3. never

The front trailer supports are up, and the trailer is resting on the tractor. Make sure that
1. there is enough clearance between the upper and lower fifth wheel
2. there is enough clearance between the tractor frame and the landing gear
3. the safety latch is in the unlocked position

The trailer hand valve works the trailer brakes. Which of these statements is true?
1. the foot brake sends air to all the brakes on the vehicle ( including the trailer(s))
2. The trailer hand valve should be used only to test the trailer brakes
3. all the above

Where should the tractor be when you inspect the landing gear after uncoupling the trailer?
1. With the fifth wheel directly beneath the kingpin
2. completely cleared from the trailer
3. with the tractor frame under the trailer

After you lock the kingpin into the fifth wheel, you should check the connection by pulling
1. the tractor ahead gently with the trailer brakes locked
2. forward 50 feet, then turning right, and then left
3. the tractor ahead sharply to release the trailer brakes

At night, when a vehicle is carrying a load that extends four feet or more beyond the rear of the body, there must be ________ at the extreme end of the load.
1. red lights
2. red flags
3. a red flag

Which type of truck-trailer combination has the greatest chance of a "crack-the-whip" rollover?
1. A tractor pulling three trailers
2. A single tractor trailer
3. A tractor pulling two trailers

Air and electrical lines from the tractor to the trailer should be...
1. pulled tight with very little slack
2. secured but with enough slack for turns
3. resting on the frame of the tractor.

Compared with a straight truck or bus, there are ________ things to inspect in combination vehicles.
1. fewer
2. more
3. the same number of

What is the emergency air line for?
1. To engage the trailer brakes in case of air pressure loss
2. To have extra air pressure in case you need it
3. To engage the front brakes of the tractor in case of an emergency

The tractor protection valve will close and the trailer _______ brakes will come on when there is a major leak in the brake line.
1. parking
2. service
3. emergency

A trailer is most likely to jackknife when it is ...
1. loaded to full capacity
2. overloaded
3. empty

When you are uncoupling a loaded trailer, lower the landing gear until it ...
1. reaches the ground
2. makes firm contact with the ground
3. makes contact with the ground, and leave the trailer off the fifth wheel

How much space should there be between the upper and lower fifth wheel after coupling?
1. Just enough to see light through it
2. About 1/4 inch
3. None

After you have coupled the trailer, you should start to raise the landing gear by using
1. low gear
2. high gear
3. intermediate gear

The fifth wheel locking lever is not locked after the jaws close around the kingpin. This means that
1. the parking lock is off and you may drive away
2. the coupling is not right and should be fixed before you drive the coupled unit
3. the trailer will not swivel on the fifth wheel

When checking the trailer emergency brakes, make sure that the tractor protection control valve is placed in the _______ position.
1. normal
2. emergency
3. neutral

You should use chocks when parking a trailer without spring brakes because
1. if the air supply leaks away, there will be no brakes
2. some states require chocking of trailer wheels
3. you dont want the trailer rolling down a hill

You are uncoupling a trailer. After you shut off the trailer air supply and lock the trailer brakes, you should
1. begin to lower the trailer landing gear
2. immediately apply your tractor parking brakes
3. back up gently to ease pressure on the fifth wheel locking jaw

While you are driving, your emergency air line breaks or gets pulled apart. The loss of pressure will cause the
1. air compressor to unload instead of pumping air
2. trailer emergency brakes to come on
3. trailer supply valve to open

You are coupling a tractor to a semi-trailer. You have backed up but are not yet under it. Before backing under the semi trailer, you should hook up
1. the electrical service cable
2. nothing. Back up and lock the fifth wheel
3. The emergency and service air lines

When backing a tractor under a trailer, you should expect that
1. the trailer will be lifter slightly when the tractor backs under it
2. the trailer landing gear is fully extended
3. the end of the kingpin is even with the top of the fifth wheel

When you drive a set of doubles, which shut0off valve must be closed in the last trailer?
1. front
2. back
3. middle

What is a tractor jackknife?
1. When you lock up the drive tires on the trailer and the trailer spins out sideways as the tractor continues to push forward
2. When you lock up the drive tires on the tractor and the tractor spins out sideways as the trailer continues to push forward
3. Neither of the above