Combination Vehicle Test

Combination Vehicle CDL Practice Tests

1 / 60

Semi trailers made before 1975 that are equipped with air brakes:

Often do not have spring brakes.

Usually need a glad hand converter.

Are easier to brake because they are heavier.

Only were equipped with spring brakes.

2 / 60

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:

The trailer supply valve to stay open.

The tractor to lose all air pressure.

The tractor protection valve to close.

The tractor protection valve to open.

3 / 60

The fifth wheel locking lever is not locked after the jaws close around the kingpin. This means that:

You can set the fifth wheel for weight balance.

The coupling is not right and should be fixed before driving the vehicle.

The parking lock is off and you may drive away.

The fifth wheel needs to be replaced.

4 / 60

The air leakage rate for a combination vehicle (engine off, brakes off) should be no more than ____ psi per minute.

5 / 60

The hand valve should be used:

To test the trailer brakes.

Only when the trailer is fully loaded.

Only in emergencies.

Only with the foot brake.

6 / 60

The driver crosses the air lines when hooking up to an old trailer. What will happen?

If the trailer has no spring brakes, you can drive away, but you will not have trailer brakes.

The brake pedal will work the trailer spring brakes instead of the air brakes.

The hand valve will apply the tractor brakes instead of the trailer brakes.

None of the above.

7 / 60

In normal driving, some drivers use the hand valve before applying the brake pedal to prevent a jackknife. Which of these statements is true?

It results in less skidding than using the brake pedal alone.

It should not be done.

It is the best way to brake and keep the truck in a straight line.

It should only be used if you're aware of the dangers.

8 / 60

The air leakage rate for a combination vehicle (engine off, brakes on) should not be more than ____ psi per minute.

2 1/2

9 / 60

If the service air line comes apart while you are driving a combination vehicle but the emergency line stays together, what will happen right away?

Nothing is likely to happen until you try to apply the brakes.

You'll come to a complete stop.

The trailer's air tank will exhaust through the open line.

The emergency tractor brakes will come on.

10 / 60

Before you back under a trailer, make sure the:

Air brakes are off.

Tractor protection valve is normal.

Landing gear is up.

Trailer brakes are locked.

11 / 60

Large combination vehicles take longer to stop...

When they are empty

When they are loaded

Than bobtail tractors

It takes the same time whether empty or loaded

12 / 60

"Off-tracking" occurs when you go around a corner and...

The rear wheels follow a different path than the front wheels

The rear trailer goes off the road

The rear wheels follow the front ones in a straight line

The front of the trailer pulls to the right

13 / 60

To prevent rollovers, remember to...

Keep the load centered

Keep the load as low as possible

Go slow around turns

All of the above

14 / 60

The service air line is controlled by...

The pressure applied to the line by the foot brake or the trailer hand brake

The relay valve which connects the trailer air tanks to the trailer air brakes

The relay valve which sends air pressure from the trailer air tank to the trailer brake chambers

All of the above

15 / 60

A device which connects the service and emergency air lines from the truck to the trailer is called...

Relay switch

Glad hands

Service couplers

Shut off valves

16 / 60

When rolling up the landing gear to complete the coupling process...

leave the landing gear half way down to make uncoupling easier later

use low gear until the tractor is supporting the trailer

use high gear to speed up the process

grease the landing gear to speed up the process

17 / 60

If you cross connect the two air lines the following will result...

Nothing, the lines are interchangeable

You will not have air going to the trailer brakes

Your tractor brakes will lock up

You could not move the tractor

18 / 60

When coupling the glad hands, you should NOT do the following...

Clean the couplers before a connection is made

Press the two seals together at a 90 degree angle

Cross air supply lines to test them for leaks

Match the colors to each other, or read the tags before connecting

19 / 60

If you start a trailer skid you should...

Step on the brakes quickly

Release the brakes to get traction back

Use the trailer hand brake

Slowly apply pressure to the brakes

20 / 60

When uncoupling, if you park the trailer at an angle...

you won't have to do as much walking around the vehicle

you'll have more room to maneuver in the yard

you'll make the process easier

you could do damage to the landing gear

21 / 60

You are coupling a tractor and semi trailer and have connected the air lines. Before backing under the trailer, you should:

Make sure that the trailer brakes are off.

Supply air to the trailer system, then pull out the air supply knob to lock the trailer brakes.

Apply the brakes twice to alert others.

All of the above.

22 / 60

Which of these statements is true?

Light vehicles need more braking power to stop than heavy ones.

Always delay braking a heavy vehicle until you have no other choice.

"Bobtail" tractors can take longer to stop than a combination vehicle loaded to the maximum gross weight.

None of the above.

23 / 60

Air lines on a combination vehicle are often colored to keep them from getting mixed up. The emergency line is ____; the service line is ____.

Red, blue

Blue, red

Black, yellow

Depends on the type of trailer

24 / 60

You have coupled with a semi trailer. In what position should you put the front trailer supports before driving away?

Three turns off the top with the crank handle secured in it's bracket.

Fully raised with the crank handle secured in its bracket.

Raised 1/2 way with the crank handle removed.

None of the above.

25 / 60

You are coupling a tractor to a semi trailer and have backed up but are not under it. What should you hook up before backing under?

The safety chain.

The electrical service cable.

Nothing, back up and lock the fifth wheel.

The emergency and service air lines.

26 / 60

When backing under a tractor under a trailer you should expect:

Trailer will be lifted slightly when the tractor backs under it.

End of the kingpin is even with the top of the fifth wheel.

Trailer landing gear is fully extended.

No movement of the trailer if you've done it correctly.

27 / 60

You have a major leak in the service line and you put on the brakes. Service air pressure will escape and cause the:

Trailer tank pressure to be lost.

Trailer emergency brakes to come on.

Tractor spring brakes to lock on.

None of the above.

28 / 60

The front trailer supports are up and the trailer is resting on the tractor. Make sure:

There is enough clearance between the tractor frame and the landing gear.

There is enough clearance between the tops of the tractor tires and the nose of the trailer.

Both a and b are correct.

None of the above.

29 / 60

The safety catch for the fifth wheel locking lever must be ____ for a coupling to be complete.

Under the locking lever

Over the locking lever

Through the locking lever

Inside the locking lever

30 / 60

Why should you lock the tractor glad hands (or dummy couplers) to each other when you are not towing a trailer?

The connected brake circuit becomes a back up air tank.

If you did not, you could never build system pressure.

It will keep dirt and water out of the lines.

You should never do this.

31 / 60

There are two things that a driver can do to prevent a roll over. They are: (1) Keep the cargo as close to the ground as possible; and (2):

Make sure that the brakes are properly adjusted.

Keep the fifth wheel's free play as tight as possible.

Go slowly around turns.

Never drive a tanker.

32 / 60

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:

Applying and releasing the trailer brakes and listening for brake sounds.

Lifting the brake pedal.

Turning on the parking brakes from the cab.

Releasing the tractor brakes.

33 / 60

Why should you be sure that the fifth wheel plate is greased as required?

To reduce heat and noise

To prevent steering problems

To ensure good electrical connections

To make uncoupling easier.

34 / 60

You supply air to the trailer tanks by:

Pushing in the trailer air supply valve.

Pulling out the trailer air supply valve.

Connecting the blue line to the red line.

Connecting the service line glad hand.

35 / 60

When should you use the hand valve to park a combination vehicle?

To park at loading docks.

Never

To park on a grade

In sub-freezing temperatures.

36 / 60

How should you test the tractor semi trailer connection for security?

Pull gently forward in low gear against the locked trailer brakes, then look at it carefully.

Put the tractor in gear and pull ahead with a sharp jerk.

Rock the trailer back and forth with the trailer brakes locked.

Don't worry. The connection should be fine.

37 / 60

When you get ready to back under the semi trailer you should line up:

About 12 degrees off the line of the trailer.

The kingpin to engage the driver's side locking jaw first.

Exactly one trailer length in back of the trailer.

Directly in front of the trailer.

38 / 60

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

The base

The shank

The shiny section

The head

39 / 60

You are coupling a semi trailer to your tractor but have not yet backed under. The trailer is at the right height when:

It will be raised slightly when the tractor is backed under it.

The kingpin is about 1 1/4 inches above the fifth wheel.

The end of the kingpin is even with the top of the fifth wheel.

The fifth wheel is sure to miss the kingpin.

40 / 60

You should not back a tractor under a trailer until the whole air system is:

Between 60 and 80 psi

Empty.

Bled down to half the maximum pressure

At normal pressure

41 / 60

The fifth wheel should be checked to see if...

There is damage or missing parts

It is properly greased

The jaws are open

All of the above

42 / 60

You should crank the landing gear until...

It is six inches off the ground

You can clear railroad tracks

The crank handle is loose

It is as far up as it will go

43 / 60

In order to inspect the coupling you should...

Make sure there is space between the upper and lower fifth wheel

Check that the locking lever is in the open position

Make sure the fifth wheel jaws are open

Use a flashlight if necessary

44 / 60

The trailer air supply control...

Is a red, triangular-shaped knob

Is a yellow, square knob

Is a red, square knob

Is a red, eight sided knob

45 / 60

Before you begin coupling...

check the condition of the tractor frame

check your path for hazards

pre-position the fifth wheel

put the spring brakes on

46 / 60

Which of the following steps comes first?

apply the trailer brakes

raise the landing gear

put the transmission in reverse

connect the air supply lines

47 / 60

The trailer should be lowered so that...

the trailer is far above the fifth wheel

the tractor strikes the nose of the trailer

you can use the landing gear to make any adjustments

it's raised slightly when the tractor's backed under it

48 / 60

A king pin is...

The pin which locks the air brake lines together

A pin which locks the trailer to the tractor on the fifth wheel

A pin which holds the wheels on the axles

The pin a driver receives for safe driving

49 / 60

The earliest way to notice a trailer skid is...

By feeling the pull on your steering wheel

By feeling a jerking in the back of the tractor

By seeing it in your mirrors

By hearing the squeal from the tires

50 / 60

When coupling the trailer, back up slowly until...

The load shifts inside the trailer

The fifth wheel just touches the trailer

You can see the rear wheels in the mirror

You hit the front of the trailer with the tractor

51 / 60

Which one of the following is controlled by the foot brake?

The service air line

The emergency air line

The shut off valve

The hose coupler

52 / 60

You can damage the landing gear if you...

back under the trailer at an angle

align the tractor and trailer

position the trailer kingpin in the center of the fifth wheel

back under the trailer in a straight line

53 / 60

Which one of the following statements about tractor protection valves is NOT true?

It keeps air in the tractor in the event the trailer air leaks

It is controlled by the trailer air supply valve in the cab

When it closes it allows air to leak from the tractor line

It will close automatically if air pressure is low

54 / 60

The trailer hand valve should be used...

Only at highway speeds

Only when parking

Only to test the trailer brakes

Both B & C above

55 / 60

When you inspect the coupling, check to ensure that...

there's a little slack in the air lines

there's no slack in the air lines

the landing gear handle is hanging free

the electrical cable is unplugged

56 / 60

If one of the glad hands on your blue air line is missing a seal...

take one off the red air line and use that as a temporary replacement

you might end up with a service line air leak

you could experience an emergency line air leak

it's not a major problem and you should continue coupling

57 / 60

In order to supply air to the trailer, you must first...

Push in the tractor protection valve.

Pull out the "air supply' knob

Stop engine so you can hear the brakes

Cross the air lines to check for leaks

58 / 60

When traveling under 40 mph, you should follow other vehicles...

Only during the day

With a distance of one second for every ten feet of your vehicle length

With a distance of one second for every twenty feet of your vehicle length

As close as possible so others don't cut in

59 / 60

If you cross your air lines on a new trailer with spring brakes...

you won't be able to release the trailer brakes

you won't be able to release the tractor brakes

you won't have any operational brakes

you'll have no way of knowing there's a problem

60 / 60

When uncoupling, it's a good practice to...

couple the glad hands together

couple the glad hands to dummy couplers

hang the electrical cable with the plug end down

all of the above are acceptable

Your score is

Free Online Combination Vehicles CDL Practice Test questions and answers to help you pass the Combination Vehicles DMV exam.

To drive a commercial vehicle AND pull any kind of trailer, you must pass the Combination Vehicles written CDL exam. Combination vehicles are usually heavier, longer, and require more driving skill than single commercial vehicles. This means that drivers of combination vehicles need more knowledge and skill than drivers of single vehicles. You must understand the important safety factors that apply specifically to combination vehicles. Our CDL Combination Vehicles practice tests will prepare you to pass the exam.

Combination Vehicle CDL Practice Tests

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Contribute to your future - start studying now.