Quiz: CDL Combination Practice Test Questions!
A combination vehicle is one that connects a tractor to one or more trailers. These types of vehicles are used to transport heavy objects and due to their uniqueness need a different driving license other than the normal commercial one. If you are training to get your CDL the combination test below is for you. Give it a shot and drive safe.
- 1.You are driving a combination vehicle. If the service air line comes apart but the emergency line stays together, what will happen right away?
- A.
The trailer's air tank with exhaust through the open line.
- B.
The emergency trailer brakes will come on.
- C.
Nothing is likely to happen until you try to apply the brakes.
- 2.If you cannot make a turn without entering another traffic lane, you should:
- A.
Turn wide before you start your turn.
- B.
Turn wide as you complete your turn.
- C.
Not make that turn.
- 3.When should you use chocks to park a trailer not equipped with spring brakes?
- A.
Never
- B.
Always
- C.
Only when it will be parked on an incline.
- 4.In general, the higher your truck's "center of gravity", the:
- A.
Easier it is to turn around corners.
- B.
More stable it is when turning.
- C.
Easier it is to turn over.
- 5.One of the things a driver can do to prevent a rollover is to keep:
- A.
Both hands firmly on the steering wheel.
- B.
The cargo as close to the ground as possible.
- C.
The fifth wheel free play as small as possible.
- 6.The trailer air supply control (or tractor protection valve control) should automatically close when the air pressure falls between ______ psi.
- A.
20 and 45
- B.
60 and 85
- C.
100 and 125
- 7.
- A.
Loaded to full capacity.
- B.
Over loaded.
- C.
Empty.
- 8.You are driving a combination vehicle. The trailer breaks away and pulls apart both air lines. You would expect the trailer brakes to come on and the:
- A.
Tractor to lose all air pressure.
- B.
Trailer supply valve to stay open.
- C.
Tractor protection valve to close.
- 9.The front trailer supports are up and the trailer is resting on the tractor. Make sure:
- A.
There is enough clearance between the upper and lower fifth wheel.
- B.
The safety latch is in the unlocked position.
- C.
There is enough clearance between the tractor frame and landing gear.
- 10.You are coupling a tractor to a semitrailer. You have backed up but are not under it. What should you hook up before backing under a semitrailer?
- A.
The emergency and service air lines.
- B.
The electrical service cable.
- C.
Nothing. Back up and lock the fifth wheel.
- 11.Which part of the kingpin should the locking jaws close around?
- A.
The shank.
- B.
The head.
- C.
The base.
- 12.You should not back a tractor under a trailer until the whole air system is:
- A.
Empty.
- B.
At normal pressure.
- C.
Between 60 and 80 psi.
- 13.You want to inspect the trailer supports. You should place the tractor transmission in which gear after you have uncoupled the trailer?
- A.
Low reverse.
- B.
Neutral.
- C.
High reverse.
- 14.What will happen if the air lines are crossed when you hook up to an old trailer with no spring brakes?
- A.
The hand valve applies the tractor brakes instead of the trailer brakes.
- B.
You could drive away with no trailer brakes.
- C.
The brake lights will not come on when you press the brake pedal.
- 15.After you supply air to the trailer, make sure the air lines are not crossed and the trailer brakes are working. You do this by:
- A.
Turning on the parking brakes from the cab.
- B.
Watching your mirrors to see if the trailer lights come on.
- C.
Applying/releasing the trailer brakes and listening for brake sounds.
- 16.Which of these statements is true?
- A.
The brake suspension system of combination vehicles work best with a light load.
- B.
Light vehicles need more braking power to stop than heavy ones.
- C.
"Bobtail" tractors can take longer to stop than a combination vehicle.
- 17.Loss of air pressure in the emergency line causes:
- A.
The relay valves to close.
- B.
An increase in air pressure to the service line.
- C.
The trailer's emergency brakes to come on.
- 18.Why should you be sure that the fifth wheel plate is greased as required?
- A.
To ensure good electrical connections.
- B.
To prevent steering problems.
- C.
To reduce heat and noise.
- 19.Glad hands are used to connect the:
- A.
Electric lines from the truck to the trailer.
- B.
Kingpin from the tractor to the locking jaws on the glide side.
- C.
Service and emergency air lines from the truck to the trailer.
- 20.When should you use the hand valve to park a combination vehicle?
- A.
To park at loading docks.
- B.
To park on a grade.
- C.
Never.
- 21.A tractor with a(n) ________ trailer requires the shortest stopping distance.
- A.
Empty.
- B.
Lightly loaded.
- C.
Fully loaded.
- 22.Under good driving conditions, you should leave at least one second of space between your vehicle and the vehicle ahead for every ______ feet of your vehicle's length.
- A.
10
- B.
20
- C.
30
- D.
Option 4
- 23.When you are uncoupling a loaded trailer, lower the landing gear until it:
- A.
Makes firm contact with the ground.
- B.
Makes contact with the ground and lifts the trailer off of the fifth wheel.
- C.
Just reaches the ground.
- 24.You have uncoupled a trailer and you want to inspect the landing gear. The tractor should be positioned:
- A.
With the tractor frame under the trailer.
- B.
Completely clear of the trailer.
- C.
With the fifth wheel directly beneath the kingpin.
- 25.When checking the trailer's emergency brakes, the tractor protection control valve should be placed in the _____ position.
- A.
Normal
- B.
Neutral
- C.
Emergency
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