A combination vehicle is one that connects a tractor to one or more trailers. These 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 vehicle test below is for you. Give it a shot and drive safe.
The trailer's air tank with exhaust through the open line.
The emergency trailer brakes will come on.
Nothing is likely to happen until you try to apply the brakes.
Turn wide before you start your turn.
Turn wide as you complete your turn.
Not make that turn.
Never
Always
Only when it will be parked on an incline.
Easier it is to turn around corners.
More stable it is when turning.
Easier it is to turn over.
Both hands firmly on the steering wheel.
The cargo as close to the ground as possible.
The fifth wheel free play as small as possible.
20 and 45
60 and 85
100 and 125
Loaded to full capacity.
Over loaded.
Empty.
Tractor to lose all air pressure.
Trailer supply valve to stay open.
Tractor protection valve to close.
There is enough clearance between the upper and lower fifth wheel.
The safety latch is in the unlocked position.
There is enough clearance between the tractor frame and landing gear.
The emergency and service air lines.
The electrical service cable.
Nothing. Back up and lock the fifth wheel.
The shank.
The head.
The base.
Empty.
At normal pressure.
Between 60 and 80 psi.
Low reverse.
Neutral.
High reverse.
The hand valve applies the tractor brakes instead of the trailer brakes.
You could drive away with no trailer brakes.
The brake lights will not come on when you press the brake pedal.
Turning on the parking brakes from the cab.
Watching your mirrors to see if the trailer lights come on.
Applying/releasing the trailer brakes and listening for brake sounds.
The brake suspension system of combination vehicles work best with a light load.
Light vehicles need more braking power to stop than heavy ones.
"Bobtail" tractors can take longer to stop than a combination vehicle.
The relay valves to close.
An increase in air pressure to the service line.
The trailer's emergency brakes to come on.
To ensure good electrical connections.
To prevent steering problems.
To reduce heat and noise.
Electric lines from the truck to the trailer.
Kingpin from the tractor to the locking jaws on the glide side.
Service and emergency air lines from the truck to the trailer.
To park at loading docks.
To park on a grade.
Never.
Empty.
Lightly loaded.
Fully loaded.
10
20
30
Option 4
Makes firm contact with the ground.
Makes contact with the ground and lifts the trailer off of the fifth wheel.
Just reaches the ground.
With the tractor frame under the trailer.
Completely clear of the trailer.
With the fifth wheel directly beneath the kingpin.
Normal
Neutral
Emergency
Wait!
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