WorksheetsCombination 4 2025
Total questions: 20
Worksheet time: 10mins
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 is the best way to brake and keep the truck in a straight line
It should not be done
You should not back a tractor under a trailer until the whole air system is:
Half the maximum pressure
Between 60 and 80 PSI
At normal pressure
After you supply air to the trailer, make sure the airlines are not crossed and the trailer brakes are working. This can be done by:
Turning on the parking brakes from the cab
Lifting the brake pedal
Applying and releasing the trailer brakes and listening for brake sounds
What is the safest way for you to make a turn without entering another traffic lane?
If you must cross into the oncoming lane to make a turn and you see vehicles coming toward you, stop and back up for them.
You should turn wide before you start the turn.
You should turn wide as you complete the turn.
Even before antilock braking systems (ABS) were required, some vehicles already had them. How can you check if your vehicle has ABS?
Look under the vehicle for the ABS test light.
Brake the vehicle on a slippery road and see if the wheels lock.
Look under the vehicle for the ECU and wheel speed sensor wires coming from the back of the brakes.
What is the emergency air line?
Air lines that control the emergency brakes of the tractor
Air lines connecting the parking brake to the trailer brakes
Air lines that control the emergency brakes on combination vehicles
You are uncoupling a trailer. After you shut off the trailer air supply and lock the trailer brakes, you should
begin to lower the trailer landing gear.
immediately apply your tractor parking brakes.
back up gently to ease pressure on the fifth wheel locking jaws.
A tractor with a(n) _______ trailer requires the shortest amount of stopping distance.
empty
lightly loaded
fully loaded
The tractor protection valve will close and the trailer_______ brakes will come on when there is a major leak in the brake line.
service
parking
emergency
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
Tractor spring brakes to lock on
Trailer emergency / spring brakes to come on
Semi-trailers made before 1975 that are equipped with air brakes:
Are easier to brake because they are heavier
Usually need a glad hand converter
None of the answers are correct
Often do not have spring brakes
How much space should be between the apron and fifth wheel after coupling?
At lease 1/2 inch
Just enough to see light through it
None
On a trailer, where is the yellow antilock brake (ABS) malfunction lamp located?
On the left side and on the front center
On the right rear corner
On the front left or rear left corner
What are the other names for the service air line?
Curved line and signal line
Straight line and control line
Control line and signal line
You should not back a tractor under a trailer until the whole air system is
bled down to half the maximum pressure.
between 60 and 80 psi.
at normal pressure.
Air and electrical lines from the tractor to the trailer should be
pulled tight with very little slack.
resting on the frame of the tractor.
secured but with enough slack for turns.
Which of these statements is true?
Always delay braking a heavy vehicle until you have no other choice
Light vehicles need more braking power to stop than heavy ones
Bobtail tractors can take longer to stop than a combination vehicle loaded to the maximum gross weight
Which part of the kingpin should the locking jaws close around?
The head
The base
The shank
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.
30
20
10
You supply air to the trailer tanks by
connecting the service line glad hand.
pulling out the trailer air supply control.
pushing in the trailer air supply control.
