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1 / 40
A. there is less traction.
B. the center of gravity is lower.
C. you're unlikely to brake as hard.
Large combination vehicles take longer to stop when they are empty than when they are fully loaded. When lightly loaded, the very stiff suspension springs and strong brakes give poor traction and make it very easy to lock up the wheels.
2 / 40
A. level with the ground.
B. tilted down toward the rear of the tractor.
C. tilted up toward the rear of the tractor.
Check if fifth wheel is in proper position for coupling: The fifth wheel should be tilted down toward rear of tractor.
3 / 40
A. On the right rear corner
B. On the left side and on the front center
C. On the front left or rear left corner
Trailers will have yellow ABS malfunction lamps on the left side, either on the front or rear corner.
4 / 40
A. Light vehicles need more braking power to stop than heavy ones
B. Always delay braking a heavy vehicle until you have no other choice
C. Bobtail tractors can take longer to stop than a combination vehicle loaded to the maximum gross weight
Be very careful about driving bobtail tractors or tractors without semitrailers. Tests have shown that bobtails can be very hard to stop smoothly and can take longer to stop than a tractor-semitrailer loaded to maximum gross weight.
5 / 40
A. emergency
B. service
C. parking
When the tractor protection valve closes, it stops any air from going out of the tractor. It also lets the air out of the trailer emergency line. This causes the trailer emergency brakes to come on
6 / 40
A. The shank
B. The base
C. The head
Go under trailer and investigate the back of the fifth wheel. Make sure the fifth wheel jaws have closed around the shank of the kingpin.
7 / 40
A. 20 to 45 psi.
B. 75 to 100 psi.
C. 50 to 75 psi.
’s specification usually 20 – 45 psi.
8 / 40
A. cross the air lines.
B. check the electrical cables.
C. check the air line connections.
If you do cross the air-lines, supply air will be sent to the service line instead of going to charge the trailer air tanks. Air will not be available to release the trailer spring brakes. If the spring brakes don't release when you push the trailer air supply control, check the air-line connections.
9 / 40
A. red lights
B. a red flag
C. red flags
According to federal regulations, if the load projects more than 4 feet behind the rear of the vehicle, the end of the load must be marked as follows: (1) with red flags, each 18 inches square, in the daytime; or (2) with two red lights at night.
10 / 40
A. Brake the vehicle on a slippery road and see if the wheels lock.
B. Look under the vehicle for the ABS test light.
C. Look under the vehicle for the ECU and wheel speed sensor wires coming from the back of the brakes.
It may be difficult to tell if some units are equipped with ABS. Look under the vehicle for the electronic control unit (ECU) and wheel speed sensor wires coming from the back of the brakes.
11 / 40
A. normal
B. neutral
C. emergency
–45 psi, the trailer air supply control knob should pop out, or the valve control should go from the "normal" to the "emergency" position.
12 / 40
A. Only when the trailer is fully loaded
B. Only with the foot brake
C. To test the trailer brakes
The trailer hand valve, also called the trolley valve or Johnson bar, works the trailer brakes. The trailer hand valve should be used only to test the trailer brakes.
13 / 40
A. Trailer brakes are locked
B. Air brakes are off
C. Tractor protection valve is normal
Pull out the air supply knob or move the tractor protection valve control from normal to emergency.
14 / 40
A. You should turn wide before you start the turn.
B. You should turn wide as you complete the turn.
C. 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.
If you are driving a truck or bus that cannot make the right turn without swinging into another lane, turn wide as you complete the turn. Keep the rear of your vehicle close to the curb. This will stop other drivers from passing you on the right.
15 / 40
A. secured but with enough slack for turns.
B. pulled tight with very little slack.
C. resting on the frame of the tractor.
Make sure air and electrical lines are not tangled, pinched, dragging against tractor parts, and have enough slack for turns.
16 / 40
A. Control line and signal line
B. Curved line and signal line
C. Straight line and control line
The service line, also called the control line or signal line, carries air controlled by the foot brake or the trailer hand brake.
17 / 40
A. The trailer is half full, and the cargo is loaded in the front of the trailer. When making a sudden movement of the steering wheel, the cargo will tend to forcefully slide to the back of the trailer, forcing the trailer to roll over.
B. When making a quick lane change or sudden movement of the steering wheel, the tractor tends to rock and sway. The velocity of the rearmost trailer forces the tractor to roll over before the trailer.
C. When making a quick lane change or sudden movement of the steering wheel, the rear trailer tends to swing out. The force of the rear trailer becomes amplified, causing it to roll over.
Trucks with trailers have a dangerous crack-the-whip effect caused by rearward amplification. When you make a quick lane change, the crack-the-whip effect can turn the trailer over. There are many accidents where only the trailer has overturned.
18 / 40
A. speed.
B. rollovers.
C. following too closely.
More than half of truck driver deaths in crashes are the result of truck rollovers.
19 / 40
A. 30
B. 10
C. 20
One good rule says you need at least one second for each 10 feet of vehicle length at speeds below 40 mph. At greater speeds, you must add 1 second for safety.
20 / 40
A. The emergency and service air lines
B. The electrical service cable
C. Nothing; back up and lock the fifth wheel
Check glad hand seals and connect tractor emergency and service air-line to trailer emergency and service glad hand. Make sure air-lines are safely supported where they won't be crushed or caught while tractor is backing under the trailer.
21 / 40
A. turn the crank a few more times to lift some weight off the tractor.
B. secure the crank handle safely.
C. turn the crank a few more times until the trailer is lifted off the fifth wheel.
If trailer is loaded, after the landing gear makes firm contact with the ground, turn crank in low gear a few extra turns. This will lift some weight off the tractor making it easier to unlatch fifth wheel, and to recouple to the trailer.
22 / 40
A. The rear wheels of the tractor
B. The rear wheels of the first trailer
C. The rear wheels of the last trailer
If there is more than one trailer, the rear wheels of the last trailer will off-track the most
23 / 40
A. step on and off the brake pedal several times.
B. flash your high-beam headlights on and off several times.
C. keep pressing the brake pedal firmly.
’s specification usually 20 – 45 psi. This will cause the spring brakes to come on.
24 / 40
A. easier it is to turn around corners.
B. easier it is to turn over.
C. more stable it is when turning.
The height of the vehicle's center of gravity is very important for safe handling. A high center of gravity means you are more likely to tip over.
25 / 40
A. Air lines that control the emergency brakes on combination vehicles
B. Air lines connecting the parking brake to the trailer brakes
C. Air lines that control the emergency brakes of the tractor
The emergency line also called the supply line has two purposes. First, it supplies air to the trailer air tanks. Second, the emergency line controls the emergency brakes on combination vehicles
26 / 40
A. pushing in the trailer air supply control.
B. connecting the service line glad hand.
C. pulling out the trailer air supply control.
The emergency line, also called the supply line, has two purposes. First, it supplies air to the trailer air tanks. Second, the emergency line controls the emergency brakes on combination vehicles.
27 / 40
A. back up gently to ease pressure on the fifth wheel locking jaws.
B. begin to lower the trailer landing gear.
C. immediately apply your tractor parking brakes.
Shut off trailer air supply to lock trailer brakes. Ease pressure on fifth wheel locking jaws by backing up gently, applying the parking brake while tractor is pushing against the kingpin.
28 / 40
A. None
B. Just enough to see light through it
C. At lease 1/2 inch
Make sure there is no space between upper and lower fifth wheel. If there is space, something is wrong, the kingpin may be on top of the closed fifth wheel jaws, and trailer would come loose very easily.
29 / 40
A. Half the maximum pressure
B. At normal pressure
C. Between 60 and 80 PSI
Make sure air pressure is up to normal.
30 / 40
A. It is the best way to brake and keep the truck in a straight line
B. It should not be done
C. It results in less skidding than using the brake pedal alone
The trailer hand valve, also called the trolley valve or Johnson bar, works the trailer brakes. The trailer hand valve should be used only to test the trailer brakes. Do not use it in driving because of the danger of making the trailer skid.
31 / 40
A. A 5-axle tractor towing a 45-foot trailer
B. A 5-axle tractor towing a 42-foot trailer
C. A 5-axle tractor towing a 52-foot trailer
When a vehicle goes around a corner the rear wheels follow a different path than the front wheels, and this is called off-tracking or "cheating." Longer vehicles will off-track more. If there is more than one trailer, the rear wheels of the last trailer will off-track the most.
32 / 40
A. 3
B. 2
C. 4
With a fully-charged air system, turn off the engine, release the parking brake; and time the air pressure drop. The loss rate should be less than three psi in one minute for combination vehicles, adding one second if the brakes are applied.
33 / 40
A. Usually need a glad hand converter
B. Often do not have spring brakes
C. None of the answers are correct
D. Are easier to brake because they are heavier
Converter dollies and trailers built before 1975 are not required to have spring brakes.
34 / 40
A. There is enough clearance between the tops of the tractor tires and the nose of the trailer
B. Both answers are correct
C. There is enough clearance between the tractor frame and the landing gear
Check for enough clearance between rear of tractor frame and landing gear and between the top of the tractor tires and the nose of the trailer.
35 / 40
A. Trailer tank pressure to be lost
B. Tractor spring brakes to lock on
C. Trailer emergency / spring brakes to come on
You may not notice a major leak in the service line until you try to put the brakes on. Then, the air loss from the leak will lower the air tank pressure quickly. If it goes low enough, the trailer emergency brakes will come on.
36 / 40
A. Applying and releasing the trailer brakes and listening for brake sounds
B. Lifting the brake pedal
C. Turning on the parking brakes from the cab
Wait until the air pressure is normal, then shut engine off so you can hear the brakes. Check brake system for crossed air-lines by: applying and releasing trailer brakes and listen for sound of trailer brakes being applied and released. You should hear the brakes move when applied and air escape when the brakes are released.
37 / 40
A. The connected brake circuit becomes a backup air tank
B. If you did not, you could never build system pressure
C. It will keep dirt and water out of the lines
If there are no dummy couplers, the glad hands can sometimes be locked together. It is very important to keep the air supply clean and free of moisture.
38 / 40
A. between 60 and 80 psi.
B. bled down to half the maximum pressure.
C. at normal pressure.
Make sure air pressure is up to normal before backing under the trailer.
39 / 40
A. lightly loaded
B. empty
C. fully loaded
The heavier the vehicle, the more work the brakes must do to stop it, and the more heat they absorb. But the brakes, tires, springs, and shock absorbers on heavy vehicles are designed to work best when the vehicle is fully loaded. Empty trucks require greater stopping distances because an empty vehicle has less traction.
40 / 40
A. The tractor protection valve to close
B. The trailer supply valve to stay open
C. System parking brake will close
D. The tractor to lose all air pressure
The tractor protection valve keeps air in the tractor or truck brake system should the trailer break away or develop a bad leak. The tractor protection valve is controlled by the trailer air supply control valve in the cab. The control valve allows you to open and shut the tractor protection valve. The tractor protection valve will close automatically if air pressure is low (in the range of 20 to 45 psi). When the tractor protection valve closes, it stops any air from going out of the tractor. It also lets the air out of the trailer emergency line. This causes the trailer emergency brakes to come on, with possible loss of control.
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