Combination Vehicles Quiz Questions

1. Air lines on a commercial vehicle are usually color coded to keep them from getting mixed up. The emergency line is ______; the service line is ______.

Red ; blue

Blue ; red

Orange ; green

Green ; blue

Air lines on a commercial vehicle are color coded to prevent them from getting mixed up. The emergency line is typically red, while the service line is usually blue. This color coding system helps to ensure that the correct lines are used for their intended purposes, maintaining the safety and functionality of the vehicle's air system.

Explanation

Air lines on a commercial vehicle are color coded to prevent them from getting mixed up. The emergency line is typically red, while the service line is usually blue. This color coding system helps to ensure that the correct lines are used for their intended purposes, maintaining the safety and functionality of the vehicle's air system.

2. Semi trailers made before 1975 and equipped with air brakes:

Often do not have spring brakes.

Usually need a glad hand converter.

Are illegal in all 50 states.

Semi trailers made before 1975 and equipped with air brakes often do not have spring brakes. This means that these trailers do not have a backup system that automatically applies the brakes if the air pressure is lost. Spring brakes are a safety feature that prevent the trailer from rolling away if there is a failure in the air brake system. Therefore, it is important for drivers of older trailers to be aware of this and take extra precautions to ensure the safety of their vehicle.

Explanation

Semi trailers made before 1975 and equipped with air brakes often do not have spring brakes. This means that these trailers do not have a backup system that automatically applies the brakes if the air pressure is lost. Spring brakes are a safety feature that prevent the trailer from rolling away if there is a failure in the air brake system. Therefore, it is important for drivers of older trailers to be aware of this and take extra precautions to ensure the safety of their vehicle.

3. The easiest way to detect a trailer skid is by looking in your mirrors.

True

False

The statement is true because when a trailer skids, it causes the trailer to swing out to the side. By looking in the mirrors, the driver can observe any unusual movement or swinging of the trailer, indicating a skid. This visual observation allows the driver to quickly detect a trailer skid and take appropriate measures to regain control and prevent accidents.

Explanation

The statement is true because when a trailer skids, it causes the trailer to swing out to the side. By looking in the mirrors, the driver can observe any unusual movement or swinging of the trailer, indicating a skid. This visual observation allows the driver to quickly detect a trailer skid and take appropriate measures to regain control and prevent accidents.

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

It is properly greased.

There are loose or missing pins in the slide mechanism of sliding 5th wheel.

Make sure locking pins are fully engaged.

All of the above.

The correct answer is "All of the above." This means that all three statements mentioned in the question should be checked when inspecting the fifth wheel. It is important to ensure that the fifth wheel is properly greased, as this helps with smooth operation. Loose or missing pins in the slide mechanism can affect the functionality of the sliding fifth wheel, so they should be checked as well. Finally, it is crucial to make sure that the locking pins are fully engaged to ensure the proper connection between the tractor and trailer.

Explanation

The correct answer is "All of the above." This means that all three statements mentioned in the question should be checked when inspecting the fifth wheel. It is important to ensure that the fifth wheel is properly greased, as this helps with smooth operation. Loose or missing pins in the slide mechanism can affect the functionality of the sliding fifth wheel, so they should be checked as well. Finally, it is crucial to make sure that the locking pins are fully engaged to ensure the proper connection between the tractor and trailer.

5. Which best describes the term 'off-tracking'?

When the fifth wheel is not secured properly.

Taking an unfamiliar route.

The path of your steer wheels vs. the trailer wheels.

Off-tracking refers to the difference in the path followed by the steer wheels and the trailer wheels while making a turn. This occurs because the trailer wheels follow a shorter path compared to the steer wheels. It is important for drivers to be aware of off-tracking as it can affect the maneuverability of the vehicle, especially when navigating tight turns or narrow spaces.

Explanation

Off-tracking refers to the difference in the path followed by the steer wheels and the trailer wheels while making a turn. This occurs because the trailer wheels follow a shorter path compared to the steer wheels. It is important for drivers to be aware of off-tracking as it can affect the maneuverability of the vehicle, especially when navigating tight turns or narrow spaces.

6. What type of trailer is most likely to get stuck on railroad crossings?

Possum-belly livestock trailers.

Dry box van trailers.

Reefer (refrigerated) trailers.

Possum-belly livestock trailers are most likely to get stuck on railroad crossings because they have a lower ground clearance compared to dry box van trailers and reefer trailers. The possum-belly design of these trailers creates a lower center of gravity which increases the risk of getting stuck on uneven surfaces like railroad crossings. Additionally, the livestock trailers may have ramps or gates at the rear that can get caught on the tracks, further increasing the chances of getting stuck.

Explanation

Possum-belly livestock trailers are most likely to get stuck on railroad crossings because they have a lower ground clearance compared to dry box van trailers and reefer trailers. The possum-belly design of these trailers creates a lower center of gravity which increases the risk of getting stuck on uneven surfaces like railroad crossings. Additionally, the livestock trailers may have ramps or gates at the rear that can get caught on the tracks, further increasing the chances of getting stuck.

7. Hand valve should be used only in combination with the service pedal (foot brake).

True

False

The hand valve should not be used in combination with the service pedal (foot brake). The hand valve is designed to be used independently of the foot brake, allowing the driver to manually control the braking force to the trailer or other auxiliary devices. Using the hand valve in combination with the foot brake can lead to uneven braking and loss of control. Therefore, the statement is false.

Explanation

The hand valve should not be used in combination with the service pedal (foot brake). The hand valve is designed to be used independently of the foot brake, allowing the driver to manually control the braking force to the trailer or other auxiliary devices. Using the hand valve in combination with the foot brake can lead to uneven braking and loss of control. Therefore, the statement is false.

8. Before backing under a trailer make sure that:

That the landing gear is in the upright position.

The trailer brakes are on.

Your air brakes are off.

The tractor protection valve is normal.

Before backing under a trailer, it is important to ensure that the trailer brakes are on. This is necessary to prevent the trailer from rolling or moving while the tractor is backing up. If the trailer brakes are not engaged, there is a risk of the trailer moving unexpectedly, which can lead to accidents or damage to the vehicle and trailer. Therefore, it is crucial to double-check and confirm that the trailer brakes are properly applied before attempting to back under a trailer.

Explanation

Before backing under a trailer, it is important to ensure that the trailer brakes are on. This is necessary to prevent the trailer from rolling or moving while the tractor is backing up. If the trailer brakes are not engaged, there is a risk of the trailer moving unexpectedly, which can lead to accidents or damage to the vehicle and trailer. Therefore, it is crucial to double-check and confirm that the trailer brakes are properly applied before attempting to back under a trailer.

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

2

3

4

5

The air leakage rate for a combination vehicle (engine off, brakes off) should be no more than 3 psi per minute. This means that the pressure in the air system should not drop by more than 3 pounds per square inch (psi) in one minute when the engine is off and the brakes are released. This is important to ensure that the air system is properly sealed and there are no leaks that could affect the performance of the brakes.

Explanation

The air leakage rate for a combination vehicle (engine off, brakes off) should be no more than 3 psi per minute. This means that the pressure in the air system should not drop by more than 3 pounds per square inch (psi) in one minute when the engine is off and the brakes are released. This is important to ensure that the air system is properly sealed and there are no leaks that could affect the performance of the brakes.

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

2

3

4

5

The air leakage rate for a combination vehicle (engine off; brakes on) should not be more than 4 psi per minute. This means that the rate at which air escapes from the system should not exceed 4 pounds per square inch per minute. This is important because excessive air leakage can lead to a loss of braking power and compromised safety while operating the vehicle. Therefore, it is crucial to ensure that the air leakage rate remains within the specified limit to maintain optimal braking performance.

Explanation

The air leakage rate for a combination vehicle (engine off; brakes on) should not be more than 4 psi per minute. This means that the rate at which air escapes from the system should not exceed 4 pounds per square inch per minute. This is important because excessive air leakage can lead to a loss of braking power and compromised safety while operating the vehicle. Therefore, it is crucial to ensure that the air leakage rate remains within the specified limit to maintain optimal braking performance.