CDL Practice Test: Video 3 Answers (25 Questions) — Questions and Answers

Question 1: What is the name of the device that controls when the air compressor will pump air into the air storage tanks?

Air tank drains
Safety valve
Governor (Correct answer)
Evaporator

Correct answer: Governor

Governor. The governor controls when the air compressor will pump air into the air storage tanks. An alcohol evaporator puts alcohol into the air system to help reduce the risk of ice in cold weather. A safety valve protects the tank and system from too much pressure. The air tank drains allow you to drain oil and moisture from the air tanks.

Question 2: What are the three types of brake systems used in a commercial vehicle air brake system?

Hand brake, parking brake, emergency brake
Service brake, parking brake, emergency brake (Correct answer)
Anti-lock brake, service brake, emergency brake
Service brake, hand brake, emergency brake

Correct answer: Service brake, parking brake, emergency brake

Commercial vehicles with air brakes utilize three distinct braking systems. The service brake is used for normal stopping, the parking brake holds the vehicle stationary when parked, and the emergency brake system uses parts of the service and parking brake systems to stop the vehicle in case of a service brake failure. These systems work together to ensure safe operation and parking.

Question 3: What will happen if your air compressor stops?

You will have an immediate loss of your brakes
Your brakes will lock up
You'll still have air pressure left in the air tanks to stop (Correct answer)
Your brakes will not be affected

Correct answer: You'll still have air pressure left in the air tanks to stop

You'll still have air pressure left in the air tanks to stop. If your compressor stops working, you will still have air pressure left in your tanks, but the air compressor will not be able to replace air lost by using your brakes.

Question 4: Which device is designed to protect the air tank and system from too much pressure?

Safety valve (Correct answer)
Drain valve
Governor
Evaporator

Correct answer: Safety valve

Safety valve. A safety relief valve is installed in the first tank that the air compressor pumps air into. A safety valve protects the tank and system from too much pressure by opening up at 150 psi. The governor controls when the air compressor will pump air into the air storage tanks. An alcohol evaporator puts alcohol into the air system to help reduce the risk of ice in cold weather.

Question 5: What device will keep air in the tanks if the air compressor develops a leak?

The tractor protection valve
The treadle valve
The safety valve
The one way check valve (Correct answer)

Correct answer: The one way check valve

A one-way check valve is a critical safety component installed between the air compressor and the first air storage tank. Its purpose is to allow compressed air to flow into the tanks but prevent it from flowing back out. This ensures that air pressure is maintained in the brake system's reservoirs, even if the air compressor or its supply line develops a leak.

Question 6: Which of the following is emergency equipment you should carry with you at all times?

Warning devices for parked vehicles.
Fire extinguisher.
Spare electrical fuses.
All of the listed answers. (Correct answer)

Correct answer: All of the listed answers.

Commercial drivers are required to carry specific emergency equipment, including warning devices for parked vehicles (like reflective triangles), spare electrical fuses, and a fire extinguisher. These items are essential for ensuring safety in the event of a breakdown, accident, or fire. Having them readily available allows drivers to protect themselves, their cargo, and other motorists on the road.

Question 7: What are the shippers of hazardous materials responsible for?

Packaging the hazardous materials.
All of the listed answers. (Correct answer)
Marking the hazardous materials.
Labeling the hazardous materials.

Correct answer: All of the listed answers.

Shippers of hazardous materials bear significant responsibility for ensuring these dangerous goods are prepared correctly for transport. This includes properly packaging the materials in approved containers to prevent leaks or spills. They are also responsible for marking the packages with necessary information and applying the correct hazard labels, all of which are critical for safety and regulatory compliance.

Question 8: Why should you cover your cargo during its transportation?

To fade.
To fail.
All of the listed answers. (Correct answer)
Chemical changes in the brake lining.

Correct answer: All of the listed answers.

Excessive heat severely degrades the performance of service brakes. It can cause brake fade, where the brakes become less effective due to overheating, and prolonged or extreme heat can lead to complete brake failure. This also causes chemical changes in the brake lining, reducing its friction properties and overall lifespan, making 'All of the listed answers' correct.

Question 9: You will lose your CDL for at least ____ days if you have committed your first violation of an out-of-service order.

30
60
45
90 (Correct answer)

Correct answer: 90

Violating an out-of-service order is a serious offense for commercial drivers, as these orders are issued to prevent unsafe operation. For a first violation, a CDL holder will be disqualified from operating a commercial motor vehicle for at least 90 days. This penalty underscores the importance of complying with all safety directives to maintain driving privileges.

Question 10: After you deliver a hazardous waste shipment, you should ______.

Destroy the original manifest.
Throw away your copy of the manifest.
E-mail the copy of the manifest to the DOT.
Keep your copy of the manifest. (Correct answer)

Correct answer: Keep your copy of the manifest.

After delivering a hazardous waste shipment, the carrier is legally required to keep their copy of the hazardous waste manifest for a specified period, typically three years. This retention is crucial for record-keeping, compliance verification, and potential audits by regulatory agencies like the EPA or DOT. The manifest serves as a legal document tracking the waste from 'cradle to grave,' ensuring accountability and proper disposal.

Question 11: ____ is another name for front-end header boards.

Dish rack.
Headache racks. (Correct answer)
Head banger.
Protective board.

Correct answer: Headache racks.

Front-end header boards are protective barriers located at the front of a truck's cargo area, behind the cab. They are commonly known as 'headache racks' because their primary purpose is to protect the driver and passengers from shifting cargo that could otherwise enter the cab during sudden stops or collisions.

Question 12: What happens when pressure is put on the air brakes?

The brake pedal overheats.
This should never be done. This could ruin your car vehicle.
The stop light switch turns on the brake lights. (Correct answer)
Nothing.

Correct answer: The stop light switch turns on the brake lights.

When pressure is applied to the air brakes, the air pressure activates a stop light switch. This switch is specifically designed to turn on the vehicle's brake lights. Illuminating the brake lights signals to drivers behind you that your vehicle is slowing down or stopping, which is a fundamental aspect of road safety.

Question 13: How many versions of the Class A Pre-trip Inspection test exist?

Two
Eight.
Three.
Four (Correct answer)

Correct answer: Four

There are four different versions of the Class A Pre-trip Inspection test. These versions are designed to cover a broad range of inspection points and ensure that applicants have a comprehensive understanding of how to check a combination vehicle for safe operation. While the specific components inspected may vary slightly between versions, the core knowledge and skills required remain consistent.

Question 14: Who is responsible for making sure the vehicle is not overloaded with cargo?

Your mom.
The shipper.
Your employer.
You, the driver. (Correct answer)

Correct answer: You, the driver.

As the commercial driver, you are ultimately responsible for ensuring that your vehicle is not overloaded with cargo. This includes checking weight limits for the vehicle, axles, and tires to comply with legal regulations and safety standards. Overloading can lead to unsafe handling, increased stopping distances, tire failure, and legal penalties, making it a critical responsibility.

Question 15: When the air system is low ________.

You should bring the vehicle to a safe stop.
All of the listed answers. (Correct answer)
Have the air brakes system fixed immediately.
It will take you longer to stop your vehicle.

Correct answer: All of the listed answers.

A low air system pressure in a commercial vehicle's air brakes is a serious safety concern. It means the brakes will not have enough power to stop the vehicle effectively, leading to significantly longer stopping distances. Therefore, if the air system is low, you must immediately bring the vehicle to a safe stop and have the air brake system inspected and repaired to prevent accidents.

Question 16: How should the outside left and right side flat mirrors be adjusted?

All of the listed answers. (Correct answer)
So you can see 200 ft. or 4 bus lengths behind the bus.
So you can see the rear tires touching the ground.
So you can see along the sides of the bus.

Correct answer: All of the listed answers.

Proper adjustment of outside flat mirrors is essential for a bus driver's visibility and safety. These mirrors should be set to allow the driver to see at least 200 feet behind the bus, providing a clear view of following traffic. Additionally, they must be adjusted to see along the sides of the bus and to see the rear tires touching the ground, which helps in judging clearances and avoiding obstacles. All these adjustments contribute to comprehensive situational awareness.

Question 17: What color are advance warning signs at passive railroad-highway crossings?

Green.
Red.
Yellow. (Correct answer)
Blue.

Correct answer: Yellow.

Advance warning signs at passive railroad-highway crossings are designed to alert drivers to the presence of a railroad crossing ahead, even if it doesn't have active warning devices like flashing lights or gates. These signs are typically round and yellow with a black 'X' and 'RR' symbol. The yellow color signifies a general warning, prompting drivers to slow down, look, and listen for trains.

Question 18: Make sure the front area of enclosed trailers does not have _______.

Holes.
All of the listed answers. (Correct answer)
Cracks.
Bulges.

Correct answer: All of the listed answers.

When inspecting the front area of enclosed trailers, it's crucial to check for any signs of structural compromise or damage. This includes looking for bulges, which could indicate shifting cargo or internal pressure; cracks, which suggest material fatigue or impact damage; and holes, which could lead to cargo loss or exposure to elements. Identifying any of these issues is vital for ensuring the trailer's integrity and the safety of its contents and other road users.

Question 19: Which of the following is emergency equipment you should carry with you at all times?

Spare electrical fuses.
Fire extinguisher.
Warning devices for parked vehicles.
All of the listed answers. (Correct answer)

Correct answer: All of the listed answers.

Commercial vehicle drivers, including bus drivers, are legally required to carry specific emergency equipment to ensure safety and preparedness for various incidents. This essential equipment typically includes a fire extinguisher for fire suppression, spare electrical fuses to address electrical malfunctions, and warning devices (such as reflective triangles or flares) to alert other motorists if the vehicle is stopped on the roadside. Having all these items readily available is crucial for responding effectively to emergencies.

Question 20: How far in advance should a school bus driver activate the amber warning lights before stopping to load or unload students?

Activation is optional if no traffic is present
At least 1,000 feet in all conditions
At least 100 to 300 feet, depending on speed and state law (Correct answer)
Only after coming to a complete stop

Correct answer: At least 100 to 300 feet, depending on speed and state law

Amber lights warn following traffic of an upcoming stop and should be activated roughly 100 to 300 feet ahead depending on speed and state requirements.

Question 21: What does a Hazardous Materials Endorsement (H) on a CDL require?

A background check and a knowledge test (Correct answer)
A second vehicle inspection
Only a vision test
Proof of vehicle ownership

Correct answer: A background check and a knowledge test

The H endorsement requires passing a knowledge test and a Transportation Security Administration background check.

Question 22: What should a driver do if shipping papers do not match the materials being loaded?

Accept the load anyway
Refuse to transport until the discrepancy is resolved (Correct answer)
Cross out the papers and continue
Guess the correct hazard class

Correct answer: Refuse to transport until the discrepancy is resolved

Drivers should not transport hazmat when papers and the actual load do not match; the issue must be corrected first.

Question 23: When must placards be readable and properly displayed on a hazmat vehicle?

Only on the driver's side
Only inside the cab
Only on the rear
On all four sides of the vehicle (Correct answer)

Correct answer: On all four sides of the vehicle

Placards must be displayed on the front, rear, and both sides of the vehicle.

Question 24: What is the main reason for keeping a fire extinguisher in proper working order on a hazmat vehicle?

It is only for decoration
To extinguish small fires before they spread to the cargo (Correct answer)
To replace the spare tire
To meet weight requirements

Correct answer: To extinguish small fires before they spread to the cargo

A working fire extinguisher lets the driver control small fires before they reach hazardous cargo.

Question 25: When approaching a railroad crossing at which you are required to stop, where should you stop?

25 to 50 feet before the nearest rail
15 to 50 feet before the nearest rail (Correct answer)
50 to 100 feet before the nearest rail
15 to 40 feet before the nearest rail

Correct answer: 15 to 50 feet before the nearest rail

Federal regulations require commercial vehicles, including buses, to stop at railroad crossings within a specific distance. The correct stopping zone is between 15 and 50 feet from the nearest rail. This distance allows the driver a clear view of the tracks in both directions to check for trains, while ensuring the vehicle is far enough away to avoid being struck.

CDL Practice Test: Video 3 Answers (25 Questions)

What is the name of the device that controls when the air compressor will pump air into the air storage tanks?

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Sources & references

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tsa.gov — Fees, renewal · verified Oct 2026
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