CDL Practice Test: Video 4 Answers (25 Questions) — Questions and Answers

Question 1: Where is compressed air stored?

Main reservoirs (Correct answer)
Pressure gauge
Air compressor
Service and emergency air lines

Correct answer: Main reservoirs

Compressed air, generated by the air compressor, is stored in large metal tanks called main reservoirs or air tanks. These tanks hold a reserve of compressed air, which is then supplied to the brake chambers and other air-operated accessories. Having these reservoirs ensures a constant supply of air pressure for braking, even if the compressor is not actively pumping.

Question 2: At what air pressure must the low air pressure warning signal come on?

45 psi
150 psi
60 psi (Correct answer)
50 psi

Correct answer: 60 psi

Federal regulations mandate that the low air pressure warning signal must activate when the air pressure in the service air tanks falls below 60 psi (or half the governor cut-out pressure on older vehicles). This warning alerts the driver to a critical loss of air pressure, indicating a potential problem with the air brake system that requires immediate attention.

Question 3: What is the alcohol evaporator's primary purpose?

Remove water and oil from the air brake system
Remove alcohol from the air brake system
Put alcohol into the air system (Correct answer)
To heat the air tank

Correct answer: Put alcohol into the air system

An alcohol evaporator, found in some older air brake systems, is designed to inject alcohol vapor into the air lines. This alcohol helps prevent moisture in the air system from freezing during cold weather, which could otherwise cause brake components to malfunction and lead to brake failure.

Question 4: What is the typical air pressure of a fully charged air brake system?

100 psi
85 psi
125 psi (Correct answer)
150 psi

Correct answer: 125 psi

125 psi. A fully charged air system typically has 125 psi of air pressure.

Question 5: Which of the following devices can be used as the low air pressure warning signal?

A mechanical arm (wig wag)
A buzzer
Red warning light
Any of the above (Correct answer)

Correct answer: Any of the above

Federal regulations require commercial vehicles with air brakes to have a low air pressure warning signal to alert the driver when system pressure drops below 60 psi. This critical warning can be provided by various means, including an audible buzzer, a visual red warning light, or a mechanical arm known as a 'wig-wag.' All these devices serve the same essential safety function.

Question 6: Containment rules are rules that _______.

Instruct the driver how to unload hazardous materials.
Instruct the driver how to transport hazardous materials.
Instruct the driver how to load hazardous materials.
All of the listed answers. (Correct answer)

Correct answer: All of the listed answers.

Containment rules are a comprehensive set of regulations designed to ensure the safe handling of hazardous materials throughout their transportation journey. These rules provide detailed instructions for drivers on how to properly load, transport, and unload hazardous materials. Adhering to these guidelines is crucial to prevent spills, leaks, and exposure, thereby protecting public safety and the environment.

Question 7: The shippers must ________.

Package the hazardous materials.
All of the listed answers. (Correct answer)
Label the hazardous materials.
Mark the hazardous materials.

Correct answer: All of the listed answers.

Shippers of hazardous materials have a comprehensive set of responsibilities to ensure the safe transportation of these dangerous goods. This includes properly packaging the materials in approved containers, accurately marking packages with necessary information, and correctly labeling them with hazard warnings. These actions are critical for compliance, safety, and informing handlers and emergency responders.

Question 8: What is one of first things you should do before unloading a hazardous material?

Call 911.
Set the parking brake. (Correct answer)
Check your tires.
Clean of your mirrors.

Correct answer: Set the parking brake.

Before beginning any unloading operation, especially with hazardous materials, safety is paramount. Setting the parking brake is one of the first and most crucial steps to ensure the vehicle remains stationary and secure. This prevents accidental movement that could lead to spills, injuries, or other dangerous situations during the unloading process.

Question 9: Shippers put a hazard warning label on all packages of hazardous materials. On most packages the hazard warning label is what shape?

Circle.
Diamond. (Correct answer)
Rectangle.
Oval.

Correct answer: Diamond.

Hazard warning labels on packages of hazardous materials are specifically designed in a diamond shape. This distinctive shape makes them easily recognizable and immediately signals the presence of dangerous goods to handlers, emergency responders, and drivers. The diamond shape is a standardized feature mandated by regulations to ensure clear and consistent identification of hazardous materials during transportation.

Question 10: If you are driving ____mph above the posted speed limit, you are considered to be speeding excessively.

3 mph.
5 mph.
15 mph. (Correct answer)
10 mph.

Correct answer: 15 mph.

Excessive speeding is a serious offense for commercial drivers, leading to significant penalties and increased accident risk. Driving 15 mph or more above the posted speed limit is generally considered excessive speeding. This threshold is important for CDL holders to be aware of, as it can result in fines, points on their license, and potential disqualification from operating a commercial motor vehicle.

Question 11: Which of the following is a necessary step to test your service brakes?

Move the vehicle forward slowly.
Release the parking brake.
All of the listed answers. (Correct answer)
Wait for normal air pressure.

Correct answer: All of the listed answers.

To properly test service brakes, several steps are necessary to ensure safety and functionality. These include waiting for normal air pressure, releasing the parking brake, and then moving the vehicle forward slowly (typically 5 mph) before applying the foot brake firmly. This allows the driver to check for proper braking action, straight stopping, and any unusual pulling.

Question 12: The air pressure governor cut-out is typically within what psi range?

120-140 psi. (Correct answer)
50-90 psi.
100-120 psi.
180-200 psi.

Correct answer: 120-140 psi.

The air pressure governor in an air brake system controls when the air compressor starts and stops. The cut-out pressure is the point at which the compressor stops pumping air into the tanks, typically set between 120-140 psi. This range ensures sufficient air pressure for safe braking while preventing over-pressurization of the system.

Question 13: You are testing your trailer's emergency brakes. First you should _____.

Push in the trailer air supply control.
Pull harshly on the trailer.
Pull gently on the trailer with the tractor.
Charge the trailer air brake system. (Correct answer)

Correct answer: Charge the trailer air brake system.

Before testing a trailer's emergency brakes, it is essential to first charge the trailer air brake system. This means connecting the air lines from the tractor to the trailer and allowing the trailer's air tanks to fill to normal operating pressure. Once the system is charged, the emergency brakes can be properly tested by applying and releasing the trailer air supply control.

Question 14: Knowing how to couple and uncouple correctly is ________.

Important for the safe operation of combination vehicles. (Correct answer)
Necessary only for drivers who are under 19.
Unimportant if the driver is competent.
Only significant for drivers operating older vehicles.

Correct answer: Important for the safe operation of combination vehicles.

Correctly coupling and uncoupling a combination vehicle is a fundamental skill for CDL drivers. Improper procedures can lead to serious accidents, such as the trailer detaching from the tractor, loss of air brakes, or damage to equipment. Therefore, mastering these procedures is crucial for ensuring the safety of the driver, the vehicle, and other road users.

Question 15: All versions of the Class A Pre-trip inspection test will include _______.

An in-cab inspection.
All of the listed answers. (Correct answer)
An engine start.
An inspection of the coupling system.

Correct answer: All of the listed answers.

All versions of the Class A Pre-trip Inspection test are designed to assess a driver's ability to thoroughly inspect a combination vehicle for safe operation. This includes a detailed in-cab inspection of controls and gauges, an engine start to check vital systems, and a comprehensive inspection of the coupling system to ensure the tractor and trailer are securely connected. These elements are fundamental to safe driving.

Question 16: Where should you lead students if the bus is on fire?

To the left of the bus.
Downwind of the bus.
To the right of the bus.
Upwind of the bus. (Correct answer)

Correct answer: Upwind of the bus.

If a bus is on fire, students should be led upwind of the bus. This means moving them to a location where the wind will carry smoke and flames away from them. Staying upwind helps protect students from inhaling toxic fumes and being exposed to the heat of the fire, ensuring their safety during an evacuation and preventing further harm.

Question 17: Passive crossings typically have?

Blue triangular warning signs.
Flashing red lights.
Yellow circular advance warning signs. (Correct answer)
Green directional signs.

Correct answer: Yellow circular advance warning signs.

Passive railroad-highway crossings are typically identified by yellow circular advance warning signs. These signs alert drivers to the presence of a railroad crossing ahead, even though there may not be active warning devices like flashing lights or gates. The yellow circular sign serves as a crucial visual cue for drivers to exercise caution, slow down, and prepare to stop and look for trains.

Question 18: At a passive railroad-highway crossing, you need to ____.

Search for any train using the tracks.
All of the listed answers. (Correct answer)
Decide if there is sufficient clear space to cross safely.
Recognize the crossing.

Correct answer: All of the listed answers.

At a passive railroad-highway crossing, which lacks active warning devices like gates or flashing lights, the driver must take full responsibility for safety. This involves recognizing the crossing, actively searching for any trains using the tracks, and deciding if there is sufficient clear space to cross safely without stopping on the tracks. All these steps are critical to prevent collisions at unguarded crossings.

Question 19: Because students may drop an object near the bus during loading and unloading, you should _______.

Watch carefully as they enter and exit the bus. (Correct answer)
Leave the students behind.
Ignore them.
All of the listed answers.

Correct answer: Watch carefully as they enter and exit the bus.

The area around a school bus during loading and unloading is a high-risk zone for students. Because students might drop objects and bend down to retrieve them, or move unpredictably, it is crucial for the driver to watch them carefully as they enter and exit the bus. This constant vigilance helps prevent accidents, ensuring students remain visible and safe from the bus's wheels or other traffic.

Question 20: When should you turn on your right turn signal indicator before pulling over?

50- 100 ft.
10-15 ft.
250-450 ft.
100-300 ft. (Correct answer)

Correct answer: 100-300 ft.

Activating your turn signal 100-300 feet before pulling over provides ample warning to other drivers and pedestrians of your intentions. This allows them sufficient time to react and adjust their speed or position, preventing sudden maneuvers and reducing the risk of collisions. This is especially important for large vehicles like buses, which require more space and time to maneuver.

Question 21: At a railroad crossing, which buses must always stop?

Only school buses on weekdays
Empty pickup trucks
Only buses over 40 feet
Buses carrying passengers (Correct answer)

Correct answer: Buses carrying passengers

Buses carrying passengers are required to stop at railroad crossings.

Question 22: Before you accept cargo or baggage with hazardous materials, you must confirm that the container has which of the following?

Material's name and identification number
Hazard label and Material Safety Data Sheet (MSDS)
Hazard label, country of origin, and material's name
Hazard label, the material's name, and identification number (Correct answer)

Correct answer: Hazard label, the material's name, and identification number

Before accepting any cargo or baggage containing hazardous materials, bus drivers must verify that the container is properly marked and labeled according to regulations. This includes ensuring it has the correct hazard label, the specific name of the material, and its corresponding identification number. These markings provide crucial information for safe handling and emergency response.

Question 23: Bus passengers should NOT

Stand in front of the standee line (Correct answer)
Stand while on a bus
Stand behind the standee line
Stand across from other passengers

Correct answer: Stand in front of the standee line

The standee line on a bus marks the forward-most point where passengers are permitted to stand. Standing in front of this line is prohibited because it obstructs the driver's view of the road and mirrors, and can interfere with the safe operation of the bus. This rule is crucial for maintaining the driver's visibility and control, especially during sudden stops or turns, ensuring passenger safety.

Question 24: Why should a bus driver avoid speaking with passengers while driving?

It can distract from safe driving (Correct answer)
It uses extra fuel
It damages the radio
It is against fare rules

Correct answer: It can distract from safe driving

Conversation with riders while in motion can distract the driver from the road.

Question 25: If you are driving a bus around a banked curve, you should

Slow down if your bus leans toward the outside of the curve (Correct answer)
Drive at the same speed as other traffic
Drive at the posted speed
Maintain your speed throughout the curve

Correct answer: Slow down if your bus leans toward the outside of the curve

When driving a bus around a banked curve, the banking helps counteract centrifugal force. However, if the bus leans excessively toward the outside of the curve, it indicates that the speed is too high for the curve's radius and banking. Slowing down reduces the centrifugal force, bringing the bus back into a safer, more stable position and preventing a potential rollover.

CDL Practice Test: Video 4 Answers (25 Questions)

Where is compressed air stored?

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Sources & references

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tsa.gov — Fees, renewal · verified Oct 2026
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