South Dakota Commercial Driver's License (CDL) Knowledge Tests — Questions and Answers

Question 1: What is the primary purpose of the 'standee line' on a bus?

To indicate the forward-most point where passengers may stand to ensure the driver's view is not obstructed. (Correct answer)
To mark the area where passengers are allowed to stand during travel.
To show the driver where to stop the front of the bus at a designated stop.
To indicate the aisle width required for wheelchair access.

Correct answer: To indicate the forward-most point where passengers may stand to ensure the driver's view is not obstructed.

The standee line, a line on the floor behind the driver's seat, marks the area that passengers may not occupy while the bus is in motion. This regulation ensures that the driver has a clear field of vision and is free from distractions or crowding by passengers.

Question 2: Which of the following descriptions on a hazardous materials shipping paper is in the correct order according to regulations?

UN1017, Chlorine, 2.3, PG I (Correct answer)
Gasoline, 3, UN1203, PG II
UN1993, Flammable Liquid, n.o.s., 3, PG III
Corrosive Liquid, 8, UN1760

Correct answer: UN1017, Chlorine, 2.3, PG I

According to 49 CFR 172.202, the basic description of a hazardous material on shipping papers must be in a specific sequence: (1) Identification Number, (2) Proper Shipping Name, (3) Hazard Class or Division, and (4) Packing Group. 'UN1017, Chlorine, 2.3, PG I' is the only option that follows this mandatory sequence.

Question 3: Which of the following is a critical safe driving rule specific to tank vehicles due to their high center of gravity and the effects of liquid surge?

Slowing down well before a curve and then accelerating slightly through it. (Correct answer)
Driving faster than the posted speed limit to minimize time on the road.
Making sudden lane changes to avoid obstacles.
Applying brakes hard and late when approaching a stop.

Correct answer: Slowing down well before a curve and then accelerating slightly through it.

Due to a high center of gravity, tankers can roll over at speeds below the posted limit for a curve. The correct technique is to slow to a safe speed before entering the curve and then accelerate gently through it to maintain stability.

Question 4: A driver is loading a dense liquid into a large tank. Even if the tank is not filled to its volume capacity, what is the most likely reason the driver must stop loading?

The legal weight limit for the vehicle has been reached. (Correct answer)
The liquid needs more outage space than less dense liquids.
The vapor recovery system has activated automatically.
The vehicle's high center of gravity becomes too unstable.

Correct answer: The legal weight limit for the vehicle has been reached.

Dense liquids are very heavy. A tank may be only partially full by volume, but the weight of the liquid can cause the vehicle to reach its maximum legal gross weight limit.

Question 5: A driver is preparing for their pre-trip inspection. If the vehicle is equipped with an alcohol evaporator, what is its primary function?

To reduce the risk of ice forming in air brake valves during cold weather (Correct answer)
To inject alcohol into the fuel system for better combustion
To cool the air compressed by the engine
To clean the air going into the tanks

Correct answer: To reduce the risk of ice forming in air brake valves during cold weather

The alcohol evaporator puts alcohol vapor into the air system. This helps to absorb moisture and reduce the chance that water will freeze in the air brake valves or lines, which could cause brake failure in cold temperatures.

Question 6: Sample question 4 for Safe Driving Practices & Hazard Awareness?

Answer D
Answer A
Answer B (Correct answer)
Answer C

Correct answer: Answer B

As this is a sample question without specific content, the correct answer 'Answer B' would represent the most appropriate or safest driving practice among the given options in a real scenario. It would align with established safety regulations and best practices for commercial vehicle operation and hazard awareness, ensuring driver and public safety.

Question 7: When descending a long, steep grade, a driver should brake until the vehicle's speed is about 5 mph below the 'safe speed' and then release the brakes. Why is this 'snub braking' technique recommended?

To allow the brake drums to cool and prevent brake fade (Correct answer)
To keep the air pressure from dropping too quickly
To dry out wet brake linings
To ensure the trailer brakes are working harder than the tractor brakes

Correct answer: To allow the brake drums to cool and prevent brake fade

Constant, light pressure on the brakes can cause them to overheat, leading to a dangerous condition called brake fade where they become less effective. The snub braking technique of applying firm pressure for a short time and then releasing allows the brakes to cool between applications, maintaining their stopping power.

Question 8: What is the maximum on-duty window (including driving time) allowed for a property-carrying CMV driver in a single shift?

11 hours
16 hours
12 hours
14 hours (Correct answer)

Correct answer: 14 hours

Property-carrying drivers cannot drive beyond the 14th consecutive hour after coming on duty, regardless of how many breaks were taken.

Question 9: Sample question 2 for CDL Laws, Endorsements & Regulations?

Answer A
Answer B (Correct answer)
Answer D
Answer C

Correct answer: Answer B

Without the actual question text and options for this South Dakota CDL sample question, a specific explanation for why 'Answer B' is correct cannot be provided. In the context of a multiple-choice exam, 'Answer B' is designated as the correct response, and its validity would depend on the specific scenario or rule being tested under CDL Laws, Endorsements & Regulations.

Question 10: A driver is preparing to make a right turn in a large truck. To execute the turn properly without hitting the curb, the driver must:

Keep the rear of the trailer as close to the curb as possible throughout the turn.
Accelerate quickly through the turn to reduce the turning radius.
Swing wide to the left before starting the turn to allow the rear wheels to clear the corner. (Correct answer)
Turn the steering wheel sharply as soon as the front of the truck reaches the corner.

Correct answer: Swing wide to the left before starting the turn to allow the rear wheels to clear the corner.

Large vehicles exhibit "off-tracking," where the rear wheels follow a shorter path than the front wheels during a turn. To compensate for this and prevent the rear wheels from running over the curb or sidewalk, the driver must steer the front of the vehicle wide into the intersection, a maneuver often called a "button hook" turn.

Question 11: Sample question 3 for Transporting Cargo & Passengers Safely?

Answer C
Answer B (Correct answer)
Answer A
Answer D

Correct answer: Answer B

Question 12: Sample question 5 for CDL Laws, Endorsements & Regulations?

Answer A
Answer D
Answer B (Correct answer)
Answer C

Correct answer: Answer B

Question 13: You are driving a bus equipped with a brake-door interlock system. What is the main function of this safety feature?

It sounds an alarm if a passenger tries to open the door while the bus is moving.
It applies the brakes and prevents the bus from moving when the passenger exit door is open. (Correct answer)
It locks the service brake in the applied position if the driver leaves their seat.
It automatically locks the passenger door when the bus exceeds 15 mph.

Correct answer: It applies the brakes and prevents the bus from moving when the passenger exit door is open.

The brake-door interlock system is a safety feature on many transit buses that automatically applies the brakes and holds them whenever the passenger exit is open. This prevents the bus from moving while passengers are boarding or alighting, reducing the risk of accidents.

Question 14: Why is checking lights and reflectors important?

They make the truck look cool
They help improve fuel economy
They are only for decoration
They ensure visibility and signaling (Correct answer)

Correct answer: They ensure visibility and signaling

Lights and reflectors are essential safety features that make a commercial vehicle visible to other drivers, especially during low light conditions, inclement weather, or at night. Properly functioning lights (headlights, tail lights, turn signals, brake lights) and clean reflectors ensure that the vehicle's presence and intended actions are clearly communicated to others on the road, preventing collisions and enhancing overall road safety.

Question 15: Which document should always be in the vehicle during operation?

Maintenance schedule
Delivery receipts
Logbook only
Registration, insurance, and inspection report (Correct answer)

Correct answer: Registration, insurance, and inspection report

Commercial vehicles are legally required to carry specific documents that prove their legality and roadworthiness. Registration confirms ownership and legal operation, insurance provides financial protection, and the inspection report verifies that the vehicle has passed safety checks. These documents are essential for legal compliance and must be readily available for law enforcement to review.

Question 16: Sample question 8 for Safe Driving Practices & Hazard Awareness?

Answer C
Answer A
Answer D
Answer B (Correct answer)

Correct answer: Answer B

Question 17: Under normal driving conditions, what holds the spring brakes in the released position?

Air pressure (Correct answer)
Mechanical linkage from the brake pedal
Hydraulic pressure
The driver manually holding a lever

Correct answer: Air pressure

Spring brakes are a safety feature. They apply automatically when air pressure drops to a low level (20-45 psi). During normal operation, sufficient air pressure in the system overcomes the force of the powerful springs, keeping them caged or released.

Question 18: Sample question 9 for CDL Laws, Endorsements & Regulations?

Answer C
Answer B (Correct answer)
Answer A
Answer D

Correct answer: Answer B

Question 19: Which of the following is the most critical rule regarding carry-on baggage on a bus?

Heavy bags should be stored at the very front of the bus for easy access.
Baggage must be stowed in a way that does not block any aisles or emergency exits. (Correct answer)
The driver is only responsible for baggage stored in the overhead compartments.
All carry-on baggage must be small enough to fit on the passenger's lap.

Correct answer: Baggage must be stowed in a way that does not block any aisles or emergency exits.

The highest priority for stowing carry-on baggage is to ensure that it does not create a hazard. All aisles, stairwells, and emergency exits must be kept completely clear at all times to allow for safe movement and rapid evacuation in an emergency.

Question 20: During a static air brake leakage test on a single vehicle, what is the maximum permissible pressure drop in one minute after the initial drop?

2 psi (Correct answer)
5 psi
1 psi
10 psi

Correct answer: 2 psi

According to FMCSA regulations for a static leakage test (engine off, brakes released), the pressure drop should not exceed 2 psi per minute for a straight truck or bus. For combination vehicles, the limit is 3 psi per minute.

Question 21: A driver is hauling a 40-foot-long, uniform piece of lumber on a flatbed trailer. What is the minimum number of tiedowns required for this load?

4 tiedowns (Correct answer)
3 tiedowns
2 tiedowns
5 tiedowns

Correct answer: 4 tiedowns

The general rule for cargo securement is to have at least one tiedown for every 10 feet of cargo. For a 40-foot load, this would be 4 tiedowns. Additionally, any cargo, no matter how small, requires a minimum of two tiedowns.

Question 22: A driver is preparing to unload a placarded load of Class 3 (Flammable Liquid). According to 49 CFR 177.834, what specific action is prohibited within 25 feet of the vehicle during this process?

Leaving the vehicle unattended.
Using a two-way radio.
Smoking or having any open flame. (Correct answer)
Listening to the vehicle's stereo.

Correct answer: Smoking or having any open flame.

Regulation 49 CFR 177.834(c) explicitly forbids smoking on or about any motor vehicle while loading or unloading any Class 3 (flammable liquid) materials. This rule is in place to prevent ignition of flammable vapors.

Question 23: A driver is transporting 1,200 lbs of a hazardous material listed on Table 2 of the placarding regulations. What is the placarding requirement for this load?

Placards are only required on the front and rear of the vehicle.
Placards are not required as the weight is under 2,000 lbs.
Placards must be displayed on all four sides of the vehicle. (Correct answer)
A 'DANGEROUS' placard must be used.

Correct answer: Placards must be displayed on all four sides of the vehicle.

According to 49 CFR 172.504, for hazardous materials listed in Table 2, placards are required on each side and each end of the transport vehicle when the aggregate gross weight is 454 kg (1,001 lbs) or more. Since 1,200 lbs exceeds this threshold, the vehicle must be placarded on all four sides.

Question 24: Sample question 8 for Transporting Cargo & Passengers Safely?

Answer D
Answer A
Answer C
Answer B (Correct answer)

Correct answer: Answer B

Question 25: When must a driver carrying hazardous materials keep the shipping papers in a pouch on the driver's door or on the driver's seat?

At all times while the vehicle is in motion.
Whenever the driver is out of the vehicle. (Correct answer)
Only when loading or unloading the material.
Only when stopped at a weigh station or for inspection.

Correct answer: Whenever the driver is out of the vehicle.

Hazardous materials regulations require that shipping papers be readily accessible to emergency responders. When the driver is not in the vehicle, the papers must be placed on the driver's seat or in the driver's side door pouch to be easily found in an emergency.

Question 26: When must a bus driver stop at a railroad-highway grade crossing?

Only when transporting more than 15 passengers.
Only when the red lights are flashing and a gate is lowered.
Only when a train is visibly approaching.
The driver must stop at all railroad crossings. (Correct answer)

Correct answer: The driver must stop at all railroad crossings.

Regardless of whether lights are flashing, gates are down, or a train is visible, regulations require all buses carrying passengers to stop at all railroad-highway grade crossings. The stop must be made between 15 and 50 feet before the nearest rail.

Question 27: Sample question 4 for CDL Laws, Endorsements & Regulations?

Answer D
Answer B (Correct answer)
Answer C
Answer A

Correct answer: Answer B

Question 28: During the in-cab portion of the pre-trip inspection, what is the minimum required tread depth for the front steering axle tires?

It is not required to check tread depth during the in-cab inspection.
4/32 inch (Correct answer)
2/32 inch
6/32 inch

Correct answer: 4/32 inch

Federal and state regulations require a minimum tread depth of 4/32 of an inch on all steering axle tires to ensure proper grip and handling. Drive and trailer tires require a minimum of 2/32 inch.

Question 29: Sample question 6 for CDL Laws, Endorsements & Regulations?

Answer C
Answer B (Correct answer)
Answer D
Answer A

Correct answer: Answer B

Question 30: What is the purpose of checking under the vehicle?

To find lost items
To check for leaks and damage (Correct answer)
To see the pavement
To clean the undercarriage

Correct answer: To check for leaks and damage

Checking under the vehicle during an inspection is crucial for identifying any fluid leaks (oil, coolant, fuel, brake fluid) that could indicate a mechanical problem or environmental hazard. It also allows drivers to spot damage to the chassis, suspension, or other components that might compromise the vehicle's safety or operational integrity. This proactive check helps prevent breakdowns and ensures safe operation.

Question 31: Sample question 9 for Transporting Cargo & Passengers Safely?

Answer A
Answer B (Correct answer)
Answer D
Answer C

Correct answer: Answer B

Question 32: Sample question 2 for Transporting Cargo & Passengers Safely?

Answer B (Correct answer)
Answer C
Answer A
Answer D

Correct answer: Answer B

Question 33: Which of the following best describes the primary purpose of a vehicle's retarder?

To engage the parking brake automatically on steep grades.
To improve traction on slippery road surfaces.
To bring the vehicle to a rapid stop in an emergency.
To help slow the vehicle and reduce wear on the service brakes. (Correct answer)

Correct answer: To help slow the vehicle and reduce wear on the service brakes.

Retarders (such as engine brakes or exhaust brakes) are designed to help slow a vehicle, particularly on long downgrades, which reduces the need to use the service brakes. This helps prevent the service brakes from overheating and fading, and it reduces wear, ensuring the brakes are in good condition for when they are truly needed for stopping.

Question 34: What should you check for during a tire inspection?

Brand name only
Cleanliness
Tread depth, inflation, and damage (Correct answer)
Color of the sidewall

Correct answer: Tread depth, inflation, and damage

During a tire inspection, checking tread depth ensures adequate grip and prevents hydroplaning, while proper inflation is vital for vehicle stability, fuel efficiency, and preventing blowouts. Inspecting for cuts, bulges, or punctures identifies potential damage that could lead to tire failure. These comprehensive checks are crucial for safe driving and preventing accidents.

Question 35: A driver is operating a combination vehicle with a dual air brake system. With the engine off and the brakes released, what is the maximum allowable air pressure leakage rate per minute?

1 PSI
2 PSI
3 PSI (Correct answer)
4 PSI

Correct answer: 3 PSI

For a combination vehicle, the Federal Motor Carrier Safety Administration (FMCSA) regulations state that the air pressure drop should not exceed 3 PSI in one minute when the engine is off and the service brakes are released.

Question 36: During the walk-around inspection of a combination vehicle, what is a critical check for the fifth wheel assembly after coupling to a trailer?

Ensuring the fifth wheel is freshly painted.
Verifying that the locking jaws are fully closed around the kingpin and the release handle is in the locked position. (Correct answer)
Confirming the air lines have been painted red and blue.
Checking that there is a visible gap between the fifth wheel and the trailer apron.

Correct answer: Verifying that the locking jaws are fully closed around the kingpin and the release handle is in the locked position.

A secure connection is paramount. The driver must visually confirm that the locking jaws have properly engaged the trailer's kingpin. There should be no gap between the trailer apron and the fifth wheel skid plate, and the release handle must be in the correct position. A tug test should also be performed.

Question 37: Which of the following components is responsible for stopping the air compressor from pumping air when the storage tanks reach their maximum pressure?

The air compressor governor (Correct answer)
The safety valve
The slack adjuster
The brake pedal

Correct answer: The air compressor governor

The air compressor governor controls when the air compressor pumps air. It stops the compressor (cuts out) when the tank pressure reaches the specified maximum (typically 125-140 psi) and allows it to start pumping again (cuts in) when the pressure drops to around 100 psi.

Question 38: Sample question 7 for Safe Driving Practices & Hazard Awareness?

Answer C
Answer D
Answer A
Answer B (Correct answer)

Correct answer: Answer B

Question 39: While transporting hazardous materials, you discover a slow leak from one of the containers. After stopping in a safe, isolated area, what is one of your immediate and primary responsibilities?

Notify local emergency responders and your carrier. (Correct answer)
Drive immediately to the nearest truck stop for help.
Wait for one hour to see if the leak stops on its own.
Attempt to patch the leak using available tools.

Correct answer: Notify local emergency responders and your carrier.

In any hazmat emergency, a driver's first priorities are safety and communication. After securing the scene, the driver must notify authorities (like 911) and their employer/carrier. This ensures a proper and timely response from trained personnel.

Question 40: Sample question 5 for Transporting Cargo & Passengers Safely?

Answer B (Correct answer)
Answer C
Answer D
Answer A

Correct answer: Answer B

Question 41: When should a driver perform a vehicle inspection?

Only if there is a problem
Only in winter
Only once a week
Before, during, and after each trip (Correct answer)

Correct answer: Before, during, and after each trip

Commercial drivers are required to perform thorough vehicle inspections before each trip to ensure the vehicle is safe and compliant. During the trip, ongoing checks (e.g., monitoring gauges, listening for unusual noises) help identify issues as they arise. A post-trip inspection documents any new defects or maintenance needs, ensuring the vehicle is ready for its next use. This comprehensive approach maximizes safety and reliability.

Question 42: Which of the following best describes 'on-duty' time under federal HOS regulations?

Time spent resting in the sleeper berth
All time from reporting for work until released from work responsibilities (Correct answer)
Only time spent actively driving the CMV
Only time spent loading and unloading cargo

Correct answer: All time from reporting for work until released from work responsibilities

On-duty time includes all time from when a driver begins work or is required to be ready to work, covering driving, loading, inspections, and waiting.

Question 43: You are driving a truck with a manual transmission. To accelerate smoothly from a stop, you should:

Slowly release the clutch while gently pressing the accelerator. (Correct answer)
Keep the clutch pressed halfway down while accelerating.
Press the accelerator to the floor before releasing the clutch.
Release the clutch quickly while pressing hard on the accelerator.

Correct answer: Slowly release the clutch while gently pressing the accelerator.

To achieve a smooth start in a manual transmission vehicle, the driver must coordinate the gradual release of the clutch with a gentle application of the accelerator. This allows the engine to engage with the transmission without jerking or stalling the vehicle. Releasing the clutch too fast or applying too much throttle will result in a rough, jerky start.

Question 44: Sample question 3 for CDL Laws, Endorsements & Regulations?

Answer C
Answer D
Answer A
Answer B (Correct answer)

Correct answer: Answer B

Question 45: When shifting up in a heavy vehicle with a non-synchronized manual transmission, the proper technique is to:

Push the clutch in once and quickly shift to the next higher gear.
Keep the accelerator pressed down while quickly shifting gears.
Release the accelerator, push the clutch in, shift to neutral, release the clutch, then push the clutch in again to shift to the next gear. (Correct answer)
Shift directly from a low gear to a high gear, skipping the gears in between.

Correct answer: Release the accelerator, push the clutch in, shift to neutral, release the clutch, then push the clutch in again to shift to the next gear.

Most heavy-duty trucks with manual transmissions are non-synchronized and require the driver to double-clutch when shifting up or down. The process involves using the clutch to move the transmission to neutral, and then using the clutch a second time to engage the next gear, matching the engine RPM to the road speed.

Question 46: You are the driver for a charter bus tour. When is the best time to make announcements regarding safety features, such as the location of emergency exits?

After all passengers have boarded and before the trip begins. (Correct answer)
Only in the event of an actual emergency.
While passengers are boarding the bus.
At the first designated rest stop of the trip.

Correct answer: After all passengers have boarded and before the trip begins.

Safety briefings, similar to those on an airplane, should be conducted before the bus begins to move. This ensures all passengers are present and can give their attention to critical information about emergency exits, fire extinguishers, and other safety procedures before any potential incident occurs.

Question 47: When backing a commercial vehicle, what is the best practice?

Back quickly to finish fast
Rely only on rear cameras
Ignore blind spots
Use a helper and check mirrors (Correct answer)

Correct answer: Use a helper and check mirrors

Backing a large commercial vehicle presents significant blind spots and challenges, making it a high-risk maneuver. Using a helper (spotter) provides an extra set of eyes to guide the driver and identify obstacles, while constantly checking mirrors helps the driver monitor their surroundings. This combination maximizes visibility and significantly reduces the risk of accidents, prioritizing safety during complex maneuvers.

Question 48: What device are most commercial motor vehicle drivers required to use to record their hours of service?

GPS tracking unit
Electronic Logging Device (ELD) (Correct answer)
Paper log book
Time card submitted to dispatch

Correct answer: Electronic Logging Device (ELD)

FMCSA regulations require most CMV drivers subject to HOS rules to use an Electronic Logging Device (ELD) to automatically record driving time.

Question 49: A driver is operating a truck with a dual air brake system. The low air pressure warning light and buzzer activate. What is the most likely pressure range in one of the systems?

100-120 psi
80-90 psi
Below 60 psi (Correct answer)
20-45 psi

Correct answer: Below 60 psi

The low air pressure warning devices (light, buzzer, or wig wag) are required to activate before the air pressure in either the primary or secondary system drops below 60 psi.

Question 50: While uncoupling a trailer, after you have lowered the landing gear and disconnected the air and electrical lines, what is the next step?

Chock the trailer wheels.
Unlock the fifth wheel by pulling the release handle. (Correct answer)
Set the trailer brakes.
Drive the tractor completely out from under the trailer.

Correct answer: Unlock the fifth wheel by pulling the release handle.

After lowering the landing gear and disconnecting the lines, the next step is to unlock the fifth wheel. This is done by pulling the release handle, which disengages the locking jaws from the trailer's kingpin, preparing the tractor to be pulled away.

South Dakota Commercial Driver's License (CDL) Knowledge Tests

This certification allows individuals to operate commercial motor vehicles (CMVs) in South Dakota, requiring passing various knowledge and skills tests.

Questions

60 min

Time Limit

80%

To Pass

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These practice questions were written with AI tools. They are not real exam questions. Exam facts are checked against the official sources listed below. Not reviewed by a subject-matter expert. Editorial policy

Sources & references

Exam facts on this page (fees, format, dates, passing scores) are checked against these official sources; the date is our last check. Editorial policy

sd.gov — Exam format, passing score, retake policy, time limit, score validity, test delivery, fees, exam information · verified Oct 2026
sdlegislature.gov — Score validity, fees · verified Oct 2026