Commercial Driver's License (CDL) General Knowledge — Questions and Answers

Question 1: What psi level is the safety relief valve set to open at?

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

Correct answer: 150 psi

The safety relief valve is a crucial safety device in the air brake system, designed to protect the air tanks and other components from excessive pressure. It is typically set to open and release air if the pressure in the system exceeds 150 psi, preventing damage or rupture of the air tanks.

Question 2: On the trailer air lines of a combination vehicle, the service line connects to the _________ on the trailer to control the pressure to the trailer brakes.

Relay valves (Correct answer)
Trailer hand valve
Tractor protection valve control
Glad hands

Correct answer: Relay valves

On a combination vehicle, the service line connects to the relay valves on the trailer. These relay valves are crucial because they quickly send air pressure from the trailer's air tanks to the brake chambers, allowing for faster and more effective braking of the trailer. This system ensures synchronized braking between the tractor and trailer.

Question 3: Why is it important to inspect the fuel tank cap during a pre-trip inspection?

Only to estimate the fuel level without a gauge
To ensure it is secure and prevents fuel spills and flammable vapor release (Correct answer)
Fuel cap inspection is performed by mechanics only at service intervals
To visually verify the fuel color

Correct answer: To ensure it is secure and prevents fuel spills and flammable vapor release

A secure fuel cap prevents fuel spills and the release of flammable vapors, reducing fire risk and preventing environmental contamination.

Question 4: What is the difference between a traffic emergency and a vehicle emergency?

Traffic emergencies occur when foreign objects or public road equipment obstruct public roadways and potentially cause accidents while vehicle emergencies occur only between two vehicles that are about to collide.
Traffic emergencies occur when two vehicles are about to collide. Vehicle emergencies occur when tires, brakes or critical parts of your vehicle fail. (Correct answer)
There is no difference. The terms are interchangeable.
Traffic emergencies involve inexperienced drivers while vehicle emergencies are typically the terms attributed to professional drivers.

Correct answer: Traffic emergencies occur when two vehicles are about to collide. Vehicle emergencies occur when tires, brakes or critical parts of your vehicle fail.

Traffic emergencies refer to situations external to your vehicle, such as impending collisions with other vehicles or unexpected road hazards. Vehicle emergencies, on the other hand, are internal issues related to the mechanical failure of your own truck, like brake failure, tire blowouts, or engine problems. The distinction is crucial for understanding the appropriate response.

Question 5: What does a diamond-shaped sign with a yellow background typically indicate?

A warning about upcoming road conditions (Correct answer)
A regulatory requirement that must be obeyed
A service or guide to nearby facilities
A construction zone speed limit

Correct answer: A warning about upcoming road conditions

Diamond-shaped signs with yellow backgrounds are warning signs in the US highway sign system. They alert drivers to upcoming conditions that may require speed adjustments or extra caution, such as curves, intersections, pedestrian crossings, or construction zones.

Question 6: Why must you secure the rear trailer and dolly with chocks or brakes when uncoupling on a slight grade?

To clean the tires
To keep the lights on
To prevent the units from rolling away once disconnected (Correct answer)
To save fuel

Correct answer: To prevent the units from rolling away once disconnected

Chocks or set brakes stop the disconnected trailer and dolly from rolling on any incline.

Question 7: What does it mean when the safety valve opens and releases air?

A and C (Correct answer)
The pressure has exceeded 150 psi
Something is wrong, and a mechanic needs to check it
The system is fully charged

Correct answer: A and C

The safety valve is designed to protect the air brake system from excessive pressure, typically opening and releasing air if the pressure in the tanks exceeds 150 psi. If this valve frequently opens, it indicates a malfunction in the air compressor governor, which should be controlling the pressure within the normal range. Therefore, both excessive pressure and a system malfunction are indicated, requiring immediate inspection by a mechanic.

Question 8: What is the maximum length of a bus' tail swing?

6 ft.
5 ft.
3 ft. (Correct answer)
4 ft.

Correct answer: 3 ft.

When a bus turns, the rear portion of the vehicle swings out in the opposite direction of the turn, a phenomenon known as 'tail swing.' This tail swing can be up to 3 feet long, posing a significant hazard to pedestrians, parked cars, or objects near the bus's rear. Drivers must be aware of this dimension to avoid collisions when maneuvering in tight spaces and ensure safety.

Question 9: How should you check that you have sufficient emergency airflow to all trailers in a set of doubles or triples?

Fully charge the air system, activate the emergency brakes and look for a 15 psi air pressure reduction
Use the trailer hand brake to supply air. Go to the rear of the last trailer, open the service line valve and listen for air escaping.
Push in the red trailer air supply knob, open the emergency line shut-off valve at the rear of the last trailer and listen for air escaping. (Correct answer)
Move the trailers and apply the emergency brakes.

Correct answer: Push in the red trailer air supply knob, open the emergency line shut-off valve at the rear of the last trailer and listen for air escaping.

To check for sufficient emergency airflow, you must activate the emergency air supply to the trailers. Pushing in the red trailer air supply knob sends air to the emergency lines. Opening the emergency line shut-off valve at the rear of the last trailer allows you to listen for escaping air, confirming that the emergency air system is fully charged and functional throughout the entire trailer combination.

Question 10: Which of the following devices indicates how much pressure you have in your air tanks?

Supply pressure gauge (Correct answer)
Low air pressure warning signal
Application pressure gauge
Ammeter

Correct answer: Supply pressure gauge

The supply pressure gauge displays the amount of air pressure stored in the primary and secondary air tanks. This gauge is crucial for the driver to monitor the system's air supply, ensuring there is sufficient pressure for safe braking and operation of other air-powered accessories.

Question 11: Before you accept cargo or baggage with hazardous materials, you must confirm that the container has which of the following?

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

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

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

Correct answer: 120-140 psi.

In an air brake system, the air compressor governor is responsible for maintaining air pressure within a safe operating range. The governor typically cuts out, stopping the compressor, when the air pressure reaches between 120-140 psi. This ensures the system has sufficient pressure for braking while preventing over-pressurization, which could damage components.

Question 13: What should you look for when inspecting wheel rims during a pre-trip inspection?

Cracks, damaged areas, and that all lug nuts are present and tightened (Correct answer)
Only verify that the rims are the correct color
Rims only need inspection following a tire blowout
Only check for rim roundness visually

Correct answer: Cracks, damaged areas, and that all lug nuts are present and tightened

Rims must be inspected for cracks, physical damage, and proper lug nut installation to prevent catastrophic wheel separation while driving.

Question 14: What does the letters 'RQ' on a shipping paper mean?

Required quantity
Refrigeration quotient
Route quality
Reportable quantity of a hazardous substance (Correct answer)

Correct answer: Reportable quantity of a hazardous substance

RQ indicates a reportable quantity, meaning a spill must be reported to authorities.

Question 15: What must a CDL driver do if safety-affecting defects are found during a pre-trip inspection?

Note them in the trip log and continue driving
Defects only need to be reported to a supervisor monthly
Report them only at the end of the trip
Have defects repaired before operating the vehicle (Correct answer)

Correct answer: Have defects repaired before operating the vehicle

Safety-affecting defects must be repaired before operating the vehicle; drivers are legally responsible for ensuring the vehicle is in safe operating condition.

Question 16: What should you inspect when checking the steering mechanism during a pre-trip inspection?

Excessive play, loose or missing nuts, and bent or damaged components (Correct answer)
Only that the wheel turns left and right
Steering is only inspected after a collision
Only confirm the steering wheel is attached

Correct answer: Excessive play, loose or missing nuts, and bent or damaged components

A proper steering check includes inspecting for excessive play (no more than 10 degrees of free movement) and checking for damaged, loose, or missing components.

Question 17: Who is responsible for properly packaging, labeling, and marking hazardous materials before shipment?

The shipper (Correct answer)
The carrier's dispatcher
The state inspector
The driver

Correct answer: The shipper

The shipper must correctly package, mark, and label hazmat and prepare the shipping papers.

Question 18: What is the proper way to test the air leakage rate?

Turn off the engine and release the parking brake (Correct answer)
Fully charge the air system and leave the engine running
Leave the engine running and release the parking brake
Depress the brake pedal and monitor the air pressure gauge

Correct answer: Turn off the engine and release the parking brake

Turn off the engine and release the parking brake. You should test for air leakage with a fully-charged air system. You should turn off the engine, release the parking brake, and time the air pressure drop. The loss rate should be less than two psi in one minute for single vehicles and less than three psi in one minute for combination vehicles.

Question 19: School bus drivers need to check that they have what emergency equipment?

Three reflective triangles.
Body fluid cleanup kit.
All of the listed answers. (Correct answer)
Emergency kit.
Spare electrical fuses.

Correct answer: All of the listed answers.

School bus drivers must ensure they have specific emergency equipment on board to handle various situations. This includes a body fluid cleanup kit for sanitation, spare electrical fuses for minor electrical repairs, and three reflective triangles for roadside warning. Having all these items readily available is crucial for maintaining safety and responding effectively to emergencies involving students.

Question 20: No matter how small the cargo you are transporting, it's a good idea to have at least ___ tie-downs holding it.

2 (Correct answer)
4
7
3

Correct answer: 2

Even for small pieces of cargo, it is a good practice to use at least two tie-downs. This ensures that the cargo is secured against movement in multiple directions, preventing it from shifting, falling, or becoming a hazard. Using two tie-downs provides redundancy and better stability compared to a single tie-down.

Question 21: The 'crack-the-whip' effect in combination vehicles refers to:

The sound brakes make when cold
A sudden steering move amplifying trailer sway and risking rollover (Correct answer)
Tire blowout vibration
Snapping the air lines during coupling

Correct answer: A sudden steering move amplifying trailer sway and risking rollover

Quick steering movements can throw the trailer sideways, and this rearward amplification can cause the trailer to roll over.

Question 22: Which of the following statements is FALSE regarding brake and accelerator interlock systems?

The interlock applies the brakes when the rear door is open
The interlock releases when you close the rear door
You can use the interlock in place of the parking brake (Correct answer)
The interlock holds the throttle in idle position when the rear door is open

Correct answer: You can use the interlock in place of the parking brake

Brake and accelerator interlock systems are safety features designed to prevent a bus from moving while the rear door is open by applying the brakes and holding the throttle in idle. However, these systems are not a substitute for the parking brake. The parking brake is a separate, dedicated system for securing the vehicle when parked, and relying on the interlock alone is unsafe and against regulations.

Question 23: Which of the following statements is true regarding front wheel braking?

Front wheel braking will cause skids on ice
You should put a front brake limiting valve (if equipped) on the slippery position in adverse conditions
Front wheel braking is ineffective in slippery conditions
Front wheel braking is good under all conditions (Correct answer)

Correct answer: Front wheel braking is good under all conditions

Modern commercial vehicles are designed with front wheel brakes that are effective and necessary for optimal stopping power under all conditions. While older systems might have had front brake limiting valves for slippery conditions, current regulations and designs ensure front brakes contribute significantly to overall braking performance without causing skids when properly maintained and operated.

Question 24: When is a CDL driver required to perform a pre-trip inspection?

Before each trip (Correct answer)
Every 500 miles during a trip
Once a week before long trips
Only after repairs have been made

Correct answer: Before each trip

Federal regulations require CDL drivers to inspect their vehicle before each trip to ensure it is safe to operate.

Question 25: HOW OFTEN WHILE ON THE ROAD MUST YOU STOP TO INSPECT YOUR CARGO?

Every 6 hours or 300 miles
Every 3 hours or 150 miles (Correct answer)
Before and after your trip
Every 1 hour or 50 miles

Correct answer: Every 3 hours or 150 miles

To ensure cargo remains secure and balanced throughout a trip, federal regulations mandate periodic inspections while on the road. Drivers must stop and inspect their cargo within the first 50 miles of a trip, and then every 3 hours or 150 miles, whichever comes first. This regular check helps prevent shifting loads, which can affect vehicle handling and safety.

Question 26: If your trailer begins to skid, you should

Apply to the trailer hand brake to straighten out the trailer
Turn the steering wheel in the direction of the skid
Maintain light pressure on your brakes until the trailer straightens out
Release your brakes until the trailer wheels grip the road again (Correct answer)

Correct answer: Release your brakes until the trailer wheels grip the road again

If your trailer begins to skid, the most effective action is to release the brakes. This allows the trailer wheels to unlock and regain traction with the road surface. Once traction is restored, the trailer can straighten out, preventing a jackknife or further loss of control.

Question 27: As you are checking your hydraulic brakes, you should pump the brake pedal three times and then hold it for how many seconds?

5 seconds. (Correct answer)
15 seconds.
30 seconds.
10 seconds.
23 seconds.

Correct answer: 5 seconds.

To properly check hydraulic brakes, the driver should pump the brake pedal three times to build up pressure, and then hold it down firmly. The pedal should not move more than an inch or two over a period of 5 seconds. If the pedal sinks further or continues to drop, it indicates a potential leak in the hydraulic system, which requires immediate attention before driving.

Question 28: WHAT PART OF THE KINGPIN SHOULD THE LOCKING JAWS CLOSE AROUND?

The head
The base
The shank (Correct answer)
All of the above answers are correct

Correct answer: The shank

The locking jaws of the fifth wheel are specifically designed to close securely around the shank (the cylindrical part) of the kingpin, just below its head. This ensures a tight and safe connection between the tractor and trailer. If the jaws do not properly engage the shank, the coupling is not secure, and the trailer could detach, leading to a dangerous situation.

Question 29: How many versions of the Class A Pre-trip Inspection test exist?

Three.
Eight.
Four. (Correct answer)
Two.

Correct answer: Four.

The CDL Class A pre-trip inspection test has four distinct versions (A, B, C, D). These different versions are used to ensure that applicants have a comprehensive understanding of vehicle inspection rather than simply memorizing a single sequence. Each version covers the same critical components but may present them in a different order or focus on specific items within a category.

Question 30: What is a wig-wag?

Another name for a brake pedal
A mechanical arm that comes into view when the air pressure falls below 60 psi (Correct answer)
A lever used to apply the spring brakes gradually
A device that cuts the normal air pressure to the front brakes by half

Correct answer: A mechanical arm that comes into view when the air pressure falls below 60 psi

A 'wig-wag' is a specific type of low air pressure warning device found on some older commercial vehicles. It is a mechanical arm that physically drops or 'wags' into the driver's view, typically in the dashboard, when the air pressure in the brake system falls below approximately 60 psi. This visual indicator serves as a critical alert to the driver about dangerously low air pressure.

Question 31: A driver must stop and check for hazmat leaks at which of the following intervals during transport?

Every 25 miles or 30 minutes, whichever comes first
Every 500 miles or at every state line
At the beginning of the trip only
Every 150 miles or every 3 hours, whichever comes first (Correct answer)

Correct answer: Every 150 miles or every 3 hours, whichever comes first

Regulations require drivers to inspect hazmat loads within the first 25 miles of a trip and then every 150 miles or every 3 hours, whichever comes first, to catch leaks or shifts before they become emergencies.

Question 32: You will lose your CDL for at least one year if you are caught committing which first offense?

Driving a CMV if your blood alcohol concentration is .04% or higher.
If you leave the scene of an accident involving a CMV.
If you refuse to undergo blood alcohol testing.
All of the listed answers. (Correct answer)

Correct answer: All of the listed answers.

According to federal CDL regulations, refusing a blood alcohol test, driving a CMV with a BAC of .04% or higher, or leaving the scene of an accident involving a CMV are all considered major offenses. Any of these first offenses will result in a disqualification of your CDL for at least one year.

Question 33: Which of the following devices can be used as the low air pressure warning signal?

Red warning light
A buzzer
A mechanical arm (wig wag)
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 34: At what air pressure must the low air pressure warning signal come on?

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

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 35: During a pre-trip inspection of the engine compartment, which items must be checked?

Oil level, coolant level, and condition of belts and hoses (Correct answer)
Just the air filter housing
Only the battery terminals
Fuel level only

Correct answer: Oil level, coolant level, and condition of belts and hoses

The engine compartment check must include oil level, coolant level, power steering fluid, and the condition of belts and hoses.

Question 36: When following behind other vehicles, you should follow

At least one second for every 20 feet of your vehicle length
At least two seconds for every 10 feet of your vehicle length, plus one second if going over 50 MPH
At least one second for every 10 feet of your vehicle length, plus one second if going over 40 MPH (Correct answer)
At least two seconds for every 10 feet of your vehicle length

Correct answer: At least one second for every 10 feet of your vehicle length, plus one second if going over 40 MPH

The 'one second for every 10 feet of vehicle length' rule provides a basic safe following distance. Adding an extra second when traveling over 40 MPH accounts for the increased stopping distance and reduced reaction time at higher speeds. This adjustment ensures adequate space to react and stop safely, especially with a large commercial vehicle.

Question 37: To perform a proper inspection of suspension mounts, you need to ______.

Check for missing bolts.
Inspect the mounts at each point where they are secured to the vehicle frame and axle[s].
All of the listed answers. (Correct answer)
Look for cracked spring hangers.

Correct answer: All of the listed answers.

To perform a proper inspection of suspension mounts, you need to examine them comprehensively. This includes looking for cracked spring hangers, checking for any missing bolts, and inspecting the mounts at each point where they are secured to the vehicle frame and axles. A thorough inspection ensures the suspension system is structurally sound and safe for operation, preventing potential failures that could compromise vehicle control.

Question 38: Which of the following devices indicates how much air pressure you are applying to your brakes?

Supply pressure gauge
Low air pressure warning signal
Governor
Application pressure gauge (Correct answer)

Correct answer: Application pressure gauge

The application pressure gauge indicates how much air pressure is being sent to the brake chambers when the driver presses the brake pedal. This gauge helps the driver monitor their braking effort and ensures that the brakes are receiving adequate pressure for effective stopping. It is distinct from the supply pressure gauge, which shows the total air pressure available in the tanks.

Question 39: Which of the following steps should you use to check the slack adjusters on S Cam brakes?

Put the parking brake on and pull on the slack adjuster
Insure that the slack adjusters move more than 1 inch where the push rod attaches to it
Pull on the slack adjusters after draining the air from the system
Use gloves and pull hard on each slack adjuster (Correct answer)

Correct answer: Use gloves and pull hard on each slack adjuster

Use gloves and pull hard on each slack adjuster. You should park on level ground and chock the wheels. The parking brakes need to be off so that you can move the slack adjusters. Using gloves, you should pull hard on each slack adjuster. If the slack adjuster moves more than about one inch where the push rod attaches to it, it probably needs adjustment.

Question 40: Glad hands are used to:

Adjust the fifth wheel angle
Connect the service and emergency air lines between tractor and trailer (Correct answer)
Raise the landing gear
Lock the kingpin

Correct answer: Connect the service and emergency air lines between tractor and trailer

Glad hands are the coupling devices used to connect the air brake lines between the tractor and trailer.

Question 41: Bus drivers can carry small amounts of certain hazardous materials. However, the total amount of hazardous materials should not exceed what amount?

50 lbs.
500 lbs. (Correct answer)
25 lbs.
250 lbs.
100 lbs.

Correct answer: 500 lbs.

Federal regulations impose a strict limit of 500 lbs. on the total amount of certain hazardous materials that a bus can carry. This restriction is a critical safety measure designed to minimize the risk associated with transporting dangerous goods in a passenger vehicle. Exceeding this limit significantly increases the potential for severe consequences in the event of an accident or spill, endangering passengers and the public.

Question 42: What is the minimum tread depth required for front tires on a commercial vehicle?

8/32 of an inch
6/32 of an inch
4/32 of an inch (Correct answer)
2/32 of an inch

Correct answer: 4/32 of an inch

Front tires must have a minimum tread depth of 4/32 of an inch, while drive and trailer tires require a minimum of 2/32 of an inch.

Question 43: When you are transporting cargo, you should inspect your cargo within the first ___ miles.

25
50 (Correct answer)
30
20
45

Correct answer: 50

CDL regulations require drivers to inspect their cargo and its securement devices within the first 50 miles of a trip. This initial inspection is crucial because cargo can settle or shift during the first part of the journey, potentially loosening tiedowns. Subsequent inspections should be performed every 3 hours or 150 miles, whichever comes first, or whenever there's a change of duty status.

Question 44: In a combination vehicle, what should the air pressure loss be with a fully charged air system?

Less than 3 psi per minute (Correct answer)
Less than 4 psi per minute
Less than 2 psi per minute
Less than 5 psi per minute

Correct answer: Less than 3 psi per minute

For a combination vehicle (tractor-trailer), the acceptable air pressure loss during a static air brake test is slightly higher than for a single vehicle due to the increased complexity and number of air lines. With a fully charged system and the brakes applied, the pressure loss should not exceed 3 psi per minute. A greater loss indicates potential leaks in the system, which must be repaired for safe operation.

Question 45: What does audible air leaking from the brake system during a pre-trip inspection indicate?

The compressor is building extra reserve pressure, which is beneficial
There is a leak in the air brake system that must be repaired before the vehicle is operated (Correct answer)
This is normal and indicates the compressor is running
Air leaks are only a concern at speeds above 60 mph

Correct answer: There is a leak in the air brake system that must be repaired before the vehicle is operated

Air leaks reduce brake system pressure, compromising stopping ability, and must be repaired before the vehicle is operated to ensure safe braking.

Question 46: What is the purpose of a converter dolly in a double or triple combination?

It acts as an additional power unit when ascending steep grades
It houses the air tanks for the rear trailer's braking system
It provides extra braking power for the rear trailers
It converts the lead trailer's kingpin into a fifth-wheel coupling for connecting an additional trailer (Correct answer)

Correct answer: It converts the lead trailer's kingpin into a fifth-wheel coupling for connecting an additional trailer

A converter dolly has a fifth wheel on top that accepts the next trailer's kingpin, converting a standard trailer into a lead unit for a double or triple combination. It does not provide independent power or extra braking beyond what is already in the air system.

Question 47: This red 8-sided traffic sign with white text is telling you what?

Make a full stop. (Correct answer)
Wrong way.
School zone.
Yield.

Correct answer: Make a full stop.

This is the universal description of a STOP sign. Its distinctive octagonal shape and red color with white lettering are designed for immediate recognition, requiring drivers to come to a complete halt before the stop line or crosswalk. Drivers must then check for cross-traffic and pedestrians before proceeding safely.

Question 48: You are testing the stopping action of service brakes on a hydraulic system. Which of the following may indicate that there is a problem with your service brakes?

The brake pedal goes to the floor.
The vehicle pulls to one side when the brake pedal is pressed.
All of the listed answers. (Correct answer)
Stopping action is delayed.

Correct answer: All of the listed answers.

When testing hydraulic service brakes, several issues can indicate a problem. If the brake pedal goes to the floor, it suggests a loss of hydraulic fluid or a major leak. If the vehicle pulls to one side when braking, it could mean uneven brake adjustment or a problem with a specific brake unit. A delayed stopping action indicates a general issue with brake effectiveness, all of which require immediate attention.

Question 49: TRAILER MADE BEFORE 1975, EQUIPPED WITH AIR BRAKES:

Usually need a glad hand converter
Are heavier and safer to use
Must be equipped with ABS
Often do not have spring brakes (Correct answer)

Correct answer: Often do not have spring brakes

Trailers manufactured before 1975, even if equipped with air brakes, often lack spring brakes as a standard feature. Spring brakes automatically apply when air pressure is lost, serving as both an emergency and parking brake. Drivers operating older trailers must be aware that their emergency braking system might rely solely on air pressure, which can be lost, requiring different safety considerations.

Question 50: If the oil pressure is low, dropping or fluctuating, you should _____.

Honk your horn to warn other drivers.
Accelerate and reach your destination as quickly as possible.
None of the listed answers.
Stop immediately. (Correct answer)

Correct answer: Stop immediately.

Low, dropping, or fluctuating oil pressure is a critical warning sign that indicates a severe problem with your engine's lubrication system. Continuing to drive with insufficient oil pressure can lead to catastrophic engine damage, as vital moving parts will not be properly lubricated. Therefore, stopping immediately is essential to prevent further damage and ensure safety.

Question 51: What should the air pressure loss be in a single vehicle with a fully charged air system?

Less than 2 psi per minute (Correct answer)
Less than 5 psi per minute
Less than 4 psi per minute
Less than 3 psi per minute

Correct answer: Less than 2 psi per minute

During a static air brake test, a single vehicle with a fully charged air system should not lose more than 2 psi in one minute after the initial pressure drop from applying the brakes. This low rate of pressure loss indicates that the air brake system is relatively free of leaks. Exceeding this limit suggests a problem that needs to be addressed for safe vehicle operation.

Commercial Driver's License (CDL) General Knowledge

The CDL General Knowledge exam certifies an individual's understanding of the fundamental rules and regulations for operating commercial motor vehicles.

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60 min

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80%

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