South Carolina CDL Driving Rules Practice Test 2

Question 1

What should a driver check in the engine compartment during a pre-trip inspection, besides belts and hoses?

Accepted Answer

Signs of leaking fluids and unusual buildup of grease, oil, or dirt.

Answer

The passenger seat adjustments.

Answer

The vehicle's registration papers.

Question 2

What is the primary reason for maintaining proper vehicle maintenance as a defensive driving technique?

Accepted Answer

To ensure brakes, lights, and tires are in good condition and prevent breakdowns.

Answer

To improve the vehicle's aesthetic appeal.

Answer

To reduce the need for pre-trip inspections.

Question 3

What should a driver do to improve visibility during adverse weather conditions like fog or heavy rain?

Accepted Answer

Slow down and use headlights and wipers.

Answer

Use high beams continuously.

Answer

Drive faster to get through it quickly.

Question 4

What is the significance of a "wig wag" device in an air brake system?

Accepted Answer

It's a visual low air pressure warning device.

Answer

It's a component of the ABS.

Answer

It's a device for automatic air tank draining.

Question 5

What is the typical "cut-in" pressure for an air compressor governor?

Accepted Answer

Around 100 psi.

Answer

Around 150 psi.

Answer

Around 125 psi.

Question 6

What is the primary purpose of a dual air brake system?

Accepted Answer

To provide a safety redundancy with two separate air brake systems.

Answer

To allow for independent control of front and rear brakes.

Answer

To provide increased braking power for heavy loads.

Question 7

What is the maximum permissible air pressure drop for a single vehicle during a static leakage test?

Accepted Answer

2 psi.

Answer

3 psi.

Answer

4 psi.

Question 8

What is the recommended action if automatic slack adjusters are found to be out of adjustment during an inspection?

Accepted Answer

Manually adjust them only as a temporary emergency measure, as it likely indicates an underlying mechanical problem.

Answer

Manually adjust them as a permanent fix.

Answer

Immediately take the vehicle out of service for repair.

Question 9

What is the purpose of the one-way check valve between the air compressor and the first air reservoir?

Accepted Answer

To prevent air from escaping if the compressor leaks.

Answer

To ensure the air tanks are properly drained.

Answer

To regulate the flow of air to the brake chambers.

Question 10

What is brake fade primarily caused by?

Accepted Answer

Excessive heat from overuse of brakes.

Answer

Under-inflated tires.

Answer

Driving too slowly.

Question 11

What is the proper technique for braking on long, steep downgrades with a CMV?

Accepted Answer

Apply brakes just enough for a definite slowdown, reduce speed by 5 mph below "safe" speed, then release and repeat.

Answer

Shift to neutral and coast.

Answer

Apply brakes continuously to maintain a constant speed.

Question 12

What is "brake lag" in air brake systems?

Accepted Answer

The delay for air to flow from the brake pedal to the brake chambers.

Answer

The time it takes for the brake pedal to return to its original position.

Answer

The time it takes for the vehicle to come to a complete stop after applying brakes.

Question 13

What is the approximate total stopping distance for a CMV at 55 mph, including brake lag?

Accepted Answer

Over 450 feet.

Answer

250 feet.

Answer

100 feet.

Question 14

What is the purpose of a "progressive" shifting technique in some newer vehicles?

Accepted Answer

To increase the RPM at which the driver shifts as they move up in gears.

Answer

To eliminate the need for double clutching.

Answer

To allow the driver to shift at lower RPMs in all gears.

Question 15

What is the importance of keeping a standardized checklist for pre-trip inspections?

Accepted Answer

It helps ensure that no part of the inspection is overlooked.

Answer

It is not necessary if the driver is experienced.

Answer

It speeds up the inspection process.

Question 16

What should a driver do if they have to pull off the road due to an issue?

Accepted Answer

Use flashers, reflective triangles, and/or road flares to alert approaching drivers.

Answer

Wait for emergency services to arrive before doing anything.

Answer

Turn off all lights to conserve battery.

Question 17

What is the recommended action for a driver if their vehicle pulls to one side during a service brake test?

Accepted Answer

This indicates a brake alignment problem and the vehicle should not be driven until repaired.

Answer

It is normal for heavy vehicles.

Answer

Continue driving cautiously.

Question 18

What is the primary concern if brake drums have cracks longer than half the friction area width?

Accepted Answer

They are unsafe and need replacement.

Answer

They will cause the vehicle to pull to one side.

Answer

They will make a loud noise.

Question 19

What is the consequence of not wearing a seat belt while driving a CMV?

Accepted Answer

It is a key contributing factor to fatal crashes and can prevent drivers from controlling their vehicles.

Answer

It can reduce fuel efficiency.

Answer

It can cause the air bags to malfunction.

Question 20

What is the primary reason for maintaining a safe following distance in heavy traffic?

Accepted Answer

To have enough space to react to sudden stops or lane changes by others.

Answer

To allow other vehicles to merge easily.

Answer

To avoid getting stuck behind slow vehicles.

Question 21

What is the purpose of the "modulating control valve" found on some vehicles?

Accepted Answer

To gradually apply spring brakes if service brakes fail.

Answer

To automatically adjust the air pressure to the service brakes.

Answer

To control the engine speed.

Question 22

What is the recommended action if spring brakes are very hot after heavy braking?

Accepted Answer

Let them cool before applying the parking brake.

Answer

Apply the parking brake immediately to secure the vehicle.

Answer

Immediately apply cold water to cool them.

Question 23

What is the recommended action if spring brakes are very wet in freezing temperatures?

Accepted Answer

Use them lightly while driving in a low gear to heat and dry them.

Answer

Pour antifreeze on them.

Answer

Apply the parking brake immediately to dry them.

Question 24

What is the primary reason for planning breaks on longer routes?

Accepted Answer

To prevent exhaustion and reduce the risk of accidents from fatigue.

Answer

To find the cheapest fuel.

Answer

To avoid toll roads.

Question 25

What is the importance of checking the load's balance and security during vehicle maintenance?

Accepted Answer

A shifting load can cause a rollover or loss of control.

Answer

To reduce the overall weight of the vehicle.

Answer

To improve the vehicle's appearance.

Question 26

What is the purpose of the "front brake limiting valve" on some older vehicles?

Accepted Answer

To cut normal air pressure to the front brakes by half in "slippery" mode to reduce skidding.

Answer

To automatically adjust front brake pressure based on speed.

Answer

To increase air pressure to the front brakes.

Question 27

What is the recommended position for the front brake limiting valve for full stopping power?

Accepted Answer

Normal position.

Answer

Slippery mode.

Answer

It doesn't matter.

Question 28

What is the primary function of the "slack adjuster" in an air brake system?

Accepted Answer

To adjust the distance the brake shoes travel to make contact with the drum.

Answer

To adjust the air pressure in the tanks.

Answer

To move the brake shoes away from the drum when the brake pedal is released.

Question 29

What is the consequence of worn brake linings that are dangerously thin (less than 1/4 inch)?

Accepted Answer

They are unsafe and need replacement.

Answer

They will improve braking efficiency.

Answer

They will last longer.

Question 30

What is the maximum air pressure that a full service brake application must deliver to all brake chambers?

Accepted Answer

Not less than 90 percent of the air reservoir pressure.

Answer

Not less than 75 percent of the air reservoir pressure.

Answer

Not less than 50 percent of the air reservoir pressure.

Question 31

What is the primary purpose of the "camLaster" brake design?

Accepted Answer

To offer an internal adjustment system for continuous proper adjustment and even contact with the brake drum.

Answer

To reduce the number of brake shoes.

Answer

To provide manual adjustment of the brakes.

Question 32

What is the primary difference in operation between wedge brakes and S-cam brakes?

Accepted Answer

Wedge brakes use air pressure to directly push a wedge between shoe ends, forcing them apart, while S-cam brakes use an S-shaped cam to spread the shoes.

Answer

Wedge brakes use hydraulic fluid, while S-cam brakes use air.

Answer

Wedge brakes are always self-adjusting, while S-cam brakes are always manual.

Question 33

What is the main characteristic of disc brakes in commercial vehicles?

Accepted Answer

They clamp a disc or rotor between brake lining pads of a caliper using a "power screw".

Answer

They use a wedge to spread brake shoes.

Answer

They are only found on older vehicles.

Question 34

What is the primary purpose of a "static leakage test" for air brakes?

Accepted Answer

To check for air leaks when the engine is off and all brakes are released.

Answer

To check for air leaks when the vehicle is moving.

Answer

To check the rate of air pressure buildup.

Question 35

What is the recommended procedure for testing the parking brake?

Accepted Answer

Set the parking brake and gently pull against it in a low gear to ensure it holds.

Answer

Drive at high speed and apply the parking brake.

Answer

Apply the parking brake and immediately turn off the engine.

Question 36

What should a driver check for regarding the overall appearance of the coach when approaching it for a pre-trip inspection?

Accepted Answer

Any damage, leaning, or anything hanging from underneath.

Answer

The interior upholstery color.

Answer

The number of passenger seats.

Question 37

What is the purpose of checking the spring tension on wiper arms and the condition of wiper blades?

Accepted Answer

To ensure they can effectively clear the windshield for visibility.

Answer

To check for electrical faults.

Answer

To ensure they are properly lubricated.

Question 38

What should be checked in luggage and service access bays during a walk-around inspection?

Accepted Answer

Unusual objects or packages, and the operation of bay doors and locking mechanisms.

Answer

The type of cargo being carried.

Answer

The number of spare tires.

Question 39

What external safety equipment should be checked during a walk-around inspection?

Accepted Answer

Spare tire, tire chains (if needed), reflective triangles, and spare fuses.

Answer

Road flares and a toolkit.

Answer

First-aid kit and fire extinguisher (if stored externally).

Question 40

What is the recommended way to check brake lights if a helper is not available?

Accepted Answer

Attempt to verify proper brake light function by watching light reflections off a close object.

Answer

Assume they are working.

Answer

Ask another driver to check them later.

South Carolina CDL Driving Rules Practice Test 2

Explanation