South Carolina CDL Driving Rules Practice Test 1

Question 1

What is the primary purpose of a pre-trip inspection for a Commercial Motor Vehicle (CMV)?

Accepted Answer

To identify mechanical or safety issues before operation.

Answer

To ensure the vehicle is clean.

Answer

To check the vehicle's fuel level.

Question 2

According to FMCSA regulations, what must a driver do with discovered deficiencies during a vehicle inspection?

Accepted Answer

Document them for company action before the vehicle is dispatched.

Answer

Fix them immediately regardless of severity.

Answer

Report them verbally to a supervisor.

Question 3

What is a Driver Vehicle Inspection Report (DVIR) used for?

Accepted Answer

To document defects or issues and verify repairs before a trip.

Answer

To record passenger complaints.

Answer

To log personal mileage for tax purposes.

Question 4

What is a common issue to check for on tires during a pre-trip inspection?

Accepted Answer

Loose or separated treads, cuts, bulges, or insufficient tread.

Answer

The brand of the tire.

Answer

The color of the tire valve stem.

Question 5

What is the "cut-out" level for an air compressor governor in an air brake system?

Accepted Answer

The pressure at which the governor stops the compressor from pumping air.

Answer

The maximum pressure the air tanks can hold.

Answer

The pressure at which the compressor starts pumping air.

Question 6

Why is it important to drain air tanks in an air brake system daily?

Accepted Answer

To remove accumulated water and compressor oil that can cause brake failure.

Answer

To increase air pressure for better braking.

Answer

To lubricate the brake components.

Question 7

What is the purpose of the safety valve in an air brake system?

Accepted Answer

To protect the system from excessive pressure.

Answer

To regulate the speed of the air compressor.

Answer

To release air for normal braking.

Question 8

When performing an applied leakage test for air brakes on a single vehicle, what is the maximum permissible air pressure drop in one minute?

Accepted Answer

3 psi.

Answer

2 psi.

Answer

4 psi.

Question 9

At what air pressure range should the low air pressure warning device activate in an air brake system?

Accepted Answer

Between 55 and 75 psi.

Answer

Below 20 psi.

Answer

Between 85 and 100 psi.

Question 10

What is the recommended maximum movement for a slack adjuster on S-cam brakes when pulled hard during an inspection?

Accepted Answer

1 inch.

Answer

0.5 inches.

Answer

2 inches.

Question 11

What is the primary reason for double clutching when shifting gears in most heavy vehicles with manual transmissions?

Accepted Answer

To ensure smooth and controlled gear changes.

Answer

To save fuel.

Answer

To reduce wear on the clutch pedal.

Question 12

When upshifting, what is the correct sequence after releasing the accelerator and shifting to neutral?

Accepted Answer

Release clutch, let engine and gears slow to the RPM for the next gear, then clutch in and shift.

Answer

Release clutch, then immediately shift to the higher gear.

Answer

Press accelerator, then shift to the higher gear.

Question 13

When should a driver downshift before starting down a hill?

Accepted Answer

To prevent the brakes from overheating and losing power.

Answer

After the vehicle gains significant speed.

Answer

Only if the vehicle is fully loaded.

Question 14

What is the recommended action before entering a curve in a CMV?

Accepted Answer

Slow down to a safe speed and downshift to the right gear.

Answer

Brake hard during the middle of the curve.

Answer

Accelerate to maintain momentum.

Question 15

What is the maximum blind spot length behind a semi-truck?

Accepted Answer

160 feet.

Answer

100 feet.

Answer

50 feet.

Question 16

What does the acronym G.O.A.L. stand for in the context of semi-truck backing?

Accepted Answer

Get Out And Look.

Answer

Go Out And Leave.

Answer

Guide Others And Listen.

Question 17

When backing a semi-truck with a spotter, who holds the ultimate responsibility for safe backing?

Accepted Answer

The driver.

Answer

Both equally.

Answer

The spotter.

Question 18

What is the recommended speed when backing a semi-truck?

Accepted Answer

Less than 1 mph.

Answer

As fast as safely possible.

Answer

Between 5-10 mph.

Question 19

What is a key defensive driving technique related to following distance for CMVs?

Accepted Answer

Maintain at least a 4-second gap.

Answer

Maintain at least a 2-second gap.

Answer

Follow as closely as possible to avoid other vehicles cutting in.

Question 20

Why do large trucks and buses require significantly longer stopping distances?

Accepted Answer

Their heavier weight and larger size increase the force needed to stop.

Answer

They are designed to coast more.

Answer

Their tires have less traction.

Question 21

What is a critical distraction that is illegal for CMV drivers while driving?

Accepted Answer

Texting.

Answer

Eating a snack.

Answer

Listening to the radio.

Question 22

When should a CMV driver use hazard lights?

Accepted Answer

When backing up or when pulled off the road to warn others of an issue.

Answer

Only when the vehicle is broken down.

Answer

Only during heavy rain.

Question 23

What is the primary risk associated with driving a CMV when fatigued?

Accepted Answer

Increased risk of causing accidents.

Answer

Reduced fuel efficiency.

Answer

Faster tire wear.

Question 24

What should a driver do if they encounter aggressive drivers on the road?

Accepted Answer

Stay calm and give them space.

Answer

Try to outmaneuver them.

Answer

Engage with them to de-escalate the situation.

Question 25

How often should a CMV driver check their mirrors according to defensive driving practices?

Accepted Answer

Every 8-10 seconds.

Answer

Only when changing lanes.

Answer

Every 30-60 seconds.

Question 26

What is the primary purpose of an alcohol evaporator in an air brake system?

Accepted Answer

To prevent ice from forming in brake valves during cold weather.

Answer

To lubricate the air compressor.

Answer

To increase air pressure in the tanks.

Question 27

What is the function of the S-cam in an S-cam drum brake system?

Accepted Answer

To force the brake shoes away from one another and against the brake drum.

Answer

To regulate air pressure to the brake chambers.

Answer

To drain water from the air tanks.

Question 28

What should a driver do if the application pressure gauge indicates increasing pressure is needed to hold the same speed?

Accepted Answer

Slow down and use a lower gear, as it indicates brake fading.

Answer

Speed up to clear the issue.

Answer

Ignore it, as it is a common occurrence.

Question 29

What is the primary benefit of Anti-lock Braking Systems (ABS) on CMVs?

Accepted Answer

To prevent wheel lock-up during hard braking, helping maintain control.

Answer

To shorten stopping distances significantly.

Answer

To automatically apply brakes without driver input.

Question 30

In a dual air brake system, what is the minimum air pressure that must be built in both systems before driving?

Accepted Answer

100 psi.

Answer

85 psi.

Answer

60 psi.

Question 31

What is the maximum permissible air pressure drop for a combination of 2 vehicles during an applied leakage test?

Accepted Answer

4 psi.

Answer

3 psi.

Answer

6 psi.

Question 32

What is the maximum permissible air pressure drop for a combination of 3 or more vehicles during a static leakage test?

Accepted Answer

5 psi.

Answer

3 psi.

Answer

2 psi.

Question 33

What should a driver do if the low air pressure warning activates while driving?

Accepted Answer

Stop safely as soon as possible.

Answer

Continue driving to the nearest service station.

Answer

Increase engine RPM to build air pressure faster.

Question 34

When should parking brakes be used?

Accepted Answer

Always when parking, unless brakes are very hot or wet in freezing temperatures.

Answer

Only if the vehicle is unattended.

Answer

Only on steep inclines.

Question 35

What is the main risk of pressing and releasing the brake pedal unnecessarily in an air brake system?

Accepted Answer

It can let air out faster than the compressor can replace it, leading to brake failure.

Answer

It can cause the brake drums to warp.

Answer

It can activate the ABS prematurely.

Question 36

How can a driver determine when to upshift if they don't use a tachometer or speedometer?

Accepted Answer

By listening to engine sounds.

Answer

By checking the outside temperature.

Answer

By observing the vehicle's shadow.

Question 37

What should a driver do if they remain too long in neutral while double clutching and have difficulty putting the vehicle into the next gear?

Accepted Answer

Return to neutral, release clutch, increase engine speed to match road speed, and try again.

Answer

Stop the vehicle completely.

Answer

Force it into gear.

Question 38

What is the approximate RPM target for downshifting in some commercial vehicles?

Accepted Answer

12 RPMs.

Answer

20 RPMs.

Answer

15 RPMs.

Question 39

When performing a walk-around inspection, what should a driver look for underneath the coach?

Accepted Answer

Any fresh fluids indicating a leak.

Answer

The color of the exhaust fumes.

Answer

The type of suspension system.

Question 40

What is the acceptable condition for a crack on a windshield during a pre-trip inspection?

Accepted Answer

Any crack not over 1-inch wide, as long as it's not intersected by any other crack.

Answer

Multiple cracks of any size.

Answer

Any crack over 1-inch wide.

South Carolina CDL Driving Rules Practice Test 1

Explanation