South Carolina General Knowledge CDL Practice Test

The CDL General Knowledge practice test covers topics such as the rules of having a CDL and driving a commercial vehicle safety. Taking this 50 question South Carolina CDL practice test will help you prepare for the exam by proving valuable insight into the areas you need to review more thoroughly.

START

When traveling down a long downgrade, you should always

Apply trailer brakes to reduce speed or maintain speed

Use the braking effect of the engine

Use stab braking

Apply brakes when your vehicle exceeds the “safe speed” by 5 mph

None

When driving in fog, you should

Increase you vehicle’s speed

Stop on the side of the road

Use low-beam headlights

All of the above

None

When fighting a fire, which is most correct?

Get downwind of the fire before using the fire extinguisher

Get as close to the fire as possible

Aim the fire extinguisher at the base of the fire

Aim the fire extinguisher at the top of the fire

None

Water will extinguish which of the following fires?

Electrical

Diesel fuel

Gasoline

Tire

None

Shifting gears properly is important because

Doing so helps you maintain control of the vehicle

It helps to keep the oil flowing through the crankcase

It keeps the radiator cool

It keeps the engine at the proper operating temperature

None

When you are driving through construction zones, you should

Speed up and hurry through them so you aren’t in them any longer than necessary

Stop before entering them, get in low gear and proceed through

Watch for uneven surfaces

Reduce your speed only if construction workers are near the roadway

None

Which of the following is true concerning cold weather driving?

Exhaust system leaks are not of concern during cold weather

If the temperature is below 32 degrees Fahrenheit, the engine cannot overheat

Using bleach on tires will provide increased traction

You should use windshield washer fluid which contains antifreeze

None

Which of the following should you NOT do?

Turn your headlights on during the day if visibility is reduced due to bad weather

Flash your brake lights to warn vehicles behind you that you are slowing down

Flash your brake lights when entering a construction zone if vehicles are close behind you

Flash your brake lights if someone is following too closely

None

Bridge formulas are designed to

Determine the total gross vehicle weight of a vehicle

Permit the same maximum axle weight for any axle spacing

Permit less maximum axle weight for axles that are closer together

Permit less maximum axle weight for axles that are further apart

None

10.

When you see a hazard in the road in front of you, you should

Steer and countersteer around it

Stop quickly and get off the roadway if possible

Stop quickly, stay in the roadway, set your reflective triangles, and go to the rear of your vehicle to flag down traffic

Turn on your 4-way flashers or flash your brakes lights to warn others

None

11.

Which of the following is true about rear drive wheel braking skids?

The vehicle’s front wheels will slide sideways

It is not a cause of jackknifing

The locked wheels have more traction than the wheels that are rolling

If it occurs with a vehicle towing a trailer, the trailer can push the towing vehicle sideways

None

12.

Controlled braking is

Applying brakes hard enough for the wheels to lock up

Pressing the brakes hard enough to lock-up the wheels, then releasing and then reapplying again

Applying firm brake pressure but not to the point of lock-up

Only used if the vehicle does not have anti-lock brakes

None

13.

The proper way to load a vehicle is

Keep the load balanced in the cargo area

Place the load at the front of the trailer to give your drive wheels better traction

Place the load at the rear of the trailer so your rear tires have better traction

It makes no difference where the cargo is placed as long as you are not over the allowable gross weight

None

14.

If you are aren’t sure that you have safe space to pass under an object, you should

Assume all clearances are of sufficient height

Height clearance is not a concern as long as you stay on state or federal Roadways

Take another route

All of the above

None

15.

Which of the following statements about causes of vehicle fires is true?

An overheated radiator is the most common type of vehicle fire

Carrying a properly charged and rated fire extinguisher will help to prevent fires

Under-inflated or flat tires will NOT cause a vehicle fire

Poor trailer ventilation can cause cargo to catch fire

None

16.

While driving you are looking ahead of your vehicle. How should you be looking?

Look to the right side of the roadway

Look back and forth and near and far

Stare straight ahead at all times

Look straight ahead and glance in your mirrors every 45 to 60 seconds

None

17.

Convex (curved) mirrors will

Make objects appear to be larger than they really are

Make objects appear to be closer than they really are

Show a narrower area than flat mirrors

Show a wider area than flat mirrors

None

18.

Which of the following conditions may produce a skid?

Driving too fast for conditions

Over braking

Over steering

All of the above

None

19.

What three factors add up to the total stopping distance for a commercial vehicle?

Perception distance, reaction distance, and braking distance

Eye lead time, reaction distance, and braking distance

Perception distance, reaction distance, and response distance

Response distance and braking distance

None

20.

If you drive through heavy rain or standing water your brakes may get wet. What can this cause when you apply the brakes?

Trailer jackknife

Your brakes to heat up

Hydroplaning

Hydroplaning if you were traveling faster than 30 mph when you applied brakes

None

21.

The Driver’s Manual says you should use your horn

To make the deer standing alongside the road move further away

When a car gets in the way

If it may help you to avoid a collision

When you begin to change lanes

None

22.

Placarding, the use of hazardous material placards and labels, is an example of

Containment

Controlling the hazardous materials risk

Communication

All of the above

None

23.

Which of the following is a sign of drowsy driving

You can’t stop yawning

You drift between lanes

Your eyes close or go out of focus by themselves

All of the above

None

24.

Use of alcohol can cause serious driving errors, including

Decreased reaction time to hazards

Increased reaction time to hazards

Gradual, smooth starts

All of the above

None

25.

When you are driving at night, you should

Dim your lights when you are within 300 feet of oncoming traffic

Watch the white line on the left side of the roadway

Adjust your vehicle speed so as to keep your stopping distance within your sight distance

Keep your high beams on at all times

None

26.

Which of the following is true?

Tires with tread separation or cuts should not be used on a vehicle

Tires of mismatched sizes should be used on a vehicle

1/32 inch tread depth is allowed on drive tires

1/32 inch tread depth is permissible for steering tires

None

27.

If you break down on a level, straight, four-lane, divided highway, where should you place the reflective warning triangles?

One 10 feet from the rear of the vehicle, one approximately 100 feet from the rear of the vehicle, and another one about 100 feet to the front of the vehicle

One 10 feet from the rear of the vehicle, one approximately 100 feet from the rear of the vehicle, and one about 200 feet from the rear of the vehicle

One 100 feet from the rear of the vehicle, one approximately 200 feet from the rear of the vehicle, and one about 300 feet from the rear of the vehicle

One 50 feet from the rear of the vehicle, one about 100 feet from the rear of the vehicle, and one about 200 feet from the front of the vehicle

None

28.

Controlled braking is used when

The goal is to keep the vehicle in a straight line while braking

You must stop as quickly as possible

Is only used with hydraulic brakes

Is only used when the vehicle is equipped with anti-lock brakes

None

29.

Your vehicle is 40 feet long and you are traveling at 50 mph. The safe following distance is

5 seconds

6 seconds

4 seconds

3 seconds

None

30.

How many missing or broken leaves in a leaf spring will cause your vehicle to be placed out-of-service?

One-fourth of the total

One-half of the total

One-third of the total

Any

None

31.

Aggressive driving is

Operating in a selfish, bold, or pushy manner, without regard for the rights or safety of others

Acceptable during rush hour in a metropolitan area

Operating in a cautious and courteous manner

All of the above

None

32.

Which of the following statements is true?

Hazards are easier to see at night than during the day

People can’t see as sharply at night

Most drivers are more alert at night than during the day

It is recommended that you use your high beams at all times during the period from 7 P.M. to 7 A.M.

None

33.

“Over-the-counter” medication used to treat the common cold

Is permissible as long as the dispatcher has given the o.k. to use it

Can only be taken when driving during daylight hours

Often can make you sleepy and should not be used while driving

Is o.k. as long as you take just half a dose

None

34.

Which of the following is true about the use of reflective emergency triangles?

The regulation requires they be placed within 5 minutes of stopping

You do not need to use them if you break down as long as your 4-way flashers are working

You do not need to use them as long as you have pulled your vehicle completely off the traveled portion of the roadway

If you stop on a hill or curve, it is permissible to place them up to 500 feet in order to provide adequate warning

None

35.

According to the Commercial Driver’s manual, why should you limit the use of your vehicle’s horn?

If your vehicle has air brakes, the air horn may not work while you are applying your brakes

It may startle other drivers

You should keep both hands on the steering wheel at all times

The Driver’s Manual does not say that a driver should limit the use of the horn

None

36.

If a state or federal inspector judges that your vehicle is unsafe, they will put the vehicle out of service

For 24 hours

For 48 hours

Until you contact you carrier and make arrangements for repair

Until it is fixed

None

37.

It you are being tailgated you should

Motion for the tailgater to pass you when it is safe

Increase your following distance

Turn your 4-way flashers on

Slam on the brakes

None

38.

As alcohol begins to build up in the body, which of the following is affected first?

Muscle control

Coordination

Kidney control

Judgment and self-control

None

39.

Which of the following statements about backing a commercial vehicle to a dock is NOT true?

Since you can’t see behind you, you should back slowly until you bump the dock

Use a helper and communicate with hand signals

You should always back toward the driver’s side when possible

Both A and C

None

40.

Can federal inspectors inspect your truck or bus?

Yes, and they have the authority to place you out-of-service

Yes, but they have no authority to place you out-of-service

Yes, but only at a port-of-entry

None

41.

The braking effect of the engine is greatest when

It is above the governed RPMs and the transmission is in the high gears

It is near the governed RPMs and the transmission is in the lower gears

It is above the governed RPMs and the transmission is in the lower gears

It is near the governed RPMs and the transmission is in the high gears

None

42.

What is hydroplaning?

An emergency situation created when an aircraft must make an emergency landing on a highway

Excessive heat built up in the radiator

Something that only occurs at high vehicle speeds

When your vehicle’s tires lose contact with a wet road and have little or no traction

None

43.

Before entering a curve, you should

Slow down to a safe speed and downshift to the correct gear

Increase your speed to increase vehicle stability

Come to a complete stop and proceed as slowly as possible

All of the above

None

44.

You are driving on a straight and level roadway at 60 mph and suddenly a tire blows out on your vehicle. What should you do first?

Immediately begin light, controlled braking

Immediately begin stab braking

Grip steering wheel firmly with both hands and stay off the brakes until the vehicle has slowed down

Immediately begin emergency braking

None

45.

Most serious skids are a result of

Driving too fast for conditions

Improper loading of the vehicle

Turning too sharply

Winter driving conditions

None

46.

Drinking alcohol can affect your

Judgment

Vision

Coordination and reaction time

All of the above

None

47.

Which of the following happens when a tire blows at highway speed?

You will experience an immediate and dramatic drop in speed

You will feel a vibration

You will hear a hissing sound

The low air pressure signal device will come on

None

48.

When backing your vehicle, you should

Do it as quickly as possible, so your wheels don’t drift

Try to position your vehicle so you can back in a straight line.

Never use your mirrors

All of the above

None

49.

Why do hazardous materials regulations exist?

To provide for safe drivers and equipment

To communicate a risk

To contain the product

All of the above

None

50.

What is the purpose of a pre-trip inspection?

To add an additional 15 minutes of time to your log book

To avoid being cited by a law enforcement official

To make sure the vehicle is safe to operate

To see if an additional 1,000 lbs. of freight can be added to maximize revenue

None

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