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South Carolina General Knowledge CDL Practice Test

Below are 25 exam-style questions for the South Carolina General Knowledge CDL knowledge test, modeled on the FMCSA-aligned content used by the South Carolina Department of Motor Vehicles. Try to answer each question on your own before reading the answer key directly under it. The questions and answer choices are shuffled deterministically per state and endorsement, so the order will stay the same on repeat visits — that lets you genuinely measure your improvement.

Heads up: this is a study tool, not a graded exam. Cover the answer with your hand or a sheet of paper for an honest practice run, then re-read the explanations for any questions you missed. Aim for 22 out of 25 or better, three times in a row, before scheduling the real exam.
Question 1 of 25
You are driving on a two-lane road and you see a driver about to pull out from a side road. You should:
  • A Cover the brake and slow down
  • B Move to the right lane
  • C Maintain speed
  • D Honk and accelerate
Correct answer: A
Anticipate the worst-case behavior. Cover the brake — keeping your foot just over it — so you can react if they pull out.
Question 2 of 25
Hydroplaning is most likely when:
  • A You brake hard on dry pavement
  • B Tires are over-inflated
  • C Tires lose contact with the road on a film of water
  • D Roads are dry but hot
Correct answer: C
Hydroplaning happens when tires ride on top of standing water at speed. Reduce risk by slowing down, keeping tires properly inflated and tread depth adequate.
Question 3 of 25
Stab braking is used:
  • A On vehicles with ABS
  • B On vehicles without ABS, to keep them straight in an emergency
  • C To save fuel
  • D On wet roads only
Correct answer: B
Stab braking — full application then release as soon as wheels lock, then re-apply — is for non-ABS vehicles. With ABS, do not pump.
Question 4 of 25
The proper response to a tire blowout on the front axle is to:
  • A Brake immediately and pull off the road
  • B Shift to neutral and coast
  • C Hold the steering wheel firmly, ease off the accelerator, and let the vehicle slow down
  • D Steer sharply toward the shoulder
Correct answer: C
Hard braking after a blowout can cause loss of control. Hold the wheel, release the accelerator, and let speed bleed off before braking gently.
Question 5 of 25
A driver may keep moving when:
  • A A vehicle is in safe operating condition
  • B Required emergency equipment is missing
  • C A passenger door is open
  • D A trailer brake light is out
Correct answer: A
Federal rules forbid driving any CMV that is not in safe operating condition. Continue only after the defect is fixed.
Question 6 of 25
Engine retarders (Jake brakes) should be turned off when:
  • A Roads are wet, icy, or snow-covered
  • B On any downgrade
  • C In residential areas only because of noise
  • D Driving in dry conditions
Correct answer: A
Retarders can cause drive-wheel skids on slippery surfaces. Turn them off when traction is reduced.
Question 7 of 25
When should you do an en-route inspection?
  • A At the end of the trip
  • B Only when the load is hazardous
  • C Within the first 25 miles, then about every 150 miles or every 3 hours
  • D Only if a warning light comes on
Correct answer: C
The FMCSA model manual recommends a check within the first 25 miles to catch loose cargo or under-inflated tires that have warmed up, then about every 150 miles or 3 hours, and any time you stop.
Question 8 of 25
Which of the following is true about cargo securement?
  • A Tying a load down once at the start is enough
  • B Federal rules do not apply to cargo securement
  • C Cargo is the shipper's responsibility, not yours
  • D You must inspect cargo and securement before driving and within the first 50 miles
Correct answer: D
49 CFR Part 393 makes the driver responsible for inspecting cargo and its securement before driving and again within the first 50 miles, then every 150 miles or 3 hours.
Question 9 of 25
A driver convicted of a major offense (DUI, leaving the scene, etc.) in a CMV faces:
  • A A fine only
  • B No federal consequence
  • C A warning
  • D CDL disqualification for at least one year for a first offense
Correct answer: D
Major offenses carry a one-year CDL disqualification minimum (three years if hauling hazardous materials), and lifetime for a second.
Question 10 of 25
Which is true about driving in rain?
  • A Roads are most slippery just after rain begins, when water mixes with road oil
  • B Tire chains are required by federal law
  • C High beams improve visibility in heavy rain
  • D It is safe to drive at the posted speed limit
Correct answer: A
The first few minutes of rain mix with oil and grime on the road and create the slipperiest conditions. Slow down and increase following distance.
Question 11 of 25
When driving at night, you should adjust speed so that you can stop within:
  • A The full range of high-beam headlights when in use
  • B Whatever speed feels safe
  • C Half the range of your low-beam headlights
  • D The range of your low-beam headlights
Correct answer: D
Always be able to stop within the distance you can see. At night with low beams, that's typically about 250 feet.
Question 12 of 25
When approaching a steep downgrade, the basic safe-driving rule is:
  • A Stay in high gear
  • B Coast in neutral
  • C Use the parking brake intermittently
  • D Select a lower gear before starting down
Correct answer: D
Get into a low gear before the descent so the engine helps hold the vehicle back.
Question 13 of 25
The proper following distance for a 60-foot truck traveling under 40 mph is at least:
  • A 6 seconds
  • B 10 seconds
  • C 4 seconds
  • D 1 second
Correct answer: A
Use one second per 10 feet of vehicle length below 40 mph: 60 ft / 10 = 6 seconds. Add one additional second above 40 mph.
Question 14 of 25
A driver should secure cargo so it:
  • A Fills the trailer floor edge to edge
  • B Cannot shift on stops, starts, or turns and is within axle weight limits
  • C Is loaded in the order it will be delivered
  • D Looks neat from the outside
Correct answer: B
The legal standard is securement against forces during normal driving conditions plus an emergency stop, and within axle and total weight limits.
Question 15 of 25
When approaching a curve, you should:
  • A Stay at the same speed
  • B Slow down before entering and accelerate gently through it
  • C Brake while in the curve
  • D Downshift in the curve
Correct answer: B
Speed should already be set before the curve. Braking or downshifting in a curve can upset the vehicle's balance.
Question 16 of 25
GCWR stands for:
  • A Gross Cargo Weight Rating
  • B General Carrier Weight Rating
  • C Government Combination Weight Reading
  • D Gross Combination Weight Rating
Correct answer: D
GCWR is the maximum allowable weight of a power unit plus a towed unit, including all cargo. It determines whether a license is Class A.
Question 17 of 25
When backing a heavy vehicle, you should:
  • A Back to the right whenever possible
  • B Use a helper and walk around the vehicle first
  • C Back without using mirrors so you can watch out the window
  • D Back fast to get it over with
Correct answer: B
Always GOAL — Get Out And Look — and use a helper. Backing to the left when possible is preferred because you can see better, not to the right.
Question 18 of 25
Which is true about communicating in heavy traffic?
  • A Never communicate; just drive
  • B Tap the horn lightly or flash lights to signal your presence
  • C Honk loudly to warn other drivers
  • D Make eye contact only when stopped
Correct answer: B
A light tap of the horn or a brief headlight flash communicates your presence without startling others. A loud, prolonged horn can provoke aggressive responses.
Question 19 of 25
How does ABS help in an emergency stop?
  • A It applies the parking brake
  • B It increases brake pressure automatically
  • C It always stops the vehicle in a shorter distance
  • D It prevents wheel lockup so the driver can keep steering
Correct answer: D
ABS keeps the wheels rolling so steering control is preserved. It is not a shorter-distance device.
Question 20 of 25
Skids are most often caused by:
  • A Properly working brakes
  • B Manual transmissions
  • C Old tires
  • D Driving too fast for conditions
Correct answer: D
The dominant cause of skids identified by the FMCSA is driving too fast for the road or weather. Sudden steering, hard braking, or hard acceleration usually triggers them.
Question 21 of 25
A Class C CDL is required to drive:
  • A Any vehicle over 26,001 lbs
  • B Class A combinations only
  • C Tractor-trailers under 26,001 lbs GCWR
  • D Vehicles designed to carry 16+ passengers including the driver, or that require hazmat placards
Correct answer: D
Class C covers vehicles that don't meet Class A or B but are designed to carry 16 or more passengers (including the driver) or carry placarded amounts of hazardous materials.
Question 22 of 25
To recover from a front-wheel skid, you should:
  • A Accelerate
  • B Brake hard immediately
  • C Release the brake, let the wheels turn freely, and let the vehicle slow down
  • D Steer sharply in the opposite direction
Correct answer: C
A front-wheel skid is usually caused by braking too hard. Release the brake to allow the front tires to grip again so steering returns.
Question 23 of 25
The most important hand position on the steering wheel is:
  • A 12 and 6
  • B Both hands at the bottom
  • C One hand at 12
  • D 10 and 2 (or 9 and 3)
Correct answer: D
A balanced grip at 10-and-2 or 9-and-3 gives the most control. One-handed and bottom-of-wheel positions reduce reaction time.
Question 24 of 25
A driver must report any accident involving a CMV to the carrier within:
  • A 1 hour
  • B 7 days
  • C A reasonable time, before going off duty
  • D 24 hours
Correct answer: C
FMCSA rules require notification of the motor carrier in a reasonable time — most policies treat that as before going off duty.
Question 25 of 25
The two main reasons why a driver's feet are kept off the brakes when not actively braking are:
  • A To save fuel and improve mileage
  • B To save brake pads and reduce drag
  • C To rest the right leg
  • D So the brake lights don't mislead following drivers and so the brakes don't overheat
Correct answer: D
Riding the brake lights confuses drivers behind you and gradually heats the friction surfaces, both of which are safety problems.

Study tips for the South Carolina General Knowledge exam

The General Knowledge portion of the South Carolina CDL exam is graded out of the bank of questions the South Carolina Department of Motor Vehicles draws from each year. While the exact bank is not published, every question is sourced from the General Knowledge chapter of the South Carolina CDL handbook, which itself is derived from the FMCSA Model Commercial Driver's License Manual. That means studying our practice tests, reading the corresponding handbook chapter, and re-reading the parts you got wrong is genuinely the most efficient route to a first-time pass.

Most successful applicants follow a simple cycle: take the practice test cold, write down every question you missed, open the matching chapter of the official South Carolina handbook, re-read the section that contains the right answer, then re-take the practice test 24 to 48 hours later. The 24-hour delay matters — sleep is when your brain commits new information to long-term memory, and CDL knowledge questions reward that kind of consolidated learning rather than cramming.

Pay particular attention to questions that include qualifier words like always, never, only, primary, or most. CDL test writers love to flip the right answer with a single qualifier. When two answer choices look almost identical, pay attention to the verb (is it must, should, or may?) and to any numbers (14 days, 100 air miles, 8 hours, 70/8 split). On endorsement tests in particular, watch for trick framing where a true statement about a different endorsement is offered as the "correct" answer to a question that is actually about General Knowledge.

Test-day logistics matter too. Bring photo ID, your Social Security card or birth certificate, your medical examiner's certificate (DOT card), and proof of state residency if you haven't already submitted those documents. The South Carolina Department of Motor Vehicles will not let you sit for the knowledge exam without your documentation, and most offices charge an additional fee for re-attempts. Arrive early — the wait at most CDL testing offices runs 30 to 60 minutes — and silence your phone before the exam begins.

Finally, keep your General Knowledge fundamentals sharp even when you're focused on the General Knowledge exam. Many states administer multiple knowledge tests in a single sitting, and questions on weight definitions (GVWR, GCWR, GAWR), stopping distance, and the pre-trip inspection routine show up across endorsements. If you're unsure on the basics, sit a fresh South Carolina General Knowledge practice test before scheduling the real exam.

Next steps

Missed more than four questions? Re-read the General Knowledge study guide and the matching chapter in the official South Carolina CDL handbook. Then come back and re-take the test. Once you can score 22 of 25 or higher on three runs in a row, you're in good shape to schedule the real exam at your local South Carolina Department of Motor Vehicles office.

Already comfortable with this endorsement? Drill another: SC Air Brakes · SC Combination Vehicles · SC Hazardous Materials · SC Passenger · SC School Bus · SC Tank Vehicle · SC Doubles / Triples

New to the CDL process in South Carolina? Read How to apply for a CDL in South Carolina for the document checklist and step-by-step timeline.