Free, full South Carolina CDL general knowledge test practice right here in your browser — real exam format (50 questions, 80% to pass), diagnostic and adaptive modes, spaced-repetition review, and a readiness dashboard. No signup, no paywall — your progress is saved automatically on this device.
The safety valve releases excess air at approximately:
C. 150 PSI — The safety valve protects the tank from over-pressurization by releasing air at about 150 PSI.
What type of CDL endorsement is needed to operate a vehicle towing a trailer with a GVWR over 10,000 lbs?
B. A CDL-A license is sufficient for all combination vehicles — A CDL Class A license authorizes the driver to operate any combination vehicle (with a GCWR of 26,001+ lbs with the towed vehicle over 10,000 lbs GVWR). No additional endorsement is needed for standard combination vehicles.
What is the required action when passengers are boarding or alighting from a stopped bus?
B. Apply the parking brake and use the hazard lights to warn other traffic — When stopped for boarding or alighting, apply the parking brake and activate hazard lights to make the stopped bus visible to other traffic, reducing the risk of rear-end collisions.
What is the difference between 'gross vehicle weight' (GVW) and 'gross vehicle weight rating' (GVWR)?
B. GVW is the actual total weight of the loaded vehicle; GVWR is the maximum weight the manufacturer certifies the vehicle to safely carry — GVW is the actual total weight of a vehicle including its load. GVWR is the maximum allowable total weight as specified by the manufacturer. Operating over GVWR is illegal and unsafe.
Standees (standing passengers on a bus) should be kept:
B. Behind the standee line — Standing passengers must stay behind the standee line marked on the floor, away from the driver and front exit area.
During a pre-trip inspection, how do you check that the trailer's rear lights are working without a helper?
B. Use the cab controls to activate each light, then walk to the rear of the trailer to verify they are functioning, or use a reflective surface — Without a helper, activate each light (running, brakes, turn signal) from the cab, then walk to the trailer rear to verify operation. Alternatively, use a reflective surface (dock door, adjacent truck) to see the lights without walking.
Under 49 CFR 396.9, who is authorized to perform a roadside inspection of a CMV?
B. Any certified CVSA (Commercial Vehicle Safety Alliance) inspector, which includes state and local law enforcement officers trained in CVSA standards — Roadside inspections are performed by CVSA-certified inspectors, typically state patrol officers or DOT enforcement officers who have completed the CVSA standardized inspector training program.
What is a 'walk-around inspection' and when is it required?
B. A systematic exterior inspection of the entire vehicle performed before each trip, checking all major components — A walk-around pre-trip inspection is a systematic exterior examination of the vehicle before each trip. It is required by 49 CFR 392.7 and must be completed before driving to ensure the vehicle is safe to operate.
You should never apply the parking (spring) brakes while:
D. The brakes are very hot, such as right after a steep downgrade — Setting spring brakes on very hot brakes can damage them or, in cold weather, let trapped moisture freeze them, so let them cool first.
CDL safety scenario 10: What is the purpose of hours-of-service rules?
A. To reduce fatigue-related crashes — To reduce fatigue-related crashes. Commercial drivers are expected to manage this situation before it becomes a crash risk. The CDL manual emphasizes controlling the vehicle, inspecting safety-critical systems, and correcting hazards promptly.
The South Carolina CDL general knowledge test has 50 questions, and you need 80% to pass — at least 40 correct answers. The practice tests on this page use the same format. The 80% passing score is a federal FMCSA standard used by every state.
80%. You can miss at most 10 of the 50 questions. The readiness dashboard on this page tracks whether you're consistently scoring above that bar.
Yes. Every practice test on this page and everything in the DMVPrep iPhone app is free — no ads, no paywall, no account.
Federal motor carrier safety regulations (FMCSA) — the same rules every state's CDL exam is drawn from. Every question in the DMVPrep app cites the regulation or handbook section it comes from.
Yes — the DMVPrep app includes all 3,745+ questions in Spanish, and the whole app works in Spanish.