South Carolina CDL: General Knowledge Practice Test

Not quite. The answer is Downshift before you enter a curve.

Before entering a curve, slow down to a safe speed and downshift to the right gear. This lets you use some power through the curve to help the vehicle be more stable while turning. It also allows you to speed up as soon as you are out of the curve. Taking a curve too fast or braking while in the curve risks a skid. When downshifting by double clutching, remember that engine speed should be higher in the lower gear that you're trying to shift into.

Not quite. The answer is It can startle other drivers.

Your horn can startle other drivers, pedestrians, or animals. Hence, it should only be used to warn others of a potential hazard, not for general communication and certainly not to express anger or frustration.

Not quite. The answer is Poisonous fumes can enter the cab or sleeping compartment.

The exhaust system is designed to help remove toxic gases produced by the engine. A leak in the exhaust system can allow poisonous carbon monoxide (CO) to seep into the cab or sleeping compartment. A buildup of CO is more likely in cold weather, when you may have the cab windows closed.

Not quite. The answer is You should never remove the radiator cap on a pressurized system until the system has cooled.

Never remove the radiator cap if the engine is overheated. Steam and boiling water could shoot out under high pressure and injure you. Wait until you can touch the radiator cap with your bare hand without it feeling excessively hot. Some vehicles have coolant overflow tanks or sight glasses that let you check the coolant level without removing the radiator cap.

Not quite. The answer is do both of the above.

In Step 4 (Turn Off Engine and Check Lights) of the Seven-Step Inspection Method, set the parking brake and turn off the engine. Turn on the low-beam headlights and four-way flashers. In Step 5 (Walk-Around Inspection), leave the cab, walk to the front of your vehicle, and make sure that these lights are working.

Not quite. The answer is the coolant temperature gauge should begin a gradual rise to normal.

Once you start the engine, check the dashboard gauges. Coolant temperature should begin a gradual rise to the normal operating range. Engine oil temperature should also rise gradually to the normal range. However, oil pressure should rise to the normal range within seconds. Don't run the engine for any length of time with low oil pressure.

Not quite. The answer is Set out warning devices to keep other vehicles from running into the accident scene.

Unless you have been injured, it is your responsibility to ensure that others can see your vehicle at the accident scene. Set out your warning devices as quickly as possible to avoid further accidents such as a pile-up.

Not quite. The answer is ten minutes.

If you must stop on a road or the shoulder of any road, you must set out your emergency warning devices within ten minutes.

Not quite. The answer is 24 hours.

If your blood alcohol concentration (BAC) is found to be 0.04% or more, you can be charged with driving under the influence (DUI). (An average 180-pound man may reach a BAC above 0.04% after drinking just two cans of beer.) Even if you are found to have any detectable amount of alcohol in your system under 0.04%, you will be placed out-of-service for 24 hours.

Not quite. The answer is use a dock plate.

Forklifts weigh an average of 9,000 pounds, and some weigh much more. Before allowing a forklift operator to drive into your trailer, take these precautions: (1) To restrain the trailer, use wheel chocks or the loading dock's own locking system (if so equipped). Don't depend entirely on your truck's parking brakes. The movements of a heavy forklift can push the trailer away from the dock even with the brakes engaged. (2) Use a dock board, not a dock plate, to bridge the gap between the trailer and the dock. Typical dock plates are too light to take the weight of a forklift and are not rated for forklift use. (3) Check the floor of your trailer for any weak spots that may not be able to take the weight of the forklift. (4) Add more lighting if it's too dark in the trailer for the forklift operator to operate safely.

Not quite. The answer is All of the above

At a roadside inspection, inspectors will place a driver out of service for any of the following violations: (1) fatigue, serious illness, or under the influence of alcohol or drugs; (2) lack of proper CDL or proper endorsements; (3) inadequate documentation of the last 7 days of duty status on a logbook or electronic logging device (ELD). Effective June 2025, inspectors at most locations will also place a driver out of service for inability to adequately communicate with the inspectors in English. However, drivers operating commercial motor vehicles in the border commercial zones along the U.S.-Mexico border who fail to demonstrate English proficiency will be cited but not placed out of service.

Not quite. The answer is Text messages

During your trip, you should keep an eye on all of your vehicle's key systems, such as the instruments, gauges, tires, voltmeter, mirrors, and cargo. Make sure you put your phone aside for the entire trip.

Not quite. The answer is any detectable amount.

If your blood alcohol concentration (BAC) is found to be 0.04% or more, you can be charged with driving under the influence (DUI). (An average 180-pound man may reach a BAC above 0.04% after drinking just two cans of beer.) If you are found to have any detectable amount of alcohol in your system under 0.04%, you will be placed out-of-service for 24 hours.

Not quite. The answer is Type of tire tread

To determine which low gear to use to begin a descent, consider the weather, the length and steepness of the downgrade, the weight of your cargo, and the road conditions.

Not quite. The answer is Ending a backing exercise while over a boundary line

Any of a variety of certain actions or inactions on your part can cause you to fail the entire CDL skills test. Of the four choices here, you must demonstrate to your test examiner that you can exit your vehicle safely whenever you have to. This includes properly securing the vehicle by setting the parking brakes and taking the ignition key with you. If you don't, you will automatically fail the entire CDL skills test. Also, failure to perform every one of the braking tests required for your vehicle, whether it's equipped with air brakes or hydraulic brakes, will constitute an automatic failure. Finally, overrunning a curb or sidewalk even slightly during the road test will also constitute an automatic failure. On the other hand, attempting to end a backing exercise while you're over a boundary line will lose you points, but it's not necessarily an automatic failure. Your examiner will tell you to move your vehicle inside the boundary lines, and your skills test will continue.

Not quite. The answer is The cargo you're carrying makes stopping mandatory under federal or state regulations.

A full stop is required at railroad grade crossings whenever (a) the nature of the cargo makes a stop mandatory under state or federal regulations, or (b) such a stop is otherwise required by law. For example, federal regulations require any CMV that is placarded for carrying hazardous materials to stop at every railroad grade crossing.

Not quite. The answer is Steering gear box

The steering gear box contains gears that translate the rotation of the steering column into rotation of the gear box's output shaft. This rotation drives the steering linkage to turn the wheels.

Not quite. The answer is Many CMV accidents occur between midnight and 6:00 a.m.

Driving through the night when you would normally be asleep increases your risk of an accident. Many CMV accidents occur between midnight and 6:00 a.m. If you've had less than 6 hours of sleep before you drive, your risk of an accident is tripled. And one study has found that going without sleep for more than 24 hours can impair your coordination and reaction time as much as being legally intoxicated.

Not quite. The answer is 5/8 - G43

The Working Load Limit (WLL) of a component of a cargo securement system is assigned by the component manufacturer or the default rating in the Working Load Limit table. (See federal regulation 49 CFR 393.108 for the table.) According to the WLL table, the only size 5/8" chain with a WLL of 13,000 pounds has a grade of 43. Therefore its links should be marked with the strength rating "5/8 - G43."

Not quite. The answer is Check your mirrors regularly.

To find out what's happening behind and to the sides of your vehicle, check your mirrors frequently. Before driving your vehicle, adjust your mirrors to show parts of your vehicle as well as what's around your vehicle.