South Carolina CDL DMV Knowledge Test Class A 1

A header board protects a driver from moving cargo in the event of a crash or emergency stop.

If you observe a crash involving an aggressive driver, you should stop a safe distance from the crash scene, wait for police to arrive, and inform them of the aggressive behavior you witnessed.

When approaching your vehicle before a trip, be sure to look underneath the vehicle for fresh oil, coolant, grease, or fuel leaks.

To improve visibility, you should use high beam headlights at night where it is safe and legal to do so. However, the glare from high beam lights can blind other drivers. You should dim your lights to their low beam setting when driving within 500 feet of an approaching vehicle.

Faster speeds create more heat in the engine and tires, so slow down to avoid dangerous overheating when the weather is very hot.

You will be denied a hazardous materials endorsement, or lose an existing endorsement, if you renounce your U.S. citizenship; are not a lawful permanent U.S. resident; are wanted for, indicted for, or convicted of certain felonies; are judged mentally defective or are committed to a mental institution; or are deemed by the Transportation Security Administration (TSA) to pose a security threat.

On long and/or steep downgrades, you should primarily use engine braking to control the speed of your vehicle. Use your brakes only as a supplement to this effect.

Backing up is always dangerous because it is impossible to see everything that is behind you. Only drive in reverse if it is absolutely necessary.

Failure of hydraulic brakes is often caused by a loss of hydraulic pressure. Hydraulic brakes may also fade because of overuse on a long downgrade.

When inspecting the engine compartment, you should check the oil level, coolant level, and windshield washer fluid level, among other things.

To ensure that you can see as well as possible, don't wear sunglasses when driving at night. If you wear eyeglasses, make sure they are clean and unscratched. Make sure you are rested and alert before driving at night.

Commercial vehicle weight, securement of cargo, covering of loads, and where large vehicles can be driven are all regulated by federal, state, and local laws. These vary from place to place, so you must be aware of the rules that apply where you will be driving. State laws in the state in which you are driving take precedence.

Brakes are designed to take a lot of heat, but drivers should not rely solely on the brakes to slow their vehicle. Brakes may fade and lose their ability to slow down the vehicle if they become too hot, so drivers should also rely on the engine braking effect.

If your on-road driving test route does not include a railroad crossing, you may be asked to explain and demonstrate the proper railroad crossing procedures to the examiner at a simulated location.

In South Carolina, CDLs are valid for five years from the date of issuance.

Anti-Lock Braking Systems (ABS) are compatible with air brakes and help a driver maintain control of their vehicle by preventing wheel lockup.

In newer vehicles with air brakes, the parking brakes are controlled by a diamond-shaped yellow knob. Pull the knob out to activate the parking brakes and push it in to release them.

Because they are exposed to less sunlight, shaded patches of road will stay cooler longer than other areas of the road. Due to the lack of direct sunlight, shady areas can remain icy and slippery after ice on other areas of the road has melted.

Because air takes time to flow through the air lines to the brakes, air brakes cannot begin working instantly. There is often a brake lag of at least one-half of a second between the moment the brake pedal is pressed and the moment the brakes begin to work.

An operator should drive with care when transporting a cargo of hanging meat. Such a load is unstable, both because it has a high center of gravity and because the swinging of the meat can affect the driver's handling of the vehicle.

Ice becomes wet when the weather is just warm enough to melt the ice slightly. Wet ice is much more slippery than ice that is not wet.

Always turn on your four-way emergency flashers if you must park on the side of the road. This is especially important when traveling at night.

During a pre-trip inspection, you should check for emergency equipment, including spare electrical fuses; three red reflective triangles, six fuses, or three liquid burning flares; and at least one properly charged and rated fire extinguisher.

On flatbed trailers and trailers without sides, cargo must be tied down. There should be at least one tie-down for every 10 feet of cargo. Regardless of the size of the cargo, at least two tie-downs must be used.

Driving with a dry bulk tank requires special care, both because dry bulk tanks have high centers of gravity and because their loads often shift in transit. Be especially careful when taking turns and curves while operating such a vehicle.

If you must drive onto the shoulder to avoid a hazard, stay on it until you come to a stop; then signal, check your mirrors, and merge back into traffic. Avoid braking on the shoulder at speeds higher than about 20 mph. To help maintain control, always keep one set of wheels on the pavement, if possible.

All U.S. states share information about CDL and CLP licenses in a computerized database. If you apply for a license in one state, a state will check this database to verify that you do not already have one such license in another state.

A tire load rating is the maximum safe weight that can be carried by a tire at a specified pressure. This number is stated on the side of each tire.

Potential warning signs of fatigued driving include difficulty focusing; frequent blinking or heavy eyelids; yawning repeatedly or rubbing one's eyes; daydreaming; wandering or disconnected thinking; trouble remembering the last few miles driven; missing exits or traffic signs; having trouble keeping one's head up; drifting from one's lane; following a vehicle too closely; hitting a shoulder rumble strip; and feeling restless or irritable.

In a vehicle with air brakes, the brake lights are activated when the brake pedal is pushed and air pressure moves an electric switch. With the application of air pressure, the switch will then turn on the brake lights.

Many large vehicles have curved, convex mirrors. Convex mirrors allow drivers to see a wider area than flat mirrors. However, they also make objects seem smaller and farther away than they really are.

Always drive cautiously around a stopped bus. Passengers may cross in front of or behind it, and the bus may prevent them from seeing your vehicle.

Special equipment, such as warning flags or flashing lights, may be required if you are transporting an over-length load. When transporting such a a load, you will need to acquire the necessary permits. Driving is often limited to certain times.

Potential problems to check for when inspecting brakes include cracked drums; shoes or pads with oil, grease, or brake fluid on them; and shoes that are missing, broken, or worn dangerously thin.

Transporting cargo that is loaded with a high center of gravity increases the risk that the transporting vehicle will tip over. Cargo should be loaded with a safe weight distribution.