South Carolina CDL Permit Test - Knowledge Test Class A

A low air pressure warning signal is required in vehicles with air brakes. The warning light is usually red and may be accompanied by a buzzer.

While speaking on a hands-free phone while driving is less dangerous than speaking on a hand-held phone, it is just as likely to mentally distract a driver. Simply engaging in conversation takes their mental focus away from the task of driving.

Hydroplaning is an effect in which a vehicle's tires lose traction with the surface of the road and instead glide along a layer of water. There does not have to be much water on the road for this to occur.

The added weight of a heavy load will make a vehicle sit lower than usual. A vehicle will often be taller when carrying a light load than when carrying a heavy load. If your vehicle fits under an overpass while carrying a full load, it is not guaranteed that it will fit under the same overpass if it is empty.

An air compressor governor will stop the compressor from pumping air once the air tanks are at an air pressure level of 125 psi. This air pressure level is referred to as the "cut-out" level.

Texting while driving is particularly dangerous because it is both a mental and physical distraction to the driver. In addition to diverting a driver's mental attention away from the road, texting requires a person to remove at least one hand from the vehicle's controls.

If you are not sure that you have enough room to safely fit underneath a bridge or other overhead object, you should slow down and seek an alternate route, if possible.