South Carolina CDL DMV Knowledge Test Class A 2

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.

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.

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.

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.

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.

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.

Air expands as its temperature increases, so air pressure in your tires is likely to increase when you are driving in very hot weather. Under such conditions, stop periodically to ensure that your tires are not at risk of blowing out or catching fire.

When checking a header board during the vehicle inspection test, you should ensure that it is secure, free of damage, and strong enough to contain cargo.

A one-way check valve is required to be between an air compressor and the first main reservoir. This valve prevents air from escaping the system if the air compressor develops a leak.

If a vehicle is coming toward you while using its high beam headlights, glance away from the headlights and toward the right side of the road until the vehicle has passed. This will keep you from being blinded by the lights.

When inspecting a vehicle's tires, you should make sure that there is no damage present on the tires.

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.

Some pre-1975 vehicles have a front brake limiting valve, which has "normal" and "slippery" settings. The idea behind these valves was to limit the air pressure available to the front brakes when driving on slippery surfaces, and thereby reduce the danger of a front-wheel skid. Studies have found that this is not actually a concern, so if your vehicle has a front brake limiting valve, leave it in the "normal" position.

Speeding up too quickly on a road with poor traction could cause a driver to lose control of their vehicle. In conditions that cause poor traction, a driver should accelerate especially smoothly and gradually.

When backing up, it is always a good idea for a driver to use a helper who can watch the vehicle's blind spots. The helper should stand near the back of the vehicle in a location where they are visible to the driver.

A vehicle's total stopping distance is made up of perception distance, reaction distance, brake lag distance, and braking distance. With all of these factors included, an air brake-equipped vehicle traveling at a speed of 55 mph under ideal driving conditions will need approximately 450 feet to come to a complete stop.

In the event of a vehicle fire, you should leave the road and stop in an open area. Do not pull into a service station as fuels at the service station could catch fire. Report the fire and your location to emergency services.

Be sure to check your mirrors before beginning a drive. Your posture may change day to day and your mirrors may need to be adjusted.

Swerving out of the way of a hazard is sometimes safer than trying to stop before reaching the hazard. You can usually turn away from something more quickly than you can come to a complete stop.

The force of gravity will cause a vehicle's speed to increase when traveling downhill.

Always signal continuously through a turn. Do not cancel a signal until the turn is finished.

Blocking and bracing are techniques to keep cargo from shifting in transit. A piece of cargo should be blocked to its front, back, and/or sides to prevent movement.

Once you have begun to drive after a tire has been changed, you should stop after a short distance to recheck the tightness of the lug nuts.

To prevent rolling backward when starting from a stop, you should partly engage the clutch before removing your foot from the brake. Apply the parking brake whenever necessary to prevent your vehicle from rolling back.

You should stay in the right lane of a multilane road if your vehicle is being slowed down by a heavy load. Allow other vehicles to pass your truck using the left lane.

When traveling at speeds under 40 mph, you should allow a minimum of one second of following distance for every 10 feet of your vehicle's length. At faster speeds, add at least one additional second.

A visual low pressure warning signal should activate before air pressure drops to a level between 55 and 75 psi. This signal could be a light, a buzzer, or a wig wag.

Federal and state laws require that CMV drivers inspect their vehicles before every trip.

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.

A driver uses a look when they open their door, leave their seated position, and walk to the back of the vehicle to check its position. During the straight line backing exercise, a driver may not exceed one look. During any other exercise, a driver may not exceed two looks.

When performing a static leakage test on a double combination vehicle with air brakes, the leakage rate should be no more than 3 psi in one minute. If the air leaks from the air brake system at a quicker rate, the vehicle should not be driven because something likely needs to be repaired.

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.

If the coolant temperature gauge goes above the highest safe temperature, you should stop driving as soon as possible and try to figure out what is wrong. There could be an issue in your vehicle that could lead to engine failure and possibly a fire.

During the on-road driving test, the examiner will be score you on specific driving maneuvers as well as on your general driving behavior. You must drive in a safe and responsible manner; obey all traffic signs, signals, and laws; and not cause an accident or commit a moving violation.