District Of Columbia CDL DMV Knowledge Test Class A 2

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.

A wig wag is a type of low air pressure warning device in an air brake system. It drops a mechanical arm into the driver's view when the air pressure in the tanks falls below 60 psi.

In bad weather, particularly when visibility is poor, it is common for automobile drivers to follow closely behind trucks. Open up the distance between your vehicle and the vehicle in front of you if you are being followed too closely.

If you are unsure of which method is appropriate to use to extinguish a fire, you should wait for firefighters to arrive and let them handle it. This is especially important when dealing with hazardous materials fires.

On vehicles with air brakes, a low air pressure warning signal will come on if the pressure in the air tanks falls below 60 psi. On large buses, the signal may activate at 80 to 85 psi.

On newer vehicles with air brakes, the parking brake is controlled by a yellow, diamond-shaped knob. The knob is pulled out to set the brakes, and pushed in to release them.

Driving while fatigued is dangerous. Warning signs of fatigue include difficulty focusing; repeated yawning or rubbing of the eyes; daydreaming or wandering thoughts; and drifting out of your lane.

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.

The suspension system keeps a vehicle's axles in place. Damaged suspension parts, such as leaking shock absorbers, may be potentially dangerous defects on a vehicle.

While driving, you should consistently check the road ahead for hazards. Develop a plan to deal with any hazards that could arise.

In an air brake system, the air storage tanks are equipped with drains to allow water and compressor oil to be removed. The water and oil can damage the brakes if left to accumulate in the system.

Backing can be dangerous, so avoid doing it whenever you can. If possible, park in such a way that allows you to pull forward to exit your parking space.

Stopping is not always the most effective response to a hazard. You can usually turn out of the path of a hazard more quickly than you can come to a complete stop. However, swerving is not without its hazards, as it may result in a rollover in a vehicle that is either top-heavy or pulling multiple trailers.

You can build up a "debt" of sleep if you do not sleep for adequate amounts of time. You can only catch up on the time that you "owe" by getting more sleep.

For safe driving, it is important to be aware of what is happening on all sides of your vehicle. A vehicle should have mirrors on both sides, which should be checked regularly.

Mismatched, bent, or cracked lock rings are dangerous and should not be used.

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.

You should not assume that signs marking the height of a bridge or overpass are exactly correct. If the road was repaved after the sign went up, or if snow is on the ground, the clearance may be different than what the sign indicates.

You should be cautious when you are near people who are not paying attention to the road. Be wary of drivers who are engaged in conversation with passengers, children near the road, and road workers.

The liver removes alcohol from the body at a fixed rate that cannot be accelerated through common tricks, such as drinking coffee or taking a cold shower. The only way to sober up after drinking is to give your body the time it requires to process the alcohol out of your system.

You should always make sure that your vehicle will be able to stop within the area of the road that you are able to see. This means that you must slow down whenever conditions reduce visibility.

Drivers who are holding conversations with others may not be paying full attention to the road and may make unsafe moves. Children do not always pay attention to traffic and may dart into the road without looking. Exercise caution when driving near road workers. This helps to keep the workers and other distracted drivers safe.

To avoid engaging in dangerous and aggressive driving behavior, you should relax and accept any delays that arise throughout a trip. To help avoid the stress of arriving late to a destination, plan for likely delays when planning your drive.

Before driving a vehicle with a dual air brake system, allow time for the air compressor to build up pressure of at least 100 psi in both the primary and secondary systems.

Black ice is a layer of ice that is thin and clear enough for the road to be visible through it. This makes the road look as if it is merely wet.

Driving while fatigued can be extremely dangerous. Strategies for preventing drowsiness while driving include getting a full night's sleep before a trip; having someone ride with you so you can take turns driving; scheduling trips for times during which you are normally awake; and avoiding medications that may cause drowsiness.

It is essential that your low pressure warning light functions properly. After allowing the system to charge, you can test the warning signal by rapidly applying and releasing the brake pedal. This will release air from the braking system and the warning signal should come on when pressure drops to a dangerous level.

Compressed air in an air brake system usually contains a certain amount of water and compressor oil. The water and oil can damage the brakes if left to accumulate in the system. Tanks must be drained regularly to remove this build-up.

Being properly rested is essential to the safe operation of a CMV. To maintain alertness, most people need eight to nine hours of sleep per night.

The weight of cargo in a vehicle needs to be balanced appropriately so that it does not interfere with the vehicle's safe handling. For example, if cargo is placed too far to the rear of a vehicle, the front axle will be under-weighted and the front wheels may not have enough traction for the driver to steer safely.

Roads are especially slippery when it first begins to rain. Rain water initially mixes with oil and grease on the road to form a slippery film. As the rain continues, this mixture will eventually wash away.

The stab braking method for emergency stops involves fully applying the brakes until they lock up. The brakes are then released until the wheels start rolling, then the process is repeated.

Mental distractions can be just as dangerous as physical ones. It is possible for a person to look right at a hazard on the road but fail to notice it because their thoughts are occupied by something else.

While driving downhill, you should hold down the brake pedal until your vehicle reaches a speed 5 mph below your safe speed, then release the brake pedal. Repeat this process.

If you are not confident that your vehicle will have enough room to safely pass under an overhead object, you should slow down and seek another route, if possible.