Nebraska CDL DMV Knowledge Test Class A 1

The majority of heavy-duty vehicles are equipped with dual air brake systems.

Front-end header boards protect the driver from the forward motion of their cargo in the event of a crash or emergency stop.

Before driving a vehicle with air brakes, you should ensure that the spring brakes come on automatically when air tank pressure falls to a level between 20 and 45 psi. You can do this by chocking the wheels and releasing air from the braking system by stepping on and off the brake pedal. Once the pressure levels drop to an unsafe level, the parking brake valve should pop out and spring brakes should come on.

On a steep downgrade, you must use the engine's braking effect as your primary method of speed control. Be sure to decelerate and downshift appropriately before beginning to drive down the hill.

You can tell that your vehicle is equipped with an Anti-Lock Braking System (ABS) if it has a yellow ABS malfunction lamp on the instrument panel.

A modulating control valve allows a driver to gradually apply spring brakes. In equipped vehicles, the valve is controlled by a lever located on the dashboard.

Eating while driving can be a dangerous distraction to the driver both because it diverts their attention away from the task at hand and requires them to remove a hand from the steering wheel.

If you must drive in fog, you should use your low beam headlights and fog lights, even during the daytime.

All commercial motor vehicles are required to be equipped with the proper emergency equipment. This may include spare electrical fuses; three red reflective triangles, six fuses, or three liquid burning flares; and at least one properly charged and rated fire extinguisher.

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.

Black ice is a layer of ice that is thin and clear enough for the road to be visible through it. The surface will look like a wet road. Always be alert to black ice if the road looks wet when the temperature is below freezing.

Mirror adjustment should be checked prior to the start of each trip. Any attached trailer should be straight while mirrors are being adjusted.

In extremely hot weather, tire pressure can increase to dangerous levels due to the expansion of the air in heat. To keep an engine from overheating, it is important that there be enough oil and coolant in the engine compartment.

In an air brake system, the air storage tanks must be drained to remove accumulated water and compressor oil. Failing to do this can cause damage. For example, water that has built up in the system could freeze in cold weather and cause brake failure.

Using the brakes after a tire failure could cause you to lose control of your vehicle. Unless you're about to hit something, stay off of the brake until the vehicle has slowed sufficiently.

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.

When inspecting cargo, a driver must ensure that the cargo is balanced and properly secured. To reduce the risk of a rollover, the weight of a load of cargo should be kept as low as possible. A trailer should not be overloaded.

Passing parked delivery or postal trucks can be dangerous because the driver may be in a hurry and pull into traffic without warning, or may they suddenly step out of the vehicle without checking for other traffic.

There are two indicators that determine when you need to shift into a higher gear. One indicator is the engine speed (rpm). You should read your vehicle's manual to learn its rpm range and shift up when you reach the top of that range. The other indicator is road speed (mph). You should learn which speeds each gear can accommodate, then keep an eye on the speedometer and shift up as needed.

If at least one-fourth of the leaves in a leaf spring are missing, the vehicle will be put out-of-service until the defect is fixed.

As a part of earning your CDL, you will have to pass an inspection test and demonstrate that your vehicle is safe for operation. During the vehicle inspection test, you will have to walk around the vehicle and point to or touch each item and explain to the examiner what you are checking and why. You will not have to crawl under the hood or under the vehicle.

In a dual air brake system, if one of the air systems gets very low on pressure, either the front or rear brakes will not be operating fully. You should bring your vehicle to a safe stop and have the air system repaired.

You should finish each exercise with your vehicle in the exact position described by the examiner. You can be penalized for failing to complete an exercise exactly in the manner described by the examiner, potentially resulting in failure of the basic control skills test.

The controlled braking method for emergency stops involves applying the brakes as hard as you can without locking the wheels. Keep steering wheel movements small when braking in this way.

It is important to know the maximum air loss rate that is safe for your specific vehicle. A double combination vehicle should have a leakage rate no higher than 4 psi in a minute during an applied leakage test.

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.

If the road appears to be wet but the wheels of other vehicles are no longer generating spray, ice has formed on the road. Drive with extra caution when operating on wet or icy roads.

Check each slack adjuster after parking on level ground, setting wheel chocks, and disengaging the parking brake. Pull the slack adjusters to make sure they do not move more than about one inch from where the push rod is attached. If they move more than one inch, they may be out of adjustment and will need to be fixed.

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.

Good drivers scan the road at least 12 to 15 seconds ahead of their vehicles. Looking ahead will allow you to identify and react to hazards before meeting them. Be sure to specifically look for vehicles that are coming onto the highway, entering into your lane, or turning.

Water and compressor oil are removed from air storage tanks through a drain valve. The water and oil can damage the brakes if left to accumulate in the system. Manually operated tanks must be drained every day to remove this build-up.

Stay as far away from a fire as possible and aim your fire extinguisher at the source or base of the fire, not at the flames. It may be appropriate to extinguish certain fires with water. If you are unsure of how to treat a specific fire, you should wait for trained firefighters to arrive.

When inspecting a vehicle with a dual air brake system, you should wait for air pressure to build from 85 to 100 psi in both the primary and secondary systems. This should take about 45 seconds.

To operate a vehicle of any size that is used to transport hazardous materials requiring placards, you must have a CDL with a hazardous materials endorsement.

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.