Iowa CDL DMV Knowledge Test Class B 1

One way to know when it is time to shift gears is to learn your vehicle's operating rpm range. You should shift up when your engine reaches the top of that range. You can also learn which speeds each gear is good for and shift up based on your speedometer.

You should accelerate very gradually when driving under slippery conditions. Using too much power in such conditions may cause you to lose control of your vehicle.

Gross Combination Weight (GCW) is the total weight of a powered unit, its trailer(s), and the cargo being carried.

Check hydraulic brakes by pumping the brake pedal three times before applying firm pressure to the pedal for five seconds. The pedal should not move. If it does, there may be a leak or some other problem in the braking system.

To avoid becoming fatigued on a long trip, you should take a break after every 100 miles or two hours of driving. Driving through the night, or during any other time when you would normally be asleep, raises the danger of fatigue.

Components of an air brake system include an air compressor, an air compressor governor, air storage tanks, air tank drains, an alcohol evaporator, a safety valve, a brake pedal, foundation brakes, supply pressure gauges, an application pressure gauge, a low air pressure warning signal, a stop light switch, a front brake limiting valve (on some older vehicles), spring brakes, and parking brake controls.

During the on-road driving test, the examiner will be scoring you on specific driving maneuvers, as well as your general driving behavior.

Blocking is used to prevent cargo from sliding while in transit.

You must have a hazardous materials endorsement to drive a vehicle of any size that is used to transport defined classes of hazardous materials.

There are several reasons why driving at night is more difficult than driving during the day. It is more difficult for drivers to see hazards, the glare of headlights can affect drivers' vision, and there are more fatigued drivers on the road.

Cargo should be restrained by at least one tie-down for every 10 feet of cargo. However, all cargo should have at least two tie-downs, no matter the size of the cargo.

If you must back up, it is safest to back toward the driver's side of the vehicle. This way, as the driver, you will have the best possible view of your path of travel.

Never attempt to beat a train to a railroad crossing. It is very difficult to accurately judge the speed of an approaching train. If you come upon a crossing that is being approached by a train, you must stop and wait for the train to pass before you attempt to cross the tracks.

When performing a static leakage test on a single vehicle with air brakes, the leakage rate should be no more than 2 psi in a 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.

On a slippery road, you must adjust your driving speed to fit conditions. Because it will take longer for your vehicle to stop on a slippery road than on a dry road, you should increase your following distance when conditions are slippery. Avoid driving in a way that requires you to change speeds frequently.

Some older vehicles have front brake limiting valves with "normal" and "slippery" settings. Setting a brake limiting valve to "slippery" reduces the vehicle's stopping power, so a driver should make sure the valve is in its "normal" position. Front wheel braking has proven to be effective in all driving conditions.

Dry bulk tanks require special care to be driven, both because they have high centers of gravity and because the weight of the load can shift in transit.

When a brake pedal is pressed and the S-cam is turned, the S-cam presses the brake shoes against the inside of the brake drum. This causes friction and will cause the vehicle to slow.

Fatigued drivers are slower to see or react to hazards than drivers who are not fatigued. Drivers are impaired in their ability to make critical decisions when they are driving drowsy.

Avoid being an aggressive driver by being realistic about your travel time, making allowance for delays, maintaining reasonable following distances, and not making hand gestures that could anger another driver.

Blocking may be used on all sides of a piece of cargo to keep it from sliding while the vehicle is in motion.

If the low pressure warning signal activates while you are driving, it is important that you safely exit the roadway as soon as possible and park your vehicle. If the air pressure gets too low, the brakes will no longer work well enough for you to stop safely.

When using your turn signals, you should signal well before the turn or lane change, signal continuously throughout the turn or lane change, and cancel the signal after you have completed your move.

When braking, push the pedal down gradually to ensure that the vehicle comes to a smooth, safe 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.

If your CMV gets stuck on railroad tracks, you should immediately leave the vehicle and get away from the tracks. Check the signposts or signal housing at the crossing for emergency contact information and call 911, or another appropriate emergency number.

A load of cargo must be properly balanced. Placing too much weight over an axle can damage the axle and make it more difficult for you to steer. Placing too little weight over an axle can cause poor traction, also leading to difficult handling.

Before beginning a trip, it is important to check the brake drums during your walk-around inspection. It is unsafe to drive if any brake drum has a crack more than one half of the width of the friction area.

While driving, you should watch your vehicle's gauges for signs of trouble. Be sure to inspect your gauges before beginning a trip to ensure that they are in proper working order.

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.

The heavier a vehicle is, the more the brakes will need to work to bring the vehicle to a complete stop.

Driving in fog is always dangerous and should be avoided entirely if at all possible. If you must drive in fog, be sure to turn on your low beam headlights and fog lights, even during the daytime.

In an air brake system, the air tanks must be periodically drained to remove accumulations of water and compressor oil. If water is not removed, it could freeze in cold weather and cause brake failure.

If you choose to use a mobile phone while operating a CMV, you may only use a hands-free mobile phone that is located close to you. However, even a hands-free mobile phone can be a dangerous distraction while driving. Make sure you are aware of all cell phone laws in the state in which you are driving.

If you must stop on the side of the road, make sure to use your four-way emergency flashers. This is particularly important at night.