West Virginia CDL: Air Brakes Practice Test

Not quite. The answer is your brakes may fail because of water freezing.

Your air tanks hold a mixture of water and compressor oil. If left inside to collect at the bottom, the water may freeze and cause brake failure.

Not quite. The answer is Air pressure

Drivers behind you must be warned whenever you brake. The air brake system does this with an electric switch that works by air pressure. The switch turns on the brake lights when you apply the air brakes.

Not quite. The answer is You will still have normal brake function and will just need to get the ABS repaired soon.

Losing the ABS function does not change the basic parts of your truck, so you will still have the same brakes that you have always had. Simply use them and get the ABS repaired as soon as possible. There is no need to panic unless your system shows other and more serious warnings.

Not quite. The answer is vehicles with air brakes.

A low air pressure warning signal is required on vehicles with air brakes. The warning is usually a red light. A buzzer may also come on. Another type of warning is the “wig wag.” This device drops a mechanical arm into your view when the pressure in the system drops between the dangerous levels.

Not quite. The answer is Stop and park safely.

If the low air pressure warning comes on, there may be a leak in the system. Pull over and park your vehicle as soon as possible. If the air pressure drops too low, the spring brakes will come on automatically, which will stop your vehicle – but not necessarily in a safe way. Sudden application of the spring brakes while you're driving might result in a skid.

Not quite. The answer is a Class A CDL without an air brakes restriction.

To legally pull a trailer whose gross vehicle weight rating (GCWR) exceeds 10,000 pounds, you'll have to obtain a Class A CDL. If you don't pass a knowledge test on air brakes, your CDL will include a restriction limiting you to driving only vehicles without air brakes.

Not quite. The answer is With ABS, you do emergency braking differently than without ABS.

Without ABS, hard braking can lock the wheels, resulting in a skid. Therefore, to do emergency braking without ABS, you should use the "stab braking" method or the "controlled braking" method. With ABS, go ahead and brake hard; the ABS computer will prevent your wheels from locking.

Not quite. The answer is All of the above

A modern Air Dryer Integrated System (AD-IS) combines the governor, air dryer, and safety valve into one system. Compressed air from the air compressor goes to the AD-IS, which removes moisture and contaminants from the air. The clean, dry air then goes to fill the primary and secondary service tanks.

Not quite. The answer is air pressure.

Spring brakes contain powerful springs that are normally held back by air pressure. If the pressure drops too low, the spring brakes will automatically kick in.

Not quite. The answer is Otherwise, you will have to get a CDL with restrictions.

If you do not pass the air brake knowledge test, your CDL will include restriction L, which will limit you to driving vehicles without air brakes. So, good luck!

Not quite. The answer is It disables the spring brake.

If your vehicle's service brakes fail, the emergency (spring) brakes will activate and stop your vehicle. Then to tow your vehicle for repairs, it will be necessary to disable the spring brakes. A technician can manually compress or "cage" the spring in each spring brake chamber. Obviously, the vehicle will be undrivable at this point because it will have no working brakes at all.

Not quite. The answer is brake normally.

Antilock brakes will automatically keep your wheels from locking so you can brake normally.

Not quite. The answer is 3 psi for single vehicles and 4 psi for combination vehicles.

After the initial drop, the maximum acceptable leakage rates per minute are 3 psi for single vehicles and 4 psi for combination vehicles. If the leakage rate is higher, check for leaks and correct them.

Not quite. The answer is Only if it's not working properly

Once properly installed and lubricated, an automatic slack adjuster should not need manual adjustment. If it does, it may be malfunctioning or there may be a problem with the foundation brake itself. Find the problem and correct it.

Not quite. The answer is 100 psi.

In a typical air brake system, pumping by the air compressor should start at about 100 psi and stop at about 125 psi. (Check the manufacturer's specifications for the actual figures.)

Not quite. The answer is You should drive faster so that you will be able to keep the trailer and tractor straight.

When driving a tractor-trailer combination vehicle that has ABS, drive the same way that you always have. Do not drive any differently just because of ABS. Only use the braking necessary to keep control, pay attention when you slow down, and brake the same way regardless of what you're driving. Never speed up unless it is part of the safe driving process already.

Not quite. The answer is They are springs that apply the brakes if air pressure drops too low.

Spring brakes are an important backup system: powerful springs that automatically apply the brakes if they sense that air pressure has dropped too low for effective braking. The spring brakes are also used as parking brakes.

Not quite. The answer is To prevent a buildup of ice in the air brake system

When the air compressor runs, an alcohol evaporator puts alcohol vapor into the air brake system to help prevent water in the lines or valves from freezing. Ice in the lines or valves can cause them to stop working.

Not quite. The answer is The brakes could fail.

Water and oil from the compressor can collect at the bottoms of the air tanks. If the air tanks are not drained regularly, the water and oil can freeze or coagulate and cause brake failure.

Not quite. The answer is 3 psi per minute.

After the initial drop, the maximum acceptable leakage rates with the service brakes on are 3 psi per minute for single vehicles and 4 psi per minute for combination vehicles. If the leakage rate is higher, check for leaks and correct them.