Air Brakes · Practice test 2

Question 1Not answered

Why check the air compressor's drive belt, if equipped, during a pre-trip inspection?

1. The belt has no connection to the air brake system
2. A worn, cracked, or loose belt can slip or fail, preventing the compressor from building air pressure properly
3. The belt only needs checking after the compressor has already failed once, since a healthy belt never shows warning signs
4. The belt only affects the radio's power supply

Question 2Not answered

Why should a driver never attempt to compensate for a maladjusted brake by simply pressing the brake pedal harder?

1. It only matters for vehicles under 10,000 pounds
2. Pressing harder does not fix uneven force distribution and the underlying mechanical problem remains
3. Pressing harder fully corrects any adjustment problem
4. It is the manufacturer-recommended fix for any maladjustment issue found during inspection

Question 3Not answered

What happens to the parking (spring) brakes when the vehicle's air pressure drops to a critically low level, even if the driver has not manually set the parking brake?

1. They apply only if the driver presses a separate emergency button on the dash
2. They stay released regardless of air pressure
3. They apply only on the trailer, never on the tractor
4. They apply automatically to prevent driving with insufficient braking capacity

Question 4Not answered

What is a sign that a vehicle's air brakes may be out of adjustment?

1. The fuel tank is less than half full, unrelated to brake condition or pedal travel
2. The mirrors need readjustment
3. The brake pushrod travels farther than it should before the brakes engage
4. The tires show even tread wear

Question 5Not answered

You are driving and both the low air buzzer and warning light activate at the same time. What does this most likely mean compared to just one activating?

1. That the vehicle has two separate warning systems both confirming the same low pressure condition, and the situation should be treated seriously either way
2. That the vehicle is about to run out of fuel, not air
3. That only the electrical system has a problem, not the air system
4. Nothing different, the two warnings always mean the same thing no matter which one triggers first, so only one needs attention

Question 6Not answered

Why does contaminated air pose a greater risk specifically in winter?

1. Moisture that would otherwise just sit in the system can freeze solid and block valves or lines completely
2. Cold weather actually removes moisture from the air system on its own
3. Air brakes are not used at all in freezing temperatures, so contamination isn't a winter issue at all
4. Winter has no particular effect on contaminated air compared to any other season

Question 7Not answered

You need to park a vehicle with air brakes overnight in freezing temperatures. What should you do?

1. Leave the vehicle in gear only, skipping both the chocks and the parking brake control entirely
2. Disconnect the air lines before parking
3. Chock the wheels, and consider leaving the parking brake off if there is a risk of it freezing set
4. Always leave the parking brake set no matter the temperature

Question 8Not answered

Why is coasting in neutral down a long grade considered dangerous in a vehicle with air brakes?

1. It is dangerous only because it burns more fuel, not because of any loss of control on the way down the grade
2. It removes the engine's braking effect entirely, leaving only the service brakes to control a vehicle that can build up dangerous speed
3. Coasting in neutral automatically engages the parking brake as a safety measure
4. Neutral has no real effect on descent speed compared to staying in gear

Question 9Not answered

What is a 'brake chamber,' and what does it do?

1. A storage tank that holds extra brake fluid for hydraulic backup in case the air system fails
2. A device that measures tire pressure
3. A component that converts air pressure into mechanical force to apply the brakes at each wheel
4. A chamber used only to filter incoming air

Question 10Not answered

You stop briefly on level ground during a delivery run. Should you rely on the parking brake alone?

1. Yes, but only if the engine is left running the whole time
2. No, wheel chocks are legally required even for the shortest of stops, regardless of the terrain or grade involved
3. No, the parking brake should never be used except overnight
4. Yes, on level ground the parking brake alone is generally sufficient for a brief stop, unlike on ice or a grade

Question 11Not answered

Why is it unsafe to release the trailer parking brakes and rely only on the tractor's parking brakes when parking a combination vehicle?

1. The trailer's spring brakes only work when connected to shore power at a terminal or yard
2. The tractor's brakes alone may not be enough to hold the full combined weight of the tractor and trailer, especially on a grade
3. Trailer parking brakes have no holding function of their own
4. It is always safe as long as the trailer is empty

Question 12Not answered

What long-term problem can result from consistently using brakes alone to control speed on grades, instead of a low gear plus snub braking?

1. There is no real difference in wear between the two techniques over time
2. Using the brakes alone actually extends brake life compared to shifting into a lower gear each time
3. The brakes wear out faster and are more likely to overheat and fade when you actually need them most
4. Brakes used this way only wear out the tires, not the brakes themselves

Question 13Not answered

Why should you never rely on the parking brake alone when parking on ice?

1. The parking brake can freeze in the applied position, or fail to hold on a slippery surface
2. The parking brake is illegal to use on ice
3. Using the parking brake drains the battery
4. The parking brake only works while the engine is running and air pressure holds steady overnight

Question 14Not answered

What might repeated low air pressure warnings on short trips suggest about the vehicle?

1. It indicates the trailer is too lightly loaded
2. There may be an air leak or a compressor that is not keeping up with system demand
3. It only means the driver is braking too gently
4. It is a normal pattern tied only to cold starts, nothing more to look into

Question 15Not answered

Why is selecting a low gear before starting down a long grade important for controlling an air brake vehicle?

1. It only helps fuel economy
2. It has no effect except engine noise
3. Engine braking in a low gear helps control speed without relying solely on the brakes, which can overheat
4. It is only needed on sharp downhill curves, not straight sections of grade, since straight roads need no extra control

Question 16Not answered

As part of a pre-trip inspection, why do you pump the brake pedal several times with the engine off before checking anything else on the air system?

1. To warm up the brake pads before driving
2. To release any residual air pressure so the low air warning and gauges can be tested from a realistic starting point
3. To make sure the parking brake light bulb is not burned out before driving, a routine bulb check unrelated to air pressure
4. To check that the horn still works

Question 17Not answered

Why do federal inspection standards set a maximum allowable pushrod stroke for each brake chamber size?

1. Beyond that stroke length, the brake cannot apply enough force to stop the vehicle safely
2. Stroke length limits apply only to steering axle brakes
3. Pushrod stroke only affects chamber noise, not the braking force produced at the wheel
4. The limit exists only to standardize brake chamber manufacturing

Question 18Not answered

As part of a pre-trip air brake check, why should you also test that the tractor protection valve closes properly?

1. It only affects trailer lighting, not any part of the braking system
2. It has already been tested once at the factory and never needs checking again, when components can wear or stick over years of service regardless of how they performed when new
3. The tractor protection valve is only relevant during trailer hookup, not while driving
4. So you know the tractor's own air will be protected if the trailer connection fails later during the trip

Question 19Not answered

What is the purpose of a runaway vehicle escape ramp found on some steep grades?

1. It's used only for routine vehicle inspections
2. It's a shortcut to bypass slow traffic
3. It's a designated rest area intended for scheduled driver breaks and overnight parking on long mountain routes
4. It gives a vehicle that has lost effective braking a way to slow down and stop safely off the main roadway

Question 20Not answered

What sign during a pre-trip inspection would suggest one brake is out of adjustment compared to the others on the same axle?

1. The tires on that axle are a different brand than the other axles
2. The mirror on that side of the vehicle is angled slightly differently
3. Both sides of the axle always travel exactly the same distance no matter the adjustment
4. One side's pushrod travels noticeably farther than the other before the brake engages

Question 21Not answered

For a combination vehicle on a long grade, why is it especially important to select the low gear before starting down rather than while already descending?

1. Combination vehicles automatically select the correct gear on grades, making manual timing unnecessary for any driver
2. Gear selection only matters for single vehicles, not combinations
3. It is actually easier and safer to shift gears mid-descent once the vehicle has picked up speed
4. Shifting gears while already moving fast downhill with a trailer can be difficult or risky, so the gear needs to be locked in before speed builds up

Question 22Not answered

What is the 'slack adjuster,' and what does it connect?

1. A device that measures air tank moisture levels
2. A linkage that connects the brake chamber pushrod to the camshaft that applies the brake shoes
3. A component found only on hydraulic brake systems, not air brake systems like this one
4. A valve that adjusts trailer air supply pressure

Question 23Not answered

Why can out-of-adjustment brakes on just one or two wheels of a vehicle be especially dangerous, beyond simply increasing stopping distance?

1. They only matter when the vehicle is empty, not when it's fully loaded
2. They cause the vehicle to steer more precisely than normal
3. They can cause uneven braking that pulls the vehicle to one side or contributes to a skid
4. They only affect fuel economy, with no impact on handling, overlooking how uneven braking force changes how the vehicle tracks

Question 24Not answered

Besides pushrod travel, what other sign during a brake inspection can point to a brake being out of adjustment?

1. The slack adjuster arm forming an angle noticeably different from the others when the brakes are applied
2. The windshield wipers moving slower than normal
3. The vehicle's interior lights flickering while braking, a sign of a loose wiring connection near the dash
4. The vehicle's radio losing signal on certain roads

Question 25Not answered

What does 'brake fade' mean in the context of a long descent?

1. The brake pedal becoming physically stuck in the fully applied position after a hard stop
2. The brake lights dimming due to a wiring issue
3. A brief loss of steering control unrelated to the brakes
4. A gradual loss of braking power caused by the brakes overheating from continuous use

Question 26Not answered

What should you never do while the parking brakes are set on the drive axle, in terms of moving the vehicle?

1. Attempt to drive forward or backward with them engaged, since this can damage the brakes
2. Turn on the engine
3. Shift into a low gear to hold the vehicle in place instead of using the brakes at all
4. Check the air pressure gauges

Question 27Not answered

What is the purpose of the alcohol evaporator found on some older air brake systems?

1. It removes oil from the fuel before it reaches the engine, a function that has nothing to do with the air system or its valves
2. It cools the compressor down after long descents
3. It cleans the windshield using leftover system air
4. It adds a small amount of alcohol to the air system to help reduce the chance of ice forming in the lines and valves during cold weather

Question 28Not answered

What should you check regarding the trailer air lines (the 'gladhands') during a pre-trip coupling inspection?

1. That they are left slightly loose for flexibility
2. That they are properly connected, not crossed, and the seals are not cracked or leaking
3. That they are left disconnected until the trailer actually starts moving down the road
4. Only that they are the same brand as the tractor's lines

Question 29Not answered

What is the purpose of the supply (emergency) air line running between a tractor and trailer?

1. It charges the trailer's air tanks and, if it breaks, triggers the trailer's emergency brakes
2. It only controls the trailer's turn signals
3. It is used solely to sound the trailer's horn, not to release the trailer's brakes in an emergency
4. It only powers the trailer's marker lights

Question 30Not answered

During the pre-trip check, why is it important to confirm both the tractor protection valve and trailer air supply valve work correctly?

1. They ensure the trailer brakes apply automatically if the air supply between tractor and trailer is lost
2. They are used only when parking on a hill
3. They regulate fuel flow to the engine
4. They control only the trailer's interior dome lighting, not any part of the braking system itself