Kansas CDL — Air Brakes: Handling Emergencies Practice Test

Question 1

Your trailer has ABS but your tractor does not. What does the trailer's ABS make less likely when you brake?

Accepted Answer

The trailer swinging out — With ABS only on the trailer, trailer swing-out becomes less likely. Steering loss or a jackknife at the tractor can still happen; if one starts, ease off the brakes (when it is safe to do so) until you regain control.

Answer

The tractor jackknifing

Answer

Losing steering control at the front

Answer

Brake lag

Question 2

Only your tractor has ABS. During a hard stop, you see in the mirror that the trailer is starting to swing out. What should you do?

Accepted Answer

Ease off the brakes, as long as you can do that safely — Tractor-only ABS helps you hold steering control and makes a jackknife less likely, but it does nothing for the trailer's wheels. Keep watching the trailer, and if it begins to swing out, let up on the brakes when it is safe to do so.

Answer

Press harder on the pedal so the tractor's ABS can steady the trailer

Answer

Pull the parking brake knob so every wheel locks at once

Answer

Hold full pressure and wait, since tractor ABS straightens the trailer

Question 3

For an emergency stop in an air-braked vehicle, which two braking methods does the manual describe?

Accepted Answer

Controlled braking and stab braking — The manual names two emergency methods. Controlled braking means braking firmly but stopping just short of wheel lockup. Stab braking means braking fully, letting off when the wheels lock, and braking fully again once they roll. Both aim to keep the vehicle straight and still able to turn.

Answer

Pump braking and coast braking

Answer

Engine braking and parking-brake braking

Answer

Trailer hand-valve braking and spring-brake braking

Question 4

How long can it take locked wheels to begin rolling again after you let off the brakes during stab braking?

Accepted Answer

Up to about one second — After you let off, it can take as long as a second for locked wheels to roll again. Wait for them to roll before braking fully again, or the vehicle won't straighten out.

Answer

About a tenth of a second

Answer

Three to five seconds

Answer

Not until the vehicle has fully stopped

Question 5

What problem in the system does the manual say a low air pressure warning might be signaling?

Accepted Answer

An air leak somewhere in the system — A low air warning may mean the system has a leak. Stop and park safely as soon as you can, while the tanks still hold enough air for controlled braking with the foot brake.

Answer

The compressor is pumping too much air

Answer

The brake linings are soaked with oil

Answer

The governor has just cut out at normal pressure

Question 6

On a long downgrade you keep leaning on the service brakes even after they start to fade. Where can that lead?

Accepted Answer

The fade can keep growing until you can no longer slow or stop the vehicle — Overusing the service brakes overheats them. The heat changes the lining so it grips less, and it expands the drums so the shoes must travel farther. If the overuse continues, fade can build until slowing or stopping is no longer possible.

Answer

The ABS will take over and cool the brakes

Answer

The fade will stop once the drums finish expanding

Answer

The spring brakes will hold you at a safe speed automatically

Question 7

Which of these is NOT a consequence the manual links to wheels locking up during hard braking in a vehicle without ABS?

Accepted Answer

Brake fade from overheated drums — Locked steering wheels take away your steering control, and locked wheels elsewhere can cause a skid, a jackknife, or a spin. Brake fade has a different cause: heat built up by overusing the brakes.

Answer

Losing steering control when the steering wheels lock

Answer

A skid

Answer

A jackknife or a spin

Question 8

A tour bus has lost main air, and you need to reposition it using the separate air tank that serves its dual parking control valves. What limitation should shape how you plan the move?

Accepted Answer

The separate tank holds only enough air to release the brakes a few times — The separate tank carries enough air for just a few releases. Use it up without a plan and the spring brakes can leave the bus stuck somewhere dangerous, so work out each move before you make it.

Answer

Each push of the release button wears out the spring brakes permanently

Answer

The release button only works while the engine runs at a fast idle

Answer

The low air warning shuts the engine off after about one minute

Question 9

In an emergency stop, when does the manual say an ABS-equipped vehicle's brakes may be pushed all the way down?

Accepted Answer

When the straight truck or combination you drive always has working ABS on all of its axles — Normally you brake as you always have, using only the force needed to stop safely and keep control, and you ease off if needed. The single exception: if your straight truck or combination always has working ABS on every axle, you may apply the brakes fully in an emergency stop.

Answer

Whenever the tractor has ABS, even if the trailer does not

Answer

Whenever the pavement is dry and the vehicle is loaded

Answer

Only once the ABS malfunction lamp has come on during the trip

Question 10

Slamming on the brakes is a driver's natural reaction when someone cuts in ahead. Under what conditions does the manual call that reaction a good one?

Accepted Answer

When you have enough room to stop and you brake correctly — Braking is the instinctive response, and it works when there is room to stop and the brakes are used properly. Brake in a way that keeps the vehicle straight and leaves you able to turn if you need to.

Answer

Always, because hard braking is the quickest way to stop

Answer

Only if the truck has ABS

Answer

Never; you should always steer around instead

Question 11

Halfway through a run, the yellow ABS malfunction lamp on your dash comes on and stays on. What does the manual advise?

Accepted Answer

You still have your regular brakes, so keep driving normally and get the ABS serviced soon — A lamp that stays on, or lights once you're moving, may mean ABS control is lost at one or more wheels. ABS only adds to your normal brakes, so without it you still have ordinary braking. Drive and brake as usual, and have the system repaired soon.

Answer

Pull over immediately, because the service brakes will no longer apply at all

Answer

Pump the brake pedal at every stop until the lamp goes back out

Answer

Set the front brake limiting valve to 'slippery' to make up for the lost ABS

Kansas CDL — Air Brakes: Handling Emergencies practice test

Study questions with answers

1. Your trailer has ABS but your tractor does not. What does the trailer's ABS make less likely when you brake?

2. Only your tractor has ABS. During a hard stop, you see in the mirror that the trailer is starting to swing out. What should you do?

3. For an emergency stop in an air-braked vehicle, which two braking methods does the manual describe?

4. How long can it take locked wheels to begin rolling again after you let off the brakes during stab braking?

5. What problem in the system does the manual say a low air pressure warning might be signaling?

6. On a long downgrade you keep leaning on the service brakes even after they start to fade. Where can that lead?

7. Which of these is NOT a consequence the manual links to wheels locking up during hard braking in a vehicle without ABS?

8. A tour bus has lost main air, and you need to reposition it using the separate air tank that serves its dual parking control valves. What limitation should shape how you plan the move?

9. In an emergency stop, when does the manual say an ABS-equipped vehicle's brakes may be pushed all the way down?

10. Slamming on the brakes is a driver's natural reaction when someone cuts in ahead. Under what conditions does the manual call that reaction a good one?

11. Halfway through a run, the yellow ABS malfunction lamp on your dash comes on and stays on. What does the manual advise?

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