Alabama CDL — Air Brakes: Handling Emergencies Practice Test

Question 1

You are pulling a trailer fitted with ABS behind a tractor that has none, and the tractor starts to jackknife. What does the manual advise?

Accepted Answer

Ease off the brake pedal, where it is safe, until control returns — Backing off the pedal lets the wheels roll again so steering comes back. Only ease off when traffic and the space ahead make releasing brake pressure a safe thing to do.

Answer

Push the pedal harder to force the tractor back into line

Answer

Hold the trailer hand valve down on its own until it straightens

Answer

Grab a lower gear and let go of the steering wheel

Question 2

If the low air pressure warning comes on while driving, why is it safer to stop while air still remains in the tanks?

Accepted Answer

You can still use the foot brakes for a controlled stop while air lasts — Controlled braking is only possible while enough air is left in the tanks; if you wait, the spring brakes may come on suddenly, and a heavily loaded vehicle takes a long distance to stop because they do not work on all axles.

Answer

The compressor cannot restart once the warning sounds

Answer

The brake lights stop working below the warning level

Answer

The parking brake knob will jam if pressure is lost

Question 3

When the low air pressure warning first comes on, what is the safest thing to do?

Accepted Answer

Bring the vehicle to a safe stop right away — You should bring the vehicle to a safe stop right away while you still have enough air to control the brakes, rather than waiting for the spring brakes to apply on their own.

Answer

Keep driving until the spring brakes apply themselves

Answer

Pump the pedal rapidly to rebuild pressure

Answer

Speed up to reach the next exit sooner

Question 4

When using the 'controlled braking' method in an emergency, how hard should you press the brakes?

Accepted Answer

As hard as you can without locking the wheels — Controlled braking means applying the brakes as hard as you can without locking the wheels while keeping steering movements small; if the wheels lock or you must steer more, release and then reapply.

Answer

Only lightly, so the wheels never slow

Answer

Hard enough to lock the wheels and hold them

Answer

In quick full-pressure pulses only

Question 5

A visible low air pressure warning must come on before tank pressure drops below what level?

Accepted Answer

Below 55 psi — Vehicles with air brakes are required to give a warning the driver can see before pressure in the tanks falls under 55 psi.

Answer

Below 20 psi

Answer

Below 100 psi

Answer

Below 125 psi

Question 6

What is the main cause of brake fade?

Accepted Answer

Excessive heat from overusing the service brakes — Brake fade comes from excessive heat that builds up when the service brakes are used too much instead of relying on the braking effect of the engine; the heat changes the lining and expands the drums, reducing braking.

Answer

Too much moisture drained from the tanks

Answer

Setting the front limiting valve to 'normal'

Answer

Filling the alcohol evaporator too often

Question 7

Once the spring brakes set themselves because tank pressure has fallen away, why can a heavily loaded truck need so much room to stop?

Accepted Answer

They are not fitted to every axle under the vehicle — Spring brakes are fitted to only some axles, so the holding force available is far below what the service brakes normally deliver and a loaded rig keeps rolling much farther.

Answer

Spring brakes begin working only below walking speed

Answer

A heavy load stops the brake drums from turning at all

Answer

Spring brakes release themselves whenever the load is heavy

Question 8

Apart from leaning on the service brakes too much, what else makes brake fade more likely?

Accepted Answer

Brakes that have slipped out of proper adjustment — A brake that has drifted out of adjustment quits carrying its share of the work, so the remaining brakes soak up extra heat and start to fade. Adjustment slips quickly once brakes run hot, so check it often.

Answer

Tires inflated well above the recommended pressure

Answer

Using the engine to help hold your speed down

Answer

Draining the air tanks more often than required

Question 9

The ABS warning lamp lights up while you are driving. What braking ability do you still have?

Accepted Answer

The ordinary air brakes keep working just as they always have — A failed antilock system does not take away your ordinary braking. Keep driving as you normally would, but arrange to have the system repaired without much delay.

Answer

Only the parking brakes will function until a repair is made

Answer

Braking is cut back to the trailer axles alone

Answer

You lose all service braking and have to coast to a halt

Question 10

While holding a steady speed you notice you must keep increasing the application pressure. What does this most likely mean?

Accepted Answer

The brakes are fading and you should slow down and use a lower gear — Needing more and more application pressure just to hold the same speed is a sign the brakes are fading; the driver should slow down and shift to a lower gear.

Answer

The compressor has switched to its backup setting

Answer

The air tanks are fully drained of moisture

Answer

The spring brakes are about to release on their own

Question 11

Which sequence describes the 'stab braking' method for an emergency stop?

Accepted Answer

Apply fully, release when the wheels lock, then reapply once they roll again — In stab braking you apply the brakes all the way, release them when the wheels lock up, and reapply fully once the wheels begin rolling again, allowing up to a second for them to start rolling.

Answer

Hold light steady pressure and never release

Answer

Pump the pedal in rapid half-second taps regardless of the wheels

Answer

Apply the parking brake and let go of the pedal

Question 12

On a long, steep downgrade, how should the brakes be used?

Accepted Answer

As a supplement to engine braking after selecting a low gear — On a long or steep grade the brakes are only a supplement to the engine's braking effect; once the vehicle is in the proper low gear, brief firm brake applications are used to control speed.

Answer

As the main way to control speed, holding them on the whole way down

Answer

Only at the very bottom of the hill

Answer

By pumping them rapidly the entire descent

Alabama CDL — Air Brakes: Handling Emergencies practice test

Study questions with answers

1. You are pulling a trailer fitted with ABS behind a tractor that has none, and the tractor starts to jackknife. What does the manual advise?

2. If the low air pressure warning comes on while driving, why is it safer to stop while air still remains in the tanks?

3. When the low air pressure warning first comes on, what is the safest thing to do?

4. When using the 'controlled braking' method in an emergency, how hard should you press the brakes?

5. A visible low air pressure warning must come on before tank pressure drops below what level?

6. What is the main cause of brake fade?

7. Once the spring brakes set themselves because tank pressure has fallen away, why can a heavily loaded truck need so much room to stop?

8. Apart from leaning on the service brakes too much, what else makes brake fade more likely?

9. The ABS warning lamp lights up while you are driving. What braking ability do you still have?

10. While holding a steady speed you notice you must keep increasing the application pressure. What does this most likely mean?

11. Which sequence describes the 'stab braking' method for an emergency stop?

12. On a long, steep downgrade, how should the brakes be used?

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