Maryland CDL — Air Brakes: Handling Emergencies Practice Test

Question 1

When the spring brakes finally set on a lightly loaded rig, or on a slick road surface, what extra danger appears?

Accepted Answer

The vehicle can slide and you may lose control of it — With little weight pressing the wheels down, or with poor traction beneath them, the sudden grab of the springs can throw the rig into a slide, which is one more reason to park before the tanks ever get that low.

Answer

The trailer brakes let go before the tractor brakes do

Answer

The compressor restarts on its own and rebuilds full pressure

Answer

The steering axle locks itself into a straight-ahead position

Question 2

What is physically going wrong inside a drum brake when too much heat makes the brakes fade?

Accepted Answer

The lining grips less and the drum swells, so the shoes reach farther and push with weaker force — Heat alters the lining chemically so it grips less, and it swells the drum outward, meaning the shoes must reach farther and then meet the drum with weaker force; keep it up and the rig may not slow at all.

Answer

The air lines soften and start bleeding pressure out of the chamber

Answer

The slack adjuster tightens up and drags the shoes against the drum

Answer

The s-cam turns the wrong way and holds the shoes apart

Question 3

On a vehicle with dual parking control valves and a separate air tank, what limits how you use it to release the spring brakes in an emergency?

Accepted Answer

The separate tank holds only enough air to release the brakes a few times — Pushing the control in draws air from a separate tank to free the spring brakes so you can move, but that tank holds only enough air to do this a few times, so you must plan the move carefully to avoid getting stranded in a dangerous spot.

Answer

It only works when the engine is running

Answer

It can only be used while parked on a downhill grade

Answer

It requires the governor to be at cut-out pressure

Question 4

The antilock system on your truck quits working while you are out on the road. What does that mean for your braking?

Accepted Answer

Your ordinary brakes still work, so keep driving normally and get the system serviced soon — A failed antilock system does not take away the braking you already had; the truck stops the way it did before ABS existed, so drive as usual and have the fault repaired without delay.

Answer

You must shut down where you are, because the vehicle can no longer be stopped

Answer

Only the parking brake control will slow you until the fault is cleared

Answer

Braking is cut back to the trailer axles alone until a mechanic resets it

Question 5

What does an antilock braking system (ABS) do during a hard brake application?

Accepted Answer

It keeps the wheels from locking up — ABS is a computerized system that keeps the wheels from locking up when you brake hard, helping you keep the vehicle under control.

Answer

It automatically increases braking force to the front axle

Answer

It shuts off the service brakes and uses only spring brakes

Answer

It raises the tank pressure during braking

Question 6

Which statement about what ABS does for your stopping is accurate?

Accepted Answer

It won't always shorten the distance to stop but helps you stay in control — ABS won't automatically cut down how far you need to stop, but it does help you hold the vehicle steady while braking hard; it simply adds to your normal brakes without changing their power.

Answer

It always cuts your stopping distance roughly in half

Answer

It replaces your normal service brakes entirely

Answer

It increases your braking power on dry pavement

Question 7

What describes the controlled braking method during an emergency stop?

Accepted Answer

Braking as firmly as you can without locking the wheels while steering gently — In controlled braking you press the brakes as firmly as possible short of locking the wheels, keeping steering inputs very small; if a wheel locks or you must steer more, ease off and reapply as soon as you can.

Answer

Braking as lightly as possible while making large steering corrections

Answer

Slamming the brakes fully and holding them locked

Answer

Using only the engine and transmission to slow down

Question 8

As soon as the low-pressure warning first comes on while you are driving, what should you do?

Accepted Answer

Immediately pull over and stop safely while you still have air to work the brakes — Don't wait for the spring brakes to set on their own; when the warning light and buzzer first activate, pull over safely while enough air still remains to work the brakes.

Answer

Speed up to reach your destination before the air runs out

Answer

Pump the brake pedal repeatedly to rebuild pressure

Answer

Ignore it until the spring brakes apply by themselves

Question 9

If you keep driving after the low air pressure warning comes on and the spring brakes finally apply, why can a heavily loaded vehicle take a long distance to stop?

Accepted Answer

Because the spring brakes don't act on every axle — When the spring brakes set at 20 to 45 psi, they don't act on every axle, so a heavily loaded rig needs a long way to stop; stopping while the tanks still hold enough air for the foot brakes is far safer.

Answer

Because the service brakes apply at double strength

Answer

Because the ABS shuts off all braking

Answer

Because the trailer brakes release automatically

Question 10

You are hauling a trailer that has antilock brakes behind a tractor that does not, and the tractor begins to jackknife. What is the right response?

Accepted Answer

Back off the brake pedal, where it is safe to do so, until you have the rig under control again — The trailer's antilock system keeps the trailer from swinging wide, but it cannot straighten a tractor that is folding; easing pressure off the pedal lets the steering wheels turn again so you can recover the rig.

Answer

Press the pedal harder to force the tractor back into line

Answer

Grab a lower gear and hold steady pressure on the pedal

Answer

Pull the parking brake knob out to straighten the combination

Question 11

Why does correct brake adjustment matter so much to the emergency and parking brake function?

Accepted Answer

The springs can only deliver their full holding force through brakes that are set correctly — The springs act through the very same shoes your service brakes use, so when adjustment has slipped, neither your everyday braking nor the emergency and parking function will do its job the way it should.

Answer

Adjustment sets the pressure at which the governor cuts out

Answer

Adjustment decides how fast the storage tanks refill after a stop

Answer

Adjustment controls whether the low pressure buzzer will sound

Question 12

How is the stab braking method carried out in an emergency stop?

Accepted Answer

Apply the brakes fully, release when the wheels lock, then reapply fully once they roll again — In stab braking you push the brakes all the way, let them off the instant the wheels lock, then press fully again once the wheels roll again; it can take up to a second for them to start rolling, and reapplying too soon keeps the vehicle from straightening out.

Answer

Hold steady, light pressure the entire time without releasing

Answer

Pump the brakes rapidly regardless of whether the wheels are rolling

Answer

Apply only the parking brake and steer straight

Maryland CDL — Air Brakes: Handling Emergencies practice test

Study questions with answers

1. When the spring brakes finally set on a lightly loaded rig, or on a slick road surface, what extra danger appears?

2. What is physically going wrong inside a drum brake when too much heat makes the brakes fade?

3. On a vehicle with dual parking control valves and a separate air tank, what limits how you use it to release the spring brakes in an emergency?

4. The antilock system on your truck quits working while you are out on the road. What does that mean for your braking?

5. What does an antilock braking system (ABS) do during a hard brake application?

6. Which statement about what ABS does for your stopping is accurate?

7. What describes the controlled braking method during an emergency stop?

8. As soon as the low-pressure warning first comes on while you are driving, what should you do?

9. If you keep driving after the low air pressure warning comes on and the spring brakes finally apply, why can a heavily loaded vehicle take a long distance to stop?

10. You are hauling a trailer that has antilock brakes behind a tractor that does not, and the tractor begins to jackknife. What is the right response?

11. Why does correct brake adjustment matter so much to the emergency and parking brake function?

12. How is the stab braking method carried out in an emergency stop?

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