Maryland CDL — Air Brakes: Handling Emergencies Practice Test

Question 1

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 2

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 3

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 4

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 5

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 6

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 7

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

Question 8

On a tractor or straight truck, the spring brakes come fully on when air pressure drops into roughly what range?

Accepted Answer

20 to 45 psi — Spring brakes on tractors and straight trucks apply fully once air pressure falls into the 20 to 45 psi band (often 20 to 30 psi).

Answer

80 to 100 psi

Answer

100 to 125 psi

Answer

125 to 150 psi

Handling Emergencies

Study questions with answers

1. 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?

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

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

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

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

6. 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?

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

8. On a tractor or straight truck, the spring brakes come fully on when air pressure drops into roughly what range?

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