Virginia CDL — Air Brakes: Handling Emergencies Practice Test

Question 1

Some buses have dual parking control valves with a separate air tank. What is that separate tank for?

Accepted Answer

To release the spring brakes a few times so the vehicle can be moved in an emergency — The extra reservoir stores air that can release the spring brakes so the vehicle can be driven a short distance in an emergency, but it holds only enough to do this a few times, so plan the move carefully.

Answer

To supply unlimited air for continued driving

Answer

To run the alcohol evaporator in winter

Answer

To power the ABS computer if the battery dies

Question 2

What is the role of the emergency brake portion of an air-brake system?

Accepted Answer

To stop the vehicle by using parts of the service and parking brakes when a failure occurs — The emergency brakes borrow components from the service and parking circuits so the vehicle can still be brought to a halt if the braking system fails.

Answer

To hold the truck in place on a hill while it is parked

Answer

To supply extra air to the trailer during a hard stop

Answer

To cool the brake drums after a long descent

Question 3

If the safety relief valve lets air escape, what does that indicate?

Accepted Answer

Something is wrong and the problem should be repaired by a mechanic — The safety valve only vents when pressure climbs too high, so if it releases air something is wrong and a mechanic should correct the fault.

Answer

The system is working normally and no action is needed

Answer

The tanks simply need to be drained

Answer

The alcohol evaporator is out of fluid

Question 4

How does the controlled braking method work in an emergency stop?

Accepted Answer

Brake as firmly as you can short of locking the wheels, keeping steering inputs small — With controlled braking you apply the brakes as hard as possible without locking the wheels while keeping steering inputs small; if you must steer more or the wheels lock, you ease off and reapply.

Answer

Lock the wheels on purpose to stop faster

Answer

Use only the trailer hand valve

Answer

Alternate between the parking brake and the pedal

Question 5

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

Accepted Answer

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

Answer

Hold steady light pressure the entire time

Answer

Pump the pedal rapidly without ever releasing fully

Answer

Apply the parking brake instead of the pedal

Question 6

The moment the low-pressure warning light and buzzer come on while you are driving, what should you do?

Accepted Answer

Bring the vehicle to a safe stop while you can still control the brakes — Don't wait for the spring brakes to set themselves; get the vehicle stopped safely without delay while you still have enough air to work the service brakes.

Answer

Keep driving until the spring brakes engage by themselves

Answer

Pump the pedal quickly to rebuild pressure

Answer

Shift to a higher gear and speed up to the next exit

Question 7

On a tractor or straight truck, the spring brakes typically come fully on when air pressure falls to what range?

Accepted Answer

20 to 45 psi — If pressure keeps dropping, the spring brakes engage on their own once it reaches somewhere in the 20 to 45 psi range (often 20 to 30 psi).

Answer

80 to 100 psi

Answer

55 to 75 psi

Answer

5 to 15 psi

Question 8

What is the purpose of a modulating control valve for the spring brakes?

Accepted Answer

It lets the driver apply the spring brakes gradually if the service brakes fail — A modulating valve lets you bring the spring brakes on gradually, with more lever movement producing harder braking, so you can still control the vehicle if the service brakes fail.

Answer

It automatically drains the air tanks when parked

Answer

It limits pressure to the front brakes on ice

Answer

It recharges the secondary system from the primary

Question 9

A visible low-air-pressure warning must activate before tank pressure drops below what level?

Accepted Answer

Below 55 psi — Regulations require a warning the driver can see to switch on before pressure falls under 55 psi (or half the governor cut-out on older trucks).

Answer

Below 20 psi

Answer

Below 100 psi

Answer

Below 125 psi

Handling Emergencies

Study questions with answers

1. Some buses have dual parking control valves with a separate air tank. What is that separate tank for?

2. What is the role of the emergency brake portion of an air-brake system?

3. If the safety relief valve lets air escape, what does that indicate?

4. How does the controlled braking method work in an emergency stop?

5. Which sequence correctly describes the stab braking method for an emergency stop?

6. The moment the low-pressure warning light and buzzer come on while you are driving, what should you do?

7. On a tractor or straight truck, the spring brakes typically come fully on when air pressure falls to what range?

8. What is the purpose of a modulating control valve for the spring brakes?

9. A visible low-air-pressure warning must activate before tank pressure drops below what level?

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