New Jersey CDL — Air Brakes: Handling Emergencies Practice Test

Question 1

Where does the emergency brake system get the parts it uses to stop a vehicle after a failure?

Accepted Answer

From parts it shares with the service and parking brakes — The emergency brakes are not a fully separate set of hardware; they draw on components shared with the service and parking brake systems to bring you to a stop when a brake failure occurs.

Answer

From a stand-alone hydraulic reserve unit

Answer

From the exhaust and engine-braking system

Answer

From a battery-powered electric brake motor

Question 2

What is the key idea behind the "controlled braking" method?

Accepted Answer

Apply the brakes as hard as possible without locking the wheels, keeping steering small — Controlled braking means squeezing on as much brake as possible short of locking the wheels, holding steering movements small and easing off only if a wheel locks or you must steer more sharply.

Answer

Lock the wheels immediately and steer hard around the hazard

Answer

Coast in neutral and use only the engine to slow down

Answer

Alternate the brakes and accelerator to keep the vehicle balanced

Question 3

Why does a heavily loaded vehicle take a long distance to stop once the spring brakes come on from low air pressure?

Accepted Answer

Because spring brakes act on only some axles, not every one — Spring brakes do not act on every axle, so a heavy load has limited braking; it is far safer to stop while there is still enough air to use the foot brakes than to let pressure fall that low.

Answer

Because spring brakes apply far more force than the foot brakes

Answer

Because the engine brake shuts off when air is low

Answer

Because the tires lose all traction when air is low

Question 4

How do you perform the "stab braking" method in an emergency stop?

Accepted Answer

Brake fully, release when the wheels lock, then reapply fully once they roll — Stab braking means fully applying the brakes, releasing them the moment the wheels lock, and then reapplying fully once the wheels begin rolling again, allowing up to a second for them to start rolling.

Answer

Press the pedal down gently and hold steady pressure

Answer

Pump the pedal lightly to keep the wheels barely turning

Answer

Apply the parking brake in short bursts instead of the pedal

Question 5

On a tractor or straight truck, in what pressure range do the spring brakes typically come fully on by themselves?

Accepted Answer

Between about 20 and 45 psi — When air pressure bleeds down into roughly the 20-to-45 psi range (often 20 to 30), the springs overcome the remaining air and apply the brakes automatically.

Answer

Between 90 and 110 psi

Answer

Between 125 and 150 psi

Answer

Between 55 and 70 psi

Question 6

As soon as the low-air warning light and buzzer come on, what should you do?

Accepted Answer

Stop safely as soon as possible while you can still control braking — Don't wait for the spring brakes to grab by themselves; pull over and park safely at once, while enough air remains for you to control braking.

Answer

Keep driving until the spring brakes apply on their own

Answer

Pump the brake pedal rapidly to build pressure back

Answer

Turn off the warning buzzer and continue to your destination

Handling Emergencies

Study questions with answers

1. Where does the emergency brake system get the parts it uses to stop a vehicle after a failure?

2. What is the key idea behind the "controlled braking" method?

3. Why does a heavily loaded vehicle take a long distance to stop once the spring brakes come on from low air pressure?

4. How do you perform the "stab braking" method in an emergency stop?

5. On a tractor or straight truck, in what pressure range do the spring brakes typically come fully on by themselves?

6. As soon as the low-air warning light and buzzer come on, what should you do?

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