New Hampshire CDL — Air Brakes: Handling Emergencies Practice Test

Question 1

Your truck has a manual-reset wig wag. With system pressure still at 45 psi, you push the arm up out of your line of sight. What does the manual say will happen?

Accepted Answer

The arm will not stay put until pressure is back above 55 psi — A wig wag drops a mechanical arm into view when system pressure goes under 55 psi. The manual-reset kind has to be put back by hand, and it will not hold in the out-of-view position while pressure remains below that level.

Answer

The arm locks in place and the warning is canceled

Answer

The spring brakes release

Answer

The compressor governor cuts out

Question 2

A failed low pressure warning lets air leak away without your noticing. The manual says a dual system will then need a longer stopping distance. What does it add about the braking you have left?

Accepted Answer

Only limited braking is possible before the spring brakes come on — Without a working warning you would not know the pressure was dropping. In a single-circuit system that could bring on sudden emergency braking. In dual systems the stopping distance grows, and the manual adds that you get only a limited amount of braking before the spring brakes apply.

Answer

Full braking remains until the tanks are completely empty

Answer

The front brakes shut off but the rear brakes are unaffected

Answer

The ABS takes over and stops the vehicle

Question 3

The manual calls hitting the brakes a good response when someone suddenly pulls out ahead of you, but only under two conditions. What are they?

Accepted Answer

You have room to stop, and you apply the brakes the right way — Braking is the natural reaction, and the manual accepts it when the distance is sufficient and the brakes are used correctly. That means braking so the vehicle stays in a straight line and can still be steered, using controlled braking or stab braking.

Answer

You have ABS on every axle, and the road is dry

Answer

You are below 35 mph, and the trailer is empty

Answer

The spring brakes are on, and the clutch is pushed in

Question 4

Controlled braking and stab braking are both emergency-stop methods. How does the way you first apply the brakes differ between them?

Accepted Answer

Controlled braking is as hard as possible without locking the wheels; stab braking is all the way on until the wheels lock — With controlled braking you brake hard but stay just short of lockup, releasing only if the wheels lock or you need a bigger steering correction. With stab braking you apply fully, let off when the wheels lock, and apply fully again once they are rolling.

Answer

Controlled braking uses the parking brake control; stab braking uses the foot pedal

Answer

Controlled braking is all the way on; stab braking is a light, steady application

Answer

Controlled braking is for vehicles with ABS only; stab braking is for trailers only

Question 5

After the low air pressure warning comes on, how long does the manual say controlled braking stays possible?

Accepted Answer

Only while enough air is left in the tanks — A warning may mean an air leak, and the remaining air is what lets you brake under control. Once pressure sinks into the 20 to 45 psi range the spring brakes apply on their own, so the manual says to stop and park safely as soon as you can.

Answer

For as long as the engine keeps running

Answer

Until the ABS malfunction lamp lights

Answer

For exactly one more full brake application

Question 6

Rig 1 has ABS on the tractor only. Rig 2 has ABS on the trailer only. Which statement matches what the manual says each rig gains under braking?

Accepted Answer

Rig 1 should keep steering control and is less likely to jackknife; Rig 2's trailer is less likely to swing out — Partial ABS still adds control, and the gain follows the unit that has it. With tractor-only ABS you should be able to keep steering and are less likely to jackknife, though the trailer can still swing out. With trailer-only ABS it is the trailer that resists swinging out, though steering control can still be lost.

Answer

Rig 1's trailer is less likely to swing out; Rig 2 should keep steering control and is less likely to jackknife

Answer

Rig 1 gains nothing; only Rig 2 has more control

Answer

Both rigs stop in half the distance, and neither can skid

Question 7

Partway through a trip your ABS malfunction lamp comes on and stays on. You still have your regular brakes. What does the manual tell you to do?

Accepted Answer

Keep driving normally, but have the system serviced soon — An ABS fault does not take away your normal brake functions, so you keep driving and braking the usual way. The manual's advice is to get the ABS serviced soon.

Answer

Stop at once and wait for a tow

Answer

Switch to stab braking for every stop

Answer

Pull the parking brake knob to reset the system

Question 8

On older vehicles, the manual ties the low air warning to the compressor governor instead of to a fixed 55 psi. If such a vehicle's governor cuts out at 120 psi, when must the visible warning come on?

Accepted Answer

Before tank pressure falls below 60 psi — For older vehicles the manual gives the warning point as one half of the compressor governor's cut-out pressure. Half of 120 psi is 60 psi, so the warning you can see has to be on before tank pressure drops under that.

Answer

Before tank pressure falls below 30 psi

Answer

Before tank pressure falls below 45 psi

Answer

Before tank pressure falls below 100 psi

Question 9

You are testing the low pressure warning signal with the engine off and the electrical power on. Pumping the brake pedal, you watch the gauge fall to 50 psi before the warning finally comes on. What does that tell you?

Accepted Answer

The signal is not working as required; it must come on before pressure drops under 55 psi — The warning has to activate before tank pressure falls to less than 55 psi. A signal that waits until 50 psi is late, and the manual warns that with a signal that does not work you could be losing air and never know it.

Answer

The signal is fine; it only has to come on before 45 psi

Answer

The signal is fine; any warning above 20 psi is acceptable

Answer

The test is invalid because the engine has to be running

New Hampshire CDL — Air Brakes: Handling Emergencies practice test

Study questions with answers

1. Your truck has a manual-reset wig wag. With system pressure still at 45 psi, you push the arm up out of your line of sight. What does the manual say will happen?

2. A failed low pressure warning lets air leak away without your noticing. The manual says a dual system will then need a longer stopping distance. What does it add about the braking you have left?

3. The manual calls hitting the brakes a good response when someone suddenly pulls out ahead of you, but only under two conditions. What are they?

4. Controlled braking and stab braking are both emergency-stop methods. How does the way you first apply the brakes differ between them?

5. After the low air pressure warning comes on, how long does the manual say controlled braking stays possible?

6. Rig 1 has ABS on the tractor only. Rig 2 has ABS on the trailer only. Which statement matches what the manual says each rig gains under braking?

7. Partway through a trip your ABS malfunction lamp comes on and stays on. You still have your regular brakes. What does the manual tell you to do?

8. On older vehicles, the manual ties the low air warning to the compressor governor instead of to a fixed 55 psi. If such a vehicle's governor cuts out at 120 psi, when must the visible warning come on?

9. You are testing the low pressure warning signal with the engine off and the electrical power on. Pumping the brake pedal, you watch the gauge fall to 50 psi before the warning finally comes on. What does that tell you?

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