Nevada CDL — Air Brakes: Handling Emergencies Practice Test

Question 1

Your tractor has ABS, but the trailer you are pulling does not. Compared with having no ABS anywhere, what does the tractor's ABS help with during hard braking?

Accepted Answer

It helps you hold steering control and makes a jackknife less likely — With ABS on the tractor alone, you should be able to keep steering control and you are less likely to jackknife. You still need to watch the trailer and ease off the brakes, if it is safe, should it begin to swing out.

Answer

It guarantees the trailer can never swing out

Answer

It roughly halves your stopping distance

Answer

It lets you stop watching the trailer while you brake

Question 2

The low air warning comes on, and you are tempted to keep driving until the spring brakes stop you. Which of these is NOT a reason the manual gives for stopping right away instead?

Accepted Answer

Spring brakes let go by themselves after a few seconds, so the vehicle will start rolling again — Spring brakes are pushed on by spring force and are held off only by air pressure, so with the air gone they will not let go on their own. The real reasons to stop early are that a heavy load needs a long distance to stop on spring brakes, a light load or slick road can skid, and you keep pedal control only while air remains.

Answer

A heavily loaded vehicle needs a long way to stop on spring brakes, since they don't act on every axle

Answer

A lightly loaded vehicle, or one on a slick road, could go into an uncontrolled skid once the spring brakes apply

Answer

You can control your braking with the pedal only while enough air is left in the tanks

Question 3

In a typical dual air brake truck, you notice the secondary system's pressure sinking while the primary holds steady. Which brakes are probably not working fully, and what should you expect?

Accepted Answer

The front-axle brakes; it will take you longer to stop — In the usual setup the secondary system works the front-axle brakes (and possibly one rear axle). When one system runs very low, the brakes it feeds don't work fully and stopping takes longer, so pull over safely and have the air system repaired.

Answer

The rear-axle brakes; your stopping distance will not change

Answer

Every brake on the truck; it will stop instantly

Answer

Only the trailer brakes; the tractor will stop as usual

Question 4

You have to brake hard on a slippery road in a truck with working ABS. Which result can you reasonably expect ABS to help with?

Accepted Answer

Avoiding a skid caused by braking too hard — ABS keeps the wheels from locking, so you can usually steer around a hazard as you brake and avoid skids brought on by over-braking. It may or may not shorten your stop, and it does not add to or take away from your normal braking power.

Answer

Stopping in about half the usual distance

Answer

Braking with more force than your normal brakes could give

Answer

Keeping the brakes working after the air pressure is gone

Question 5

Your pre-trip check shows air pressure building more slowly than it should. Besides being a repair item, why does the manual say this matters on the road?

Accepted Answer

Pressure could drop too low while you drive, forcing an emergency stop — If pressure does not build fast enough, it may fall too low during a trip and leave you needing an emergency stop, so the manual says not to drive until the problem is fixed. At operating rpm, a dual system should climb from 85 to 100 psi in no more than 45 seconds.

Answer

The safety valve will open and vent all the air

Answer

The ABS will shut off until the tanks are full

Answer

The spring brakes will refuse to apply when you park

Question 6

During your pre-trip leakage test, the air pressure falls faster than the allowed rate. What does the manual say to do, and why?

Accepted Answer

Find and fix the leaks before driving, or you could lose your brakes on the road — An air loss rate above the limit is too much to drive with. Check for the leaks and get them fixed first; otherwise the brakes could fail while you are driving.

Answer

Drive gently to the next shop, since leaks only matter under hard braking

Answer

Drain the air tanks and run the test again until it passes

Answer

Raise the governor cut-out pressure to make up for the leak

Question 7

Some buses have dual parking control valves fed by a separate air tank. What is that separate tank there to do?

Accepted Answer

Release the spring brakes so the bus can be moved in an emergency after main air is lost — Losing main air pressure makes the spring brakes apply. The separate tank lets you push in the spring-loaded control and release them so you can move the bus out of danger, but it holds only enough air to do that a few times.

Answer

Keep the service brakes working normally after main air is lost

Answer

Supply air to the horn and wipers when the compressor stops

Answer

Refill the main tanks when the governor fails

Question 8

Your trailer has ABS, but your tractor does not. During a hard stop, the tractor starts to jackknife. What should you do?

Accepted Answer

Ease up on the brakes, if that's safe, until you regain control — With ABS only on the trailer, the trailer is less prone to swinging out, but the tractor can still lose steering control or jackknife. If that starts to happen, the manual says to ease off the brakes, as long as it is safe, until you have control again.

Answer

Hold the brakes fully on so the trailer's ABS can straighten the rig

Answer

Pump the brakes rapidly until the trailer's ABS lamp comes on

Answer

Pull the trailer hand valve to brake only the trailer

Question 9

You're using controlled braking in an emergency stop when you realize you need a bigger steering correction than small movements allow. What should you do?

Accepted Answer

Release the brakes, then put them back on as soon as you can — Controlled braking means braking as firmly as possible while stopping short of wheel lockup, with only very small steering movements. If a bigger steering correction is needed, or the wheels lock up, come off the brakes and get back on them as soon as you can.

Answer

Keep full pressure on the pedal and steer harder

Answer

Switch to the parking brake and steer with both hands

Answer

Pump the pedal lightly while making the larger turn

Question 10

While driving, you glance at your supply gauge and see it reading 50 psi, yet no low air warning of any kind has come on. What does this tell you?

Accepted Answer

The warning has failed, because it should have come on before pressure fell below 55 psi — A visible low air warning has to activate before tank pressure drops under 55 psi. At 50 psi with no warning, the warning device has failed, and you are already low on air, so get stopped safely and have the system repaired.

Answer

Nothing is wrong; the warning is meant to come on at about 20 psi

Answer

The gauge must be broken, because tank pressure never drops below 100 psi

Answer

The warning waits for the governor cut-in point before it turns on

Question 11

On a newer tractor, the ABS malfunction lamp does its start-up bulb check but then stays lit instead of going out. What may this mean?

Accepted Answer

ABS may no longer be working at one or more wheels — On newer vehicles the lamp lights briefly at start-up as a bulb check, then shuts off. If it stays on after that, or comes on while you are driving, ABS may have quit at one or more wheels. Your regular brakes still work, so drive normally and have the ABS serviced soon.

Answer

Your normal service brakes have stopped working

Answer

The spring brakes are about to apply

Answer

Nothing; the lamp always stays on until the air is fully built up

Question 12

Your truck's low air warning is an automatic wig wag, and its arm has dropped into view. Once the compressor brings system pressure back above 55 psi, what does the arm do?

Accepted Answer

It rises back out of view by itself — An automatic wig wag lifts itself back out of your line of sight when pressure climbs above 55 psi. Only the manual-reset type has to be moved out of view by hand.

Answer

It stays down until a mechanic resets it

Answer

It stays down until the engine is shut off and restarted

Answer

It must be pushed up by hand before it will clear

Nevada CDL — Air Brakes: Handling Emergencies practice test

Study questions with answers

1. Your tractor has ABS, but the trailer you are pulling does not. Compared with having no ABS anywhere, what does the tractor's ABS help with during hard braking?

2. The low air warning comes on, and you are tempted to keep driving until the spring brakes stop you. Which of these is NOT a reason the manual gives for stopping right away instead?

3. In a typical dual air brake truck, you notice the secondary system's pressure sinking while the primary holds steady. Which brakes are probably not working fully, and what should you expect?

4. You have to brake hard on a slippery road in a truck with working ABS. Which result can you reasonably expect ABS to help with?

5. Your pre-trip check shows air pressure building more slowly than it should. Besides being a repair item, why does the manual say this matters on the road?

6. During your pre-trip leakage test, the air pressure falls faster than the allowed rate. What does the manual say to do, and why?

7. Some buses have dual parking control valves fed by a separate air tank. What is that separate tank there to do?

8. Your trailer has ABS, but your tractor does not. During a hard stop, the tractor starts to jackknife. What should you do?

9. You're using controlled braking in an emergency stop when you realize you need a bigger steering correction than small movements allow. What should you do?

10. While driving, you glance at your supply gauge and see it reading 50 psi, yet no low air warning of any kind has come on. What does this tell you?

11. On a newer tractor, the ABS malfunction lamp does its start-up bulb check but then stays lit instead of going out. What may this mean?

12. Your truck's low air warning is an automatic wig wag, and its arm has dropped into view. Once the compressor brings system pressure back above 55 psi, what does the arm do?

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