Wyoming CDL — Air Brakes: Handling Emergencies Practice Test

Question 1

Section 11M explains why the air lines running to a trailer are inspected. What does it say a low air condition in those lines will cause?

Accepted Answer

The trailer's spring brakes to apply suddenly — According to Section 11M, low air to the trailer makes its spring brakes apply suddenly, which can mean loss of control and a crash. It adds that losing air to the trailer costs the towed unit some or all of its braking.

Answer

The tractor's governor to cut out early

Answer

The trailer's ABS lamp to go dark

Answer

The trailer's service brakes to release and stay released

Question 2

Air is leaking away steadily as you drive a straight truck. According to the figures in Wyoming's Section 5, in what order do things happen as the pressure falls?

Accepted Answer

The low air warning comes on before 60 psi; the spring brakes come fully on somewhere between 20 and 45 psi — The warning has to come on before tank pressure drops below 60 psi, and tractor and straight truck spring brakes come fully on when pressure reaches the 20 to 45 psi range. The gap between the two is the driver's chance to stop while the brakes can still be controlled.

Answer

The spring brakes come fully on at 60 psi; the low air warning follows at 45 psi

Answer

The safety valve opens at 60 psi; the low air warning follows at 20 psi

Answer

The governor cuts out at 60 psi; the spring brakes come on at 100 psi

Question 3

If a driver ignores a low air warning, falling pressure will eventually bring the spring brakes on by themselves. Which pairing of vehicle and risk matches the manual?

Accepted Answer

Heavily loaded vehicle: a long stopping distance, because spring brakes do not act on every axle — A heavy vehicle takes a long way to stop on spring brakes alone, since they are not on all axles. A lightly loaded vehicle, or any vehicle on a slick road, may instead skid out of control, so the manual says to stop while there is still air for the foot brakes.

Answer

Lightly loaded vehicle: no effect, because spring brakes need a full load to apply

Answer

Heavily loaded vehicle: an abrupt stop, because its weight adds braking force

Answer

Lightly loaded vehicle: a longer stop than a loaded one, because the springs apply slowly

Question 4

You are driving a large bus when the low air warning comes on, yet the gauge still reads a little above 80 psi. Does that mean the warning device is faulty?

Accepted Answer

Not necessarily; on large buses the warning commonly signals at 80 to 85 psi — The manual notes that on large buses the low pressure warning commonly signals at 80 to 85 psi, well above the 60 psi mark it gives for other vehicles. A warning at that reading is what the manual describes, and it still means stopping and parking safely.

Answer

Yes, it should stay quiet until 60 psi

Answer

Yes, a warning above 60 psi means the governor has failed

Answer

Not necessarily; bus warnings are set to match the 125 psi cut-out

Question 5

Wig-wag low air warnings come in an automatic type and a manual reset type. How do they differ once pressure is back above the warning level?

Accepted Answer

The automatic arm rises out of view by itself; the manual reset arm has to be put out of view by hand — An automatic wig-wag lifts out of the driver's view by itself once system pressure is back over 60 psi. With the manual reset kind, the driver has to move the arm to the out-of-view position, and it will not stay there until pressure is above 60 psi.

Answer

The automatic arm has to be pushed up by hand; the manual reset arm rises by itself

Answer

Both arms stay down until the engine is shut off

Answer

The automatic arm sounds a buzzer; the manual reset arm lights a red lamp

Question 6

The emergency brake system on an air-braked vehicle borrows parts from both the service brakes and the parking brakes. When is it meant to stop the vehicle?

Accepted Answer

When there is a brake system failure — Section 5 describes air brakes as three systems. The service brakes handle normal driving, the parking brakes are worked by the parking brake control, and the emergency system is there to stop the vehicle if the brake system fails.

Answer

On every stop made from highway speed

Answer

Whenever the vehicle is parked on a grade

Answer

When ABS is working on a slippery road

Question 7

As a dual-system truck airs up, its low air light and buzzer go quiet when the gauges pass 50 psi. How does that compare with Wyoming's manual?

Accepted Answer

It is too early: the shut-off value is set by the manufacturer but must be above 60 psi — The manual says the light and buzzer should go off once both systems have climbed to a value the manufacturer sets, and that value has to be greater than 60 psi. The same section says the warning should come on before pressure in either system falls below 60 psi.

Answer

It is correct: the warning should shut off at half the cut-out pressure

Answer

It is too late: the warning should shut off by 30 psi

Answer

It is correct: any shut-off point between 20 and 45 psi is acceptable

Question 8

ABS is meant to prevent skids and jackknifes that braking sets off. Which kind of skid do the manual's ABS safety reminders say it will NOT prevent?

Accepted Answer

A skid from spinning the drive wheels or taking a turn too fast — The safety reminders say ABS should prevent brake-induced skids and jackknifes, but not power skids or turning skids. Those come from spinning the drive wheels or going into a turn at too high a speed.

Answer

A skid from locking the steering wheels under hard braking

Answer

A trailer swing set off by overbraking

Answer

A jackknife caused by braking too hard on a wet road

Question 9

Controlled braking and stab braking start out differently. Which statement gets the difference right?

Accepted Answer

Controlled braking stops just short of locking the wheels; stab braking applies the brakes all the way — In controlled braking you brake as hard as you can without the wheels locking. In stab braking you put the brakes on fully, release them when the wheels lock, and apply them fully again once the wheels start to roll.

Answer

Controlled braking applies the brakes all the way; stab braking stops just short of locking the wheels

Answer

Both begin with the lightest pedal pressure that slows the vehicle

Answer

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

Question 10

A driver figures that careful footwork on the pedal can do everything ABS does. How does the manual compare the two when a wheel is about to lock?

Accepted Answer

ABS works far faster than a driver can respond — Sensors detect that a wheel may lock, and the electronic control unit cuts brake pressure to keep it rolling, all more quickly than a driver could react. The rest of the time the brakes work normally.

Answer

ABS and a skilled driver respond at about the same speed

Answer

ABS responds more slowly, but with more braking force

Answer

ABS only warns the driver, who must then ease off the pedal

Wyoming CDL — Air Brakes: Handling Emergencies practice test

Study questions with answers

1. Section 11M explains why the air lines running to a trailer are inspected. What does it say a low air condition in those lines will cause?

2. Air is leaking away steadily as you drive a straight truck. According to the figures in Wyoming's Section 5, in what order do things happen as the pressure falls?

3. If a driver ignores a low air warning, falling pressure will eventually bring the spring brakes on by themselves. Which pairing of vehicle and risk matches the manual?

4. You are driving a large bus when the low air warning comes on, yet the gauge still reads a little above 80 psi. Does that mean the warning device is faulty?

5. Wig-wag low air warnings come in an automatic type and a manual reset type. How do they differ once pressure is back above the warning level?

6. The emergency brake system on an air-braked vehicle borrows parts from both the service brakes and the parking brakes. When is it meant to stop the vehicle?

7. As a dual-system truck airs up, its low air light and buzzer go quiet when the gauges pass 50 psi. How does that compare with Wyoming's manual?

8. ABS is meant to prevent skids and jackknifes that braking sets off. Which kind of skid do the manual's ABS safety reminders say it will NOT prevent?

9. Controlled braking and stab braking start out differently. Which statement gets the difference right?

10. A driver figures that careful footwork on the pedal can do everything ABS does. How does the manual compare the two when a wheel is about to lock?

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