Alaska CDL — Air Brakes: Handling Emergencies Practice Test

Question 1

Spring brakes on tractors and straight trucks come fully on somewhere between 20 and 45 psi. What narrower range does the manual call typical?

Accepted Answer

20 to 30 psi — The manual gives 20 to 45 psi as the full range and 20 to 30 psi as typical. It also warns you not to wait for that: stop safely the moment the low air warning first shows.

Answer

30 to 45 psi

Answer

40 to 45 psi

Answer

35 to 40 psi

Question 2

Your air compressor stops working while you are on the road. What does the manual say about the air already held in the storage tanks?

Accepted Answer

It is enough to let you use the brakes several times — Air storage tanks hold a reserve of compressed air. The manual says that reserve allows several brake applications even with the compressor out of action, which is a long way from normal braking for hours.

Answer

It will keep the brakes working normally for the rest of the day

Answer

It is vented at once, so the brakes lock immediately

Answer

It can release the parking brakes but cannot apply the service brakes

Question 3

The manual tells drivers to use only the braking force needed to stop safely, with one exception. Who may fully apply the brakes in an emergency stop?

Accepted Answer

A driver whose straight truck or combination always has working ABS on all axles — Normally you brake the same way with or without ABS and ease off when you need to stay in control. The single exception the manual gives is a vehicle with working ABS on all of its axles, where the brakes can be fully applied in an emergency stop.

Answer

Any driver whose tractor has working ABS, no matter what the trailer behind it is equipped with

Answer

Any driver whose trailer has working ABS, whatever the tractor is equipped with

Answer

Any driver braking on dry pavement, whether or not the vehicle has ABS at all

Question 4

The low pressure warning signal has failed on a vehicle with a single-circuit air system, and air is leaking away without the driver knowing. What does the manual say this could cause?

Accepted Answer

Sudden emergency braking — Without a working warning you could lose air and never know it. In a single-circuit system the manual says that can bring on sudden emergency braking; in a dual system the stopping distance grows, and only limited braking is left before the spring brakes apply.

Answer

A gradual, gentle stop with no risk

Answer

The compressor running backward

Answer

The ABS taking over the braking

Question 5

Brake fade comes from too much heat. What does the manual say that heat does to the brake lining?

Accepted Answer

It causes chemical changes in the lining that cut friction — Overusing the service brakes overheats them. The manual explains that the heat changes the lining chemically, which lowers friction, and that it also makes the drums expand.

Answer

It makes the lining swell and grab harder

Answer

It welds the lining to the drum

Answer

It hardens the lining so it grips better and lasts longer on the next grade

Question 6

A car darts out ahead of you and you brake hard. According to the manual, what should the way you brake allow?

Accepted Answer

The vehicle stays in a straight line and you can still turn if you have to — Braking is a good response when there is enough distance and the brakes are used correctly. The manual's aim is to hold a straight line while leaving you able to steer, using either controlled braking or stab braking.

Answer

The wheels lock so the tires bite into the road

Answer

The spring brakes come on quickly to add to the stopping force of the service brakes

Answer

The trailer brakes apply before the tractor brakes

Question 7

You move from driving a truck to driving a large bus. How does the manual say the bus's low pressure warning commonly differs?

Accepted Answer

It commonly signals at a higher pressure, about 80 to 85 psi — On most vehicles the warning comes on before 55 psi. The manual adds that large buses commonly have warning devices that signal earlier, at 80 to 85 psi.

Answer

It is not required on buses

Answer

It signals only once pressure has fallen under 20 psi in both tanks

Answer

It is a blue light instead of a red one

Question 8

The low air pressure warning must normally come on before tank pressure falls below 55 psi. What different mark does the manual give for older vehicles?

Accepted Answer

One half of the compressor governor's cut-out pressure — A warning you can see is required on air-braked vehicles. It has to come on before pressure drops below 55 psi, or on older vehicles before it drops below half of the governor cut-out pressure.

Answer

The governor's cut-in pressure

Answer

The safety valve's opening pressure

Answer

Ten psi above the range where the spring brakes come on

Question 9

On a bus with dual parking control valves, you hold in the spring-loaded control to move the bus after main air pressure is lost. What happens when you let go of it?

Accepted Answer

The spring brakes come back on — Pushing that control in sends air from a separate tank to release the spring brakes so the vehicle can be moved in an emergency. The control is spring loaded toward the 'out' position, so releasing it puts the spring brakes on again.

Answer

The control stays in and the brakes stay released

Answer

The main air tanks refill from the separate tank

Answer

The service brakes return to full power

Question 10

A bus's spring brakes have come on after a loss of main air pressure, and you can release them with air from a separate tank. Why does the manual tell you to plan your move carefully?

Accepted Answer

The separate tank holds air for only a few releases, and you could be left stopped somewhere dangerous — The separate air supply is small. Once it runs out the spring brakes stay on, so the manual warns that poor planning could leave you stuck in a dangerous spot.

Answer

Using the separate tank disables the ABS

Answer

The separate tank refills only while the bus is rolling, so stopping too early leaves it empty for the next driver

Answer

Each release shortens the life of the brake linings

Question 11

Your truck's wig wag is the manual reset type. Its arm has dropped, and you try to put it back while pressure is still under 55 psi. What happens?

Accepted Answer

It will not stay out of view until system pressure is above 55 psi — An automatic wig wag lifts away by itself once pressure recovers. The manual reset kind has to be moved back by hand, and it won't hold there until the system is back above 55 psi.

Answer

It locks out of view and cancels the warning until the next time you start the engine

Answer

It releases the spring brakes

Answer

It makes the compressor cut in early

Question 12

An air brake system includes an emergency brake system. How does the manual describe what it is made of?

Accepted Answer

Pieces borrowed from the service brake and parking brake systems, which stop the vehicle if the brakes fail — The manual counts three braking systems in an air brake setup: service, parking and emergency. The emergency system is not separate hardware; it draws on parts of the other two to bring the vehicle to a stop when the brake system fails.

Answer

A separate hydraulic circuit with its own fluid reservoir

Answer

The engine retarder and exhaust brake, which need no air and work apart from the brake system

Answer

A hand-operated cable that clamps the driveshaft

Alaska CDL — Air Brakes: Handling Emergencies practice test

Study questions with answers

1. Spring brakes on tractors and straight trucks come fully on somewhere between 20 and 45 psi. What narrower range does the manual call typical?

2. Your air compressor stops working while you are on the road. What does the manual say about the air already held in the storage tanks?

3. The manual tells drivers to use only the braking force needed to stop safely, with one exception. Who may fully apply the brakes in an emergency stop?

4. The low pressure warning signal has failed on a vehicle with a single-circuit air system, and air is leaking away without the driver knowing. What does the manual say this could cause?

5. Brake fade comes from too much heat. What does the manual say that heat does to the brake lining?

6. A car darts out ahead of you and you brake hard. According to the manual, what should the way you brake allow?

7. You move from driving a truck to driving a large bus. How does the manual say the bus's low pressure warning commonly differs?

8. The low air pressure warning must normally come on before tank pressure falls below 55 psi. What different mark does the manual give for older vehicles?

9. On a bus with dual parking control valves, you hold in the spring-loaded control to move the bus after main air pressure is lost. What happens when you let go of it?

10. A bus's spring brakes have come on after a loss of main air pressure, and you can release them with air from a separate tank. Why does the manual tell you to plan your move carefully?

11. Your truck's wig wag is the manual reset type. Its arm has dropped, and you try to put it back while pressure is still under 55 psi. What happens?

12. An air brake system includes an emergency brake system. How does the manual describe what it is made of?

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