Nevada CDL — Air Brakes: Safe Driving Practices Practice Test

Question 1

On your walk-around, you find a brake fitted with an automatic slack adjuster that is out of adjustment. What does the manual recommend?

Accepted Answer

Take the vehicle to a repair shop promptly so the fault can be fixed — An automatic adjuster that is out of adjustment points to a mechanical fault, so the manual recommends getting the vehicle to a repair shop promptly. Hand-adjusting it is meant only as a temporary fix in an emergency, because it usually hides the problem rather than solving it.

Answer

Back the adjuster off so the brake drags less

Answer

Leave it, since it will correct itself on the next hard stop

Answer

Adjust it by hand and treat the matter as fixed

Question 2

The safety relief valve on the first air tank protects the system from too much pressure. At about what pressure is it usually set to open?

Accepted Answer

About 150 psi — The safety valve is normally set to open at about 150 psi, well above the governor's cut-out of around 125 psi. If it ever releases air, something is wrong and a mechanic should fix it.

Answer

About 55 psi

Answer

About 100 psi

Answer

About 250 psi

Question 3

How does the manual have you fit the extra air brake items into a pre-trip inspection?

Accepted Answer

Do the regular seven-step inspection and add each air brake check in the step where it belongs — Air-braked vehicles are inspected with the same basic seven-step procedure, but there are more items to check. The manual places each one in the step where it fits: the compressor belt in the engine compartment step, the slack adjusters, drums, linings and hoses in the walk-around, and the final air brake checks in place of the hydraulic brake check in Step 7.

Answer

Skip the seven-step inspection and do only the air brake checks

Answer

Finish the seven steps, then do every air brake item as a separate eighth step

Answer

Do the air brake checks only when the low air warning has come on

Question 4

You're several hours into a trip in an air-braked truck. Which gauge does the manual list, for air brake vehicles, among the instruments to keep checking while you drive?

Accepted Answer

The air pressure gauge — The manual's list of things to check regularly during a trip includes the air pressure gauge if your vehicle has air brakes, along with the other gauges, mirrors, tires, cargo, and lights.

Answer

No gauges; they are checked only during the pre-trip inspection

Answer

Only the fuel gauge

Answer

Only the tachometer

Question 5

In the Nevada manual's suggested air brake check, you keep pumping the foot brake to bring pressure down toward roughly 20 to 40 psi. What are you watching for at that stage?

Accepted Answer

The tractor protection valve and parking brake knob popping out — Nevada's suggested sequence has you pump down to about 20 to 40 psi and look for both the tractor protection valve and the parking brake knob to pop out. That shows the spring brakes are applying as air runs low.

Answer

The governor cutting the compressor back in

Answer

The low air warning light switching off

Answer

The safety relief valve venting air

Question 6

In an air brake system, where are the foundation brakes found?

Accepted Answer

At each wheel — Foundation brakes are the braking units used at every wheel. The s-cam drum brake is the most common type; wedge brakes and disc brakes are also used but are less common.

Answer

Only on the steering axle

Answer

Only on the drive axles

Answer

Inside the first air tank

Question 7

According to the manual, what must be true for air brakes to stay a good, safe way of stopping large, heavy vehicles?

Accepted Answer

They must be kept well maintained and used properly — The manual praises air brakes for big, heavy vehicles, but only on the condition that they are kept in good repair and the driver uses them the right way.

Answer

They must be backed up by a second air compressor

Answer

They must be paired with hydraulic brakes on the front axle

Answer

They must be released only with the engine shut off

Question 8

Compressed air in a brake system usually carries a little water. Why does the manual single that water out as a hazard in cold weather?

Accepted Answer

It can freeze and cause the brakes to fail — Water and compressor oil in the air are both bad for the brake system, and in cold weather the water can freeze and lead to brake failure. They collect at the bottom of each tank, which is why tanks without automatic drains need to be drained at the close of each working day.

Answer

It thins the compressor oil so the compressor overheats

Answer

It makes the safety valve open at a lower pressure

Answer

It fogs the supply pressure gauge so you can't read it

Question 9

Your truck's air system has an alcohol evaporator. During a stretch of cold weather, how often should you check its alcohol container and top it up as needed?

Accepted Answer

Every day — In cold weather the manual wants the alcohol container checked, and refilled if needed, daily. The alcohol helps keep ice from forming in brake valves and similar parts, and ice inside the system can stop the brakes from working.

Answer

Once a week

Answer

Only when the low air warning comes on

Answer

Only at the yearly brake service

Question 10

During the service brake test, you creep forward at about 5 mph and brake firmly with the pedal. Which of these should you be watching for?

Accepted Answer

The truck pulling to one side, an odd feel, or slow stopping — The point of this low-speed test is to catch trouble before you need the brakes in traffic. Note whether the vehicle pulls to one side, whether the brakes feel unusual, or whether the stop comes late.

Answer

The low air warning coming on as you stop

Answer

The spring brakes popping on as the truck stops

Answer

The governor cutting the compressor back in

Question 11

Over one week you drive three tractor-trailers: one with ABS only on the tractor, one with ABS only on the trailer, and one with ABS on both. How should your braking technique change from rig to rig?

Accepted Answer

It shouldn't; brake the same way, using only enough force to stop safely and keep control — The manual says to brake as you always have no matter which units carry ABS: use only as much braking force as you need to stop safely and keep control, and watch the tractor and trailer so you can ease off if you need to. The one exception: if you always drive a truck or combination that has working ABS on all its axles, the manual allows full braking in an emergency stop.

Answer

Brake harder on the rig with ABS on both units, since it cannot skid

Answer

Pump the brakes on the rig with ABS on the tractor only

Answer

Use the trailer hand valve alone on the rig with ABS on the trailer only

Question 12

You open the valve on a manually drained air tank at the end of the day. How much should you let out?

Accepted Answer

Drain the tank completely so the water and oil are removed — Water and compressor oil settle at the bottom of each tank and are harmful to the air brake system, so the manual tells you to empty the tanks completely rather than just cracking the valve.

Answer

Only a quick burst, so you don't lose any working pressure

Answer

Just enough to hear air escaping, then close the valve

Answer

None while the tank is cold; wait until the next morning

Nevada CDL — Air Brakes: Safe Driving Practices practice test

Study questions with answers

1. On your walk-around, you find a brake fitted with an automatic slack adjuster that is out of adjustment. What does the manual recommend?

2. The safety relief valve on the first air tank protects the system from too much pressure. At about what pressure is it usually set to open?

3. How does the manual have you fit the extra air brake items into a pre-trip inspection?

4. You're several hours into a trip in an air-braked truck. Which gauge does the manual list, for air brake vehicles, among the instruments to keep checking while you drive?

5. In the Nevada manual's suggested air brake check, you keep pumping the foot brake to bring pressure down toward roughly 20 to 40 psi. What are you watching for at that stage?

6. In an air brake system, where are the foundation brakes found?

7. According to the manual, what must be true for air brakes to stay a good, safe way of stopping large, heavy vehicles?

8. Compressed air in a brake system usually carries a little water. Why does the manual single that water out as a hazard in cold weather?

9. Your truck's air system has an alcohol evaporator. During a stretch of cold weather, how often should you check its alcohol container and top it up as needed?

10. During the service brake test, you creep forward at about 5 mph and brake firmly with the pedal. Which of these should you be watching for?

11. Over one week you drive three tractor-trailers: one with ABS only on the tractor, one with ABS only on the trailer, and one with ABS on both. How should your braking technique change from rig to rig?

12. You open the valve on a manually drained air tank at the end of the day. How much should you let out?

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