Nevada CDL — Air Brakes Practice Test 8

1.Which rule does the manual give for leaving an air-braked vehicle unattended?

Chock the wheels only when parked on a gradeLeave the engine running so the air pressure stays upSet the parking brakes or chock the wheels every timeSkip the parking brakes if you'll be back within an hour

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

Hold the brakes fully on so the trailer's ABS can straighten the rigPump the brakes rapidly until the trailer's ABS lamp comes onEase up on the brakes, if that's safe, until you regain controlPull the trailer hand valve to brake only the trailer

3.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?

About 55 psiAbout 100 psiAbout 150 psiAbout 250 psi

4.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?

A heavily loaded vehicle needs a long way to stop on spring brakes, since they don't act on every axleA lightly loaded vehicle, or one on a slick road, could go into an uncontrolled skid once the spring brakes applySpring brakes let go by themselves after a few seconds, so the vehicle will start rolling againYou can control your braking with the pedal only while enough air is left in the tanks

5.You're in the proper low gear at the top of a long, steep downgrade. How does the manual describe the role of your service brakes on the way down?

They should hold the truck at a steady speed with light, constant pressureThey back up the engine's braking, which does the main workThey do most of the work, with the engine as a backupThey are needed only if the ABS lamp comes on

6.A dual air brake system is really two separate air brake systems. How does the driver work them?

With a separate brake pedal for each systemWith one pedal for normal driving and a hand valve for the second systemBy switching between the two systems with a dash selectorWith a single set of brake controls that serves both systems

7.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?

It stays down until a mechanic resets itIt stays down until the engine is shut off and restartedIt must be pushed up by hand before it will clearIt rises back out of view by itself

8.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?

The governor cutting the compressor back inThe tractor protection valve and parking brake knob popping outThe low air warning light switching offThe safety relief valve venting air

9.On a newer air-braked truck, what does the parking brake control look like, and how do you set the brakes with it?

A round blue knob; push it in to set the brakesA red, eight-sided knob; give it a quarter turn to set the brakesA yellow, diamond-shaped knob; push it in to set the brakesA yellow, diamond-shaped knob; pull it out to set the brakes

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

Back the adjuster off so the brake drags lessLeave it, since it will correct itself on the next hard stopAdjust it by hand and treat the matter as fixedTake the vehicle to a repair shop promptly so the fault can be fixed