Massachusetts CDL — Air Brakes Practice Test 2

1.How often should tanks with manually operated drain valves be emptied?

At the end of every day of drivingOnce a weekOnly when the low-air warning soundsEach time you stop for fuel

2.What is a "wig wag" device?

A gauge showing how fast the tanks refillA mechanical arm that drops into your view when system pressure falls below about 55 psiA valve that cuts pressure to the front brakesA lever for applying the spring brakes gradually

3.As soon as the low-air warning light and buzzer come on, what is the correct action?

Keep going until the spring brakes apply themselvesPump the pedal to build pressure back upStop the vehicle somewhere safe immediately, while you still have enough air to control brakingPull the parking-brake knob out while still moving

4.What does a supply pressure gauge tell you?

How hard the brakes are being applied right nowThe temperature of the brake drumsHow much air pressure is stored in the tanksWhether the ABS is functioning

5.Why is it a poor habit to press and release the brake pedal more than you need to?

It can wear out the stop light switchIt forces the safety valve openIt overfills the alcohol evaporatorIt can let air escape more quickly than the compressor can rebuild it

6.Your tractor has ABS but the trailer behind it does not, and during a hard stop the trailer begins to swing out. What does the manual advise?

Push harder on the pedal so the tractor pulls the trailer straightBack off the brake pedal, when it is safe to do so, until the trailer falls back into linePull out the parking-brake control to set the spring brakesSteer sharply toward the side the trailer is swinging to

7.When should you NOT rely on the parking brakes to hold the vehicle?

Any time the vehicle is on level groundWhen the brakes are very hot from a steep grade, or very wet in freezing temperaturesWhenever the tanks are fully chargedWhen the ABS lamp is off

8.You notice you must apply more and more pressure to hold the same speed. What does that usually mean, and what should you do?

The brakes are fading, so slow down and drop to a lower gearThe tanks are overfilled, so drain them at onceThe parking brakes are dragging, so pull the knob outThe governor has failed, so keep driving carefully

9.Which sequence describes the "stab braking" method?

Press the brakes fully, release when the wheels lock, then reapply fully once the wheels start rolling againPump the pedal gently while steering hardSet the parking brake, then add the foot brakeHold steady, light pressure all the way to a stop

10.Using the recommended braking technique on a long, steep downgrade, when do you release the brakes after a snub?

As soon as you touch the pedalAfter your speed has dropped to about 5 mph below your safe speedOnly when you reach the bottom of the hillAfter a full 30 seconds of braking