Massachusetts CDL — Air Brakes Practice Test 1

11.The governor stops the compressor from pumping at the "cut-out" point. About what pressure is that?

About 55 psiAbout 125 psiAbout 100 psiAbout 150 psi

12.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

13.You always drive a rig whose antilock system is working on every axle. According to the manual, what does that change about an emergency stop?

You may follow other traffic more closely, since the stop will always be shorterYou should still pump the pedal in short stages the way stab braking calls forNothing changes; controlled braking is required no matter what equipment you haveYou may press the brake pedal all the way down rather than metering it short of lockup

14.If one half of a dual air brake system loses most of its pressure while driving, what is the result?

The vehicle stops instantly with no warningEither the front or the rear brakes lose full power, so it takes longer to stopThe other half shuts down as wellNothing changes, since the halves are identical

15.With the system fully charged, the engine off, and the parking brake released, the air loss on a single vehicle should stay under how much per minute?

2 psi3 psi4 psi6 psi

16.Some buses have dual parking control valves fed by a small separate air tank. What is that tank for?

Keeping the alcohol evaporator topped offReleasing the spring brakes a limited number of times so the vehicle can be moved during an emergencySupplying extra pressure to the front brakesPowering the ABS computer

17.For an average driver on dry pavement in good conditions, the total stopping distance of an air-brake vehicle at 55 mph is roughly how far?

About 60 feetAbout 250 feetMore than 450 feetAbout 100 feet

18.On a dual air system running at operating rpm, roughly how long should it take pressure to climb from 85 to 100 psi?

10 seconds45 seconds2 minutes3 minutes

19.How can brakes that are out of adjustment lead to a complete loss of braking on a long grade?

They quit carrying their share, so the remaining brakes take the extra heat, fade, and leave too little stopping powerThey lock their wheels first, which actually shortens the stopThey force the governor to cut the compressor out earlyThey raise the pressure at which the spring brakes apply

20.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