Massachusetts CDL — Air Brakes Practice Test 9

11.According to the manual, which defect turns up most often during roadside inspections?

Brakes that are out of adjustmentWorn or bald tiresCracked windshieldsBurned-out lights

12.What does the manual say about braking with the front wheels?

Front brakes should be shut off on wet roadsFront brakes should be used only above 55 mphFront-wheel braking is the leading cause of jackknifingFront-wheel braking helps in all conditions, and skids from it are unlikely even on ice

13.With the system charged, the engine off, and the foot brake fully applied, the pressure on a combination vehicle should not fall more than how much in one minute?

2 psi3 psi4 psi6 psi

14.What is the role of the service brake system?

It applies and releases the brakes with the pedal during ordinary drivingIt holds the vehicle still after you park and walk awayIt stops the vehicle only when an air line rupturesIt feeds compressed air to the tires

15.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

16.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

17.How are your brake lights switched on when you apply the air brakes?

By a cable linked to the pedalBy an electric switch operated by air pressureBy the ABS control unitBy the governor when it cuts out

18.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

19.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

20.If the safety valve begins letting air escape, what does that indicate?

The governor has just cut the compressor inThe tanks are correctly charged and nothing is wrongYou should keep driving until the pressure falls on its ownSomething is wrong and a mechanic should fix it