Louisiana CDL — Air Brakes Practice Test 4

11.What is the 'wig wag' low-air warning device?

A buzzer that sounds only below 60 psiA mechanical arm that drops into the driver's view when pressure falls below 60 psiA red light on the trailer's rear cornerA gauge needle that points to the cut-in level

12.What is 'brake lag' in an air brake system?

The short delay for air to reach the brakes after you press the pedalThe time the compressor takes to reach cut-outThe delay before the ABS lamp turns offThe wait before the spring brakes release

13.On vehicles with dual parking control valves and a separate air tank to release the spring brakes, why must you plan your moves carefully?

The separate tank refills only when the vehicle is parkedThe spring brakes will release just once each dayThe separate tank holds only enough air to release the spring brakes a few timesThe valve locks out the service brakes while moving

14.Before driving a vehicle with a dual air system, the compressor should build a minimum of what pressure in both systems?

60 psi45 psi125 psi100 psi

15.Which statement about ABS is accurate?

ABS increases your normal braking powerABS works even during gentle, everyday brakingABS removes the need for regular brakesABS does not necessarily shorten stopping distance but helps you keep control during hard braking

16.What should you do when the low air pressure warning first comes on?

Keep driving until the spring brakes apply on their ownStop the vehicle safely without delay, while you still have enough air to control itPump the brake pedal to rebuild pressureRelease the parking brake control to add air

17.What does a supply pressure gauge tell the driver?

How hard the brakes are being appliedThe temperature of the brake drumsWhether the parking brakes are setHow much air pressure is in the storage tanks

18.How does the emergency brake system stop a vehicle when the brakes fail?

By using a completely separate hydraulic circuitBy pumping extra air directly from the compressorBy drawing on components shared with the service and parking brakesBy locking the transmission in a low gear

19.On the application pressure gauge, needing more and more pressure to hold the same speed is a sign of what?

The brakes are fading, so slow down and use a lower gearThe tanks are overfilled with airThe governor has failedThe parking brakes are dragging

20.Why should you avoid pressing and releasing the brake pedal more than necessary?

It overheats the safety valveIt forces the governor to cut in earlyIt fills the tanks with waterIt can release air faster than the compressor can replace it, dropping pressure until the brakes fail