Texas CDL — Air Brakes Practice Test 8

1.On newer air-braked vehicles the parking brake control is a yellow, diamond-shaped knob. On older vehicles, what might it look like instead?

A red octagonal button on the steering columnA green square switch on the floorA foot pedal to the left of the clutchA round blue knob or a lever

2.If a leak drains all the air out of the brake system while you drive, what physically applies the spring brakes?

Hydraulic backup pressureThe force of powerful springs no longer held back by air pressureThe electric stop light switchVacuum stored in a reserve tank

3.How does having antilock brakes affect the stopping distance of an air-braked truck?

It always cuts the stopping distance roughly in half on dry pavementIt adds extra brake lag, so the stopping distance gets longerIt lets you safely follow other vehicles more closely than you could without itIt may not shorten the stop, but it helps you keep control during hard braking

4.Some buses have dual parking control valves and a separate air tank that can release the spring brakes after main air pressure is lost. Why must you plan carefully before using it to move?

The separate tank holds only enough air to release the brakes a few timesUsing it disables the service brakes until the whole system is repaired by a mechanicIt releases the spring brakes on the front axle onlyIt works only while the engine is shut off

5.You want a Texas CDL with no air brake restriction. Which pair of requirements must you meet?

Complete 40 hours of range training and pass a road sign quizHold the license for one year and file a medical certificatePass only the general knowledge test and pay an extra endorsement feePass the air brakes knowledge test and test in an air-braked vehicle

6.What is the main reason some vehicles have a modulating control valve that applies the spring brakes gradually?

To hold the vehicle on a hill while the driver shifts gearsTo test the leakage rate during the pre-trip inspectionTo let you brake with the springs if the service brakes failTo keep the spring brakes from applying when air pressure drops

7.While driving down a long hill, you notice you must push the pedal harder and harder to get the reading shown on the application pressure gauge to hold the same speed. What does this increasing application pressure tell you?

The brakes are fading and you should slow down and use a lower gearThe governor cut-out setting is too highThe air compressor is overcharging the tanksThe stop light switch has failed

8.Why does an air-braked vehicle need a greater following distance than a car traveling the same speed?

Brake lag adds stopping distance that hydraulic brakes do not haveAir brakes only work below 45 mphTrucks have better tires, so they can follow closer if neededThe governor limits how hard the pedal can be pressed

9.You park an air-braked truck and leave the cab to make a delivery. What does safe practice require you to do first?

Leave the engine running so tank pressure cannot dropApply the parking brakes by pulling the yellow diamond-shaped knob outPush the yellow knob in to lock the spring brakesHold the treadle valve down with a block of wood

10.Your air compressor has its own oil supply instead of using engine oil. What should you do before driving?

Drain the oil so it cannot reach the air tanksCheck the compressor's oil levelAdd alcohol to the compressor oil reservoirNothing, because the governor monitors compressor oil automatically