Texas CDL — Air Brakes Practice Test 2

1.By law, when must the low air pressure warning signal in an air-braked vehicle activate?

Before tank pressure drops below 55 psiOnly after the spring brakes have appliedWhen pressure exceeds 125 psiWhen pressure drops below 20 psi

2.Your tractor has a front brake limiting valve with a "normal" and a "slippery" setting. What did the slippery setting do on these older systems, and how should the control be set?

It doubled front brake pressure; use slippery only in rainIt reduced front brake air pressure by half; leave the valve in normalIt disconnected the rear brakes; use slippery on ice onlyIt engaged the spring brakes; never move it while driving

3.For a normal stop in a vehicle with air brakes and a manual transmission, how should you use the brake pedal?

Stab the pedal repeatedly so the linings stay coolPush the clutch in first, then coast to the stopUse the parking brake knob for all routine stopsBrake smoothly to a safe stop, clutching only near idle rpm

4.Using the proper snub braking technique on a long downgrade, the safe speed is 40 mph. When and how should you brake?

Hold light, steady pedal pressure all the way down the gradeBrake only if you exceed 55 mph, then stop completely on the shoulderAt 40 mph, brake firmly down to about 35 mph, release, and repeatApply the parking brake in short pulls every few hundred feet

5.What does an "L" restriction on a commercial driver license mean?

The driver may only operate vehicles in intrastate commerceThe driver may not operate a CMV with any type of air brakesThe driver may not tow trailers over 10,000 poundsThe driver must wear corrective lenses while driving

6.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

7.In Texas, you take the CDL skills test in a truck that is not equipped with air brakes. What happens to your license?

It is issued with a restriction prohibiting you from driving air-braked vehiclesIt is denied until you retake the general knowledge testNothing changes, since air brakes are covered by the vision screeningYou receive a temporary 30-day air brake permit

8.What is "controlled braking" in an emergency stop?

Pumping the pedal rapidly to keep the brake lights flashingUsing only the trailer hand valve to slow graduallyBraking as hard as possible without locking the wheelsLetting the spring brakes make the stop for you

9.Your brakes got soaked while you drove through deep water, and the temperature is near freezing. What should you do about the wet brakes?

Set the parking brake hard right away so the wet shoes seat firmly against the drumsDrive in a low gear while lightly applying the brakes so the heat dries themSpray the drums with alcohol from the evaporatorDrain the air tanks twice to pull the water out of the brakes

10.During inspection you check push rod travel on an s-cam brake with a manual slack adjuster. When you pull hard on the push rod, about how much movement means the brake needs adjustment?

More than one inchMore than one quarter inchMore than three inchesAny movement at all