Maryland CDL — Air Brakes Practice Test 9

1.Which statement about what ABS does for your stopping is accurate?

It always cuts your stopping distance roughly in halfIt replaces your normal service brakes entirelyIt increases your braking power on dry pavementIt won't always shorten the distance to stop but helps you stay in control

2.On a tractor or straight truck, the spring brakes come fully on when air pressure drops into roughly what range?

80 to 100 psi20 to 45 psi100 to 125 psi125 to 150 psi

3.During the air leakage test on a single vehicle with the engine off and brakes released, what is the maximum acceptable pressure loss?

Up to 10 psi in one minuteLess than two psi in one minuteLess than six psi in one minuteAny loss under 20 psi in one minute

4.What is brake lag, the extra delay that air brakes add to stopping?

The distance you coast before noticing a hazardThe short delay while air travels through the lines to the brakesThe time it takes the compressor to refill the tanksThe gap between the tractor and the trailer brakes

5.What is the air compressor's job in the brake system?

It bleeds moisture out of the reservoirsIt forces air into the storage tanks or reservoirsIt measures how much pressure remains in the tanksIt automatically applies the parking brakes when you stop

6.Why must you drain the water and oil out of the air tanks?

To make the compressor run more quietlyBecause trapped water can freeze and lead to brake failureTo raise the governor cut-out pressureTo keep the brake lights from staying on

7.What should you always do before leaving your vehicle unattended?

Leave the engine running to keep the tanks chargedRelease the parking brakes so the vehicle can be movedApply the parking brakes or chock the wheelsOpen the air tank drains to empty the reservoirs

8.Total stopping distance for an air brake vehicle is made up of which four parts?

Perception, reaction, cornering, and braking distancePerception, reaction, coasting, and braking distanceReaction, braking, skidding, and rolling distancePerception, reaction, brake lag, and braking distance

9.What is physically going wrong inside a drum brake when too much heat makes the brakes fade?

The air lines soften and start bleeding pressure out of the chamberThe lining grips less and the drum swells, so the shoes reach farther and push with weaker forceThe slack adjuster tightens up and drags the shoes against the drumThe s-cam turns the wrong way and holds the shoes apart

10.In a dual air brake system, what is the effect if one of the two systems gets very low on pressure?

Nothing changes because the other system compensates fullyIt will take you longer to stopThe parking brakes release automaticallyThe vehicle stops more quickly than normal