Maryland CDL — Air Brakes Practice Test 4

1.In a dual air brake system, which brakes does the primary system typically operate?

The service brakes on the rear axle or axlesOnly the parking brakesOnly the trailer's brakesThe front axle brakes exclusively

2.What does an antilock braking system (ABS) do during a hard brake application?

It keeps the wheels from locking upIt automatically increases braking force to the front axleIt shuts off the service brakes and uses only spring brakesIt raises the tank pressure during braking

3.The antilock system on your truck quits working while you are out on the road. What does that mean for your braking?

Your ordinary brakes still work, so keep driving normally and get the system serviced soonYou must shut down where you are, because the vehicle can no longer be stoppedOnly the parking brake control will slow you until the fault is clearedBraking is cut back to the trailer axles alone until a mechanic resets it

4.What is the purpose of an alcohol evaporator in an air brake system?

It lowers the chance of ice building up in the valves during cold weatherIt boosts the octane of the fuel supplyIt replaces the need to check tire pressureIt cools the brake drums after long descents

5.Why is having air storage tanks important on a vehicle with air brakes?

They keep the engine oil cool during long tripsThey add weight to improve traction on the drive axleThey hold enough air to brake several times even if the compressor stopsThey filter road dust out of the incoming air

6.On newer air brake vehicles, how do you set the parking brakes?

Pull out the yellow, diamond-shaped knobPush in the yellow, diamond-shaped knobHold down the brake pedal for several secondsTurn the ignition key to the accessory position

7.On large buses, at about what pressure do the low air pressure warning devices usually signal?

About 20 to 30 psiAbout 80 to 85 psiAbout 100 to 110 psiAbout 40 to 45 psi

8.As soon as the low-pressure warning first comes on while you are driving, what should you do?

Speed up to reach your destination before the air runs outPump the brake pedal repeatedly to rebuild pressureIgnore it until the spring brakes apply by themselvesImmediately pull over and stop safely while you still have air to work the brakes

9.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

10.With the foot brake fully applied for one minute, what pressure loss is too much for a combination vehicle?

More than one psi in one minuteMore than two psi in one minuteMore than three psi in one minuteMore than four psi in one minute