CDL Air Brake Practice Test with Verified Answers
Latest 2025 Graded A+
The parking or emergency brake on a heavy vehicle can only be held in position by
something that cannot leak away, like:
a. Fluid pressure
b. Spring pressure
c. Air pressure
d. Any of the above - Answer- b. Spring pressure
A straight truck or bus air brake system should not leak at a rate of more than __ psi per
minute with the engine off and the brake released.
a. 1
b. 2
c. 3
d. 4 - Answer- c. 3
Your vehicle has dual air brake system. If low air pressure warning comes on for the
secondary system or for one system, you should:
a. Bring the vehicle to a safe stop and continue only when the system is fixed.
b. Reduce your speed, and test the remaining system while under-way.
c. Reduce your speed, and drive to the nearest garage for repairs.
d. Continue at normal speed if only the secondary system fails. - Answer- a. Bring the vehicle
to a safe stop and continue only when the system is fixed.
If your vehicle has an alcohol evaporator, it is there to:
,a. Rid the wet tank of alcohol that condenses and sits at the bottom.
b. Eliminate the need for daily tank draining.
c. Boost tank pressure the same way that superchargers boost engines.
d. Reduce the risk of ice in the air brake valves in cold weather. - Answer- d. Reduce the risk
of ice in the air brake valves in cold weather.
Air braking takes more time than hydraulic because air:
a. Brakes use different brake drums.
b. Takes more time to flow through the lines than hydraulic fluid.
c. Brakes require heavier return springs.
d. Is always leaking through airline fittings. - Answer- b. Takes more time to flow through the
lines than hydraulic fluid.
The brake pedal in an air brake system:
a. Controls the speed of the air compressor.
b. Always needs to be held down halfway during normal driving.
c. Controls the air pressure applied to put on the brakes.
d. Is connected to slack adjusters by a series of rods and linkages. - Answer- c. Controls the
air pressure applied to put on the brakes.
With air brake vehicles, the parking brakes should be used:
a. Whenever you leave the vehicle unattended.
b. To hold your speed when going downhill.
c. As little as possible.
, d. Only during pre and post-trip inspections. - Answer- a. Whenever you leave the vehicle
unattended.
For emergency stab braking, you should:
a. Pump the brake pedal rapidly and lightly.
b. Press on the brake pedal as hard as you can, release the brakes when the wheels lock, and
when the wheels start rolling put on the brakes fully again.
c. Brake hard until the wheels lock, then get off the brakes for as much time as the wheels
were locked.
d. Press hard on the brake pedal and apply full hand valve until you stop. - Answer- b. Press
on the brake pedal as hard as you can, release the brakes when the wheels lock, and when
the wheels start rolling put on the brakes fully again.
If your truck or bus has dual parking control valves, you can use pressure from a separate
tank to:
a. Release the spring emergency/ parking brakes to move a short distance.
b. Apply more brake pressure if the main tank is getting low.
c. Stay parked twice as long with your service air pressure.
d. Balance the service brake system whenever you are parked. - Answer- a. Release the
spring emergency/ parking brakes to move a short distance.
Modern air brakes systems combine three different systems. They are the service, parking,
and the _________ brakes.
a. Emergency
b. Foot
c. S-cam
d. Drum - Answer- a. Emergency
Latest 2025 Graded A+
The parking or emergency brake on a heavy vehicle can only be held in position by
something that cannot leak away, like:
a. Fluid pressure
b. Spring pressure
c. Air pressure
d. Any of the above - Answer- b. Spring pressure
A straight truck or bus air brake system should not leak at a rate of more than __ psi per
minute with the engine off and the brake released.
a. 1
b. 2
c. 3
d. 4 - Answer- c. 3
Your vehicle has dual air brake system. If low air pressure warning comes on for the
secondary system or for one system, you should:
a. Bring the vehicle to a safe stop and continue only when the system is fixed.
b. Reduce your speed, and test the remaining system while under-way.
c. Reduce your speed, and drive to the nearest garage for repairs.
d. Continue at normal speed if only the secondary system fails. - Answer- a. Bring the vehicle
to a safe stop and continue only when the system is fixed.
If your vehicle has an alcohol evaporator, it is there to:
,a. Rid the wet tank of alcohol that condenses and sits at the bottom.
b. Eliminate the need for daily tank draining.
c. Boost tank pressure the same way that superchargers boost engines.
d. Reduce the risk of ice in the air brake valves in cold weather. - Answer- d. Reduce the risk
of ice in the air brake valves in cold weather.
Air braking takes more time than hydraulic because air:
a. Brakes use different brake drums.
b. Takes more time to flow through the lines than hydraulic fluid.
c. Brakes require heavier return springs.
d. Is always leaking through airline fittings. - Answer- b. Takes more time to flow through the
lines than hydraulic fluid.
The brake pedal in an air brake system:
a. Controls the speed of the air compressor.
b. Always needs to be held down halfway during normal driving.
c. Controls the air pressure applied to put on the brakes.
d. Is connected to slack adjusters by a series of rods and linkages. - Answer- c. Controls the
air pressure applied to put on the brakes.
With air brake vehicles, the parking brakes should be used:
a. Whenever you leave the vehicle unattended.
b. To hold your speed when going downhill.
c. As little as possible.
, d. Only during pre and post-trip inspections. - Answer- a. Whenever you leave the vehicle
unattended.
For emergency stab braking, you should:
a. Pump the brake pedal rapidly and lightly.
b. Press on the brake pedal as hard as you can, release the brakes when the wheels lock, and
when the wheels start rolling put on the brakes fully again.
c. Brake hard until the wheels lock, then get off the brakes for as much time as the wheels
were locked.
d. Press hard on the brake pedal and apply full hand valve until you stop. - Answer- b. Press
on the brake pedal as hard as you can, release the brakes when the wheels lock, and when
the wheels start rolling put on the brakes fully again.
If your truck or bus has dual parking control valves, you can use pressure from a separate
tank to:
a. Release the spring emergency/ parking brakes to move a short distance.
b. Apply more brake pressure if the main tank is getting low.
c. Stay parked twice as long with your service air pressure.
d. Balance the service brake system whenever you are parked. - Answer- a. Release the
spring emergency/ parking brakes to move a short distance.
Modern air brakes systems combine three different systems. They are the service, parking,
and the _________ brakes.
a. Emergency
b. Foot
c. S-cam
d. Drum - Answer- a. Emergency
