CDL AIR BRAKE PRACTICE TEST 2026
QUESTIONS WITH CORRECT ANSWERS
◉ Which of the following can cause brakes to fade or fail? Answer: "
brakes being out of adjustment"
" excessive use of service breaks"
" not relying enough on breaking"
"All the above"
Explanation: Brakes fade in failure are usually due to incorrect use of
the brakes that cause excessive heat. This may be caused by
incorrect brake adjustment, not enough reliance on engine braking,
excessive use of the service brakes, another mechanical factor or a
human error.
◉ Which of the following will be true about your break function if
you're anti-lock brake system (ABS) fails? Answer: " you will still
have normal brake function and will just need to get the ABS
repaired soon"
Explanation: losing the ABS function does not change the basic parts
of your truck, so you will still have the same brakes that you have
always had. Simply use them and get the ABS repaired as soon as
,possible. There is no need to panic unless your system shows other
and more serious warnings.
◉ Which of the following is NOT part of the braking process when
you're driving a tractor-trailer with a antilock braking system (ABS)?
Answer: " you should drive faster so that you'll be able to keep the
trailer and tractor straight"
Explanation: when driving a tractor-trailer combination vehicle that
has ABS, drive the same way that you will always have. Don't drive
any differently just because of ABS. Only use the braking necessary
to keep control pay attention when you slow down, and break the
same way regardless of what you're driving. Never speed up unless
it is part of The safe driving process already.
◉ What is the best way to test if your vehicle spring brakes come on
automatically? Answer: "Continue to step on and off the brake pedal
until the manufactures low psi specification of spring breaks to
deploy has been met".
"On tractor-trailer vehicles, continue to step on and off the brake
pedal until the parking brake valve pops out"
" on single vehicles, continue to step on and off the brake pedal and
tell the parking brake valve pops out"
" all of the above are correct"
,Explanation: On both tractor trailers and single vehicles, to test
whether the spring breaks will come on automatically, use the same
method you use for testing the low air pressure warning signal: step
on and off the brake pedal, this time until you reach an even lower
psi reading and the parking brake valve closes and pops out.
◉ An antilock braking system (ABS)? Answer: " activates when your
wheels are about to lock up"
Explanation: ABS does not have much affect on your every day
driving. It does not affect your braking capability or necessarily
shorten your stopping distance. It just helps you keep control of
your vehicle by activating when your wheels are about to lock up.
◉ What is the best way to test your vehicle is low air pressure
warning signal? Answer: "With the engine off, step on and off the
brake pedal to lower the air pressure below 60 psi"
Explanation: the best way to test the low air pressure warning signal
is to turn off the engine while leaving the electrical power on. Then
step on and off the brake pedal. The low air pressure warning signal
should come on when that pressure falls below 60 PSI. You should
never need to get down to 30 psi.
◉ Spring breaks are? Answer: " made up of powerful springs that
are held back by air pressure while you are driving"
, " brakes that come on automatically on a truck or tractor when the
PSI drops too low"
" not going to take the full affect until your psi drops to a certain
range, typically 20 to 30 psi"
Explanation: spring breaks are an important back up system:
powerful springs that automatically apply to the brakes if they sense
that the air pressure has been lost for some reason, such as a leak.
They will also apply the brakes if the psi gets too low although
ideally, you should take control of your breaks before that happens.
◉ The tractor protection valve? Answer: " Will close automatically if
the air supply drops to a certain level"
" provides the air supply for the brake system"
" Will close if you apply the parking brakes"
" does all of the above"
Explanation: the tractor protection valve protects your air brake
system by providing the air supply, closing automatically if the air
supply drops too low, and closing if you apply the parking brakes.
◉ How do brakes work on a long, steep downgrade? Answer: " as a
supplement to the breaking effect of your engine"
QUESTIONS WITH CORRECT ANSWERS
◉ Which of the following can cause brakes to fade or fail? Answer: "
brakes being out of adjustment"
" excessive use of service breaks"
" not relying enough on breaking"
"All the above"
Explanation: Brakes fade in failure are usually due to incorrect use of
the brakes that cause excessive heat. This may be caused by
incorrect brake adjustment, not enough reliance on engine braking,
excessive use of the service brakes, another mechanical factor or a
human error.
◉ Which of the following will be true about your break function if
you're anti-lock brake system (ABS) fails? Answer: " you will still
have normal brake function and will just need to get the ABS
repaired soon"
Explanation: losing the ABS function does not change the basic parts
of your truck, so you will still have the same brakes that you have
always had. Simply use them and get the ABS repaired as soon as
,possible. There is no need to panic unless your system shows other
and more serious warnings.
◉ Which of the following is NOT part of the braking process when
you're driving a tractor-trailer with a antilock braking system (ABS)?
Answer: " you should drive faster so that you'll be able to keep the
trailer and tractor straight"
Explanation: when driving a tractor-trailer combination vehicle that
has ABS, drive the same way that you will always have. Don't drive
any differently just because of ABS. Only use the braking necessary
to keep control pay attention when you slow down, and break the
same way regardless of what you're driving. Never speed up unless
it is part of The safe driving process already.
◉ What is the best way to test if your vehicle spring brakes come on
automatically? Answer: "Continue to step on and off the brake pedal
until the manufactures low psi specification of spring breaks to
deploy has been met".
"On tractor-trailer vehicles, continue to step on and off the brake
pedal until the parking brake valve pops out"
" on single vehicles, continue to step on and off the brake pedal and
tell the parking brake valve pops out"
" all of the above are correct"
,Explanation: On both tractor trailers and single vehicles, to test
whether the spring breaks will come on automatically, use the same
method you use for testing the low air pressure warning signal: step
on and off the brake pedal, this time until you reach an even lower
psi reading and the parking brake valve closes and pops out.
◉ An antilock braking system (ABS)? Answer: " activates when your
wheels are about to lock up"
Explanation: ABS does not have much affect on your every day
driving. It does not affect your braking capability or necessarily
shorten your stopping distance. It just helps you keep control of
your vehicle by activating when your wheels are about to lock up.
◉ What is the best way to test your vehicle is low air pressure
warning signal? Answer: "With the engine off, step on and off the
brake pedal to lower the air pressure below 60 psi"
Explanation: the best way to test the low air pressure warning signal
is to turn off the engine while leaving the electrical power on. Then
step on and off the brake pedal. The low air pressure warning signal
should come on when that pressure falls below 60 PSI. You should
never need to get down to 30 psi.
◉ Spring breaks are? Answer: " made up of powerful springs that
are held back by air pressure while you are driving"
, " brakes that come on automatically on a truck or tractor when the
PSI drops too low"
" not going to take the full affect until your psi drops to a certain
range, typically 20 to 30 psi"
Explanation: spring breaks are an important back up system:
powerful springs that automatically apply to the brakes if they sense
that the air pressure has been lost for some reason, such as a leak.
They will also apply the brakes if the psi gets too low although
ideally, you should take control of your breaks before that happens.
◉ The tractor protection valve? Answer: " Will close automatically if
the air supply drops to a certain level"
" provides the air supply for the brake system"
" Will close if you apply the parking brakes"
" does all of the above"
Explanation: the tractor protection valve protects your air brake
system by providing the air supply, closing automatically if the air
supply drops too low, and closing if you apply the parking brakes.
◉ How do brakes work on a long, steep downgrade? Answer: " as a
supplement to the breaking effect of your engine"
