The CDL Combination Vehicles test is a mandatory exam for anyone seeking a Class A CDL to operate tractor-trailers, doubles, or triples. It typically consists of 20 multiple-choice questions, requiring an 80% passing score (at least 16 correct).
DRIVING-TESTS. ORG
THE TOP 75 MOST COMMON
Combinatio
vehicles
QUESTIONS
Lose the fear of the unknown. Study the most common
CDL combination vehicles questions so you'll know
what to expect on the big test day.
Know what
to expect
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documents into the knowledge
exam room to cheat with
The term used to mean a sheet of notes that you kept with you to
cheat on an exam. Today, it has also come to mean a quick reference or ready
reference of the most important or frequently used items. That’s how we intend
our “cheat sheets” to be used: As quick references for you to browse to help
you study for your written knowledge test.
“cheat sheet”
1. What is true about stopping distances?
"Bobtail" tractors can take longer to stop than
a combination vehicle loaded to the maximum
gross weight.
When a combination vehicle is empty or lightly
loaded, its braking distance increases. The very
stiff suspension springs and strong brakes give
poor traction and make it very easy to lock the
wheels. Likewise, "bobtail" tractors (tractors
without semitrailers) can take longer to stop
than a fully loaded tractor-trailer. Be very careful
when driving a "bobtail" tractor.
2. Under good driving conditions, you
should leave at least one second of space
between your vehicle and the vehicle ahead
for every _________ feet of your vehicle's
length.
10
Because sudden turns or steering adjustments
can cause a large vehicle to tip over, and
braking takes longer time and distance the
bigger a load, you should keep a safe distance
from other vehicles, give yourself at least 1
second for every 10 feet of your truck's length,
and another second if you're travelling faster
than 40 mph.
3. Semi-trailers made before 1975 that are
equipped with air brakes
often do not have spring brakes.
Trailers and converter dollies built before 1975
are not required to have spring brakes. Instead,
they rely on emergency brakes that hold using
air pressure. Because air pressure can leak
away, always use wheel chocks when parking
such vehicles.
4. What are the other names for the service
air line?
Control line and signal line.
The service air line is also known as the control
line or signal line.
5.
A
ir lines on a combination vehicle are often
colored to keep them from getting mi
x
ed up.
T
he emergency line is _________
;
the
service line is _________.
red
;
blue
To keep the air lines from being mismatched,
they can be labeled with metal tags or color
coded. Blue is used for the service lines, and
red is used for the emergency lines. Couple the
air lines of the same color.
6
.
I
f the brakes did not release when you
pushed the trailer air supply valve, you
should
check the air line connections.
If you cross the emergency and service air lines,
air will
fl
ow to the service line instead of the
trailer air tanks.
A
ir won't be available to release
the spring brakes. Therefore, if the spring
brakes don't release when you push the trailer
air supply control, check the air line
connections.
7.
Y
ou supply air to the trailer tanks by
pushing in the trailer air supply valve.
O
n newer vehicles, the trailer air supply control
is an eight-sided red knob on the dashboard of
the tractor. The knob may be labeled "
P
ull to
exhaust...
P
ush to supply" or something similar.
When you push the knob in, air will
fl
ow through
the trailer's emergency air lines to charge the
trailer air brake system.
8
. When you turn suddenly while pulling
doubles, which trailer is most likely to turn
over?
The rear trailer is twice as likely to turn over
as the tractor.
Because of rearward ampli
fi
cation, the last
trailer on a combination vehicle has the highest
probability of rolling over. This is called the
crack-the-whip effect.
The top 75 most common Combination Vehicles questions
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