CLP/CDL COMBINATION VEHICLES
TEST QUESTIONS WITH CORRECT
DETAILED ANSWERS
v What two things are important to prevent rollover? (6.1.1) - 1. Keep cargo as close to the ground as
possible
2. Drive slowly around turns
When you turn suddenly while pulling doubles, which trailer is most likely to turn over? (6.1.2) - The rear
most trailer
What is the "crack-the-whip" effect? (6.1.2) - When you make a quick lane change or sudden movement
of your steering wheel, the rear trailer tends to swing out. The force of the rear trailer becomes
amplified, causing it to roll over (rearward amplification).
What is the proper following distance formula? (6.1.2) - Maintain at least 1 second of following distance
for each 10 feet of your vehicle length.
Add 1 second for speeds above 40mph.
Large combination vehicles take longer to stop when they are ______ than when they are _______.
(6.1.3) - EMPTY
FULLY LOADED
Why should you not use the trailer hand brake to straighten out a jackknifing trailer? (6.1.5) - Because
the brakes on the trailer wheels caused the skid in the first place. Once the trailer wheels grip the road
again, the trailer will start to follow the tractor and straighten out.
What type of trailers can get stuck on railroad-highway crossings? (6.1.4) - - Low slung trailers, like car
carriers, moving vans, and possum-belly livestock trailers
- Single-axle tractor pulling a long trailer with its landing gear set to accommodate a tandem-axle tractor
How do you stop a trailer skid / jackknife? (6.1.5) - 1. Recognize the skid by looking at your mirrors when
braking to make sure that it is where it should be
, 2. Release the brakes to get traction back. Once the trailer wheels grip the road again, the trailer will
start to follow the tractor and straighten out.
What is off tracking? (6.1.6) - When the rear wheels follow a different path than the front wheels when a
vehicle goes around a corner. Refer to Figures 6.3 & 6.4
What should you do if you cannot complete your turn without entering another traffic lane? (6.1.6) -
Turn wide as you complete the turn. This is better than swinging wide to the left before starting the turn
because it will keep other drivers from passing you on the right. If drivers pass on the right, you may
collide with them when you turn.
When you back a trailer, you should position your vehicle so you can back in a curved path to the
DRIVER'S SIDE. True or False? (6.1.7) - TRUE! Backing to the driver's side allows you to see your path
better through the mirrors.
When you back a trailer, you should position your vehicle so you can back in a straight line. True or False?
(6.1.7) - TRUE!
Why should you not use the trailer hand valve while driving? (6.2.1) - Because of the danger of making
the trailer skid! It should only be used to test the trailer service brakes.
Which set of brakes sends air to all the brakes on the vehicle and the trailer(s)? (6.2.1) - The foot brake.
There is much less danger of causing a skid or jackknife when using just the foot brake.
Why should you use wheel chocks when parking a trailer without spring brakes? (6.2.1) - Because if the
air pressure leaks away, there will be no brakes.
Never use the hand valve for parking because all the air might leak out, unlocking the brakes (in trailers
that do not have spring brakes.) Always use the parking brakes when parking. If the trailer does not have
spring brakes, use wheel chocks to keep the trailer from moving.
What does the tractor protection valve do? (6.2.2) - Keeps air in the tractor or truck brake system should
the trailer and break away or develop a bad leak
What controls the tractor protection valve? (6.2.2) - It is controlled by the "trailer air supply" control
valve in the cab
Describe what the trailer air supply control does. (6.2.2-3) - The control valve allows you to open and
shut the tractor protection valve.
It is used to supply the trailer with air, shut the air off, and put on the trailer emergency brakes.
What does the trailer air supply control look like? (6.2.3) - On newer vehicles, a red eight-sided knob
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