Doubles and Triples CDL Practice Test

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Question 1

What three methods can you use to secure a second trailer before coupling?

A
Chock the tires, park on level ground and charge the trailer air tank if it does not have spring brakes.
B
All of the above
C
Park the rear trailer against another trailer, chock the tires and lock the trailer door.
D
Park on level ground, put chock on the tires, and charge the air tank
Question 1 Explanation: 
Chock the tires, park on level ground and charge the trailer air tank if it does not have spring brakes.
Question 2

Doubles and triples must be driven very smoothly to avoid rollover or jackknife

A
True
B
False
Question 2 Explanation: 
True! Doubles and triples are extremely prone to control issues and must be driven with care to avoid losing control
Question 3

What should you check for when inspecting a converter dolly?

A
Make sure safety chains are secured to the trailers
B
All of the above
C
Make sure the converter dolly air tank drain valve is closed
D
Make sure the spare tire is secured, if it has one
Question 3 Explanation: 
All of the above. Ensuring the safety of the public starts with a thorough inspection of all equipment
Question 4

Why should you pull a dolly out from under a trailer before you disconnect it
from the trailer in front?

A
The dolly tow bar may fly up, possibly causing injury, and making it very difficult to re-couple
B
Because the book says so
C
You can if you want to, it does not matter
D
The dolly tow bar may fly away, possibly causing panic, and making it very difficult to re-capture it.
Question 4 Explanation: 
The dolly tow bar may flip up causing bodily injury and making it very difficult to recouple.
Question 5

Should the shut off valves on the rear of the first trailer be open or closed on a set
of double trailers?

A
Open
B
Closed
Question 5 Explanation: 
Open. The shut off valves prevent air from going any further. If there is a trailer behind the shut-off valve then they need to remain open
Question 6

You should look into the back of the fifth wheel on a dolly to see if it is locked
onto the kingpin

A
False
B
True
Question 6 Explanation: 
True! Never pull any trailer without visually inspecting the fifth wheel locking bar and ensuring it is secure.
Question 7

A safe speed on a curve for a straight truck or a single trailer combination
vehicle may be too fast for double or triple trailers

A
True
B
False
Question 7 Explanation: 
True! Speed for other vehicles is often too fast for a multi-combination unit!
Question 8

What is a converter dolly?

A
A coupling device of one or two axles and a sixth wheel by which a semitrailer can be coupled to the rear of a tractor-trailer combination forming a double bottom rig
B
A coupling device of one or two axles and a fifth wheel by which a semitrailer can be coupled to the rear of a tractor-trailer combination forming a double bottom rig
C
None of the above
D
A connection device of one axle used to disconnect a semitrailer combination vehicle converting it into two trailers
E
A coupling device of three or four axles and a fifth wheel by which a semitrailer can be coupled to the rear of a tractor-trailer combination forming a hexagon bottom rig
Question 8 Explanation: 
Careful of the wording! It's a fifth wheel, not a sixth wheel
Question 9

Should the pintle hook be latched or unlatched when backing a dolly under the
second trailer?

A
Unlatched.
B
Latched.
Question 9 Explanation: 
The pintle hook should always be secure when the vehicle is in motion.
Question 10

What do you check when making a visual check of coupling?

A
That there is some space between the upper and lower fifth wheel. Locking jaws open on kingpin.
B
That there is no space between upper and lower sixth wheel. Locking jaws closed on kingpin
C
None of the above.
D
That there is no space between upper and lower fifth wheel. Locking jaws closed on kingpin.
E
That there is grease between upper and lower fifth wheel. Locking jaws closed on King pin
Question 10 Explanation: 
Make sure to visually inspect the fifth wheel and that the locking mechanism is securely fastened.
Question 11

How can you test that air flows to all trailers?

A
Open the shut-off valves at the rear of the last trailer and listen for air flow.
B
None of the above
C
Only a certified diesel mechanic can check this.
D
Disconnect the glad-hand at the front of the first trailer and listen for air flow
E
Charge the system and pump the brakes with the window down.
Question 11 Explanation: 
Opening the shut off valves on the rear most trailer will ensure the lines are flowing air throughout the system. If there is air there, then there is air towards the cab...
Question 12

When connecting two trailers the converter dolly is connected to the rear trailer
first

A
True
B
False
Question 12 Explanation: 
You want to hook up to the first trailer, then the converter dolly while it is lined up in front of the second trailer. Once that's complete, then its an easy push back and the second trailer will be connected
Question 13

How do you know if your converter dolly is equipped with antilock brakes?

A
The dolly will have a yellow lamp on the right side
B
The dolly will have a red lamp on the left side
C
The dolly will have a yellow lamp on the left side
D
None of the above
E
The dolly will have a red lamp on the right side
Question 13 Explanation: 
The dolly will have a yellow lamp on the drivers (left) side. All ABS equipped units will have a lamp on the drivers side. If this lamp is illuminated and does not go out, then there is a problem with the ABS system.
Question 14

Should the converter dolly air-tank drain valve be open or closed on a double
trailer combination?

A
Closed
B
Open
Question 14 Explanation: 
Unless you are draining the condensation out of the air tank, then the drain valve should remain in the closed position.
Question 15

The front trailer in a set of double trailers is most likely to turn over due to the
Crack-the-Whip effect

A
True
B
False
Question 15 Explanation: 
The “crack the whip” effect will topple the rear trailer first.
Question 16

Do converter dollies have spring brakes?

A
None of the above.
B
They all do, it is required.
C
Never.
D
Some do
E
Yes.
Question 16 Explanation: 
Some do. Typically depends on the axle count. If the dolly is a two axle unit then 1 axle will have spring brakes due to the weight of the unit
Question 17

Should the shut-off valves on the trailers be open or closed on a set of double
trailers?

A
All shut-off valves should be open
B
The rear trailers shut-off valves should be open and the front closed.
C
The rear trailers shut-off valves should be closed and the front open.
D
The rear trailer does not have shut-off valves.
E
All shut-off valves should be closed.
Question 17 Explanation: 
The rear trailers shut off valves should be closed and the front open to allow air to the rear trailer.
Question 18

How do you check to make sure the trailer height is correct before coupling?

A
Trailer height never changes!
B
Visually check to make sure that the lead trailer is slightly higher than the center of the fifth wheel, so trailer is raised slightly when dolly is pushed under it.
C
The height is always the same.
D
Visually check to make sure that the rear trailer is slightly lower than the center of the fifth wheel, so trailer is raised slightly when dolly is pushed under it.
E
None of the above
Question 19

When you're trying to correct a drive-wheel braking skid why should you stop
braking?

A
None of the listed answer
B
You need to stop braking because it's necessary for you to speed up
C
You shouldn't stop braking. You need to brake in order to regain control.
D
This will let the rear wheels roll again and keep the rear wheels from sliding
Question 19 Explanation: 
When you are in a drive-wheel braking skid, the first thing to do is STOP BRAKING! That split second that you release the brakes will allow them to match the vehicles road speed and start spinning again, in turn stopping your skid
Question 20

What types of trailers can get stuck on raised crossings?

A
Car carriers
B
Moving vans
C
All of the listed answers
D
Possum-belly livestock trailers
E
Lowboys
Question 20 Explanation: 
All the listed answers would be correct. Any trailer with a reduced ground clearance can and will get stuck on a raised railroad crossing
Question 21

You should reduce your speed by about _____ on a wet road.

A
2/3
B
1/2
C
1/4
D
1/3
Question 21 Explanation: 
1/3 For example: If you are traveling 60 MPH and it begins to rain, your suggested safe speed would be 40 MPH. Remember however, that is just a suggestion. If you feel unsafe slow down even further, or better yet, find a safe haven and park until the weather passes.
Question 22

A vehicle transporting hazardous materials is required to display placards where?

A
On each side of the vehicle
B
All of the listed answers.
C
On the back.
D
On the front.
Question 22 Explanation: 
Hazardous materials must be placarded on all four sides of EACH Trailer. If there is Flammable materials in the front trailer then it must have the placards on that trailer. Watch the wording of the question AND the answers...
Question 23

A good and safe driver will always look out for ______.

A
Brake lights from slowing vehicles.
B
All of the listed answers.
C
Vehicles coming onto the highway.
D
Vehicles turning into your lane
Question 23 Explanation: 
A safe driver will look for all of the above. A 360 degree area of awareness is paramount to safe driving
Question 24

If one air system is very low on pressure _______.

A
Only the rear brakes will not work.
B
Either the front or the rear brakes will not work properly or fully.
C
Nothing happens.
D
Only the front brakes will not work.
Question 24 Explanation: 
A low air buzzer will go off indicating something is wrong and either the front or the rear brakes will not work properly. Stop the vehicle by gearing down and sparingly utilize the brakes.
Question 25

What is the most common foundation brake found on heavy vehicles?

A
S-cam brakes.
B
C-Clamps.
C
Wedge brakes.
D
Disc brakes.
Question 25 Explanation: 
S-cam brakes are the most common style brakes on large trucks today
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About the Doubles and Triples CDL Test

The Doubles and Triples CDL test:

  • 20 questions.
  • You need 16 correct answers (80%).
  • You may be timed. Time limit varies by state. 

Double and triple trailers increase not only the operator’s risk of safety, but also the other motorists around him. Doubles and triples are more likely to overturn than other combination vehicles because of the “whip cracking” effect. Driving doubles/triples is also more dangerous in hot and cold weather driving, as well as on mountain roads.

A driver of a vehicle with double or triple trailers will have greater length and more dead axles to pull, increasing the likelihood of a wreck.

The topics with which you will want to be expertly familiar are:

  • Inspecting doubles and triples
  • Prevent trailer from rolling over
  • Avoiding the Crack-the-Whip effect
  • Complete inspection
  • Manage space
  • Coupling and uncoupling doubles
  • Coupling and uncoupling triples
  • Doubles and triples air brake tests

There isn’t as much information to be studied in the classroom or in the CDL manual regarding doubles and triples, so in-lot and on-the-road practice will help you pass this test.

Safety should never take second place, so know your stuff! What is a converter dolly? What three methods can you use to secure a second trailer before coupling? What should you check for when inspecting the converter dolly and the pintle hook?

 

About The Author
Contributor: Luke Nold (Experienced truck driver for 5+ years and published writer for Fleet Magazine).

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