CDL Doubles and Triples Test Question and Answers 2025 [PDF]

CDL Doubles and Triples Test Question and Answers 2025 [PDF]: Commercial Driver’s License Doubles and Triples Endorsements Knowledge Test. Try our free CDL Doubles and Triples Test Question and Answers Quiz online.

Take special care when pulling two and three trailers. There are more things that can go wrong, and doubles/triples are less stable than other commercial vehicles. You will not be tested on uncoupling twins unless you want to get a double/triple trailer endorsement on your license.

CDL Doubles and Triples Test Question and Answers

Test Name	CDL Practice Test 2025
Language	English
License	Endorsements Permit
Total Questions	30 MCQs
Test For	Commercial Driver License
Test Preparation	Doubles and Triples Endorsements
Country	USA
Explanation	No

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CDL Doubles/Triples Test

1 / 30

It is important to check the height of the trailer before connecting a converter dolly to a trailer. The trailer is at the correct height when

A) it is raised slightly by the converter dolly’s backing under it.

B) the trailer and the converter dolly are lined up.

C) the trailer is raised high above the converter dolly.

D) the kingpin is above the fifth wheel.

2 / 30

In order to supply air to the air tanks of a second trailer, you must ______ shut-off valves at the rear of the first trailer and ________ the shut-off valves at the rear of the second trailer.

A) open . . . close

B) close . . . open

C) open . . . open

D) close . . . close

3 / 30

What is one function of the tractor protection valve?

A) To indicate that the parking brake is on

B) To stop any air from going out of the tractor if air pressure drops into the range of 50 to 65 psi

C) To keep air in the trailer should the tractor develop a bad leak

D) To keep air in the tractor should the trailer develop a bad leak

4 / 30

When coupling twin trailers, you should _______ the pintle hook and secure the dolly support in the _______ position.

A) lock . . . coupled

B) lock . . . raised

C) release . . . lowered

D) disconnect . . . raised

5 / 30

Which of the following is true about loading cargo into double or triple trailers?

A) It doesn’t matter if the cargo in the first trailer is uncentered.

B) Always pile the heavier cargo on top of the lighter cargo.

C) Keep the cargo as close to the ground as possible in every trailer.

D) Cargo may be piled as high as possible in the first trailer.

6 / 30

While doing a walkaround inspection of a double or triple, the converter dolly air tank drain valve should be _______, and the pintle hook should be _______.

A) open . . . locked

B) latched . . . open

C) closed . . . locked

D) closed . . . open

7 / 30

Which of the following must be connected when coupling tractor to trailer or trailer to trailer?

A) Air hoses

B) Safety chains

C) Light cords

D) All of the above

8 / 30

When doing a walkaround inspection of a double or triple trailer, the shut-off valves should be _______ at the rear(s) of the front trailer(s) and ________ at the rear of the last trailer.

A) latched . . . open

B) closed . . . open

C) open . . . latched

D) open . . . closed

9 / 30

When coupling twin trailers, a converter dolly is

A) needed between the tractor and the first trailer.

B) needed between both the tractor and the first trailer and the first trailer and the second trailer.

C) needed between the first and second trailers.

D) not needed.

10 / 30

Trucks with trailers have a dangerous “crack-the-whip” effect. Because of this, which of the following vehicle parts is most likely to tip over?

A) The rear trailer of a double

B) The truck itself

C) The rear trailer of a triple

D) The entire rig

11 / 30

The braking systems of double and triple trailers are different than those of straight trucks because doubles and triples

A) have two emergency lines.

B) never have spring brakes.

C) have two service lines.

D) have extra parts which control the trailer brakes.

12 / 30

You open the emergency line shut-off valve at the rear of the last trailer and hear air escaping. This means

A) the entire service air line system is charged.

B) there is a leak somewhere in the service air line.

C) the entire emergency air line system is charged.

D) the shut-off valves on the other trailer(s) and dolly(ies) are in the closed position.

13 / 30

During a jackknife, it is best to

A) jam on the brakes.

B) release the brakes to get traction back.

C) simply wait for the trailer to straighten out.

D) apply the trailer hand brake.

14 / 30

You are driving a tractor with multiple trailers. Which of the following statements about off tracking is true?

A) Longer vehicles will offtrack more.

B) The front wheels of the last trailer are most likely to off-track.

C) The rear wheels of a single trailer will offtrack more than the rear wheels of a double trailer.

D) The rear wheels of the last trailer follow the same path as the front wheels of the tractor.

15 / 30

Converter dollies often do not have

A) air tank drain valves.

B) one or more air tanks.

C) spring brakes.

D) All of the above

16 / 30

Which of the following will probably happen if you are driving a double rig and a set of trailer wheels goes into a skid?

A) Your trailer will jackknife.

B) The entire vehicle will slide into the other lane.

C) Nothing: the wheels will straighten themselves out quickly.

D) Your brakes will fail.

17 / 30

_______ should be tested with the hand valve but controlled in normal operation with the foot pedal.

A) The tractor brakes

B) The trailer brakes

C) The tractor protection valve

D) The parking brake

18 / 30

The pintle hook plays a part in

A) coupling and uncoupling converter dollies and trailers.

B) locking shut-off valves at the rear of the last trailer.

C) uncoupling converter dollies and trailers only.

D) locking glad hands together.

19 / 30

What is most likely to happen if the trailer protection valve of a double or triple trailer does not function correctly?

A) The truck will fill with air.

B) An air hose or trailer brake leak could drain all the air from the tractor.

C) Air pressure will rise.

D) The emergency brakes will not work.

20 / 30

You are driving a triple trailer and there is a loss of air pressure in the emergency line. Which of the following will occur?

A) The emergency brakes of all three trailers will come on.

B) The emergency brakes of the first two trailers only will come on.

C) The vehicle will lose all braking power and it will be necessary to use an escape route to stop

D) The tractor’s emergency brakes will come on.

21 / 30

When uncoupling, you should never unlock the _______ with the dolly still under the rear trailer.

A) pintle hook

B) emergency air line

C) landing gear

D) service air line

22 / 30

In double and triple trailers, the trailer air supply control should pop or _________ when air pressure drops into the range of 20 to 45 psi.

A) go from “emergency” to “normal” position

B) go from “normal” to “emergency” position

C) begin blinking

D) make a buzzing noise

23 / 30

Trucks that are empty or lightly loaded

A) have flexible suspension springs.

B) have poor traction, making it easy to lock up the wheels.

C) have little chance of jackknifing.

D) have a shorter stopping time.

24 / 30

When turning a double or triple at an intersection, the turn often cannot be completed without swinging wide. Which diagram shows the best way to turn?

A) Diagram D

B) Diagram C

C) Diagram A

D) Diagram B

25 / 30

When checking the coupling system, make sure that the locking jaws are around the shank of the

A) kingpin

B) landing gear.

C) fifth wheel.

D) emergency air line.

26 / 30

When you are pulling trailers, which of the following statements is true about steering?

A) If you make a sudden or large steering adjustment, you could tip over one or all of your trailers.

B) The crack-the-whip effect does not apply to doubles and triples.

C) There is no difference between steering a straight truck and steering a double or triple.

D) It is not dangerous to make quick lane changes.

27 / 30

While inspecting your converter dolly coupling, you should make sure there is _______ between the upper and lower fifth wheel.

A) one inch of space

B) no space

C) a little space

D) 1/2 inch of space

28 / 30

When driving a double or triple trailer, greater care must be given to

A) vehicle inspection.

B) space management.

C) following distance.

D) All of the above

29 / 30

If you are driving a 200-foot triple at 35 mph, what is the minimum amount of space (in seconds) that you should keep ahead of you?

A) 25

B) 10

C) 30

D) 20

30 / 30

You are driving with more than one trailer. Which trailer should come first behind the tractor?

A) The heaviest trailer

B) The lightest trailer

C) The newest trailer

D) The oldest trailer

Your score is

The average score is 60%

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