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

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

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

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

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

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

2 / 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 vehicle will lose all braking power and it will be necessary to use an escape route to stop

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

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

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

3 / 30

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

A) Safety chains

B) Light cords

C) Air hoses

D) All of the above

4 / 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 kingpin is above the fifth wheel.

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

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

5 / 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 brakes will fail.

B) Your trailer will jackknife.

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

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

6 / 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 A

B) Diagram D

C) Diagram C

D) Diagram B

7 / 30

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

A) The tractor protection valve

B) The parking brake

C) The tractor brakes

D) The trailer brakes

8 / 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) 30

B) 25

C) 10

D) 20

9 / 30

Converter dollies often do not have

A) air tank drain valves.

B) spring brakes.

C) All of the above

D) one or more air tanks.

10 / 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 “normal” to “emergency” position

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

C) begin blinking

D) make a buzzing noise

11 / 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) closed . . . open

B) open . . . closed

C) open . . . latched

D) latched . . . open

12 / 30

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

A) fifth wheel.

B) kingpin

C) emergency air line.

D) landing gear.

13 / 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) close . . . close

B) open . . . open

C) open . . . close

D) close . . . open

14 / 30

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

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

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

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

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

15 / 30

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

A) lock . . . raised

B) release . . . lowered

C) lock . . . coupled

D) disconnect . . . raised

16 / 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) have two service lines.

C) never have spring brakes.

D) have extra parts which control the trailer brakes.

17 / 30

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

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

B) the entire service air line system is charged.

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

D) the entire emergency air line system is charged.

18 / 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

19 / 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 tractor should the trailer develop a bad leak

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

20 / 30

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

A) Air pressure will rise.

B) The emergency brakes will not work.

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

D) The truck will fill with air.

21 / 30

The pintle hook plays a part in

A) locking glad hands together.

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

C) coupling and uncoupling converter dollies and trailers.

D) uncoupling converter dollies and trailers only.

22 / 30

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

A) 1/2 inch of space

B) a little space

C) no space

D) one inch of space

23 / 30

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

A) All of the above

B) space management.

C) following distance.

D) vehicle inspection.

24 / 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 truck itself

B) The rear trailer of a double

C) The entire rig

D) The rear trailer of a triple

25 / 30

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

A) emergency air line

B) pintle hook

C) service air line

D) landing gear

26 / 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) not needed.

D) needed between the first and second trailers.

27 / 30

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

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

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

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

D) Longer vehicles will offtrack more.

28 / 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) latched . . . open

B) closed . . . locked

C) open . . . locked

D) closed . . . open

29 / 30

During a jackknife, it is best to

A) apply the trailer hand brake.

B) jam on the brakes.

C) simply wait for the trailer to straighten out.

D) release the brakes to get traction back.

30 / 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.

Your score is

The average score is 58%

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