To uncouple the rear trailer, the first thing you do is

park the vehicle in a straight line on firm level ground.

park the vehicle at a 45-degree angle on level ground.

park the vehicle at a 45-degree angle on an incline.

The official CDL manual's section on double and triple trailers usually describes how to couple and uncouple

only the more common types of combinations.

only doubles; look elsewhere to find out how to do triples.

Which of these statements about managing space to the sides is true?

You should avoid traveling alongside other vehicles whenever possible.

Always keep your vehicle to the right side of your lane.

High winds are not a problem for doubles and triples.

Which of the following statements about steering is true?

The more sharply you turn, the greater the chances of a skid or rollover.

It is not necessary to keep both hands on the wheel.

Always apply the brakes when turning.

Coupling a triple trailer is different from coupling other combinations because

you couple the third trailer to the second trailer before you couple them to the first trailer.

you couple the second trailer to the first trailer and then couple them both to the tractor.

you do not have to use a converter dolly.

Why must you inspect your double or triple combination vehicle more extensively than a vehicle with only one such semitrailer?

There are more critical parts to check.

Its design makes it more likely to have problems.

The types of cargoes it carries make it more likely to have problems.

Some large trucks have convex or “spot” mirrors. Such mirrors

make things look smaller and farther away than they really are.

are against the law in most states.

do not need to be checked as often as flat mirrors because they show a larger area.

Which of the following will result in the best control on a curve?

Slow to a safe speed before entering the curve, then accelerate slightly through it.

Brake and downshift in the curve.

Slow to a safe speed before entering the curve, then coast through it.

If your test of the tractor protection valve is successful,

the tractor protection valve control (trailer air supply control) will pop out or go from "normal" to "emergency."

the low air pressure warning signal will come on.

the parking brake valve will pop out.

What is the definition of "off-tracking?"

How the rear wheels follow a different path from the front wheels in a turn

How the rear wheels are more likely to leave the roadside or "track"

Stopping for too long on breaks and getting "off the track" of your original schedule

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Colorado CDL: Double & Triple Trailers Practice Test

20 double & triple trailers questions for the Colorado CDL Knowledge Test, out of 101 in the app. Answer each to see whether you got it right and why. The real Colorado Double/Triple Trailers test has 20 questions and you need 16 correct (80%) to pass.

Facts updated Oct 26, 2026
Official source: law.cornell.edu
Independent, not affiliated with the DMV. How we write our questions

How it works

1Pick an answer20 questions, one tap each.
2See the ruleRight or wrong, every answer is explained.
3Get your scoreCompared with the real 80% pass mark.

Start the test

0/20 answered0 correctPass mark 80%

1Question 1 of 20
To uncouple the rear trailer, the first thing you do is
Not quite. The answer is park the vehicle in a straight line on firm level ground.
To uncouple the rear trailer, the first thing you do is park the vehicle in a straight line on firm level ground. Apply the parking brakes to keep the vehicle from moving. If the second trailer doesn't have spring brakes, chock its wheels.
2Question 2 of 20
The official CDL manual's section on double and triple trailers usually describes how to couple and uncouple
Not quite. The answer is only the more common types of combinations.
The official CDL manual's section on double and triple trailers usually describes how to couple and uncouple the more common types of double and triple combinations. However, there are other ways of coupling and uncoupling the many types of truck-trailer and tractor-trailer combinations that are in use. To learn how to couple and uncouple the vehicles you will be driving, consult the manufacturer's or owner's specifications.
3Question 3 of 20
During normal operation, the brakes on double and triple trailers are controlled with the
Not quite. The answer is foot pedal.
You can use the trailer hand valve (also known as a spike or Johnson bar) to test the trailer service brakes. During normal driving, however, all the service brakes on your vehicle are controlled with the foot pedal, which applies air to the service brakes at all the wheels.
4Question 4 of 20
Which of these statements about managing space to the sides is true?
Not quite. The answer is You should avoid traveling alongside other vehicles whenever possible.
Whenever another vehicle is traveling alongside yours, there's always a chance that the vehicle might try to move into your lane and accidentally hit your vehicle. Also, the vehicle is blocking you from changing lanes. It's safer to find an open spot where there are no vehicles on either side of you. (Of course, that may not be possible in heavy, congested traffic.)
5Question 5 of 20
What is the main difference between a B-dolly (or C-dolly), and an A-dolly?
Not quite. The answer is An additional drawbar
The type of converter dolly described in your official state CDL manual is an A-dolly. It has a single drawbar, whose eye fits over the pintle hook in the rear of a semitrailer. The A-dolly can pivot or articulate on that pintle hook. In contrast, a B-dolly (or C-dolly) has two drawbars, each with its own eye. These fit over two pintle hooks in the rear of a trailer. These two connections prevent the B-dolly from pivoting on the pintle hooks, thus eliminating one articulation or pivot point. B-dollies are used to connect B-doubles (also called B-train doubles).
6Question 6 of 20
When you're pulling triples, it is safest for the lightest trailer to be positioned in the
Not quite. The answer is rear.
Vehicles with double or triple trailers can experience a dangerous "crack-the-whip" effect, caused by rearward amplification. If you make a quick lane change, the crack-the-whip effect can turn the trailers over. (There have been many accidents where only the trailer overturned.) Rearward amplification is strongest at the rearmost trailer. Therefore, position your heaviest trailer at the front and your lightest trailer at the rear.
7Question 7 of 20
Which of the following statements about steering is true?
Not quite. The answer is The more sharply you turn, the greater the chances of a skid or rollover.
Don't turn any more than needed to clear whatever is in your way. The more sharply you turn, the greater the chances of a skid or rollover.
8Question 8 of 20
Coupling a triple trailer is different from coupling other combinations because
Not quite. The answer is you couple the third trailer to the second trailer before you couple them to the first trailer.
A triple combination vehicle has four units (not counting the converter dollies): a tractor and three trailers. You couple a triple as follows: 1. Couple the first trailer to the tractor the same way that you couple any combination vehicle. 2. Couple the third trailer to the second trailer using the method for coupling doubles (which will involve the use of a converter dolly). 3. Move another converter dolly into position. 4. Couple the tractor and first trailer to the second and third trailer using the method for coupling doubles (which will involve another converter dolly).
9Question 9 of 20
During your walk-around inspection of your vehicle, check each landing gear to be sure that
Not quite. The answer is both of the above are true.
Check each landing gear to be sure that it is fully raised. Also check that no parts are missing and it isn't bent or damaged.
10Question 10 of 20
When you're coupling a set of doubles, which of the following is a way to secure the second trailer before coupling?
Not quite. The answer is Use wheel chocks.
If the second trailer doesn’t have spring brakes, drive the tractor close to the trailer, connect the emergency line, charge the trailer air tank, and disconnect the emergency line. This will set the trailer emergency brakes (assuming the slack adjusters are correctly adjusted). However, if you have any doubt about the effectiveness of the trailer's braking system, chock the wheels.
11Question 11 of 20
When inspecting coupled doubles or triples, make sure that the pintle hooks are
Not quite. The answer is latched.
When coupling a converter dolly to the trailer in front of it, place the dolly's pintle eye on the trailer's pintle hook. Latch the pintle hook closed. Secure the dolly's safety chains to the trailer.
12Question 12 of 20
Why must you inspect your double or triple combination vehicle more extensively than a vehicle with only one such semitrailer?
Not quite. The answer is There are more critical parts to check.
There is nothing inherently wrong with double or triple trailers. There are just more critical parts to check. For a triple, you must check the critical parts of three trailers and two converter dollies, problems in any of which can cause serious trouble.
13Question 13 of 20
Which of these is likely the longest?
Not quite. The answer is Turnpike double trailer
A double pup trailer consists of two 28.5-foot trailers, known as "pup trailers." A double pup trailer is also known as an STAA trailer, named for the Surface Transportation Assistance Act (STAA). This is the only type of double trailer that is allowed nationwide. A Rocky Mountain double trailer consists of a 40- to 53-foot trailer followed by a 28.5-foot pup trailer. Rocky Mountain doubles are allowed in certain Western states. A turnpike double trailer consists of two 48-foot trailers. Turnpike doubles can be found traveling on expressways in the Eastern states.
14Question 14 of 20
You wish to turn right from one two-lane, two-way street into another. The truck is too long to turn without swinging wide. You should turn as shown in path
Not quite. The answer is B.
If you swing wide to the left before you turn right, another vehicle may try to pass you on your right while you are turning. Instead, as shown in path B, make the right turn with the rear of your vehicle as close to the curb as possible and turn wide as you complete the turn. This will deny other vehicles enough room on the right to try to pass you.
15Question 15 of 20
Compared with single trailers, double and triple trailers are
Not quite. The answer is more likely to turn over.
In a double or triple combination, each trailer is more likely to roll over than the one in front of it. The rear trailer of a triple is 3.5 times as likely to roll over as a five-axle tractor-trailer. This is known as the "crack-the-whip" effect, caused by rearward amplification. For safety, position the heaviest trailer in front and the lightest trailer in the rear.
16Question 16 of 20
Some large trucks have convex or “spot” mirrors. Such mirrors
Not quite. The answer is make things look smaller and farther away than they really are.
A convex mirror has a wider field of view than a flat mirror. However, objects viewed in a convex mirror look smaller and farther away. Remember this when you're trying to judge the distance of an object that you're viewing in a convex mirror.
17Question 17 of 20
Which of the following will result in the best control on a curve?
Not quite. The answer is Slow to a safe speed before entering the curve, then accelerate slightly through it.
The safest way to take a curve is to slow down before the curve and then accelerate slightly through the curve. Braking in a curve risks a skid.
18Question 18 of 20
Which of these double-trailer configurations includes just one 28.5-foot pup trailer?
Not quite. The answer is Rocky Mountain double
A double pup trailer consists of two 28.5-foot trailers, known as "pup trailers." A double pup trailer is also known as an STAA trailer, named for the Surface Transportation Assistance Act (STAA). This standard-double configuration is the only type of double trailer that is allowed nationwide. A Rocky Mountain double trailer consists of a 40- to 53-foot trailer followed by a 28.5-foot pup trailer. Rocky Mountain doubles are allowed in certain Western states. A turnpike double trailer consists of two 48-foot trailers. Turnpike doubles can be found traveling on expressways in the Eastern states.
19Question 19 of 20
If your test of the tractor protection valve is successful,
Not quite. The answer is the tractor protection valve control (trailer air supply control) will pop out or go from "normal" to "emergency."
When you test the tractor protection valve, the tractor protection valve control (also called the trailer air supply control) should pop out or go from the "normal" to the "emergency" position. This shows that the tractor protection valve has closed automatically to keep the air pressure from falling too far.
20Question 20 of 20
What is the definition of "off-tracking?"
Not quite. The answer is How the rear wheels follow a different path from the front wheels in a turn
Off-tracking is defined as the different paths taken by the front and rear wheels in a turn. The longer the vehicle, the greater the difference will be. As a result, the path followed by a tractor will be wider than the path of the rig itself. To compensate, you must steer the tractor wider to keep the rig from overrunning the curb or hitting some object.

Questions people ask

Is this Colorado CDL: Double & Triple Trailers Practice Test like the real Colorado CDL Knowledge Test?

The questions are written in the same style as the real test, from official sources, with an explanation for each answer. The real test has 20 questions; this free test has 20.

How many questions are on the Colorado CDL Knowledge Test?

The General Knowledge test has 20 questions. Each class and endorsement adds its own test.

What score do you need to pass the Colorado CDL Knowledge Test?

You need 16 out of 20 correct (80%).

How old do you have to be to take the Colorado CDL Knowledge Test?

You can take it from age 18.

Where can I practice more questions?

The Driving Exam Prep app has the full question bank for your test, a step-by-step roadmap, a mistakes review and a readiness score against the real pass mark.

Official sources

Our questions are written from these official sources. Always study your official handbook too: rules change, and our practice questions may differ from your real test.

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To uncouple the rear trailer, the first thing you do is

The official CDL manual's section on double and triple trailers usually describes how to couple and uncouple

During normal operation, the brakes on double and triple trailers are controlled with the

Which of these statements about managing space to the sides is true?

What is the main difference between a B-dolly (or C-dolly), and an A-dolly?

When you're pulling triples, it is safest for the lightest trailer to be positioned in the

Which of the following statements about steering is true?

Coupling a triple trailer is different from coupling other combinations because

During your walk-around inspection of your vehicle, check each landing gear to be sure that

When you're coupling a set of doubles, which of the following is a way to secure the second trailer before coupling?

When inspecting coupled doubles or triples, make sure that the pintle hooks are

Why must you inspect your double or triple combination vehicle more extensively than a vehicle with only one such semitrailer?

Which of these is likely the longest?

You wish to turn right from one two-lane, two-way street into another. The truck is too long to turn without swinging wide. You should turn as shown in path

Compared with single trailers, double and triple trailers are