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.

When you're pulling doubles or triples, you should do which of the following?

Allow a greater following distance than for smaller commercial vehicles.

Apply the brakes on the rear trailer first.

Place the lightest cargo in the front trailer.

To uncouple a triple-trailer combination, which of these do you do first?

Uncouple the third semitrailer from the second dolly.

Uncouple the second semitrailer from the first dolly.

Uncouple the first semitrailer from the tractor.

When uncoupling a set of standard doubles, which of the following steps is done first?

Lower the second semitrailer's landing gear.

Release the pintle hook on the first semitrailer.

Which of these statements about speed management and braking is true?

You need about four times as much braking distance at 40 mph as at 20 mph.

The stopping distance of a truck is the distance it takes to stop once the brakes are applied.

Speed limits posted on curves are safe for all trucks.

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 the following statements about checking your mirrors is true?

Check your mirrors to keep an eye on your tires.

Check your mirrors every 20 minutes.

Your mirrors allow you to see all around your truck.

Which of these statements about checking your mirrors is true?

Use your mirrors to keep an eye on your tires.

Proper adjustment of your mirrors can eliminate blind spots.

You can adjust your mirrors accurately only when you're driving in traffic.

When you uncouple twin trailers, the last step is to

slowly pull clear of the converter dolly.

release the brakes on the converter dolly.

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Pennsylvania CDL: Double & Triple Trailers Practice Test

20 double & triple trailers questions for the Pennsylvania CDL Knowledge Test, out of 101 in the app. Answer each to see whether you got it right and why. The real Pennsylvania 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 DOT. 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
Antilock brakes (ABS) have been required on all converter dollies built since
Not quite. The answer is March 1998.
Antilock brakes have been required on all tractors built since March 1, 1997. Antilock brakes have been required on all trailers, converter dollies, buses, and single trucks built since March 1, 1998.
2Question 2 of 20
The converter dolly air tank drain valve on coupled doubles or triples should be
Not quite. The answer is closed.
A pre-trip inspection of a double or triple combination vehicle includes an inspection of each converter dolly in the vehicle. Among other things, check that the converter dolly air tank drain valve is closed.
3Question 3 of 20
In normal driving of a double or triple combination vehicle, you should operate the brakes with the
Not quite. The answer is foot pedal.
The trailer hand valve (also called the Trolley Valve or Johnson Bar) operates only the trailer brakes, not the tractor brakes. Hence, use it only when you want to test the trailer brakes. Don't use it in normal driving because braking the trailers and not the tractor can cause a trailer to skid. The foot brake sends air to all the brakes on the vehicle – the tractor and all trailers. There is much less danger of causing a skid or jackknife when using just the foot brake.
4Question 4 of 20
Under federal regulations, before you can be trained to pull triples, you must have at least 6 months' prior experience doing what?
Not quite. The answer is Either (a) or (b)
Federal regulation 49 CFR 380.205 states that you must meet various requirements before you can start training to operate a triple long combination vehicle. These requirements include 6 months' immediately prior experience driving either a tractor/semi-trailer combination or a tractor/semi-trailer/trailer combination, with a gross combination weight rating (GCWR) of at least 26,001 pounds.
5Question 5 of 20
When you're checking the coupling of a double trailer, the landing gear of the rear trailer should be
Not quite. The answer is slightly raised.
When connecting the rear trailer to the converter dolly, lock the trailer brakes and raise the trailer landing gear slightly off the ground so it won't be damaged if the trailer moves. Then pull forward with the trailer brakes still locked, to check that the rear trailer is locked onto the converter dolly. If it's not, at least the landing gear will keep the rear trailer from falling onto the ground.
6Question 6 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.
7Question 7 of 20
When you're pulling doubles or triples, you should do which of the following?
Not quite. The answer is Allow a greater following distance than for smaller commercial vehicles.
Doubles and triples need more space because they can’t be turned or stopped suddenly. Allow a greater following distance behind the vehicle in front of you.
8Question 8 of 20
When you're pulling more than one trailer, which trailer should be the first one behind the tractor?
Not quite. The answer is The heaviest trailer
The rearmost trailer is much more likely to roll over than the front trailer. Position the heaviest trailer directly behind the tractor and position the lightest trailer at the rear.
9Question 9 of 20
To uncouple a triple-trailer combination, which of these do you do first?
Not quite. The answer is Uncouple the third semitrailer from the second dolly.
To couple a triple-trailer combination, you couple the tractor and first semitrailer to the second and third semitrailers. But to uncouple the triple-trailer combination, you start by just uncoupling the third semitrailer from the rest of the combination.
10Question 10 of 20
When uncoupling a set of standard doubles, which of the following steps is done first?
Not quite. The answer is Lower the second semitrailer's landing gear.
When uncoupling a set of standard doubles, the first unit to be uncoupled is the second semitrailer. To do this, lower its landing gear just enough to take some weight off the dolly. Then close the air shut-off valves on the first semitrailer and on the dolly (if so equipped). Disconnect the dolly's air and electrical lines from the second semitrailer. Release the dolly's fifth wheel latch, and pull the tractor forward so it pulls the dolly out from under the second semitrailer. After this is done, start to uncouple the dolly from the first semitrailer. These steps include lowering the dolly's landing gear and unhooking the dolly from the first semitrailer's pintle latch.
11Question 11 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).
12Question 12 of 20
Which of these statements about speed management and braking is true?
Not quite. The answer is You need about four times as much braking distance at 40 mph as at 20 mph.
Your total stopping distance is the sum of your perception distance (how far your vehicle goes from when you see the hazard until your brain processes it), reaction distance (how far the vehicle goes from when your brain orders your foot to take action until your foot actually starts to brake), and braking distance (how far the vehicle continues to travel once you apply the brake). Your vehicle's braking distance increases as the square of your speed. For example, you need about four times as much braking distance at 40 mph as you do at 20 mph.
13Question 13 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.
14Question 14 of 20
Which of the following statements about checking your mirrors is true?
Not quite. The answer is Check your mirrors to keep an eye on your tires.
Use the mirrors to keep an eye on your tires. It's one way to spot a tire fire. But your mirrors don't eliminate all blind spots. Your truck still has large blind spots, often called No-Zones.
15Question 15 of 20
During your walk-around inspection of a double or triple combination, check that the shut-off valves are _______ at the rear of each trailer except the last trailer, where they should be _______.
Not quite. The answer is open; closed
When you are inspecting a double or triple combination, make sure that the service and emergency line shut-off valves are open at the rear of each trailer except the last trailer, where they must be closed.
16Question 16 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.
17Question 17 of 20
Which of these statements about checking your mirrors is true?
Not quite. The answer is Use your mirrors to keep an eye on your tires.
Clean and adjust your mirrors as part of your pre-trip inspection, when your vehicle is parked. Adjust each mirror to show some part of your vehicle as well as the roadway. You can adjust your mirrors accurately only when your trailers are straight. While you're driving, use your mirrors to keep an eye on your tires. It's one way to spot a tire fire. However, no matter how carefully you adjust your mirrors, there will still be blind spots that your mirrors cannot show you.
18Question 18 of 20
The crack-the-whip effect that troubles trucks with trailers is most likely to tip over
Not quite. The answer is the rear trailer of a triple.
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 rearward amplification or the "crack-the-whip effect." For safety, position the heaviest trailer in front and the lightest trailer in the rear.
19Question 19 of 20
When you uncouple twin trailers, the last step is to
Not quite. The answer is slowly pull clear of the converter dolly.
The last step in the process of uncoupling twin trailers is to slowly pull clear of the converter dolly. The other two choices are previous steps in this process.
20Question 20 of 20
A converter dolly consists of a ______ wheel and ________ axles.
Not quite. The answer is fifth; one or two
A semitrailer can be connected to a converter dolly because, like the rear of a typical tractor, it has a fifth wheel and one or two axles.

Questions people ask

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

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

How old do you have to be to take the Pennsylvania 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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Pennsylvania CDL: Double & Triple Trailers Practice Test

Antilock brakes (ABS) have been required on all converter dollies built since

The converter dolly air tank drain valve on coupled doubles or triples should be

In normal driving of a double or triple combination vehicle, you should operate the brakes with the

Under federal regulations, before you can be trained to pull triples, you must have at least 6 months' prior experience doing what?

When you're checking the coupling of a double trailer, the landing gear of the rear trailer should be

Which of the following statements about steering is true?

When you're pulling doubles or triples, you should do which of the following?

When you're pulling more than one trailer, which trailer should be the first one behind the tractor?

To uncouple a triple-trailer combination, which of these do you do first?

When uncoupling a set of standard doubles, which of the following steps is done first?

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

Which of these statements about speed management and braking is true?

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

Which of the following statements about checking your mirrors is true?

During your walk-around inspection of a double or triple combination, check that the shut-off valves are _ at the rear of each trailer except the last trailer, where they should be _.

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

Which of these statements about checking your mirrors is true?

The crack-the-whip effect that troubles trucks with trailers is most likely to tip over

When you uncouple twin trailers, the last step is to

A converter dolly consists of a wheel and __ axles.

More topic

Questions people ask

Official sources

Keep going

Your license is one lesson closer.

Antilock brakes (ABS) have been required on all converter dollies built since

The converter dolly air tank drain valve on coupled doubles or triples should be

In normal driving of a double or triple combination vehicle, you should operate the brakes with the

Under federal regulations, before you can be trained to pull triples, you must have at least 6 months' prior experience doing what?

When you're checking the coupling of a double trailer, the landing gear of the rear trailer should be

Which of the following statements about steering is true?

When you're pulling doubles or triples, you should do which of the following?

When you're pulling more than one trailer, which trailer should be the first one behind the tractor?

To uncouple a triple-trailer combination, which of these do you do first?

When uncoupling a set of standard doubles, which of the following steps is done first?

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

Which of these statements about speed management and braking is true?

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

Which of the following statements about checking your mirrors is true?

During your walk-around inspection of a double or triple combination, check that the shut-off valves are _______ at the rear of each trailer except the last trailer, where they should be _______.

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

Which of these statements about checking your mirrors is true?

The crack-the-whip effect that troubles trucks with trailers is most likely to tip over

When you uncouple twin trailers, the last step is to

A converter dolly consists of a ______ wheel and ________ axles.

More topic

Questions people ask

Official sources

Keep going

Your license is one lesson closer.

During your walk-around inspection of a double or triple combination, check that the shut-off valves are _ at the rear of each trailer except the last trailer, where they should be _.

A converter dolly consists of a wheel and __ axles.