25 realistic Doubles and Triples practice questions for New Mexico CDL applicants. Required for: Drivers pulling more than one trailer. Official test: 20 questions, 16 correct to pass.
Question 1 of 25 · Vehicle Dynamics
When making a turn, the front trailer of a doubles set:
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A.
Tracks like a single trailer
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B.
Off-tracks more than the tractor
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C.
Stays in line with the tractor
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D.
Off-tracks less than the rear trailer
Correct answer: D.
The rear trailer off-tracks more than the front, so the rear is more likely to hit obstacles.
Question 2 of 25 · Inspection
Why must drivers inspect the dolly before connecting?
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A.
To check for damage and proper operation
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B.
To verify the brakes work
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C.
To inspect the pintle hook
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D.
All of the above
Correct answer: D.
Dolly inspection includes structure, brakes, and pintle hook condition.
Question 3 of 25 · Coupling
What's the role of safety chains on a converter dolly?
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A.
To support the dolly when uncoupled
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B.
To prevent the trailer from coming loose if the pintle hook fails
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C.
To improve traction
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D.
To act as a brake
Correct answer: B.
Safety chains keep the trailer attached if the pintle hook fails.
Question 4 of 25 · Adverse Conditions
What's the safest way to handle wind with doubles or triples?
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A.
Slow down and grip the wheel firmly
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B.
Speed up to clear the area
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C.
Use engine retarder
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D.
Lock the brakes
Correct answer: A.
Reduce speed and steer firmly. Wind affects long combinations more than singles.
Question 5 of 25 · Coupling
How should you uncouple a converter dolly?
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A.
Lower the dolly support, disconnect, and pull the tractor and first trailer away
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B.
Disconnect and drive away
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C.
Use the trailer parking brake
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D.
Cut the air lines
Correct answer: A.
Lower support, disconnect lines and pin, then pull the lead unit away.
Question 6 of 25 · Adverse Conditions
What's the safe way to handle a doubles or triples on a wet road?
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A.
Reduce speed and increase following distance
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B.
Drive at posted speed
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C.
Use chains
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D.
Both A and C
Correct answer: A.
Slower speeds and more space are essential on wet roads.
Question 7 of 25 · Cargo
Doubles and triples are most stable when:
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A.
All trailers are properly loaded
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B.
Trailers are empty
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C.
The lead trailer is empty
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D.
The rear trailer is heaviest
Correct answer: A.
Proper loading on every trailer is key to stability.
Question 8 of 25 · Vehicle Dynamics
How do you reduce off-tracking in doubles?
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A.
Make wider turns
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B.
Slow down
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C.
Use mirrors carefully
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D.
All of the above
Correct answer: D.
Wider turns, slower speed, and careful mirror use minimize off-tracking impact.
Question 9 of 25 · Coupling
What is the converter dolly?
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A.
A type of tractor
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B.
A coupling device used between trailers in doubles and triples
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C.
A trailer brake
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D.
A type of cargo
Correct answer: B.
The converter dolly connects two trailers in a combination set.
Question 10 of 25 · Lane Changes
What's the major risk when changing lanes with doubles or triples?
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A.
The rear trailer may not follow exactly
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B.
Other vehicles may not see the long combination
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C.
The trailer may swing out
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D.
All of the above
Correct answer: D.
Visibility and rear-trailer tracking are both major lane-change risks.
Question 11 of 25 · Coupling
What's a common mistake when coupling doubles?
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A.
Not properly aligning the dolly with the second trailer
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B.
Forgetting to connect air lines
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C.
Not testing the brakes
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D.
All of the above
Correct answer: D.
Alignment, air lines, and brake tests are common areas for mistakes.
Question 12 of 25 · CDL Rules
Why are doubles and triples drivers required to have additional training?
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A.
They handle differently and require more skill
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B.
Federal regulations require training
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C.
They have higher rollover risk
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D.
All of the above
Correct answer: D.
Skill, regulation, and rollover risk all justify extra training.
Question 13 of 25 · Cargo
What's the impact of overloading a trailer in a doubles set?
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A.
Increased rollover risk
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B.
Poor handling
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C.
Brake problems
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D.
All of the above
Correct answer: D.
Overloading creates a chain of safety problems for the whole combination.
Question 14 of 25 · Operation
How should drivers approach intersections with doubles or triples?
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A.
Slow down and signal early to allow for the turn
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B.
Drive at full speed
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C.
Cut across lanes if needed
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D.
Use the engine retarder
Correct answer: A.
Slow down and signal well in advance to give time for the long combination.
Question 15 of 25 · Combination Air
What's the role of glad hands in doubles and triples?
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A.
They connect air lines between each unit
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B.
They are coupling devices
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C.
They are safety chains
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D.
They are landing gear
Correct answer: A.
Glad hands connect service and emergency air lines between every unit.
Question 16 of 25 · Following Distance
What's the best way to manage following distance with doubles?
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A.
Maintain extra distance compared to single trailers
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B.
Same as single trailers
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C.
Less distance
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D.
No following distance needed
Correct answer: A.
Doubles need more space because of longer stopping distances and reduced visibility.
Question 17 of 25 · Following Distance
What's the safe way to handle a doubles in heavy traffic?
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A.
Maintain extra following distance and signal early
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B.
Speed up to keep with traffic
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C.
Use the shoulder
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D.
Drive aggressively
Correct answer: A.
Extra space and early signals are critical in heavy traffic with combinations.
Question 18 of 25 · Inspection
When inspecting doubles and triples, what should you check?
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A.
Each trailer's lights and brakes
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B.
Each converter dolly
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C.
Each fifth wheel and pintle hook
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D.
All of the above
Correct answer: D.
Inspect every trailer, dolly, fifth wheel, and pintle hook before driving.
Question 19 of 25 · Coupling
Where should the heaviest trailer go in a doubles or triples set?
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A.
First (closest to the tractor)
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B.
Last (farthest from the tractor)
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C.
Anywhere
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D.
In the middle
Correct answer: A.
Place the heaviest trailer behind the tractor for best stability.
Question 20 of 25 · Vehicle Dynamics
What is "crack-the-whip"?
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A.
A driver discipline rule
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B.
When the rear trailer swings out due to sudden steering inputs
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C.
A type of weight distribution
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D.
A coupling procedure
Correct answer: B.
The rear trailer can swing far wider than the tractor, magnifying steering inputs.
Question 21 of 25 · Skids
What should you do if a trailer starts to skid?
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A.
Release the brakes to allow trailer wheels to roll
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B.
Apply more brake
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C.
Steer hard right
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D.
Accelerate
Correct answer: A.
Release brakes to let trailer wheels roll; steer to recover.
Question 22 of 25 · Hazard Awareness
What is "blind spot" risk for doubles and triples?
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A.
It's minimal due to long mirrors
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B.
It's significant especially behind and to the right
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C.
It's only at night
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D.
It only affects single trailers
Correct answer: B.
Long combinations have large blind spots — especially behind and to the right.
Question 23 of 25 · Vehicle Dynamics
Doubles and triples have ____ rollover risk than single trailers.
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A.
Lower
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B.
Higher
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C.
The same
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D.
No rollover risk
Correct answer: B.
Multiple trailers have higher rollover risk because of greater articulation and "crack-the-whip" effect.
Question 24 of 25 · Operation
What's the safest way to merge into traffic with doubles?
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A.
Use turn signals early and merge gradually
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B.
Speed up to merge quickly
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C.
Force other drivers to yield
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D.
Drive on the shoulder
Correct answer: A.
Signal early and merge gradually so other drivers can adjust.
Question 25 of 25 · Inspection
What's the impact of poor maintenance on doubles or triples?
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A.
Increased risk of breakdowns and accidents
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B.
Poor fuel efficiency
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C.
Legal issues
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D.
All of the above
Correct answer: D.
Poor maintenance leads to safety, efficiency, and legal problems.
About the Doubles and Triples Test
The Doubles and Triples test covers pulling double and triple trailers, coupling and uncoupling, inspecting doubles and triples, antilock brake systems, and safe driving with multiple trailers. Doubles and triples are more likely to roll over than single trailers and are extremely sensitive to steering inputs at the rear trailer.
The New Mexico Motor Vehicle Division administers this knowledge test as part of its commercial driver license program. To earn the Doubles/Triples (T) on your New Mexico CDL, you need to score at least 16 out of 20 on the official version.
Topics covered on this practice test
- Coupling: 5 questions
- Vehicle Dynamics: 4 questions
- Inspection: 3 questions
- Adverse Conditions: 2 questions
- Cargo: 2 questions
- Operation: 2 questions
- Following Distance: 2 questions
- Lane Changes: 1 question
- CDL Rules: 1 question
- Combination Air: 1 question
- Skids: 1 question
- Hazard Awareness: 1 question
How to use this practice test
- Read each question carefully. CDL questions are written precisely — small wording differences matter.
- Click "Show Answers & Explanations" only after answering every question. Don't peek mid-test.
- Read the explanation for every question, even ones you got right. The reasoning is more important than the answer.
- Repeat the test until you score 100%. The questions are deterministic per state, so you can track your improvement over multiple sessions.
- Move on to the other endorsement tests for New Mexico until you're ready for the official exam.
Tips specific to the Doubles and Triples test
Doubles and Triples questions emphasize the "crack-the-whip" effect, converter dolly inspection and use, pintle hooks, safety chains, the heaviest-trailer-first loading rule, and the higher rollover risk of multi-trailer combinations. Many states prohibit triples; check local rules.