Traffic Laws Test
Alabama Traffic Laws Test – 20 Questions with Answers
20 questions · 15 min · Medium
Doubles & Triples Test – 20 Questions with Answers
Test your CDL knowledge of doubles and triples combination vehicles with questions covering coupling, uncoupling, converter dollies, air brakes, off-tracking, rollover risks, inspections, cargo distribution, and safe driving practices.
- 20
- Questions
- 15 min
- Time limit
- Medium
- Difficulty
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Defensive Driving Test
Alabama Defensive Driving Test – 20 Questions with Answers
20 questions · 15 min · Medium
All 20 questions and answers Spoilers: this shows the questions and answers. Try the quiz first! Open
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1. What is a major safety concern when driving a vehicle with doubles or triples trailers?
- A. The vehicle is easier to stop
- B. The rear trailers can swing outward or off-track during turns
- C. The vehicle requires less following distance
- D. The rear trailer always follows the exact path of the tractor
Show answer
B. The rear trailers can swing outward or off-track during turns
Doubles and triples have multiple articulation points, increasing off-tracking and swing-out risks during turns.
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2. What is a converter dolly used for in a doubles combination?
- A. To connect the second trailer to the first trailer
- B. To increase engine power
- C. To control the steering axle
- D. To replace the tractor's fifth wheel
Show answer
A. To connect the second trailer to the first trailer
A converter dolly is used to connect one trailer to another in a doubles or triples combination.
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3. What component on a converter dolly connects to the trailer ahead of it?
- A. Kingpin
- B. Landing gear
- C. Steering wheel
- D. Brake chamber
Show answer
A. Kingpin
The converter dolly's upper coupler connects to the trailer's fifth wheel through its kingpin.
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4. Why should the heaviest trailer generally be placed closest to the tractor in a doubles combination?
- A. To improve stability and reduce the risk of trailer sway
- B. To make the rear trailer turn faster
- C. To reduce the tractor's braking ability
- D. To eliminate off-tracking
Show answer
A. To improve stability and reduce the risk of trailer sway
Proper trailer placement and weight distribution help maintain stability and reduce handling problems.
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5. What can happen if a doubles or triples combination enters a curve too fast?
- A. The trailers become shorter
- B. The rear trailer may roll over
- C. The steering becomes automatic
- D. The brakes automatically increase stopping distance
Show answer
B. The rear trailer may roll over
Rear trailers can be particularly vulnerable to rollover because they follow a different path and can experience amplified lateral forces.
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6. What does off-tracking mean when operating doubles or triples?
- A. The rear wheels follow a path inside the path of the tractor's wheels
- B. The tractor loses engine power
- C. The trailer brakes stop working
- D. The vehicle travels above the speed limit
Show answer
A. The rear wheels follow a path inside the path of the tractor's wheels
Off-tracking occurs when the rear wheels take a shorter, more inside path than the tractor during a turn.
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7. What is trailer whip in a doubles or triples combination?
- A. Movement of the rear trailer that can become amplified during sudden steering
- B. A method of checking tire pressure
- C. A type of air brake
- D. A way to connect the landing gear
Show answer
A. Movement of the rear trailer that can become amplified during sudden steering
Trailer movement can become increasingly pronounced toward the rear of a doubles or triples combination.
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8. Why should sudden steering movements be avoided with doubles and triples?
- A. They can increase trailer swing and rollover risk
- B. They make the engine run cooler
- C. They eliminate off-tracking
- D. They shorten the vehicle
Show answer
A. They can increase trailer swing and rollover risk
Sudden steering can cause amplified movement through the multiple trailers and increase the risk of loss of control.
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9. What should you check when inspecting the connections between trailers in a doubles combination?
- A. Only the paint condition
- B. Couplings, safety devices, air lines, and electrical connections
- C. Only the trailer license plate
- D. Only the rear bumper
Show answer
B. Couplings, safety devices, air lines, and electrical connections
All coupling and connection components should be inspected to ensure the trailers are safely connected.
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10. What is a common danger when backing a doubles or triples combination?
- A. The trailers are easier to control than a single trailer
- B. The trailers can move unpredictably and may jackknife
- C. The rear trailer cannot move
- D. The tractor automatically centers the trailers
Show answer
B. The trailers can move unpredictably and may jackknife
Backing multiple trailers is difficult because movement at one coupling affects the trailers behind it.
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11. What is the safest practice when backing a doubles or triples combination?
- A. Back quickly before the trailers can move
- B. Use a spotter when possible and back slowly
- C. Avoid checking mirrors
- D. Turn the steering wheel sharply and continuously
Show answer
B. Use a spotter when possible and back slowly
Backing slowly with proper observation and a spotter when available helps reduce the risk of collision or jackknife.
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12. Why is adequate following distance especially important with doubles and triples?
- A. They require considerable distance to stop
- B. They always have weak headlights
- C. They cannot use their brakes
- D. They stop faster than passenger vehicles
Show answer
A. They require considerable distance to stop
The greater length and weight of these combinations can require substantial stopping distance.
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13. What can happen if the air lines between trailers are damaged or leaking?
- A. The trailers may lose proper braking capability
- B. The engine automatically increases power
- C. The tires inflate automatically
- D. The trailer becomes easier to steer
Show answer
A. The trailers may lose proper braking capability
Air leaks or damaged air lines can reduce or eliminate proper air-brake operation on the affected trailer.
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14. What should you do before coupling a converter dolly to a trailer?
- A. Make sure the dolly and trailer are properly positioned and secure
- B. Disconnect all safety equipment
- C. Raise the trailer's rear wheels
- D. Remove the dolly's brakes
Show answer
A. Make sure the dolly and trailer are properly positioned and secure
Proper positioning and securing of the equipment are essential before coupling.
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15. What is one reason doubles and triples require careful speed control on curves?
- A. The rear units can experience greater lateral forces
- B. The tractor cannot turn
- C. The trailers become lighter in curves
- D. The brakes cannot be used on curves
Show answer
A. The rear units can experience greater lateral forces
Lateral forces can increase toward the rear of a multiple-trailer combination, increasing rollover risk.
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16. What is a jackknife in a doubles or triples combination?
- A. A condition where one or more trailers fold toward the tractor or another trailer
- B. A method for checking brake pressure
- C. A type of trailer suspension
- D. A normal turning technique
Show answer
A. A condition where one or more trailers fold toward the tractor or another trailer
A jackknife occurs when the units swing out of alignment at an articulation point.
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17. What should you do if a doubles or triples combination begins to skid?
- A. Make sudden steering movements
- B. Accelerate sharply
- C. Avoid sudden braking and steering and regain control smoothly
- D. Turn sharply toward the shoulder
Show answer
C. Avoid sudden braking and steering and regain control smoothly
Abrupt braking or steering can worsen a skid or cause the trailers to swing or jackknife.
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18. Why must cargo be properly distributed in doubles and triples?
- A. To maintain stability and keep axle weights within legal limits
- B. To make the rear trailer heavier than the tractor
- C. To eliminate the need for inspections
- D. To increase off-tracking
Show answer
A. To maintain stability and keep axle weights within legal limits
Proper cargo distribution helps maintain vehicle stability and prevents excessive loading on individual axles.
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19. When should the brakes and connections of a doubles or triples combination be checked?
- A. Only after a breakdown
- B. During the required pre-trip inspection and whenever necessary during operation
- C. Only once a year
- D. Only when driving downhill
Show answer
B. During the required pre-trip inspection and whenever necessary during operation
A thorough inspection helps identify defective brakes, couplings, air lines, electrical connections, and other safety problems.
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20. What is an important defensive-driving practice when operating doubles or triples in strong winds?
- A. Increase speed to reduce wind exposure
- B. Reduce speed and maintain firm control of the vehicle
- C. Drive close to other vehicles for protection
- D. Make frequent sudden steering corrections
Show answer
B. Reduce speed and maintain firm control of the vehicle
Multiple trailers can be affected significantly by wind. Reducing speed and maintaining control helps reduce the risk of trailer sway or loss of control.