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Delaware Doubles / Triples CDL Practice Test

Below are 25 exam-style questions for the Delaware Doubles / Triples CDL knowledge test, modeled on the FMCSA-aligned content used by the Delaware Division of Motor Vehicles. Try to answer each question on your own before reading the answer key directly under it. The questions and answer choices are shuffled deterministically per state and endorsement, so the order will stay the same on repeat visits — that lets you genuinely measure your improvement.

Heads up: this is a study tool, not a graded exam. Cover the answer with your hand or a sheet of paper for an honest practice run, then re-read the explanations for any questions you missed. Aim for 22 out of 25 or better, three times in a row, before scheduling the real exam.
Question 1 of 25
When the second trailer is empty:
  • A Better fuel mileage
  • B It can sway and lift more easily; drive carefully
  • C No change in handling
  • D It is harder to roll over
Correct answer: B
Empty trailers are surprisingly prone to swing and roll because the wheels lock up easily under braking.
Question 2 of 25
When the converter dolly's air tank is empty:
  • A Skip the charge
  • B Charge it before coupling and verify pressure
  • C Couple without checking
  • D Use the trailer hand valve to charge
Correct answer: B
Charging the dolly's tank ensures the trailer brakes will release properly.
Question 3 of 25
A doubles combination on a slick road:
  • A Should change lanes frequently
  • B Can maintain normal speed
  • C Should brake hard
  • D Should be driven slowly with extra following distance
Correct answer: D
Slick road + multiple trailers = extra caution.
Question 4 of 25
When pulling doubles or triples, the heaviest trailer should be:
  • A It does not matter
  • B First (closest to the tractor)
  • C Last (furthest from the tractor)
  • D In the middle
Correct answer: B
Heavier trailer first reduces sway and improves handling.
Question 5 of 25
When inspecting doubles or triples, you should check:
  • A All of the above
  • B Pintle hooks and safety chains
  • C Glad hands and seals at every connection
  • D Dolly air-tank pressure
Correct answer: A
Each connection point is a potential failure; check thoroughly.
Question 6 of 25
When approaching a curve in a doubles combination:
  • A Maintain speed
  • B Brake within the curve
  • C Slow down before the curve to reduce rollover risk and trailer swing
  • D Increase speed
Correct answer: C
Speed reduction before the curve prevents rollover.
Question 7 of 25
A converter dolly is used to:
  • A Test the brakes
  • B Move cargo within the trailer
  • C Connect a semitrailer to another trailer to form a combination
  • D Replace the fifth wheel on the tractor
Correct answer: C
Converter dollies turn semitrailers into trailers that can be coupled in series.
Question 8 of 25
When the air-supply line to the second trailer disconnects accidentally:
  • A Nothing happens
  • B The tractor brakes apply
  • C The first trailer accelerates
  • D The second trailer's emergency brakes apply automatically
Correct answer: D
Loss of supply pressure triggers emergency brakes — the failsafe.
Question 9 of 25
When the converter dolly is stored:
  • A Connect it to a random trailer
  • B Disable the brakes
  • C Leave it on a slope
  • D Park it on level ground with the parking brake set or wheels chocked
Correct answer: D
Stable parking with brakes set or chocks is safe storage.
Question 10 of 25
A doubles/triples driver should be especially aware of:
  • A Lane changes that swing the rear
  • B Potential rollover at curves
  • C All of the above
  • D Crosswind effects on the rear trailer
Correct answer: C
All three considerations apply to multi-trailer combinations.
Question 11 of 25
Safety chains on a doubles combination:
  • A Are required only on triples
  • B Carry electrical signals
  • C Are decorative
  • D Provide a backup connection in case the primary coupling fails
Correct answer: D
Safety chains hold the trailer if the primary coupling fails.
Question 12 of 25
The trailer hand valve on a doubles/triples combination operates:
  • A Tractor and trailer brakes
  • B Only the first trailer brakes
  • C All trailer service brakes simultaneously
  • D Only the rear trailer brakes
Correct answer: C
Hand valve applies all trailer service brakes; do not use as a parking brake.
Question 13 of 25
When backing doubles, you should:
  • A Avoid backing whenever possible; use a spotter when needed
  • B Skip the spotter
  • C Use only mirrors
  • D Back at full speed
Correct answer: A
Backing doubles is high-risk and rarely necessary; avoid when possible.
Question 14 of 25
In a doubles combination, the second (rear) trailer:
  • A Is less likely to roll
  • B Cannot roll
  • C Is more likely to roll than the first
  • D Has the same rollover risk
Correct answer: C
Rear trailer in a doubles is the most rollover-prone unit.
Question 15 of 25
A "coupling device" on a converter dolly:
  • A Includes a pintle hook on the front and a fifth wheel on the back
  • B Is electrical only
  • C Is a single hook
  • D Is the same as a tractor fifth wheel
Correct answer: A
Converter dollies have both ends: pintle hook to attach to the lead trailer, fifth wheel for the trailing trailer's kingpin.
Question 16 of 25
A doubles/triples driver should know:
  • A Coupling and uncoupling procedures
  • B All of the above
  • C How to inspect each connection point
  • D State and federal route restrictions
Correct answer: B
Comprehensive knowledge is essential for safe operation.
Question 17 of 25
A doubles/triples driver should plan routes to:
  • A Take the shortest route regardless
  • B Avoid restricted roads and minimize sharp curves and steep grades
  • C Drive only at night
  • D Avoid freeways
Correct answer: B
Route planning reduces handling demands.
Question 18 of 25
A doubles driver should be aware of:
  • A Tractor length only
  • B Trailer length only
  • C No specific length
  • D Total combination length when turning, parking, and changing lanes
Correct answer: D
Total length affects every maneuver.
Question 19 of 25
When pulling doubles, the driver should be alert to:
  • A Reduced visibility around the second trailer
  • B All of the above
  • C Crosswind sensitivity
  • D Increased rollover risk in curves
Correct answer: B
All three are inherent to multi-trailer operations.
Question 20 of 25
A doubles combination requires:
  • A Air lines from tractor to first trailer to dolly to second trailer
  • B No air-brake system
  • C Mechanical brakes only
  • D Air lines only on the tractor
Correct answer: A
Air system extends through the entire combination via glad hands at each connection.
Question 21 of 25
When you need to make a lane change in heavy traffic with doubles:
  • A Change quickly to fit in
  • B Skip the signal
  • C Cut between cars
  • D Plan the change well in advance, signal early, and change when there is ample space
Correct answer: D
Planning and patience prevent collisions.
Question 22 of 25
A doubles/triples driver should test the trailer brakes:
  • A Before pulling away from the coupling site
  • B Never; the dispatcher tests them
  • C Once a year
  • D Only at the destination
Correct answer: A
Test trailer brakes immediately after coupling and before any movement.
Question 23 of 25
A doubles/triples combination has more:
  • A Drivers
  • B Engines
  • C Air lines, electrical lines, and connection points
  • D Fuel tanks
Correct answer: C
More connections = more inspection points and more potential failure modes.
Question 24 of 25
When the rear trailer of a doubles combination begins to sway:
  • A Accelerate
  • B Reduce speed gradually and avoid sudden steering inputs
  • C Steer sharply to correct
  • D Brake hard
Correct answer: B
Smooth reduction in speed allows the trailer to settle.
Question 25 of 25
When the driver brakes a doubles combination:
  • A Only the rear trailer brakes
  • B All trailers should brake together if the system is functioning correctly
  • C Brakes are uneven
  • D Only the first trailer brakes
Correct answer: B
Air-brake system applies all wheels simultaneously when functioning correctly.

Study tips for the Delaware Doubles / Triples exam

The Doubles / Triples portion of the Delaware CDL exam is graded out of the bank of questions the Delaware Division of Motor Vehicles draws from each year. While the exact bank is not published, every question is sourced from the Doubles / Triples chapter of the Delaware CDL handbook, which itself is derived from the FMCSA Model Commercial Driver's License Manual. That means studying our practice tests, reading the corresponding handbook chapter, and re-reading the parts you got wrong is genuinely the most efficient route to a first-time pass.

Most successful applicants follow a simple cycle: take the practice test cold, write down every question you missed, open the matching chapter of the official Delaware handbook, re-read the section that contains the right answer, then re-take the practice test 24 to 48 hours later. The 24-hour delay matters — sleep is when your brain commits new information to long-term memory, and CDL knowledge questions reward that kind of consolidated learning rather than cramming.

Pay particular attention to questions that include qualifier words like always, never, only, primary, or most. CDL test writers love to flip the right answer with a single qualifier. When two answer choices look almost identical, pay attention to the verb (is it must, should, or may?) and to any numbers (14 days, 100 air miles, 8 hours, 70/8 split). On endorsement tests in particular, watch for trick framing where a true statement about a different endorsement is offered as the "correct" answer to a question that is actually about Doubles / Triples.

Test-day logistics matter too. Bring photo ID, your Social Security card or birth certificate, your medical examiner's certificate (DOT card), and proof of state residency if you haven't already submitted those documents. The Delaware Division of Motor Vehicles will not let you sit for the knowledge exam without your documentation, and most offices charge an additional fee for re-attempts. Arrive early — the wait at most CDL testing offices runs 30 to 60 minutes — and silence your phone before the exam begins.

Finally, keep your General Knowledge fundamentals sharp even when you're focused on the Doubles / Triples exam. Many states administer multiple knowledge tests in a single sitting, and questions on weight definitions (GVWR, GCWR, GAWR), stopping distance, and the pre-trip inspection routine show up across endorsements. If you're unsure on the basics, sit a fresh Delaware General Knowledge practice test before scheduling the real exam.

Next steps

Missed more than four questions? Re-read the Doubles / Triples study guide and the matching chapter in the official Delaware CDL handbook. Then come back and re-take the test. Once you can score 22 of 25 or higher on three runs in a row, you're in good shape to schedule the real exam at your local Delaware Division of Motor Vehicles office.

Already comfortable with this endorsement? Drill another: DE General Knowledge · DE Air Brakes · DE Combination Vehicles · DE Hazardous Materials · DE Passenger · DE School Bus · DE Tank Vehicle

New to the CDL process in Delaware? Read How to apply for a CDL in Delaware for the document checklist and step-by-step timeline.