Delaware · Doubles & Triples CDL Practice Test

The same federal Doubles & Triples question pool used by the Delaware Division of Motor Vehicles, with 50 practice questions and detailed explanations.

About the Doubles & Triples exam in Delaware

To add the Doubles & Triples endorsement to a CDL issued by Delaware, drivers complete the same federal knowledge exam covered on this site, then pay Delaware's endorsement add-on fee of approximately $12 per endorsement. The state schedules the written test at most full-service driver license offices and accepts walk-ins at many locations, though appointments are encouraged in metropolitan areas.

The Doubles & Triples (T) test in Delaware draws from the same federal question pool used nationwide. Practice with the questions on this page reflects the topics, format, and difficulty you will encounter at the counter. Some states also require an additional state-specific supplement for certain endorsements; check Delaware's CDL manual cover page for any state-specific addenda before your test date.

Once the Doubles & Triples endorsement is added, it appears as the letter T on the back of your physical license and in the state CDLIS record visible to employers and motor carrier safety auditors. The endorsement remains valid as long as the underlying CDL stays current and any federal prerequisites — such as the TSA security threat assessment for Hazmat — remain in good standing.

For drivers preparing for the Doubles & Triples endorsement test in Delaware, additional context — including federal manual excerpts, employer hiring practices, and DOT medical guidance — is widely available from industry resources. Continue reading on a recommended industry resource for further detail. Always cross-check anything you read with the current edition of your state CDL manual, since enforcement guidance is updated periodically.

How to schedule the written test in Delaware

Most the Delaware Division of Motor Vehicles offices accept walk-in CDL written-test applicants during posted hours, though appointments are strongly recommended in larger metro areas to avoid long waits. Bring your current driver's license, a current DOT medical examiner's certificate, and any documents required to satisfy the federal REAL ID identity-and-residency check if you have not already done so.

If you fail the Doubles & Triples exam in Delaware, you can retake it after a state-determined waiting period (commonly one business day, but in some counties, longer). Most jurisdictions cap the number of retakes within a single application cycle; check with your local the Delaware Division of Motor Vehicles office to confirm.

Doubles & Triples · Practice Quiz

Same federal question pool. Read the question, choose the best answer, then expand the explanation.

Question 1

In a double or triple combination, the heaviest trailer should be:
- A At the rear
- B In the middle
- C Directly behind the tractor Correct answer
- D It does not matter
Show explanation

Heaviest first reduces the crack-the-whip effect at the rear and improves handling stability.
Question 2

The "crack-the-whip" effect is:
- A Amplification of steering inputs at the rear of a multi-trailer combination Correct answer
- B A coupling failure
- C A type of skid
- D A type of brake
Show explanation

A small steering input at the tractor amplifies into a large lateral movement at the last trailer. Avoid sudden steering.
Question 3

The crack-the-whip effect is most dangerous on:
- A The dolly
- B The lead trailer
- C The rearmost trailer Correct answer
- D The tractor
Show explanation

The rearmost trailer experiences the largest amplification and is most likely to roll over from sudden inputs.
Question 4

A converter dolly is used to:
- A Cool the engine
- B Hold cargo down
- C Connect a second or third trailer to the combination Correct answer
- D Carry fuel
Show explanation

Converter dollies have a fifth wheel mounted on a single or tandem axle, used to attach additional trailers.
Question 5

When coupling a converter dolly, you should:
- A Drive away immediately
- B Verify that the safety pin or latch is in place after coupling Correct answer
- C Use only the brake
- D Skip the safety check
Show explanation

Safety pins and latches prevent dolly disconnection. Always verify after coupling.
Question 6

Before coupling the second trailer:
- A Make sure the first trailer is properly coupled and the dolly tongue is at the correct height Correct answer
- B Disconnect the first trailer
- C Move the cargo
- D Skip the inspection
Show explanation

Proper sequence: first trailer, dolly, second trailer. Each connection must be inspected before proceeding to the next.
Question 7

Inspect the converter dolly air lines for:
- A Length only
- B Brand
- C Color matching only
- D Damaged lines, leaks, and proper routing Correct answer
Show explanation

Dolly air lines must be intact and properly routed; failures can disable trailer brakes.
Question 8

Check the dolly's air tank for:
- A Drained moisture and proper pressure Correct answer
- B Weight
- C Brand
- D Color
Show explanation

Dolly air tanks accumulate moisture like other reservoirs and must be drained.
Question 9

When driving a double or triple combination:
- A Coast through curves
- B Speed up for turns
- C Brake hard at intersections
- D Slow down for turns more than with a single trailer Correct answer
Show explanation

Off-tracking is more pronounced and crack-the-whip is more dangerous. Slow turns prevent both problems.
Question 10

Lane changes in doubles and triples:
- A Should be sharp
- B Should be smooth and gradual to minimize crack-the-whip Correct answer
- C Should be done at speed
- D Are unnecessary
Show explanation

Smooth, gradual lane changes prevent amplification of lateral movement at the rear trailers.
Question 11

On slippery roads, doubles and triples:
- A Have no special concerns
- B Are more stable
- C Are more prone to jackknife than single combinations Correct answer
- D Stop better
Show explanation

More articulation points mean more potential failure modes on slick surfaces. Slow and increase following distance.
Question 12

Pre-trip on doubles requires:
- A Only the first trailer
- B Only the tractor
- C Only the rear trailer
- D Inspection of every trailer, every dolly, and every coupling Correct answer
Show explanation

Every component must be inspected. Failure at any one point can cause loss of control.
Question 13

Backing a double trailer combination is:
- A Done at high speed
- B Easy
- C Same as a single trailer
- D Difficult and best avoided Correct answer
Show explanation

Doubles back into different angles than singles; uncoupling and backing single trailers is usually safer than backing the combination.
Question 14

When coupling the second trailer, the dolly tongue should:
- A Be on the ground
- B Point upward
- C Be at the correct height to engage the lead trailer's pintle hook Correct answer
- D Point sideways
Show explanation

Pintle hook coupling requires the dolly tongue at the correct height. Use the dolly's landing gear or jack to set height.
Question 15

After coupling, the safety chains:
- A Should be connected and crossed under the tongue if specified Correct answer
- B Should be tied to the trailer
- C Should hang loose
- D Should be removed
Show explanation

Safety chains provide backup if the primary connection fails. Cross under the tongue per manufacturer specs.
Question 16

When meeting heavy crosswinds, doubles and triples:
- A Improve stability
- B Are more sensitive to crosswinds than singles Correct answer
- C Are unaffected
- D Reduce wind drag
Show explanation

Multi-trailer combinations have more sail area and articulation points. Slow down and grip the wheel firmly in heavy winds.
Question 17

Some highways prohibit doubles or triples on:
- A No highways
- B Specific routes — check state regulations Correct answer
- C All highways
- D Only at night
Show explanation

States and individual highways may restrict multi-trailer combinations. Verify routes before driving.
Question 18

A "pintle hook" is:
- A The hook on the lead trailer that connects to the dolly tongue Correct answer
- B A type of mirror
- C A brake component
- D A steering component
Show explanation

Pintle hooks are eye-and-hook couplings between the lead trailer and the converter dolly's tongue.
Question 19

When inspecting the second trailer, you should check:
- A Only the lights
- B Only the cargo
- C The same items as on the first trailer plus the coupling to the dolly Correct answer
- D Only the brakes
Show explanation

Each trailer is independently inspected for the standard items, plus its coupling integrity.
Question 20

Converter dollies built after March 1, 1998:
- A Are not subject to ABS rules
- B Must have hydraulic brakes
- C Must be equipped with antilock brakes Correct answer
- D Must have manual brakes only
Show explanation

Federal regulation required ABS on converter dollies built on or after March 1, 1998.
Question 21

A yellow ABS lamp on the dolly:
- A Means engine failure
- B Means total brake failure
- C Is normal
- D Indicates an ABS fault — the brakes still function Correct answer
Show explanation

Yellow ABS lamp means the antilock function has failed; standard brakes still work and the system should be serviced soon.
Question 22

In strong crosswinds, doubles and triples:
- A Should brake hard
- B Should park immediately
- C Should speed up
- D Should slow down significantly Correct answer
Show explanation

High side surfaces catch wind. Slowing reduces the destabilizing force.
Question 23

Following distance for doubles and triples should be:
- A The same as singles
- B Greater than for single trailers Correct answer
- C Less than singles
- D Half the legal minimum
Show explanation

Longer combinations need more space to stop and to recover from any control input.
Question 24

When passing in a double or triple, you should:
- A Use only the right lane
- B Allow significantly more time and distance than with a single trailer Correct answer
- C Pass quickly
- D Honk continuously
Show explanation

Multi-trailer combinations accelerate slowly and require longer pass distance. Allow generous gap.
Question 25

Mountain driving in doubles and triples:
- A Should be done in highest gear
- B Is easier than singles
- C Requires no special technique
- D Requires extra attention to engine braking and gear selection Correct answer
Show explanation

More mass means more brake heat. Engine braking and proper gear selection are even more important.
Question 26

Off-tracking in doubles and triples is:
- A Eliminated
- B The same as singles
- C Less than singles
- D Greater than in single combinations Correct answer
Show explanation

Each trailer adds off-tracking. Swing wider on turns to keep all wheels clear.
Question 27

Before pulling the second trailer, the trailer brakes should be:
- A Released by charging the trailer's air supply through the dolly Correct answer
- B Set permanently
- C Removed
- D Disconnected
Show explanation

Charge the trailer's air through the dolly's air lines, releasing the spring brakes for normal operation.
Question 28

When uncoupling a double, you should:
- A Just unhook the rear trailer
- B Follow the reverse of the coupling procedure carefully Correct answer
- C Disconnect everything at once
- D Drive away with brakes set
Show explanation

Reverse the coupling sequence: secure rear trailer, uncouple, secure dolly, uncouple lead trailer.
Question 29

Air lines between trailers and dollies:
- A Can hang loose
- B Can be coiled freely
- C Must be properly secured to prevent damage during turning Correct answer
- D Can drag on the ground
Show explanation

Properly secured air lines prevent damage from rubbing or stretching during turns and articulation.
Question 30

Electrical lines between trailers:
- A Are optional
- B Carry only auxiliary power
- C Are not used
- D Must be intact for lights and ABS communication Correct answer
Show explanation

Trailer electrical lines power lights and carry ABS signals. Damaged lines disable safety systems.
Question 31

Tracking in a triple combination:
- A Only the rear tracks differently
- B Each trailer tracks slightly differently than the one ahead of it Correct answer
- C All track identically
- D Only the lead tracks differently
Show explanation

Each articulation point introduces tracking variation. The rearmost trailer can be substantially off the tractor's path.
Question 32

When entering a freeway in a triple, you should:
- A Use the right lane only
- B Match traffic immediately
- C Stop on the on-ramp
- D Allow extra acceleration distance Correct answer
Show explanation

Triples accelerate slowly. Allow extra runway to reach traffic speed before merging.
Question 33

Crosswinds affect:
- A Only the tractor
- B Empty trailers more than loaded ones Correct answer
- C Only the lead trailer
- D No part of the truck
Show explanation

Empty trailers have less weight to resist lateral wind force. Be especially careful with empty rear trailers.
Question 34

A "fifth wheel" on a converter dolly:
- A Connects to the dolly tongue
- B Connects to the engine
- C Holds the cargo
- D Connects to the kingpin of the second trailer Correct answer
Show explanation

The dolly's fifth wheel works exactly like the tractor's fifth wheel — it locks around the kingpin of the next trailer.
Question 35

When coupling, the dolly's fifth wheel should:
- A Be removed
- B Be painted
- C Be dry
- D Be properly lubricated and inspected for damage Correct answer
Show explanation

Like a tractor fifth wheel, the dolly's fifth wheel needs lubrication and inspection.
Question 36

Sharp braking in doubles and triples:
- A Reduces stopping distance
- B Improves control
- C Has no effect
- D Can cause the rear trailer to swing or roll Correct answer
Show explanation

Sharp braking can cause the rear trailer to swing on the dolly pivot or to lift and roll. Use gradual, controlled braking.
Question 37

When driving doubles and triples:
- A Pass on the right
- B Stay in your lane and avoid weaving Correct answer
- C Use the median
- D Drift between lanes
Show explanation

Lane discipline reduces the chance of triggering crack-the-whip movement at the rear of the combination.
Question 38

When inspecting the dolly:
- A Check only the wheels
- B Check the air lines, electrical connector, tire condition, and lights Correct answer
- C Check only the tongue
- D Skip dolly inspection
Show explanation

The dolly is a critical component and must be inspected as thoroughly as the trailers themselves.
Question 39

Backing a triple-trailer combination is:
- A Not recommended — uncouple to back Correct answer
- B Identical to backing a single
- C Easy with practice
- D Done only at low speed
Show explanation

Backing a triple is impractical and dangerous. Uncouple and back the trailers individually if needed.
Question 40

Excessive weight on the rear of the combination:
- A Improves traction
- B Improves braking
- C Has no effect
- D Can cause unstable handling and increase rear-trailer rollover risk Correct answer
Show explanation

Heavy at the rear amplifies crack-the-whip and reduces the load on the tractor's drive tires.
Question 41

When driving a triple in heavy traffic:
- A Tailgate
- B Match car speeds
- C Maintain extra following distance and avoid sudden lane changes Correct answer
- D Drive aggressively
Show explanation

Triples need space to maneuver and stop. Defensive driving is the only safe approach.
Question 42

A trailer ABS system fault is signaled by:
- A A green lamp
- B A red lamp
- C A blue lamp
- D A yellow lamp on the dashboard or trailer Correct answer
Show explanation

Yellow lamps indicate ABS faults. Red lamps indicate critical brake-system failures.
Question 43

Cracked welds or damaged frames on a dolly:
- A Can be ignored
- B Improve flexibility
- C Are normal wear
- D Are out-of-service violations Correct answer
Show explanation

Frame damage on dollies is a serious structural failure point. Take the dolly out of service.
Question 44

When the dolly is being moved into position for coupling:
- A Use the dolly's landing gear or jack to set the proper height Correct answer
- B Tow it with the tractor
- C Lift it by hand
- D Drag it
Show explanation

Landing gear or hand jacks set the tongue height for safe pintle-hook coupling.
Question 45

When driving doubles and triples in tunnels:
- A Drive faster to clear quickly
- B Verify any restrictions; some tunnels prohibit longer combinations Correct answer
- C Drive on the wrong side
- D Use only one trailer in the tunnel
Show explanation

Some tunnels restrict combination length or hazmat. Verify route restrictions in advance.
Question 46

Visibility around doubles and triples is:
- A Limited — be especially aware of blind spots Correct answer
- B Same as cars
- C Better than singles
- D Unaffected by length
Show explanation

Longer combinations have more blind-spot area. Use mirrors more frequently and be patient with smaller vehicles.
Question 47

On highways, doubles and triples should:
- A Use the median
- B Drive on the shoulder
- C Drive in the left lane
- D Generally stay in the right lane except to pass Correct answer
Show explanation

Right-lane driving is standard for slower or longer commercial vehicles. Move left only to pass and return promptly.
Question 48

Loading sequence for doubles:
- A No specific order
- B Heaviest trailer first (closest to tractor); progressively lighter at the rear Correct answer
- C Lightest first
- D Only the front matters
Show explanation

Heaviest first reduces the destabilizing rear weight that amplifies crack-the-whip and rollover risk.
Question 49

Checking trailer hoses between dolly and second trailer:
- A Check brand
- B Skip the check
- C Check color only
- D Verify integrity, no kinks, and good seals Correct answer
Show explanation

Hose integrity is essential. Failures cause loss of brakes or lights.
Question 50

Triple combinations are:
- A Allowed only on toll roads
- B Allowed only on certain routes by state authorization Correct answer
- C Allowed everywhere
- D Banned everywhere
Show explanation

Triples are restricted to specific routes in states that authorize them. Check state regulations before driving.

Delaware · Doubles & Triples CDL Practice Test

About the Doubles & Triples exam in Delaware

How to schedule the written test in Delaware

In a double or triple combination, the heaviest trailer should be:

The "crack-the-whip" effect is:

The crack-the-whip effect is most dangerous on:

A converter dolly is used to:

When coupling a converter dolly, you should:

Before coupling the second trailer:

Inspect the converter dolly air lines for:

Check the dolly's air tank for:

When driving a double or triple combination:

Lane changes in doubles and triples:

On slippery roads, doubles and triples:

Pre-trip on doubles requires:

Backing a double trailer combination is:

When coupling the second trailer, the dolly tongue should:

After coupling, the safety chains:

When meeting heavy crosswinds, doubles and triples:

Some highways prohibit doubles or triples on:

A "pintle hook" is:

When inspecting the second trailer, you should check:

Converter dollies built after March 1, 1998:

A yellow ABS lamp on the dolly:

In strong crosswinds, doubles and triples:

Following distance for doubles and triples should be:

When passing in a double or triple, you should:

Mountain driving in doubles and triples:

Off-tracking in doubles and triples is:

Before pulling the second trailer, the trailer brakes should be:

When uncoupling a double, you should:

Air lines between trailers and dollies:

Electrical lines between trailers:

Tracking in a triple combination:

When entering a freeway in a triple, you should:

Crosswinds affect:

A "fifth wheel" on a converter dolly:

When coupling, the dolly's fifth wheel should:

Sharp braking in doubles and triples:

When driving doubles and triples:

When inspecting the dolly:

Backing a triple-trailer combination is:

Excessive weight on the rear of the combination:

When driving a triple in heavy traffic:

A trailer ABS system fault is signaled by:

Cracked welds or damaged frames on a dolly:

When the dolly is being moved into position for coupling:

When driving doubles and triples in tunnels:

Visibility around doubles and triples is:

On highways, doubles and triples should:

Loading sequence for doubles:

Checking trailer hoses between dolly and second trailer:

Triple combinations are: