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CDL Doubles/Triples (T) Endorsement knowledge test study guide

CDL Doubles/Triples (T) Endorsement knowledge test, administered by State DMV/DOT under FMCSA, is mapped here as 7 topic areas; the heaviest are Coupling (25%), Air System (20%) and Safe Operation (17%).

About this course: Hook the set. Learn the coupling order, the valve map, and heavy-first - one step at a time.

CDL Doubles/Triples (T) Endorsement knowledge test at a glance

Questions
20
Time allowed
untimed/state-set
Passing standard
80% (16 of 20 typical; verify state count)
Format
multiple choice, knowledge only (no skills test, no TSA, no ELDT for T)
Standard / edition
current state CDL manual
Administered by
State DMV/DOT under FMCSA

Source: current state CDL manual, State DMV/DOT under FMCSA. Confirm current details with the exam owner before you book.

Topic areas and weights

Topic areaWeightConceptsGuide
Coupling25%5Section below
Uncoupling15%3Section below
Air System20%4Section below
Placement8%2Section below
Safe Operation17%3Section below
Inspection10%1Section below
Triples and LCV5%1Section below

Study plan in this course

  1. Hook the Set: Coupling Order: Coupling a Set of Doubles — 5 cards · free
  2. Dolly Out Before Pintle Open: Uncoupling and the Pintle Rule — 3 cards · free
  3. Air System: Air Valves and Air Checks — 4 cards · full course
  4. Heavy Leads, Light Follows: Trailer Placement — 3 cards · full course
  5. Last Trailer, First to Flip: Rollover and Space Management — 4 cards · full course
  6. More Tires, More Brakes, More to Check: Inspecting Doubles and Triples — 3 cards · full course
  7. Where Triples Are Legal - and What the T Covers: Triples and LCV Rules — 3 cards · full course

Coupling

Coupling carries 25% of the CDL Doubles/Triples (T) Endorsement knowledge test blueprint used in this course, the largest of its 7 weighted areas. It spans 5 concepts. The course teaches it in 1 study unit: Coupling a Set of Doubles.

What Coupling covers

  • What is the correct order to couple a set of doubles? — State CDL Manual - Doubles and Triples section
  • When you build a set of doubles, which trailer goes right behind the tractor? — State CDL Manual - Doubles and Triples section
  • After you connect the dolly to the lead trailer, what holds the connection if the tow bar fails? — State CDL Manual - Doubles and Triples section
  • How do you know the dolly fifth wheel is properly coupled under the rear trailer? — State CDL Manual - Doubles and Triples section
  • What must you check before you move a newly coupled set of doubles? — State CDL Manual - Doubles and Triples section

How Coupling connects to other areas

Official references for Coupling

  • State CDL Manual - Doubles and Triples section

In the app this area comes with 5 memory cards and 8 module-quiz questions and is part of the free starting modules.

Uncoupling

Uncoupling carries 15% of the CDL Doubles/Triples (T) Endorsement knowledge test blueprint used in this course, the 4th-largest of its 7 weighted areas. It spans 3 concepts. The course teaches it in 1 study unit: Uncoupling and the Pintle Rule.

What Uncoupling covers

  • What is the one rule you must never break when uncoupling a set of doubles? — State CDL Manual - Doubles and Triples section
  • Why is it dangerous to open the pintle hook with the dolly still under the rear trailer? — State CDL Manual - Doubles and Triples section
  • What is the correct order to uncouple a set of doubles? — State CDL Manual - Doubles and Triples section

How Uncoupling connects to other areas

Official references for Uncoupling

  • State CDL Manual - Doubles and Triples section

In the app this area comes with 3 memory cards and 5 module-quiz questions and is part of the free starting modules.

Air System

Air System carries 20% of the CDL Doubles/Triples (T) Endorsement knowledge test blueprint used in this course, the second-largest of its 7 weighted areas. It spans 4 concepts. The course teaches it in 1 study unit: Air Valves and Air Checks.

What Air System covers

  • On a set of doubles, which air-line shut-off valves must be OPEN and which must be CLOSED? — State CDL Manual - Combination Vehicles section
  • How do you check that air actually reaches the brakes on the last trailer of a set? — State CDL Manual - Combination Vehicles section
  • What happens if the glad hands are crossed on a trailer? — State CDL Manual - Combination Vehicles section
  • Why must the shut-off valves at the very back of the last trailer stay closed? — State CDL Manual - Combination Vehicles section

Official references for Air System

  • State CDL Manual - Combination Vehicles section

In the app this area comes with 4 memory cards and 7 module-quiz questions in the full course.

Placement

Placement carries 8% of the CDL Doubles/Triples (T) Endorsement knowledge test blueprint used in this course, the 6th-largest of its 7 weighted areas. It spans 2 concepts. The course teaches it in 1 study unit: Trailer Placement.

What Placement covers

  • How do you decide which trailer goes where in a set of doubles or triples? — State CDL Manual - Doubles and Triples section
  • Why is the heaviest-trailer-first rule a safety rule, not just a preference? — State CDL Manual - Doubles and Triples section

Official references for Placement

  • State CDL Manual - Doubles and Triples section

In the app this area comes with 3 memory cards and 4 module-quiz questions in the full course.

Safe Operation

Safe Operation carries 17% of the CDL Doubles/Triples (T) Endorsement knowledge test blueprint used in this course, the third-largest of its 7 weighted areas. It spans 3 concepts. The course teaches it in 1 study unit: Rollover and Space Management.

What Safe Operation covers

  • What is the crack-the-whip effect on a set of doubles or triples? — State CDL Manual - Doubles and Triples section
  • About how much more likely is a rollover with doubles and with triples compared to a tractor-semi? — State CDL Manual - Doubles and Triples section
  • Should you back up a set of doubles, and why or why not? — State CDL Manual - Doubles and Triples section

Official references for Safe Operation

  • State CDL Manual - Doubles and Triples section

In the app this area comes with 4 memory cards and 7 module-quiz questions in the full course.

Inspection

Inspection carries 10% of the CDL Doubles/Triples (T) Endorsement knowledge test blueprint used in this course, the 5th-largest of its 7 weighted areas. It spans 1 concept. The course teaches it in 1 study unit: Inspecting Doubles and Triples.

What Inspection covers

  • Why does inspecting a set of doubles or triples take longer than any other rig? — State CDL Manual - Doubles and Triples section

Official references for Inspection

  • State CDL Manual - Doubles and Triples section

In the app this area comes with 3 memory cards and 6 module-quiz questions in the full course.

Triples and LCV

Triples and LCV carries 5% of the CDL Doubles/Triples (T) Endorsement knowledge test blueprint used in this course, the 7th-largest of its 7 weighted areas. It spans 1 concept. The course teaches it in 1 study unit: Triples and LCV Rules.

What Triples and LCV covers

  • What does the T endorsement require beyond the written knowledge test? — FMCSA Entry-Level Driver Training rule

Official references for Triples and LCV

  • FMCSA Entry-Level Driver Training rule

In the app this area comes with 3 memory cards and 4 module-quiz questions in the full course.

Official references

  • State CDL Manual - Doubles and Triples section
  • State CDL Manual - Combination Vehicles section
  • FMCSA Entry-Level Driver Training rule

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