• 63 questions

Doubles and Triples Endorsement Practice Test From the Federal Rules

Tap an answer to see the right choice and its CFR section.

Which endorsement code on a CDL covers double and triple trailers?

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Exam mode: 25 questions, no time limit, 20 right to pass (80%).

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Unofficial practice questions, not affiliated with the FMCSA or any state licensing agency. Bank checked October 3, 2026.

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All 63 questions

The T endorsement and its test 9

  • A driver holds a Class A CDL with no endorsements. Which vehicle is off limits until a T endorsement is added? 49 CFR 383.93(b)(1)
  • Section 383.115 lists what an applicant for the double/triple trailers endorsement must know. Which item is on that list? 49 CFR 383.115(b)
  • Section 383.115(d) lists problems a set of doubles creates for other motorists. Which group is on that list? 49 CFR 383.115(d)
  • What is the first knowledge area 49 CFR 383.115 lists for the double/triple trailers endorsement? 49 CFR 383.115(a)
  • What testing does the double/triple trailers endorsement require under the federal standard? 49 CFR 383.93(c)(1)
  • Which endorsement code on a CDL covers double and triple trailers? 49 CFR 383.153(a)(9)(i)
  • Which endorsements may a state place on a commercial learner's permit? 49 CFR 383.93(a)(2)
  • Which freeway problem does 49 CFR 383.115(d) name for double and triple trailers? 49 CFR 383.115(d)
  • Which handling terms does 49 CFR 383.115(c) name for the doubles and triples knowledge test? 49 CFR 383.115(c)
Show all 63 questions (54 more)

Tow-bars, pintle hooks and dollies 9

  • A combination runs in a straight line on a level, smooth, paved surface. How far may a towed vehicle's path stray from the path of the vehicle towing it? 49 CFR 393.70(a)
  • A semitrailer is set on a converter dolly. How does 49 CFR 390.5T classify the pair? 49 CFR 390.5T
  • Does the fifth wheel mounting rule in 49 CFR 393.70(b) reach the fifth wheel on a converter dolly? 49 CFR 393.70(b)(1)(i)
  • How much play may the connection between a tow-bar and the towing vehicle have? 49 CFR 393.70(c)(3)
  • What does 49 CFR 393.70(c)(4) require at the tow-bar connection? 49 CFR 393.70(c)(4)
  • What makes a trailer a full trailer under 49 CFR 390.5T? 49 CFR 390.5T
  • What must every full trailer be equipped with under 49 CFR 393.70(c)? 49 CFR 393.70(c)
  • What must the mounting of a pintle hook on the towing vehicle include? 49 CFR 393.70(c)(4)
  • Which parts make up a converter dolly under 49 CFR 393.5? 49 CFR 393.5

Safety chains and cables 16

  • A bridle, or two chains sharing one attachment point, hooks to the towing vehicle. Where may that point be? 49 CFR 393.70(d)(8)(ii)
  • A carrier fits a safety device that is not a chain or a cable. What standard must it meet? 49 CFR 393.70(d)(7)
  • A pintle hook forging made before July 1, 1973 has an attachment place that is independent of the hook itself. May the safety device attach there? 49 CFR 393.70(d)(1)
  • A single length of cable is formed into a bridle. How must the forward bridle eye be made? 49 CFR 393.70(d)(5)
  • A solid-tongue converter dolly uses one safety chain. Where must the chain run? 49 CFR 393.70(d)(6)(ii)
  • How much slack may a safety chain or cable between two trailers have? 49 CFR 393.70(d)(2)
  • How must the hook be fastened to a safety chain or cable? 49 CFR 393.70(d)(5)
  • How strong must a safety device and its attachments be? 49 CFR 393.70(d)(3)
  • If a tow-bar fails or comes loose, what must the safety device prevent besides the trailer breaking away? 49 CFR 393.70(d)(4)
  • Safety chains are used on a full trailer that has a hinged tow-bar. What is the minimum arrangement? 49 CFR 393.70(d)(5)
  • To what part of the towing vehicle must a dolly's safety device be coupled? 49 CFR 393.70(d)(1)
  • Two safety chains attach to the towing vehicle at separate points. Where must those points be? 49 CFR 393.70(d)(8)(i)
  • Where must a bridle attach on the towed vehicle? 49 CFR 393.70(d)(5)
  • Where on a solid-tongue converter dolly may its safety device be attached? 49 CFR 393.70(d)(6)(iii)
  • Which towed vehicle may use a single safety chain or cable by itself? 49 CFR 393.70(d)(6)(i)
  • Which units in a set of doubles must be coupled to the vehicle ahead with a safety device such as chains or cables? 49 CFR 393.70(d)

Dolly brakes, lamps and inspection 15

  • A converter dolly is towed by itself behind a tractor, not as part of a full trailer. Which rear lamps and reflectors must the dolly carry? 49 CFR 393.11, Table 1, footnote 5
  • A drawbar tongue has a slider. How much movement between the slider and its housing fails the periodic inspection? 49 CFR Part 396, Appendix A, 2.d(1)
  • A trailer built on or after March 1, 2001 is designed to tow another air-braked trailer. What must its ABS malfunction circuit be able to do? 49 CFR 393.55(d)(3)
  • All brakes on a vehicle must be able to operate at all times. Which converter dolly falls outside that rule? 49 CFR 393.48(c)(3)
  • An air-braked converter dolly must have an antilock brake system if it was built on or after what date? 49 CFR 393.55(c)(2)
  • During a periodic inspection, which pintle hook condition fails the vehicle? 49 CFR Part 396, Appendix A, 2.b
  • How much wear on the horn of a pintle hook fails the periodic inspection? 49 CFR Part 396, Appendix A, 2.b(2)(c)
  • How worn may a safety chain be before it fails the periodic inspection? 49 CFR Part 396, Appendix A, 2.e(3)(a)
  • The second trailer of a set of doubles hides the rear identification lamps of the first trailer. Must those lamps be lit? 49 CFR 393.11, Table 1, footnote 3
  • When must a converter dolly towed singly have its own rear turn signals and hazard warning flashers? 49 CFR 393.11, Table 1, footnote 5
  • Where does a converter dolly built on or after March 1, 1998 show an ABS malfunction? 49 CFR 393.55(e)
  • Which air-braked unit is excepted from the FMVSS No. 121 parking brake requirement in 49 CFR 393.41(b)? 49 CFR 393.41(b)
  • Which lamp rules apply to an older converter dolly? 49 CFR 393.11(a)(2)
  • Which of these is an improper repair to a safety chain under Appendix A to Part 396? 49 CFR Part 396, Appendix A, 2.e(3)(b)
  • Which safety cable condition fails the periodic inspection? 49 CFR Part 396, Appendix A, 2.e(4)

Twin trailer limits, LCVs and the LCV certificate 14

  • A driver holds an LCV Driver-Training Certificate for LCV Doubles. May the carrier assign that driver to an LCV Triple? 49 CFR 380.113(a)(2)
  • A tractor pulls twin 28-foot trailers at 78,000 pounds gross on an Interstate highway. Is it an LCV under 49 CFR 380.105? 49 CFR 380.105(b)
  • Does a T endorsement by itself qualify a driver to pull an LCV for a motor carrier in interstate commerce? 49 CFR 380.113(a)(1)
  • LCV weights and cargo-carrying lengths are frozen at the limits in effect on or before what date? 23 CFR 658.23(a)(2)
  • May a state cap the overall length of a tractor pulling twin 28-foot trailers on the National Network? 23 CFR 658.13(b)(3)
  • On the National Network, what is the shortest length limit a state may set on either trailer of a tractor-semitrailer-trailer combination? 23 CFR 658.13(b)(2)
  • Twin 28-foot trailers usually ride on single axles. What is the federal single-axle weight limit on the Interstate System? 23 CFR 658.17(c)
  • Unless grandfathered, what must a driver complete before operating an LCV in interstate commerce? 49 CFR 380.107(a)
  • What is the National Network? 23 CFR 658.5
  • What makes a combination a longer combination vehicle (LCV) in the federal rules? 23 CFR 658.5
  • Where do the federal length protections for twin trailers apply? 23 CFR 658.13(a)
  • Where may a state allow LCVs to run on the Interstate System? 23 CFR 658.23(a)(1)
  • Which doubles may run on the National Network regardless of the cargo-carrying unit freeze? 23 CFR 658.23(b)(1)
  • Which statement about tractor-semitrailer-trailer combinations on the National Network is true? 23 CFR 658.13(b)(4)

How this list was compiled: Written from the Electronic Code of Federal Regulations: Title 49, Parts 380 (subpart A), 383, 390, 393 and 396 (Appendix A), at https://www.ecfr.gov/current/title-49, text in force on 2026-10-01, and Title 23, Part 658, at https://www.ecfr.gov/current/title-23/part-658, text in force on 2026-10-01. Both checked 2026-10-03. Each question names its section. Definitions are cited to section 390.5T, the text in force while section 390.5 is suspended. Licence: Own work. Questions, answer choices and explanations were written for this site from the regulation text; nothing is copied from a state CDL manual, the AAMVA test item pool or another practice test.

How it works

This unofficial doubles and triples endorsement practice test asks 63 questions on the T endorsement's written rules, checked 3 October 2026: tow-bars, pintle hooks, safety chains and converter dollies. Handling is left to state manuals.

Read the full guide

The sources, and 14 questions that go further

49 CFR 383.115 lists the knowledge areas for the double/triple trailers endorsement. The federal text behind them sits in 49 CFR 393.70, the Part 393 dolly rules and Appendix A to Part 396. One topic goes past that list: 14 questions from 23 CFR Part 658 and 49 CFR Part 380 on twin 28-foot trailers and longer combination vehicles.

A doubles and triples practice test, one topic at a time

Set Start from, under the question, to Safety chains and cables: 16 questions from one paragraph, 393.70(d). Exam mode asks 25 questions and passes at 20 right, the 80 percent in 49 CFR 383.135.

  • A safety chain goes to the frame, never the pintle hook, with no more slack than a turn needs.
  • The T endorsement takes a knowledge test only (49 CFR 383.93), and it cannot go on a learner's permit.
  • Misses wait under Missed in More options until you get them right.

Questions and answers

How much of the T endorsement test does this bank cover?

The rules part. 49 CFR 383.115 names five areas: assembly and hookup, placement of the heaviest trailer, handling and stability, problems in traffic, and other operating practices. Federal text speaks to hookup hardware and inspection defects. The rest is in your state manual.

Does this doubles and triples practice test cover coupling steps?

No. The order of steps for hooking up a converter dolly is taught in state CDL manuals. This bank asks what the CFR says: what a tow-bar connection needs, where safety chains attach and which coupling defects fail an inspection.

Is the T endorsement enough for any doubles or triples?

Not for a longer combination vehicle. 23 CFR 658.5 defines an LCV as a tractor with two or more trailers on the Interstate System at over 80,000 pounds gross. Under 49 CFR 380.113 its driver needs an LCV Driver-Training Certificate or a Certificate of Grandfathering.

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