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CDL · Pulling Doubles and Triples

What is the typical maximum legal length of a doubles combination?

Reviewed by Jordan Morley, Editorial Lead at 247SimpleTests. Written by the 247SimpleTests Editorial Team from the official source material cited on every question.

Correct answer

Federal law allows doubles up to 28-foot trailers each (with a typical maximum combination length around 65-75 feet); some states allow longer, including 'longer combination vehicles' under permit

  1. A 100 feet on all highways
  2. B Doubles combinations have no length limit
  3. C Federal law allows doubles up to 28-foot trailers each (with a typical maximum combination length around 65-75 feet); some states allow longer, including 'longer combination vehicles' under permit
  4. D 53 feet maximum

Why this is the answer

Federal law established a minimum federal standard for doubles: each trailer up to 28 feet (the classic 'doubles' or 'pups') and the combination at typical lengths around 65-75 feet depending on tractor and configuration. States may allow longer combinations under permits ('Longer Combination Vehicles' or LCVs), with triples, turnpike doubles, and Rocky Mountain doubles authorized in specific states (especially in the western US). LCV operations have additional driver qualification requirements and route restrictions. Driving outside legal length limits is a serious violation. Always check state-specific rules for the routes you operate on.
Source: FMCSA CDL Manual 7.0 Doubles and Triples

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About this topic: Pulling Doubles and Triples

Pulling doubles and triples means managing the most unstable combination on the road: the rear trailer whips, rolls and jackknifes more easily, following distance must grow, and the sequence of air-line and brake checks is longer. These questions cover the handling rules specific to multiple trailers. This is one of 29 Doubles and Triples questions on pulling doubles and triples, each with a full explanation on a single study page.

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