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CDL · Inspection

What additional items must be inspected on a doubles or triples combination beyond a single trailer?

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

Each coupling point and converter dolly — pintle hooks, dolly fifth wheels, kingpins, safety chains, the air and electric lines between trailers, and the glad hands and shut-off (cut-out) cocks — must all be checked

  1. A Only the first trailer's tires
  2. B Each coupling point and converter dolly — pintle hooks, dolly fifth wheels, kingpins, safety chains, the air and electric lines between trailers, and the glad hands and shut-off (cut-out) cocks — must all be checked
  3. C Only the tractor
  4. D Nothing extra is required

Why this is the answer

Doubles and triples have more connections than a single trailer, and every one is part of the inspection. The driver checks each pintle hook (latched, not worn), every converter dolly (its fifth wheel, axles, tires, and lights), all kingpins and fifth wheel locks, the safety chains, and the air and electric lines running between the trailers. The glad hands must be connected and sealed, and the air shut-off (cut-out) valves at the rear of each trailer except the last must be open, with the very last trailer's shut-off closed. Any failure in these between-trailer connections can cause a breakaway or loss of trailer brakes.
Source: FMCSA CDL Manual 7.3.1 Inspecting Doubles and Triples

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About this topic: Inspection

Air brake inspection is its own structured procedure: build-up, leakage rate, low-air warning, and spring-brake activation must all check out before you drive. This is one of 15 Doubles and Triples questions on inspection, each with a full explanation on a single study page.

New to this exam? Our CDL exam guide explains the format, scoring, and how to prepare.

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