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CDL · Driving Tank Vehicles

What is 'fishtailing' in a tank truck context?

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

When the trailer swings side to side due to surge or hard maneuvering

  1. A A type of brake adjustment
  2. B When the trailer swings side to side due to surge or hard maneuvering
  3. C A specific type of cargo damage
  4. D A required safety check

Why this is the answer

Fishtailing is when the rear of a vehicle (especially a trailer) swings side to side in an uncontrolled or semi-controlled motion, often initiated by surge in a tank, sudden steering input, brake application during a turn, or slick road conditions. Once fishtailing starts in a tank vehicle, the surge of liquid amplifies each swing in the way rearward amplification works in multi-trailer combinations. Recovery requires releasing the brake (if applied), easing off acceleration, and steering smoothly to track straight rather than counter-steering aggressively. Prevention is far better than cure: smooth inputs, conservative speed, and large following distances reduce the conditions that trigger fishtailing in the first place.
Source: FMCSA CDL Manual 8.2.6 Fishtailing

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About this topic: Driving Tank Vehicles

Driving a tank vehicle means managing a high centre of gravity and a shifting load: slow for curves well below the posted speed, brake early and smoothly, and never make sudden steering changes. These questions cover the handling rules for liquid loads. This is one of 21 Tanker questions on driving tank vehicles, each with a full explanation on a single study page.

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