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CDL · Driving Tank Vehicles

Why should drivers slow down well below the posted speed before entering a curve or an on/off ramp with a tank vehicle?

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

Because tank vehicles have a high center of gravity and posted curve/ramp speeds are set for ordinary vehicles, so a loaded tank can roll over at the posted speed

  1. A Only empty tanks need to slow for curves
  2. B Because tank vehicles cannot turn at posted speeds
  3. C Posted ramp speeds already account for the high center of gravity of loaded tanks
  4. D Because tank vehicles have a high center of gravity and posted curve/ramp speeds are set for ordinary vehicles, so a loaded tank can roll over at the posted speed

Why this is the answer

Posted advisory speeds for curves and ramps are intended for typical passenger vehicles, not for high-center-of-gravity tank trucks. A loaded liquid tank carries much of its weight high, which makes it prone to rolling over. The manual advises driving well below the posted speed on curves and ramps — often 5 mph or more under the sign — and never relying on the posted figure. Combined with liquid surge, taking a ramp too fast is one of the most common causes of tanker rollovers. Slow to a safe speed before the curve, then maintain a steady speed through it rather than braking mid-curve.
Source: FMCSA CDL Manual 8.2.4 Curves

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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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