CDL · Driving Tank Vehicles

A tanker driver is told to take a highway exit ramp marked with a 40 mph advisory speed. What speed is appropriate for a loaded tanker?

Correct answer

Well below 40 mph — the advisory speed is set for passenger vehicles; a loaded tanker with a high center of gravity and liquid surge should take the ramp significantly slower to prevent rollover

  1. A 40 mph exactly
  2. B Above 40 mph to keep traffic moving
  3. C Well below 40 mph — the advisory speed is set for passenger vehicles; a loaded tanker with a high center of gravity and liquid surge should take the ramp significantly slower to prevent rollover
  4. D Speed doesn't matter on ramps

Why this is the answer

EXIT RAMP SPEED FOR TANKERS: Highway exit and entrance ramp advisory speeds are calculated for typical PASSENGER VEHICLES — they do not account for the high center of gravity and liquid surge of a loaded tanker. SAFE SPEED: Well below the posted advisory (a 40 mph ramp may require a loaded tanker to enter at 25-30 mph or less); RAMPS ARE A LEADING ROLLOVER LOCATION: The combination of a curve (ramp), deceleration, and a high-center-of-gravity load with surge causes many tanker rollovers; slow down BEFORE the ramp curve; SURGE: Decelerating on the ramp causes forward surge; the curve causes lateral surge — together they strain stability; DRIVER GUIDANCE: Reduce speed on the straight approach before the ramp; take the ramp slowly and steadily; don't brake hard in the curve; accelerate gently when straightening out; ROLLOVER THRESHOLD: A loaded tanker can roll at ramp speeds a car handles with ease; many rollover crashes happen on ramps where drivers followed the posted advisory speed; for tankers, the posted speed is a maximum for cars, not a target for the tanker — always go slower.
Source: FMCSA CDL Manual — Tanker Ramp Speed

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