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

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.