What is 'liquid surge' and why is it dangerous?

Liquid surge is the wave-like movement of liquid inside a partially-filled tank as the vehicle accelerates, brakes, or changes direction. The liquid mass slams against the front of the tank when you brake (pushing the truck forward even as you slow), against the back when you accelerate, and side-to-side during lane changes or curves. Effects: vehicles surge through stops even with brakes applied; the rear of the trailer swings during steering inputs; rollover risk increases dramatically in curves. The bigger the empty space (the 'outage'), the worse the surge. A tank that is either nearly full or nearly empty surges less than one that is half-full. Some tanks have baffles or bulkheads (interior dividers) to limit surge.