Why does liquid surge create a special hazard specifically during starting, slowing down, and stopping a tank vehicle, rather than during steady-speed driving?

49 CFR 383.119(a) (causes, prevention, and effects of cargo surge on vehicle handling); AAMVA CDL Manual Section 8.2.2, p.8-8-1 (surge mechanics) combined with Section 8.3.1 'Drive Smoothly,' p.8-8-2 ('Because of the high center of gravity and the surge o

Because surge happens exactly when you speed up, slow down, or stop, abrupt inputs make the problem worse instead of controlling it. Smooth, gradual braking and acceleration give the liquid less opportunity to slam back and forth inside the tank. This is why tank endorsement training emphasizes gentle driving habits above almost everything else.