Why might a tanker hauling a partial load of liquid require different driving habits than one hauling a completely full load of the same liquid?

49 CFR § 383.119(a)/(b) (causes of cargo surge; stopping techniques when a tank is full, partially filled, or empty); AAMVA CDL Manual §8.2.2, p.8-8-1

A tanker's required driving technique isn't one-size-fits-all; how full the tank is changes the hazards a driver faces. Because surge is a function of partially filled tanks, a driver moving between partial and full loads needs to adjust habits like brake timing and curve speed accordingly. This adaptability is exactly what the tank endorsement knowledge test, and real-world safety, depend on.