Why should you avoid hard braking when there are slick surfaces and a partial load in a tank?

Slick surfaces reduce tire grip while surge adds an unpredictable forward force on the truck during braking. The combination is much more dangerous than either factor alone. Hard braking on a slick surface causes wheels to lock (or ABS to activate); locked or slipping wheels cannot resist the forward surge of the liquid; the trailer pushes the tractor sideways and the vehicle fishtails or jackknifes. On a slick surface with a partial tank load, brake very gently and very early, leave large following distances, and avoid hard maneuvering of any kind. If you must stop quickly, the calmest steady-pressure stop you can make is far safer than slamming the brakes.