What is the primary cause of cargo tank rollovers?

The vast majority of cargo tank rollovers are caused by driver error, most often excessive speed in curves. A tanker's high center of gravity and the surge of liquid cargo make it tip easily when entering a curve too fast. The posted curve speed on signs is for cars; tankers need to enter substantially slower, often 5 to 15 mph below the posted advisory speed. The risk is greatest in two situations: highway ramps (off-ramps and cloverleaf interchanges, where drivers underestimate the curve and over-rely on momentum) and city turns (where the curb-side wheels can come off the ground without the driver realizing). Even seemingly mild curves can roll a half-empty tanker due to liquid surge. Slow down before the curve, not in it.