Rollover Risks and Safe Speed Control
Rollover is the most lethal combination vehicle crash, and it is almost always a speed and center-of-gravity problem. Understand the center of gravity: a loaded trailer with a high or off-center load raises the CG and makes the rig tipsy. Centrifugal force in a turn pushes the vehicle outward, and if it exceeds the vehicle's stability, the rig rolls. The rearward amplification effect means the last trailer swings widest and can roll first. Ramp and curve speed limits are not suggestions - they are calculated for cars, and a loaded rig must go slower.
Traps: questions implying that a heavy load makes a rig harder to roll (it can make it more stable in some cases but raises stopping distance and, if high, raises the CG - read carefully); questions about braking in a curve (brake before the curve, not in it); and questions about downgrades (use a low gear, stab braking, and never coast in neutral). Know that speed is the single biggest factor: doubling speed quadruples the force in a turn.
Worked example: a ramp posted at 25 mph for cars. In a loaded 80,000-lb rig, slow to well below the posted speed before the curve, and if the rig feels like it is leaning, you are already too fast - slow further before the curve, not in it.
Rule of thumb: enter every curve slow enough that you could stop within the distance you can see, and never let a curve surprise you. On downgrades, select a gear low enough that you rarely need the brakes.