Why are doubles and triples more prone to rollover than single-trailer combinations?

Rearward amplification (also called the 'crack-the-whip' effect) is the most dangerous characteristic of multi-trailer combinations. A lane-change or steering input at the tractor produces a small movement at the front trailer, a larger movement at the second trailer, and an even larger movement at a third trailer if present. Doubles typically have around 2× the lateral acceleration at the rear trailer compared to the tractor; triples around 3×. This means a maneuver that feels routine at the tractor can roll the rear trailer. The defense is steering smoothness: avoid sudden lane changes, do not whip the wheel to dodge debris, do not weave, and increase following distance so you have time to slow gradually rather than swerve.