Trailer Sway, Off-Tracking, and Rearward Amplification
This domain covers the dynamics that make combination vehicles behave differently from single units. Off-tracking is the difference between the path of the tractor's rear wheels and the trailer's rear wheels; the trailer cuts the corner, and the effect increases with trailer length and sharpness of the turn. Trailer sway (fishtailing) happens when the trailer swings side to side, often from speed, wind, or abrupt steering; the correct response is to ease off the accelerator and steer gently, not to brake hard or overcorrect. Rearward amplification means that a steering input at the front produces a larger swing at the rear of the combination, so small corrections are magnified down the length of the vehicle. Traps: thinking you should brake hard during sway, confusing off-tracking with sway, or believing a longer trailer off-tracks less. Another trap is assuming rearward amplification only matters at high speed. Rule of thumb: make small, smooth steering inputs and slow down before curves, because the rear of the combination moves more than the front. Worked example: in a tight right turn, the trailer's rear wheels may track several feet inside the tractor's path, so leave extra room on the inside.