Tractor-Trailer Turning, Off-Tracking, and Lane Control
What this domain covers
Turning questions test off-tracking, swept path, and lane control. A tractor-semitrailer does not turn like a car: the trailer's rear wheels cut inside the tractor's path, and the trailer's body can sweep over curbs or adjacent lanes.
Core rules
- Off-tracking increases with wheelbase and trailer length. A 53-foot trailer can cut several feet inside the tractor's track in a tight turn.
- For a right turn, keep the tractor close to the right edge, but delay the turn until the trailer's rear wheels will clear the curb. Do not swing left before the turn; that exposes you to passing traffic.
- For a left turn, watch the trailer in the outside mirror and keep the trailer inside the intended lane.
- Use both mirrors through the turn and proceed slowly. If the trailer wheels approach a curb, stop and pull forward to correct rather than forcing the turn.
- Maintain lane control by looking ahead and making small steering inputs; a combination amplifies steering and can sway.
Worked example
You are turning right from a four-lane road into a narrow street. If you begin the turn as soon as the tractor's front bumper reaches the corner, the trailer's rear wheels will track over the curb. Instead, move forward until the tractor is well into the intersection, then turn while watching the trailer's right-side wheels in the mirror.
Traps that cost marks
Cutting the corner; swinging wide left before a right turn; assuming the trailer follows the tractor; looking only at the tractor; and turning from the wrong lane. Also, do not use the trailer hand valve to steer the trailer in a turn.