Driving Combination Vehicles Safely: Turns, Braking, Off-Tracking, and Speed
This domain tests how a combination vehicle behaves in turns, braking, off-tracking, and speed selection. The key idea is that the tractor and trailer do not follow the same path, and the trailer's weight and brakes change stopping distance.
Core rules
- Off-tracking means the rear wheels follow a shorter path than the front wheels. The longer the wheelbase and the sharper the turn, the greater the cut-in. Watch the trailer in both mirrors through every turn.
- For a right turn, begin wide enough to keep the trailer tires out of the curb, but do not swing into another traffic lane. Complete the turn slowly and check the right mirror for pedestrians, signs, and the curb.
- Slow before a curve, not in it. Enter at a speed that lets you stay in your lane without hard braking. Hard braking in a curve can lock wheels and cause a skid.
- On a downgrade, select a low gear before the descent and use engine braking with controlled foot braking. Do not ride the brakes or use the trailer hand valve for normal stopping.
- A loaded combination needs more stopping distance than a light one. Brake early, smoothly, and progressively; keep space ahead.
Worked example
A 53-foot trailer is turning right at a tight city corner. The tractor clears the curb, so the driver keeps steering and accelerates. The trailer's rear tires off-track inside the tractor path and strike the curb. Reasoning: clearing the curb with the tractor does not clear the trailer. The driver should have started the turn wide, kept speed low, and watched the trailer tires in the right mirror until they cleared the curb.
Traps that cost marks
Cutting a right turn; watching only the tractor; braking hard inside a curve; entering a ramp or curve too fast; and assuming trailer brakes will compensate for poor speed control.