Off-Tracking on a Tight Right Turn
You are driving a 53-foot trailer with the tandems set all the way to the rear, gross weight 76,000 pounds, through an older urban intersection. You need to make a right turn from a two-lane road onto a two-lane road. The corner has a stop sign, a raised concrete curb with a pedestrian island on the inside of the turn, and a traffic signal pole about 12 feet from the curb on the outside of the turn. A cyclist is stopped at the crosswalk on your right, waiting to cross. Your tractor's wheelbase is 240 inches.
1. How should you set up and execute this turn, and why does the tandem position matter?
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Set up wide. Approach in the left portion of your lane, or swing slightly left if the lane allows, so the trailer has room to cut the corner without crossing the curb. Signal early, check mirrors on both sides, and move slowly enough that you can stop if the cyclist moves. Do not begin the turn until you have checked the right mirror and confirmed the trailer's rear wheels will clear the island.
The tandem position matters because moving the tandems to the rear increases off-tracking. With the axles at the rear of a 53-foot trailer, the trailer's rear wheels track well inside the tractor's path, and the amount of cut increases with the wheelbase and the sharpness of the turn. At a tight urban corner with a 240-inch tractor wheelbase, the trailer's rear wheels can track several feet inside the tractor's rear wheels. That is why you must swing wide and watch the right mirror through the entire turn, not just at the start.
2. The cyclist is still waiting at the crosswalk as you begin to move. What do you do, and what is the risk if you proceed?
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Stop and wait. The cyclist has the right of way at the crosswalk, and more importantly, you cannot see the right side of your trailer clearly enough during a tight right turn to guarantee the cyclist is clear of your path. The trailer's rear wheels will swing toward the inside of the turn, which is exactly where the cyclist is waiting.
The risk is a right-turn squeeze: the rear of the trailer sweeps toward the curb and the crosswalk, and a cyclist or pedestrian in that space can be struck even though the tractor cab has already cleared them. Because the trailer's rear wheels off-track toward the inside, the danger zone is on your right, not your left. Wait until the cyclist has crossed and the crosswalk is clear, then complete the turn slowly with continuous mirror checks. If the cyclist hesitates, wave them across rather than proceeding.