That's actually a poor misconception on the part of Americans who often don't know how to drive properly. The so called zipper algorithm optimizes throughput and minimizes congestion by making everyone drive as close to the narrowing as safely possible while mandating that each driver on the right continuing lane lets one person from the left in. Never understood the boorish aggressiveness, not letting any cars in, therefore maximizing congestion as everyone gets into a single file 2 miles ahead. This should be taught in driving school.
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