Studies by the Texas Transportation Institute, Minnesota Department of Transportation and Federal Highway Administration have shown that the zipper merge (thus named because both lanes are used and drivers take turns merging one car at a time, like the teeth of a zipper) improves traffic flow by as much as 15 percent, according to the Detroit News. MnDOT also found it reduces the total length of a backup by as much as 50 percent, and commonly by 40 percent.
"Although motorists seem to believe that a single lane of traffic flowing into a work zone should flow through unrestricted and much faster without a slowdown for merging traffic, this just does not happen in the real world of traffic hazards," MnDOT says. "Motorists slow down because of the uncertainty of the drivers' actions ahead, poor visibility beyond, signs/drums/barricades and (other obstructions). That slows down the rest of the line of traffic, and the longer the queue, the more it slows down and a longer time before it regains speed."
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https://www.cars.com/articles/2014/...ng-motorists-isnt-a-snap/#6YsWTEDtebuVJIKU.99