Is zipper merging more efficient for traffic than early merging?

Zipper merging in construction zones can save drivers time and reduce traffic congestion.

A zipper merge occurs when drivers use both lanes of traffic until reaching a merging point, where motorists then take turns moving into a single lane. Early merging is when motorists move to the open lane as soon as possible before a lane closure.

The Minnesota Department of Transportation said zipper merging can reduce the length of backups by 40% and limit crashes. Another study said congestion can be reduced by up to 50%. Several states have encouraged zipper merging by using signage and public awareness campaigns. 

In Sioux Falls, Mayor Paul TenHaken held a news conference June 11, 2025, while wearing a shirt saying, “I feel the urge to zipper merge.”

“For some reason (in South Dakota), it’s considered rude (to zipper merge),” TenHaken said. “And it’s not rude, it’s very effective,” TenHaken said.