DOT: 'Zipper merge' keeps highway traffic zipping along
Posted July 30, 2014
Raleigh, N.C. — One accident, one construction sign, sometimes even one set of flashing lights can bring a highway commute to a crawl.
Kevin Lacy, an engineer with the state Department of Transportation, says a little inspiration from the fashion world – and a bit of politeness on the part of drivers – could keep traffic moving faster when vehicles have to merge because of closed lanes.
As long as traffic is moving at regular speeds, Lacy says drivers should move into the open lane as soon as possible when a lane is closed ahead. When traffic backs up, however, DOT engineers are looking at a solution now in use in Washington state and Minnesota called a "zipper merge."
With the zipper merge, drivers use both lanes approaching a construction zone or accident site. Once they get to the point where a lane is closed, each lane takes turns allowing drivers to file into the open lane.
"What you'll see is that it will operate much more efficiently," Lacy said, adding that persuading drivers to take turns is easier said than done.
"You're going to have to get over that urge not to let people get in front of you, he said. "What I'm telling you is, allow that gap, keep things moving. You'll be better off."
DOT engineers are concerned about merging around more than just lane closures, he said, noting that they also are looking at tweaking lane-marking in interchanges to make regular highway merging easier.