You know the dirty looks we all give drivers who refuse to merge until the last possible second, bypassing everyone who followed etiquette and moved over earlier? According to transportation officials, those who wait to merge until the lane closes are correct. The rest of us — usually honking and cursing — are actually increasing traffic congestion.
It's called the "zipper merge," and state officials from Arizona to Minnesota have been urging people for years to adopt it in heavy traffic situation. Kansas even went so far to create a zipper merge PSA with some talking traffic cones:
As the cones explain, the idea is for drivers to fill in both lanes, with those in the lane that's about to close alternating at the merge with the open lane traffic. When everyone is on the same page, both lanes should never cease moving.
"I’ve been amazed at how consistent the flow is," Ken Johnson, a Minnesota State Work Zone, Pavement Marking, and Traffic Devices engineer told Ars Technica. "You don’t have to put your foot on the brake at all. You just coast ahead and take turns at the merge point."
According to Johnson, zipper merging can reduce congestion by as much as 40 percent during high traffic volumes, while also making the merging process significantly safer. Early merging, while effective in low congestion, actually increases traffic gridlock because a lane goes unused.
Unfortunately, zipper merging is dependent on one big factor: driver participation. Efforts to spread the word nationwide are increasing, but motorists are still wary to "cut the line" or give space to someone perceived as attempting to do the same.
“We know that the majority of people understand that it is legal for them to use both lanes, but that they don’t because they don’t want to be the person that is perceived as barging in,” Sue Groth, director of Minnesota's Office of Traffic Safety and Technology, told the Star Tribune. "We are hoping that by telling them it is OK — and in fact, we want them to do it because it helps reduce backups — they will be more willing to participate.”
As the below video shows, not all drivers are hip to zip. With more states now teaching the practice in driving courses and manuals, the hope is that lane merging congestion will one day feature less rude gestures and more waves of thanks.