MINNESOTA AND WASHINGTON ENDORSE THE ZIPPER MERGE. I posted here about the pros and cons of the zipper merge, in which whenever two lanes of traffic are being reduced to one, the cars keep both lanes filled until, in the last few yards, the cars take turns merging. (Annalisa commented that the first time it came up when she was learning to drive and cars were merging onto the turnpike: “I asked [Pater Familias] urgently how to merge. He replied calmly, “Oh, they sort themselves out.” And it worked out.)
This article on the arstechnica web site by Sam Machkovech (link via Marginal Revolution) tells how Washington has now joined Minnesota in officially endorsing the zipper merge (the headline says: “…why you should drive ruder”). A Minnesota traffic engineer says that zipper merging can reduce backups by an average of 40%.
Machkovech notes that there is a catch: for maximum efficiency every driver has to use the zipper merge. A lot of drivers believe that a zipper merge is not polite, However, a Minnesota advertising campaign to encourage zipper merging raised the approval rate for zipper merging from 20% in 2010 to 73% in 2010.